two stage turbo
two stage turbo
04-23-2009, 05:26 AM
#1
I see those OM603 Mynamonsters are smokin like crazy before the boost builds up. I hate smoke
. Is there any way to get around this with two different sized turbos with the small-snailhouse workin at low- and the big at highpowersettings like on the BMW 535d/123d. NOT to be confused with- one feeding the other to get crazy racing engines.
Can anybody explain how those are interconnected and controlled.. link?
Anybody done/tried something similar?
Would it be possible to control two such turbos without electronics..?
I like the idea of a cheap easy available big HX at the toppower, but there is something missing below giving it a bad throttleresponse and high boosttreshold(rpm). Not a daily driver.
Would a small low inertia VW 1.9tdi turbocharger work taking care of throttleresponse and lower boosttreshold (get rid of BLACK NASTY smoke) , and the HX taking over at say 15psi?
Pretty much for the same reasons as some myna modified cars are using SC to solve this problem, I want to hear about two stg turbos..
All comments are appreciated. btw -how much boost are those 400hp mynamachines requiring?
Hey!
I see those OM603 Mynamonsters are smokin like crazy before the boost builds up. I hate smoke. Is there any way to get around this with two different sized turbos with the small-snailhouse workin at low- and the big at highpowersettings like on the BMW 535d/123d.
NOT to be confused with- one feeding the other to get crazy racing engines.
Can anybody explain how those are interconnected and controlled.. link?
Anybody done/tried something similar?
Would it be possible to control two such turbos without electronics..?
I like the idea of a cheap easy available big HX at the toppower, but there is something missing below giving it a bad throttleresponse and high boosttreshold(rpm). Not a daily driver.
Would a small low inertia VW 1.9tdi turbocharger work taking care of throttleresponse and lower boosttreshold (get rid of BLACK NASTY smoke) , and the HX taking over at say 15psi?
Pretty much for the same reasons as some myna modified cars are using SC to solve this problem, I want to hear about two stg turbos..
All comments are appreciated. btw -how much boost are those 400hp mynamachines requiring?
04-23-2009, 02:29 PM
#2
'78 300D, OM617.912: 4spd manual, TB03 at 10PSI, 26*BTDC, DV's turned, HVAC, emissions system removed, e-fan, short ram, 3" downpipe to straight exhaust, W126 Bendix brakes, MR2 Spyder seats. 2890lbs
Variable geometry turbo solves this issue. Spools up like a small turbo and acts like a big one to continuously supply boost.
'78 300D, OM617.912: 4spd manual, TB03 at 10PSI, 26*BTDC, DV's turned, HVAC, emissions system removed, e-fan, short ram, 3" downpipe to straight exhaust, W126 Bendix brakes, MR2 Spyder seats. 2890lbs
04-23-2009, 03:24 PM
#3
ForcedInduction
04-23-2009, 03:24 PM
#3
Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
04-24-2009, 05:46 AM
#4
(04-23-2009, 03:24 PM)ForcedInduction Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
Oki, thanks for reply and see what you guys are saying, but why is BMW attaching 2 VNT-snailhouses to their top of the line 4 and 6 cyl diesels..? They are not doing that without research just to increase cost if it did not increase performance/drivability.. -So one VNT is not enough if you are lookin for high performance (100+hp per liter) with superb drivability and throttle response from idle to top-rev. -This is where I think the mynas are falling through (low revs-smoke and bad throttle response), eventhough it is a hiperformance eng. Race only in my mind..
And as I understand everybody is having a hard time controlling a VNT on a custom 60X/617 setup.. Or am i wrong?
But anyway, I want to keep it "simple" and cheap with two junkyard turbos.
Back to topic
, Does anybody have a pics, thoughts or experience with two diff sized turbos with this philosophy in mind? lookin for compressorair-/exhaust flowdirections and valves/wastegate setups to control those turbos to get a smooth MAP transition from small to big turbo, and avoid turbosurge, high exhaust press and EGT`s. Thanks, Lars -All constructive replies are appreciated -neg/pos
(04-23-2009, 03:24 PM)ForcedInduction Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
Oki, thanks for reply and see what you guys are saying, but why is BMW attaching 2 VNT-snailhouses to their top of the line 4 and 6 cyl diesels..? They are not doing that without research just to increase cost if it did not increase performance/drivability.. -So one VNT is not enough if you are lookin for high performance (100+hp per liter) with superb drivability and throttle response from idle to top-rev. -This is where I think the mynas are falling through (low revs-smoke and bad throttle response), eventhough it is a hiperformance eng. Race only in my mind..
And as I understand everybody is having a hard time controlling a VNT on a custom 60X/617 setup.. Or am i wrong?
But anyway, I want to keep it "simple" and cheap with two junkyard turbos.
Back to topic
, Does anybody have a pics, thoughts or experience with two diff sized turbos with this philosophy in mind? lookin for compressorair-/exhaust flowdirections and valves/wastegate setups to control those turbos to get a smooth MAP transition from small to big turbo, and avoid turbosurge, high exhaust press and EGT`s. Thanks, Lars -All constructive replies are appreciated -neg/pos
04-24-2009, 01:05 PM
#5
(04-24-2009, 05:46 AM)lars Oki, thanks for reply and see what you guys are saying, but why is BMW attaching 2 VNT-snailhouses to their top of the line 4 and 6 cyl diesels..?Emissions? Marketing? Cost cutting? I don't know. I do know it was a huge step back in technology, reliability and simplicity. Mercedes is making the same mistake. They are making a poor choice using 1990's technology.
Quote:So one VNT is not enough if you are lookin for high performance (100+hp per liter) with superb drivability and throttle response from idle to top-rev.Actually, it is.
Quote:And as I understand everybody is having a hard time controlling a VNT on a custom 60X/617 setup.. Or am i wrong?Yep. Not a single problem on mine in 3 years of operation. I can make 10psi off the line at 1800rpm and 14psi at 2200rpm. If you think controlling a VNT would be tough, getting a sequential system timed properly to operate smoothly and evenly will be far more difficult.
Just look at the vacuum diagrams of some twinturbo cars.
1992 Mazda RX7
![[Image: vacuum.jpg]](http://autosportracetech.com/RX-7/vacuum.jpg)
1990 Supra
![[Image: Under_Bonnet_Vacuum_Lines.jpg]](http://www.max-boost.co.uk/max-boost/images/supra/Under_Bonnet_Vacuum_Lines.jpg)
Then compare to a VNT from a TDi. With the EGR and shutdown throttle removed its just 1 vacuum line and a solenoid.
![[Image: turbo_tdi_N75_N18_N239m_EGR_VNT_Act.jpg]](http://i265.photobucket.com/albums/ii219/avaly21/MAF%20VW%20Passat/turbo_tdi_N75_N18_N239m_EGR_VNT_Act.jpg)
My VNT control uses the stock vacuum system with 1 vacuum hose going to the vacuum actuator and a wastegate actuator going directly to the intake manifold. No electrical, 100% mechanical and automatic. The only non-stock valve is to eliminate the vacuum actuator from the equation when maximum response is desired.
This post was last modified: 04-24-2009, 01:20 PM by ForcedInduction.
ForcedInduction
04-24-2009, 01:05 PM
#5
(04-24-2009, 05:46 AM)lars Oki, thanks for reply and see what you guys are saying, but why is BMW attaching 2 VNT-snailhouses to their top of the line 4 and 6 cyl diesels..?Emissions? Marketing? Cost cutting? I don't know. I do know it was a huge step back in technology, reliability and simplicity. Mercedes is making the same mistake. They are making a poor choice using 1990's technology.
Quote:So one VNT is not enough if you are lookin for high performance (100+hp per liter) with superb drivability and throttle response from idle to top-rev.Actually, it is.
Quote:And as I understand everybody is having a hard time controlling a VNT on a custom 60X/617 setup.. Or am i wrong?Yep. Not a single problem on mine in 3 years of operation. I can make 10psi off the line at 1800rpm and 14psi at 2200rpm. If you think controlling a VNT would be tough, getting a sequential system timed properly to operate smoothly and evenly will be far more difficult.
Just look at the vacuum diagrams of some twinturbo cars.
1992 Mazda RX7
1990 Supra
Then compare to a VNT from a TDi. With the EGR and shutdown throttle removed its just 1 vacuum line and a solenoid.
My VNT control uses the stock vacuum system with 1 vacuum hose going to the vacuum actuator and a wastegate actuator going directly to the intake manifold. No electrical, 100% mechanical and automatic. The only non-stock valve is to eliminate the vacuum actuator from the equation when maximum response is desired.
04-24-2009, 05:41 PM
#6
Simple is good, I feel that the addition of a non-vnt LP turbo in a compound setup wouldn't be too big of a set-up issue (challenging yes, issue no) and we'll have all the air for our STD engines.
Should this be joined to the 'Compound Turbo' thread???
This post was last modified: 04-24-2009, 05:51 PM by Telecommbrkr.
'Jurgen' - 1982 300sd cream paint with palimino MB tex interior. Now running with new cooling system
.......discovered oil cooler has pinhole @#$%@ Nitrile gloves back on......'Otto' - 1985 300sd anthracite? grey/silver? with grey leather interior. (heated front seats!!!!
) Euro headlightsMods are in the works...
Telecommbrkr
04-24-2009, 05:41 PM #6This is good stuff.........
Simple is good, I feel that the addition of a non-vnt LP turbo in a compound setup wouldn't be too big of a set-up issue (challenging yes, issue no) and we'll have all the air for our STD engines.
Should this be joined to the 'Compound Turbo' thread???
'Jurgen' - 1982 300sd cream paint with palimino MB tex interior. Now running with new cooling system
.......discovered oil cooler has pinhole @#$%@ Nitrile gloves back on......'Otto' - 1985 300sd anthracite? grey/silver? with grey leather interior. (heated front seats!!!!
) Euro headlightsMods are in the works...
04-24-2009, 08:52 PM
#7
(04-24-2009, 05:41 PM)Telecommbrkr Should this be joined to the 'Compound Turbo' thread???
Compound and sequential turbocharging are very different in how they work. Sequential is for rapid response, compound is for high pressure.
ForcedInduction
04-24-2009, 08:52 PM
#7
(04-24-2009, 05:41 PM)Telecommbrkr Should this be joined to the 'Compound Turbo' thread???
Compound and sequential turbocharging are very different in how they work. Sequential is for rapid response, compound is for high pressure.
04-29-2009, 09:37 AM
#11
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
willbhere4u
04-29-2009, 09:37 AM #11in our shop we have a cummins with compound turbos the stock turbo stayes conected like normal then a large turbo takes the exhaust after the first small turbo used it then the boost goes in the first turbo multiplying the boost aka compounding it
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
05-05-2009, 10:54 AM
#14
Gota love Mercedes Diesels!
.
DeliveryValve
05-05-2009, 10:54 AM #14That supercharger in the picture is from a Ford Thunderbird Super Coupe. The setup is interesting in that the supercharger is mounted on the wheel. If I recall during the lemons race, they had issues with the custom idler. I bet if they had more time to mount on the engine, it would of been more reliable.
Gota love Mercedes Diesels!
.
05-05-2009, 12:11 PM
#15
Anybody have a link to a finnish w201 with 6cyl myna diesel (603?) turbo and SC? I think the car is white or yellow. I can`t find the link again
Sequential system with SC on low- and Turbo on higher revs/power seems like a smooth thing. Links to other cars with same setup is also appreciated
Sweet with SC!
Anybody have a link to a finnish w201 with 6cyl myna diesel (603?) turbo and SC? I think the car is white or yellow. I can`t find the link again
Sequential system with SC on low- and Turbo on higher revs/power seems like a smooth thing. Links to other cars with same setup is also appreciated
05-06-2009, 01:44 AM
#16
![[Image: twinchargedbenz1.jpg]](http://i17.photobucket.com/albums/b59/triple-d-racing/twinchargedbenz1.jpg)
![[Image: twinchargedbenz2.jpg]](http://i17.photobucket.com/albums/b59/triple-d-racing/twinchargedbenz2.jpg)
nom nom nom
'78 300D, OM617.912: 4spd manual, TB03 at 10PSI, 26*BTDC, DV's turned, HVAC, emissions system removed, e-fan, short ram, 3" downpipe to straight exhaust, W126 Bendix brakes, MR2 Spyder seats. 2890lbs
05-06-2009, 08:59 AM
#17
GREASY_BEAST
05-06-2009, 08:59 AM #17Did that engine ACTUALLY fail? That just seems too beautiful to have died its alleged death...
11-15-2009, 07:07 AM
#18
(04-23-2009, 03:24 PM)ForcedInduction Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
Making life in this old thread..
What brand/model vnt will make 530nm @1500revs and 350hp(chiptuned hp rating) on a 602/603?
Or do we have a big problem with being IDI or low-flow 2valve layout, so we will never meet these bottom-to-top numbers?
http://autospeed.com/cms/title_BMWs-Twin...ticle.html
Many modern CR single-vnt diesels have LOTS of torque starting at 1500ish rpm. Nobody has that here?? We have to reduce bottom end boost to avoid compressor surge. How can they make it, but we cannot? Are these keywords.. IDI, low-flow, insufficient vnt control?
(04-23-2009, 03:24 PM)ForcedInduction Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
Making life in this old thread..
What brand/model vnt will make 530nm @1500revs and 350hp(chiptuned hp rating) on a 602/603?
Or do we have a big problem with being IDI or low-flow 2valve layout, so we will never meet these bottom-to-top numbers?
http://autospeed.com/cms/title_BMWs-Twin...ticle.html
Many modern CR single-vnt diesels have LOTS of torque starting at 1500ish rpm. Nobody has that here?? We have to reduce bottom end boost to avoid compressor surge. How can they make it, but we cannot? Are these keywords.. IDI, low-flow, insufficient vnt control?
11-15-2009, 05:35 PM
#19
(11-15-2009, 07:07 AM)lars What brand/model vnt will make 530nm @1500revs and 350hp(chiptuned hp rating) on a 602/603?Something in the GT30, GT32 or GT35 range with a 67-76mm compressor. The smallest turbo you can use to support your maximum power, the quicker you'll get the torque.
Quote:Many modern CR single-vnt diesels have LOTS of torque starting at 1500ish rpm. Nobody has that here?? We have to reduce bottom end boost to avoid compressor surge. How can they make it, but we cannot?2-valve head. Modern Diesels benefit from computational fluid dynamics to optimize swirl, flow and restriction. 4-valves help tremendously as well, as does having a very small turbo. MB's V6 uses a GT2056VK, which would be considered small even for a 617.
A 617 has 85% VE at best, the 602/3 a little higher due to larger port diameter in it's crossflow head.
Thats not to say torque is bad, I can get 10psi boost and over 200lb/ft torque at 1800rpm with only 5.5mm plungers.
This post was last modified: 11-15-2009, 05:36 PM by ForcedInduction.
ForcedInduction
11-15-2009, 05:35 PM
#19
(11-15-2009, 07:07 AM)lars What brand/model vnt will make 530nm @1500revs and 350hp(chiptuned hp rating) on a 602/603?Something in the GT30, GT32 or GT35 range with a 67-76mm compressor. The smallest turbo you can use to support your maximum power, the quicker you'll get the torque.
Quote:Many modern CR single-vnt diesels have LOTS of torque starting at 1500ish rpm. Nobody has that here?? We have to reduce bottom end boost to avoid compressor surge. How can they make it, but we cannot?2-valve head. Modern Diesels benefit from computational fluid dynamics to optimize swirl, flow and restriction. 4-valves help tremendously as well, as does having a very small turbo. MB's V6 uses a GT2056VK, which would be considered small even for a 617.
A 617 has 85% VE at best, the 602/3 a little higher due to larger port diameter in it's crossflow head.
Thats not to say torque is bad, I can get 10psi boost and over 200lb/ft torque at 1800rpm with only 5.5mm plungers.
11-16-2009, 05:09 AM
#20
(04-23-2009, 03:24 PM)ForcedInduction Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
Bit of a thread-dredge, but two turbos in a compound/sequential arrangement are far more versatile than a single variable vane.
The average variable vane turbo still has a fixed geometry compressor and there's only soo much range that can be gained from variable exhaust stator blades.
There is also the advantage that compound turbos can be more efficient than a variable. Variable turbos trade efficiency for a wider operating range.
For Lars, compound turbos don't have to be about big boost. The #1 gain they have is a wider operating range, you can wastegate the boost to the level required.
(04-23-2009, 03:24 PM)ForcedInduction Yep. Variable geometry turbine turbos have made sequential turbos obsolete on Diesels.
Bit of a thread-dredge, but two turbos in a compound/sequential arrangement are far more versatile than a single variable vane.
The average variable vane turbo still has a fixed geometry compressor and there's only soo much range that can be gained from variable exhaust stator blades.
There is also the advantage that compound turbos can be more efficient than a variable. Variable turbos trade efficiency for a wider operating range.
For Lars, compound turbos don't have to be about big boost. The #1 gain they have is a wider operating range, you can wastegate the boost to the level required.
11-16-2009, 05:44 AM
#21
BMW's system is primitive compared to the rest of the engine's technology. Its design is little different than traditional sequential turbos used by 80's/90's g@ssers except in the cold side plumbing.
Two VNT's would be more efficient and simple. The VNT vanes completely eliminate the exhaust control valves while retaining all the benefits of a single VNT and a modulated two-stage. Specifically, a larger 2nd stage turbo could be used for even more top-end power and the low range turbo would take less time to relight as RPM's drop. Traditional turbos were probably used as a cost cutting measure to bring production cost closer to the g@sser. You're already paying a $3,600 "diesel tax" for a 335d over a 335i, adding another $300 would make the option even less attractive to "diesel curious" buyers.
This post was last modified: 11-16-2009, 06:12 AM by ForcedInduction.
ForcedInduction
11-16-2009, 05:44 AM
#21
BMW uses a compound-sequential system (modulated two-stage). The small spools up very fast for low end torque, the big joins in as a compound for big low-middle range torque then the big takes over completely for free flowing (as free as that tangled mess can be) high rpm HP.
BMW's system is primitive compared to the rest of the engine's technology. Its design is little different than traditional sequential turbos used by 80's/90's g@ssers except in the cold side plumbing.
Two VNT's would be more efficient and simple. The VNT vanes completely eliminate the exhaust control valves while retaining all the benefits of a single VNT and a modulated two-stage. Specifically, a larger 2nd stage turbo could be used for even more top-end power and the low range turbo would take less time to relight as RPM's drop. Traditional turbos were probably used as a cost cutting measure to bring production cost closer to the g@sser. You're already paying a $3,600 "diesel tax" for a 335d over a 335i, adding another $300 would make the option even less attractive to "diesel curious" buyers.
11-16-2009, 12:19 PM
#22
Concerning bigtorque @ 1500ish rpm.. Poor 2valve VE can be compensated for in a 602 with enough boost down there, and 7mm?
Cold side..The compound effect comes in when the bigboy is feeding the small, until the bigturbo`s psi reaches the small`s psi -and the controlvalve opens to bypass the small? I think I am getting it
?I like the cold side of the BMW system, and it should not be too hard (I think) getting a double acting actuator (or to opposing singles) to control the "cold valve"..
I Dislike the 535d hot side, because it seems hard replicate a butterflyvalve-system upstream the bigboy, to divert the exhaustflow accurately between the two turbines.
On the hot side, using two VNT`s, I think it would be easier to arrange like a conventional compound setup, with a he351? first and a gt2052/gt17? downstream. A wastegate-bypass is needed parallell to the smallguy. Maybe even an exhaustbrakesize-butterfly wastegate (to bypass the smaller after the compounding effect is over) to handle the he351`s high topend exhaustflow..?
Or any oyther hot/cold suggestions?
controlling boostlevels at the different throttle inputs should make no more headaches than a single vnt..
Thanks guys. Cool beans
Concerning bigtorque @ 1500ish rpm.. Poor 2valve VE can be compensated for in a 602 with enough boost down there, and 7mm?
Cold side..The compound effect comes in when the bigboy is feeding the small, until the bigturbo`s psi reaches the small`s psi -and the controlvalve opens to bypass the small? I think I am getting it?
I like the cold side of the BMW system, and it should not be too hard (I think) getting a double acting actuator (or to opposing singles) to control the "cold valve"..
I Dislike the 535d hot side, because it seems hard replicate a butterflyvalve-system upstream the bigboy, to divert the exhaustflow accurately between the two turbines.
On the hot side, using two VNT`s, I think it would be easier to arrange like a conventional compound setup, with a he351? first and a gt2052/gt17? downstream. A wastegate-bypass is needed parallell to the smallguy. Maybe even an exhaustbrakesize-butterfly wastegate (to bypass the smaller after the compounding effect is over) to handle the he351`s high topend exhaustflow..?
Or any oyther hot/cold suggestions?
controlling boostlevels at the different throttle inputs should make no more headaches than a single vnt..
11-16-2009, 01:39 PM
#23
(11-16-2009, 12:19 PM)lars Concerning bigtorque @ 1500ish rpm.. Poor 2valve VE can be compensated for in a 602 with enough boost down there, and 7mm?The more the better. Boost at low RPM is limited mainly by what the compressor can do and what the engine/drivetrain can handle.
Quote:Cold side..The compound effect comes in when the bigboy is feeding the small, until the bigturbo`s psi reaches the small`s psi -and the controlvalve opens to bypass the small? I think I am getting itThats how I understand it. I'd like to get a boost gauge on a factory 335d and see exactly how long and under what conditions BMW has it work as a compound.
Modulated two-stages seem massively overcomplicated to me. You've basically got the performance of a sequential and a compound, but not the efficiency of a compound since the smaller turbo is not feeding its used exhaust to the larger one. A simple compound system should spool up just as fast but have higher thermal efficiency and be able to maintain that high torque throughout the RPM range.
ForcedInduction
11-16-2009, 01:39 PM
#23
(11-16-2009, 12:19 PM)lars Concerning bigtorque @ 1500ish rpm.. Poor 2valve VE can be compensated for in a 602 with enough boost down there, and 7mm?The more the better. Boost at low RPM is limited mainly by what the compressor can do and what the engine/drivetrain can handle.
Quote:Cold side..The compound effect comes in when the bigboy is feeding the small, until the bigturbo`s psi reaches the small`s psi -and the controlvalve opens to bypass the small? I think I am getting itThats how I understand it. I'd like to get a boost gauge on a factory 335d and see exactly how long and under what conditions BMW has it work as a compound.
Modulated two-stages seem massively overcomplicated to me. You've basically got the performance of a sequential and a compound, but not the efficiency of a compound since the smaller turbo is not feeding its used exhaust to the larger one. A simple compound system should spool up just as fast but have higher thermal efficiency and be able to maintain that high torque throughout the RPM range.
11-16-2009, 02:40 PM
#24
(11-16-2009, 01:39 PM)ForcedInduction Modulated two-stages seem massively overcomplicated to me. You've basically got the performance of a sequential and a compound, but not the efficiency of a compound since the smaller turbo is not feeding its used exhaust to the larger one. A simple compound system should spool up just as fast but have higher thermal efficiency and be able to maintain that high torque throughout the RPM range.
Yes. See your point now(takes time)
!!! I see one issue with this setup though. You NEED a WG to bypass the HP turbine!? In my mind a HP gt2052v will create a massive EGP buildup with 7mm. -Even with full open vanes.?!
(11-16-2009, 01:39 PM)ForcedInduction Modulated two-stages seem massively overcomplicated to me. You've basically got the performance of a sequential and a compound, but not the efficiency of a compound since the smaller turbo is not feeding its used exhaust to the larger one. A simple compound system should spool up just as fast but have higher thermal efficiency and be able to maintain that high torque throughout the RPM range.
Yes. See your point now(takes time)
!!! I see one issue with this setup though. You NEED a WG to bypass the HP turbine!? In my mind a HP gt2052v will create a massive EGP buildup with 7mm. -Even with full open vanes.?!
11-16-2009, 04:17 PM
#25
(11-16-2009, 02:40 PM)lars You NEED a WG to bypass the HP turbine!? In my mind a HP gt2052v will create a massive EGP buildup with 7mm. -Even with full open vanes.?!
Thats because a GT20 is very small. A VNT needs to be sized to the engine so that the vanes never reach 100% open at full load, otherwise you lose the ability to control boost pressure.
Here is a comparison of a GT20 to a GT22 turbine. Not only is the 20 smaller in size, its got more blades obstructing flow.
Here is a GT22 to a GT25.
The difference in spool up time would be negligible with a 56mm or 59mm compressor, it will still be along the surge line as it accelerates, but the turbine will flow much better on the high-end.
ForcedInduction
11-16-2009, 04:17 PM
#25
(11-16-2009, 02:40 PM)lars You NEED a WG to bypass the HP turbine!? In my mind a HP gt2052v will create a massive EGP buildup with 7mm. -Even with full open vanes.?!
Thats because a GT20 is very small. A VNT needs to be sized to the engine so that the vanes never reach 100% open at full load, otherwise you lose the ability to control boost pressure.
Here is a comparison of a GT20 to a GT22 turbine. Not only is the 20 smaller in size, its got more blades obstructing flow.
Here is a GT22 to a GT25.
The difference in spool up time would be negligible with a 56mm or 59mm compressor, it will still be along the surge line as it accelerates, but the turbine will flow much better on the high-end.
11-16-2009, 05:27 PM
#26
(11-16-2009, 05:44 AM)ForcedInduction Two VNT's would be more efficient and simple.
Simpler plumbing yes, but not more efficient. Fixed geometry turbos have far more efficient turbines than variable geometry turbines.
The difference in turbine efficiency means more exhaust backpressure and lower engine efficiency.
This ends up costing both power and fuel economy.
If BMW could have acheived the same result (or better) with a couple of VNT's, they would have done it. Guaranteed.
More top end power (we're already talking 180kw on a 3L diesel) is not as simple as a bigger LP turbo. It's already a speed limited car, so how much more power can you really use? Faster acceleration is not acheived by more top end power, but higher average power.
Lars.
With a compound system you don't need a massive wastegate to bypass the HP turbine unless it's massively undersized. Keeping the HP turbo in the loop means it's passing no more air/exhaust volume than it would as a single turbo. It's just at a higher density.
(11-16-2009, 05:44 AM)ForcedInduction Two VNT's would be more efficient and simple.
Simpler plumbing yes, but not more efficient. Fixed geometry turbos have far more efficient turbines than variable geometry turbines.
The difference in turbine efficiency means more exhaust backpressure and lower engine efficiency.
This ends up costing both power and fuel economy.
If BMW could have acheived the same result (or better) with a couple of VNT's, they would have done it. Guaranteed.
More top end power (we're already talking 180kw on a 3L diesel) is not as simple as a bigger LP turbo. It's already a speed limited car, so how much more power can you really use? Faster acceleration is not acheived by more top end power, but higher average power.
Lars.
With a compound system you don't need a massive wastegate to bypass the HP turbine unless it's massively undersized. Keeping the HP turbo in the loop means it's passing no more air/exhaust volume than it would as a single turbo. It's just at a higher density.
11-16-2009, 07:31 PM
#27
(11-16-2009, 05:27 PM)Kiwibacon Fixed geometry turbos have far more efficient turbinesThe turbine itself, yes. But they have a wastegate. All the exhaust energy flows through a VNT.
Quote:The difference in turbine efficiency means more exhaust backpressure and lower engine efficiency.Thats not true. I have yet to see a single person install a VNT and report reduced fuel economy or power. In fact the opposite, all have gained 2-4mpg and significant power across the range.
This ends up costing both power and fuel economy.
Quote:If BMW could have acheived the same result (or better) with a couple of VNT's, they would have done it. Guaranteed.Costs. This isn't the 70's/80's where engineers rule decisions, bean counters always have the last word today. The diesel option already costs $3,600. For the same psychological reason things sell better at $0.99 than $1.00, $4,000 would look much worse to a customer. Not to mention the hidden cost of the maintaining urea system as well.
Inconel (vanes) costs around $28/lb vs $2/lb for iron. Thats $10.50 per turbo in weight alone, not counting machining costs, welding the vanes to the stems and time-consuming assembly. Figure a min. of $300 per VNT housing compared to ~$100 for 1 wastegated housing and you can see why bean counters want the wastegated 2-stage instead.
Hell, I bet the engineers only got piezo injectors instead of solenoids because they needed it to meet emissions limits.
When you need $4,000 worth of exhaust treatment devices just to meet the limit, every penny spent on the engine counts.Quote:More top end power (we're already talking 180kw on a 3L diesel) is not as simple as a bigger LP turbo.For a diesel, it is. A WG turbo has to be closely sized matched to the engine, a trade-off must be chosen; A restrictive turbine A/R used to spool it up quickly for low-end power or a bigger A/R for top-end power but slower spooling. Thats why people often choose a T3/T04 hybrid instead of a normal T04.
A VNT has both fast spooling and high flow in 1 package. Like an SSD vs a fast HD in computers, the SSD costs more/GB but it performs better in every way than a HD.
Quote:It's already a speed limited car, so how much more power can you really use?How many people can use a 604HP S-Class? How much more than 88hp can you really use? Why did Mercedes add a turbo to a car that could already do 96mph? Why did we start this forum when the stock car could already keep up with everyday traffic very well?
I hear the 20hp Model T sold sold well too, something like 15 million, give or take a few hundred thousand. Who really needs to drive faster than 45mph?
Quote:Faster acceleration is not achieved by more top end power, but higher average power.Which a VNT will do as seen on my very own vehicles.
BMW is basically using a single big turbo on the top-end with a small turbo to spool it up, the exact same can be done with a single VNT. The only benefit to BMW's system is the short compound period that boosts the low-end a little more.
BMW dyno chart.
Looking at my last dyno graph, we can see my curves are nearly the same as BMW's. Take away the numbers and the curves would be difficult to tell apart by somebody that hasn't seen them before.
This post was last modified: 11-16-2009, 07:36 PM by ForcedInduction.
ForcedInduction
11-16-2009, 07:31 PM
#27
(11-16-2009, 05:27 PM)Kiwibacon Fixed geometry turbos have far more efficient turbinesThe turbine itself, yes. But they have a wastegate. All the exhaust energy flows through a VNT.
Quote:The difference in turbine efficiency means more exhaust backpressure and lower engine efficiency.Thats not true. I have yet to see a single person install a VNT and report reduced fuel economy or power. In fact the opposite, all have gained 2-4mpg and significant power across the range.
This ends up costing both power and fuel economy.
Quote:If BMW could have acheived the same result (or better) with a couple of VNT's, they would have done it. Guaranteed.Costs. This isn't the 70's/80's where engineers rule decisions, bean counters always have the last word today. The diesel option already costs $3,600. For the same psychological reason things sell better at $0.99 than $1.00, $4,000 would look much worse to a customer. Not to mention the hidden cost of the maintaining urea system as well.
Inconel (vanes) costs around $28/lb vs $2/lb for iron. Thats $10.50 per turbo in weight alone, not counting machining costs, welding the vanes to the stems and time-consuming assembly. Figure a min. of $300 per VNT housing compared to ~$100 for 1 wastegated housing and you can see why bean counters want the wastegated 2-stage instead.
Hell, I bet the engineers only got piezo injectors instead of solenoids because they needed it to meet emissions limits.
When you need $4,000 worth of exhaust treatment devices just to meet the limit, every penny spent on the engine counts.Quote:More top end power (we're already talking 180kw on a 3L diesel) is not as simple as a bigger LP turbo.For a diesel, it is. A WG turbo has to be closely sized matched to the engine, a trade-off must be chosen; A restrictive turbine A/R used to spool it up quickly for low-end power or a bigger A/R for top-end power but slower spooling. Thats why people often choose a T3/T04 hybrid instead of a normal T04.
A VNT has both fast spooling and high flow in 1 package. Like an SSD vs a fast HD in computers, the SSD costs more/GB but it performs better in every way than a HD.
Quote:It's already a speed limited car, so how much more power can you really use?How many people can use a 604HP S-Class? How much more than 88hp can you really use? Why did Mercedes add a turbo to a car that could already do 96mph? Why did we start this forum when the stock car could already keep up with everyday traffic very well?
I hear the 20hp Model T sold sold well too, something like 15 million, give or take a few hundred thousand. Who really needs to drive faster than 45mph?
Quote:Faster acceleration is not achieved by more top end power, but higher average power.Which a VNT will do as seen on my very own vehicles.
BMW is basically using a single big turbo on the top-end with a small turbo to spool it up, the exact same can be done with a single VNT. The only benefit to BMW's system is the short compound period that boosts the low-end a little more.
BMW dyno chart.
Looking at my last dyno graph, we can see my curves are nearly the same as BMW's. Take away the numbers and the curves would be difficult to tell apart by somebody that hasn't seen them before.
11-16-2009, 10:21 PM
#28
Quote: I hear the 20hp Model T sold sold well too, something like 15 million, give or take a few hundred thousand. Who really needs to drive faster than 45mph?
Not to take this off topic but a model T with a two speed rear end could do 90mph!
not that the suspension and wheels could handle it well! My buddy got in to a death wobble across 3 lanes of traffic on the interstate in a restored 1917 model T at 90 mph! said he would never try that again!!!
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
willbhere4u
11-16-2009, 10:21 PM #28Quote: I hear the 20hp Model T sold sold well too, something like 15 million, give or take a few hundred thousand. Who really needs to drive faster than 45mph?
Not to take this off topic but a model T with a two speed rear end could do 90mph!
not that the suspension and wheels could handle it well! My buddy got in to a death wobble across 3 lanes of traffic on the interstate in a restored 1917 model T at 90 mph! said he would never try that again!!!
1987 300SDL 6spd manual om606.962 swap project
1985 300td euro 5spd wagon running
11-16-2009, 10:33 PM
#29
(11-16-2009, 07:31 PM)ForcedInduction The turbine itself, yes. But they have a wastegate. All the exhaust energy flows through a VNT.
At cruising rpms where fuel economy is made or lost, wastegates are closed.
Hence better turbo efficiency is better fuel economy.
(11-16-2009, 07:31 PM)ForcedInduction Thats not true. I have yet to see a single person install a VNT and report reduced fuel economy or power. In fact the opposite, all have gained 2-4mpg and significant power across the range.
It's very true. Your observations of replacing a 1970-1980 T3 with a modern VNT are not comparable.
(11-16-2009, 07:31 PM)ForcedInduction Inconel (vanes) costs around $28/lb vs $2/lb for iron. Thats $10.50 per turbo in weight alone, not counting machining costs, welding the vanes to the stems and time-consuming assembly. Figure a min. of $300 per VNT housing compared to ~$100 for 1 wastegated housing and you can see why bean counters want the wastegated 2-stage instead.
Hell, I bet the engineers only got piezo injectors instead of solenoids because they needed it to meet emissions limits.
An OEM won't pay $US300 difference between VNT and wastegated turbos. I'd be surprised if they paid $US300 total for a turbo.
BMW use VNT turbos on the lower power version of the same engine. They stepped up to two turbos when they had to. This engine runs 42psi boost.
Solenoid injectors can't react fast enough compared to piezo. They aren't an option.
(11-16-2009, 07:31 PM)ForcedInduction A VNT has both fast spooling and high flow in 1 package. Like an SSD vs a fast HD in computers, the SSD costs more/GB but it performs better in every way than a HD.
Computer analogies don't cut it.
(11-16-2009, 07:31 PM)ForcedInductionQuote:Faster acceleration is not achieved by more top end power, but higher average power.Which a VNT will do as seen on my very own vehicles.
You're still quite a way off the 335d.
(11-16-2009, 07:31 PM)ForcedInduction BMW is basically using a single big turbo on the top-end with a small turbo to spool it up, the exact same can be done with a single VNT.
No it can't. Show me a VNT which can produce 42psi at 1400rpm and the airflow needed for a 180kw diesel.
Put simply, you can't acheive this with a single compressor, which is what all the current VNT's use.
The VNT version of this exact same BMW engine has 10% less torque and 20% less power in it's best configuration.
(11-16-2009, 07:31 PM)ForcedInduction The turbine itself, yes. But they have a wastegate. All the exhaust energy flows through a VNT.
At cruising rpms where fuel economy is made or lost, wastegates are closed.
Hence better turbo efficiency is better fuel economy.
(11-16-2009, 07:31 PM)ForcedInduction Thats not true. I have yet to see a single person install a VNT and report reduced fuel economy or power. In fact the opposite, all have gained 2-4mpg and significant power across the range.
It's very true. Your observations of replacing a 1970-1980 T3 with a modern VNT are not comparable.
(11-16-2009, 07:31 PM)ForcedInduction Inconel (vanes) costs around $28/lb vs $2/lb for iron. Thats $10.50 per turbo in weight alone, not counting machining costs, welding the vanes to the stems and time-consuming assembly. Figure a min. of $300 per VNT housing compared to ~$100 for 1 wastegated housing and you can see why bean counters want the wastegated 2-stage instead.
Hell, I bet the engineers only got piezo injectors instead of solenoids because they needed it to meet emissions limits.
An OEM won't pay $US300 difference between VNT and wastegated turbos. I'd be surprised if they paid $US300 total for a turbo.
BMW use VNT turbos on the lower power version of the same engine. They stepped up to two turbos when they had to. This engine runs 42psi boost.
Solenoid injectors can't react fast enough compared to piezo. They aren't an option.
(11-16-2009, 07:31 PM)ForcedInduction A VNT has both fast spooling and high flow in 1 package. Like an SSD vs a fast HD in computers, the SSD costs more/GB but it performs better in every way than a HD.
Computer analogies don't cut it.
(11-16-2009, 07:31 PM)ForcedInductionQuote:Faster acceleration is not achieved by more top end power, but higher average power.Which a VNT will do as seen on my very own vehicles.
You're still quite a way off the 335d.
(11-16-2009, 07:31 PM)ForcedInduction BMW is basically using a single big turbo on the top-end with a small turbo to spool it up, the exact same can be done with a single VNT.
No it can't. Show me a VNT which can produce 42psi at 1400rpm and the airflow needed for a 180kw diesel.
Put simply, you can't acheive this with a single compressor, which is what all the current VNT's use.
The VNT version of this exact same BMW engine has 10% less torque and 20% less power in it's best configuration.
11-17-2009, 02:33 AM
#30
(11-16-2009, 10:33 PM)Kiwibacon At cruising rpms where fuel economy is made or lost, wastegates are closed.No. At cruise, there is no control of boost other than by engine load. A VNT can set exactly the boost the engine needs and let the rest freely pass through the turbine.
Hence better turbo efficiency is better fuel economy.
Quote:Your observations of replacing a 1970-1980 T3 with a modern VNT are not comparable.Nope. Turbo is a turbo. Unless its got some fancy ceramic turbine, titanium compressor or ball bearings, a VNT beats a wastegate in efficiency every time.
Quote:This engine runs 42psi boost.Only for a very brief period during "compound mode". 42psi is the peak pressure, not continuous.
Quote:Solenoid injectors can't react fast enough compared to piezo.Which is why they are needed to meet emissions, they need those 5 injection events per cycle to control NOx adequately.
Quote:Computer analogies don't cut it.Quite the contrary, its like comparing Red Delicious to Granny Smith.
Quote:You're still quite a way off the 335d.No kidding, note the "Take away the numbers and the curves would be difficult to tell apart by somebody that hasn't seen them before."
Quote:Show me a VNT which can produce 42psi at 1400rpm and the airflow needed for a 180kw diesel.Again, 42psi is the PEAK pressure, it does not see that across the RPM band, only at low RPMS when the turbos are in "compound mode".
Quote:Put simply, you can't acheive this with a single compressor, which is what all the current VNT's use.No single turbo can do what compounds can, but they can very easily best the top-end power produced by the larger turbo when the small is bypassed.
Quote:The VNT version of this exact same BMW engine has 10% less torque and 20% less power in it's best configuration.PEAK torque and power. Add a LP compound to that single VNT and it would easily best that 10/20% difference.
As you said it, "Faster acceleration is not achieved by more top end power (low-end in this example), but higher average power."
It doesn't matter if you have 800lb/ft of torque and 100psi at 1400rpm is rapidly falling by 3000rpm! Thats one reason why a similar displacement g@sser with much less torque can keep up with a diesel, its torque remains flatter with raising RPMs instead of peaking early and falling off.
This post was last modified: 11-17-2009, 02:42 AM by ForcedInduction.
ForcedInduction
11-17-2009, 02:33 AM
#30
(11-16-2009, 10:33 PM)Kiwibacon At cruising rpms where fuel economy is made or lost, wastegates are closed.No. At cruise, there is no control of boost other than by engine load. A VNT can set exactly the boost the engine needs and let the rest freely pass through the turbine.
Hence better turbo efficiency is better fuel economy.
Quote:Your observations of replacing a 1970-1980 T3 with a modern VNT are not comparable.Nope. Turbo is a turbo. Unless its got some fancy ceramic turbine, titanium compressor or ball bearings, a VNT beats a wastegate in efficiency every time.
Quote:This engine runs 42psi boost.Only for a very brief period during "compound mode". 42psi is the peak pressure, not continuous.
Quote:Solenoid injectors can't react fast enough compared to piezo.Which is why they are needed to meet emissions, they need those 5 injection events per cycle to control NOx adequately.
Quote:Computer analogies don't cut it.Quite the contrary, its like comparing Red Delicious to Granny Smith.
Quote:You're still quite a way off the 335d.No kidding, note the "Take away the numbers and the curves would be difficult to tell apart by somebody that hasn't seen them before."
Quote:Show me a VNT which can produce 42psi at 1400rpm and the airflow needed for a 180kw diesel.Again, 42psi is the PEAK pressure, it does not see that across the RPM band, only at low RPMS when the turbos are in "compound mode".
Quote:Put simply, you can't acheive this with a single compressor, which is what all the current VNT's use.No single turbo can do what compounds can, but they can very easily best the top-end power produced by the larger turbo when the small is bypassed.
Quote:The VNT version of this exact same BMW engine has 10% less torque and 20% less power in it's best configuration.PEAK torque and power. Add a LP compound to that single VNT and it would easily best that 10/20% difference.
As you said it, "Faster acceleration is not achieved by more top end power (low-end in this example), but higher average power."
It doesn't matter if you have 800lb/ft of torque and 100psi at 1400rpm is rapidly falling by 3000rpm! Thats one reason why a similar displacement g@sser with much less torque can keep up with a diesel, its torque remains flatter with raising RPMs instead of peaking early and falling off.
11-17-2009, 03:18 AM
#31
(11-17-2009, 02:33 AM)ForcedInduction No. At cruise, there is no control of boost other than by engine load. A VNT can set exactly the boost the engine needs and let the rest freely pass through the turbine.
There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.
Further, there is far more in turbo wheel and housing design than you seem aware of. Efficiencies vary considerably, often inversely to flow range.
(11-17-2009, 02:33 AM)ForcedInduction No kidding, note the "Take away the numbers and the curves would be difficult to tell apart by somebody that hasn't seen them before."
Achieving a curve shape at 80kw and acheiving the same shape at 180kw are two massively different outcomes.
Let me know when you've got comparable numbers, not shapes. I can get similar shapes from a non turbo motor.
As I said earlier, hit 42psi at 1400rpm and flow enough for 180kw at the top end (roughly 26psi) and let me know what single turbo can do that. VNT or otherwise.
(11-17-2009, 02:33 AM)ForcedInduction No. At cruise, there is no control of boost other than by engine load. A VNT can set exactly the boost the engine needs and let the rest freely pass through the turbine.
There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.
Further, there is far more in turbo wheel and housing design than you seem aware of. Efficiencies vary considerably, often inversely to flow range.
(11-17-2009, 02:33 AM)ForcedInduction No kidding, note the "Take away the numbers and the curves would be difficult to tell apart by somebody that hasn't seen them before."
Achieving a curve shape at 80kw and acheiving the same shape at 180kw are two massively different outcomes.
Let me know when you've got comparable numbers, not shapes. I can get similar shapes from a non turbo motor.
As I said earlier, hit 42psi at 1400rpm and flow enough for 180kw at the top end (roughly 26psi) and let me know what single turbo can do that. VNT or otherwise.
11-17-2009, 04:07 AM
#32
(11-17-2009, 03:18 AM)Kiwibacon There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.
It's not like that. A correct controlled VNT reduces backpressure while cruising. I saw it in my TDI. Pushing the pedal during cruise will close the vanes immediately. This means during cruising or better lifting the foot the backpressure is respected in the control.
Tom
(11-17-2009, 03:18 AM)Kiwibacon There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.
It's not like that. A correct controlled VNT reduces backpressure while cruising. I saw it in my TDI. Pushing the pedal during cruise will close the vanes immediately. This means during cruising or better lifting the foot the backpressure is respected in the control.
Tom
11-17-2009, 04:24 AM
#33
(11-17-2009, 04:07 AM)tomnik(11-17-2009, 03:18 AM)Kiwibacon There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.
It's not like that. A correct controlled VNT reduces backpressure while cruising. I saw it in my TDI. Pushing the pedal during cruise will close the vanes immediately. This means during cruising or better lifting the foot the backpressure is respected in the control.
Tom
Sorry, I was referring to backpressure for a given boost. The more efficient turbo has a better boost:backpressure ratio. Regardless of boost.
This is Buchi's law of turbocharging.
(11-17-2009, 04:07 AM)tomnik(11-17-2009, 03:18 AM)Kiwibacon There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.
It's not like that. A correct controlled VNT reduces backpressure while cruising. I saw it in my TDI. Pushing the pedal during cruise will close the vanes immediately. This means during cruising or better lifting the foot the backpressure is respected in the control.
Tom
Sorry, I was referring to backpressure for a given boost. The more efficient turbo has a better boost:backpressure ratio. Regardless of boost.
This is Buchi's law of turbocharging.
11-17-2009, 11:58 AM
#34
I`d rather take a less complicated approach..
I am always coming up with new ideas
. -BMW 335 setup on cold side.
-For the hot side make it similar to regular compound. GT2256 (or another vnt, as small as possible, that doesn`t need to be wastegated at WOT) and a HX35? downstream.
-As I see it, this setup will not require the turbos to be that accurately flow-matched, unlike a regular compund. Greater chance for success
-No controlvalves is needed on hotside, unlike 335 setup.
Sounds good and "simple"??
Is a vnt overkill on the big turbo, or will a regular do just as good job?
I have read through a long thread on compound now. It is a good setup in many ways, but seems very hard to find matching turbos. For the cummins, people have trailed and errored, but for MB 60x nobody has showed the way publically yet, with hard numbers and graphs.. Who is first man out for the expeirment?
I`d rather take a less complicated approach..
I am always coming up with new ideas.
-BMW 335 setup on cold side.
-For the hot side make it similar to regular compound. GT2256 (or another vnt, as small as possible, that doesn`t need to be wastegated at WOT) and a HX35? downstream.
-As I see it, this setup will not require the turbos to be that accurately flow-matched, unlike a regular compund. Greater chance for success
-No controlvalves is needed on hotside, unlike 335 setup.
Sounds good and "simple"??
Is a vnt overkill on the big turbo, or will a regular do just as good job?
11-17-2009, 12:07 PM
#35
(11-16-2009, 10:33 PM)Kiwibacon At cruising rpms where fuel economy is made or lost, wastegates are closed. Hence better turbo efficiency is better fuel economy.
(11-17-2009, 04:24 AM)Kiwibacon Sorry, I was referring to backpressure for a given boost. The more efficient turbo has a better boost:backpressure ratio. Regardless of boost.
With a typical mechanical wastegate the turbo will generate boost regardless of the need for it. The efficiency for a given boost may be better, but, if you are spending the energy to create boost you don't need, the system is less efficient. My roommate's 6.5L has a vacuum controlled wastegate that maintains the optimum boost for that specific engine operating point (min boost pressure, compressor efficiency, VE, load, RPM, etc). A VNT turbo does the same thing, but possibly allows a less restrictive flow path (going around a wastegate valve probably hurts airflow). With the VNT and vacuum wastegate, the backpressure will be very low at cruising speeds. All in all, mechanical wastegate is the worst of the bunch and vacuum controlled wastegates are probably a wash with VNTs.
(11-17-2009, 02:33 AM)ForcedInduction Nope. Turbo is a turbo. Unless its got some fancy ceramic turbine, titanium compressor or ball bearings, a VNT beats a wastegate in efficiency every time.
Uhhh... not exactly. Compressor and turbine efficiencies have greatly improved over the years. Going from a T3 to a GT series turbo, even at the same boost/flow levels will result in less backpressure and less heating of the intake air... AKA better efficiency.
ForcedInductionKiwibacon Solenoid injectors can't react fast enough compared to piezo.
Which is why they are needed to meet emissions, they need those 5 injection events per cycle to control NOx adequately.
We're talking micro seconds. Solenoids aren't going to work that fast even if there was only one injection event.
Kiwibacon Show me a VNT which can produce 42psi at 1400rpm and the airflow needed for a 180kw diesel.
ForcedInduction No single turbo can do what compounds can, but they can very easily best the top-end power produced by the larger turbo when the small is bypassed.
With the BMW example we're talking about, there is no way that a VNT can produce that level of boost at that low of an RPM. Sure, you can get a VNT to make the top end power, but you won't have the same amount of boost down low that BMW needed to produce the power output they wanted.
IMHO, You guys are all really splitting hairs on the efficiency debate. My CDI gets 32mpg with the cruise set at 90mph, and it has 370 lb/ft of torque at 1800 rpm. It has a VNT turbo... I think they figured out how to deal with the slightly less efficient VNT turbine and/or I'm totally happy with the slight efficiency loss for that low end power!
(11-17-2009, 11:58 AM)lars Who is first man out for the expeirment?
I spent all day yesterday working on a compound turbo calculator. It is essentially the Not2Fast calculator in Excel and supports compound turbos, Intercooler, and Aftercooler. It has resulted in some pretty interesting numbers and interactions. Suffice to say the "LP" designation is very misleading as far as what pressure ratios you need to use on it so the "HP" turbo doesn't choke. I'm still not quite finished with it. I'll post it in another thread when I'm done.
(11-17-2009, 11:58 AM)lars I`d rather take a less complicated approach..
I would probably start with a single VNT then... If you look around on the forum there are some mechanical VNT controls that work, but they do require a good bit of tuning. Once you get comfortable with that then you can start to work on compounding.
(11-17-2009, 11:58 AM)lars Is a vnt overkill on the big turbo, or will a regular do just as good job?
No idea... I think having a VNT as the LP turbo will make things much more complicated control wise, but will allow for significantly higher boost levels at a lower RPM.
This post was last modified: 11-17-2009, 12:29 PM by Tymbrymi.
John Robbins
'05 E320 CDI - 118k - Faaaaaast!!
'87 300TD - 317k - Cracked head... but an OM606 is on the way!
'79 300SD - 295k - Bad engine = project car!
(11-16-2009, 10:33 PM)Kiwibacon At cruising rpms where fuel economy is made or lost, wastegates are closed. Hence better turbo efficiency is better fuel economy.
(11-17-2009, 04:24 AM)Kiwibacon Sorry, I was referring to backpressure for a given boost. The more efficient turbo has a better boost:backpressure ratio. Regardless of boost.
With a typical mechanical wastegate the turbo will generate boost regardless of the need for it. The efficiency for a given boost may be better, but, if you are spending the energy to create boost you don't need, the system is less efficient. My roommate's 6.5L has a vacuum controlled wastegate that maintains the optimum boost for that specific engine operating point (min boost pressure, compressor efficiency, VE, load, RPM, etc). A VNT turbo does the same thing, but possibly allows a less restrictive flow path (going around a wastegate valve probably hurts airflow). With the VNT and vacuum wastegate, the backpressure will be very low at cruising speeds. All in all, mechanical wastegate is the worst of the bunch and vacuum controlled wastegates are probably a wash with VNTs.
(11-17-2009, 02:33 AM)ForcedInduction Nope. Turbo is a turbo. Unless its got some fancy ceramic turbine, titanium compressor or ball bearings, a VNT beats a wastegate in efficiency every time.
Uhhh... not exactly. Compressor and turbine efficiencies have greatly improved over the years. Going from a T3 to a GT series turbo, even at the same boost/flow levels will result in less backpressure and less heating of the intake air... AKA better efficiency.
ForcedInductionKiwibacon Solenoid injectors can't react fast enough compared to piezo.
Which is why they are needed to meet emissions, they need those 5 injection events per cycle to control NOx adequately.
We're talking micro seconds. Solenoids aren't going to work that fast even if there was only one injection event.
Kiwibacon Show me a VNT which can produce 42psi at 1400rpm and the airflow needed for a 180kw diesel.
ForcedInduction No single turbo can do what compounds can, but they can very easily best the top-end power produced by the larger turbo when the small is bypassed.
With the BMW example we're talking about, there is no way that a VNT can produce that level of boost at that low of an RPM. Sure, you can get a VNT to make the top end power, but you won't have the same amount of boost down low that BMW needed to produce the power output they wanted.
IMHO, You guys are all really splitting hairs on the efficiency debate. My CDI gets 32mpg with the cruise set at 90mph, and it has 370 lb/ft of torque at 1800 rpm. It has a VNT turbo... I think they figured out how to deal with the slightly less efficient VNT turbine and/or I'm totally happy with the slight efficiency loss for that low end power!
(11-17-2009, 11:58 AM)lars Who is first man out for the expeirment?
I spent all day yesterday working on a compound turbo calculator. It is essentially the Not2Fast calculator in Excel and supports compound turbos, Intercooler, and Aftercooler. It has resulted in some pretty interesting numbers and interactions. Suffice to say the "LP" designation is very misleading as far as what pressure ratios you need to use on it so the "HP" turbo doesn't choke. I'm still not quite finished with it. I'll post it in another thread when I'm done.
(11-17-2009, 11:58 AM)lars I`d rather take a less complicated approach..
I would probably start with a single VNT then... If you look around on the forum there are some mechanical VNT controls that work, but they do require a good bit of tuning. Once you get comfortable with that then you can start to work on compounding.
(11-17-2009, 11:58 AM)lars Is a vnt overkill on the big turbo, or will a regular do just as good job?
No idea... I think having a VNT as the LP turbo will make things much more complicated control wise, but will allow for significantly higher boost levels at a lower RPM.
John Robbins
'05 E320 CDI - 118k - Faaaaaast!!
'87 300TD - 317k - Cracked head... but an OM606 is on the way!
'79 300SD - 295k - Bad engine = project car!
11-17-2009, 01:08 PM
#36
(11-17-2009, 03:18 AM)Kiwibacon There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.No. Because the VNT runs the engine only at the pressure needed, excessive boost is not produced and backpressure is minimized. A VNT can run 0-3psi on the highway while a WG turbo will typically be in the 5psi area.
Quote:Further, there is far more in turbo wheel and housing design than you seem aware of.Not really. The GT overhaul increased efficiency by a few percent and modern metallurgy and machining techniques have reduced weight, but the basic design hasn't changed. Turbos are still working in the 60-78% efficiency range as they have for decades.
Quote:Achieving a curve shape at 80kw and acheiving the same shape at 180kw are two massively different outcomes.No kidding, my numbers are much smaller. Give me more fuel, a bigger VNT and a stronger drivetrain and I could easily exceed BMW's power figures. Fuel economy, that would be a different story.
Quote:let me know what single turbo can do that.That occurred in post #3 of this thread.
PSI is merely flow against a restriction. 42psi is meaningless. To get the same flow as BMW on a 2-valve OM617 would require far higher pressure.
So in other words, to get the same power at 1400RPM, all thats needed is a reduction of flow resistance. After porting, removing the cats, etc, a single turbo could produce the same figures AND more power at the top end from the increased flow across the range.
Don't forget that the VNT equipped BMW also didn't have a DPF or SCR cat, it only had to push through an OxCat. A DPF alone causes significant exhaust obstruction.
International's (ford) 6.4L compared to the 6.0L is another great example.
It has 0.4L more displacement, compound turbos and 15psi more boost. Yet, it only makes 25hp and 80lb/ft more torque. Why is that? The displacement increase alone should produce that much difference. Why is a 7% increase in displacement and 50% increase in boost needed for a 10-15% increase in power?
The exact same is true of BMW. They need that 50% increase in boost to overcome restrictions and limits added by the 2009+ emissions standards. Simple as that.
This post was last modified: 11-17-2009, 01:27 PM by ForcedInduction.
ForcedInduction
11-17-2009, 01:08 PM
#36
(11-17-2009, 03:18 AM)Kiwibacon There is no such thing as "freely exit". At cruise the more efficient turbo produces less backpressure. This is not the VNT turbo.No. Because the VNT runs the engine only at the pressure needed, excessive boost is not produced and backpressure is minimized. A VNT can run 0-3psi on the highway while a WG turbo will typically be in the 5psi area.
Quote:Further, there is far more in turbo wheel and housing design than you seem aware of.Not really. The GT overhaul increased efficiency by a few percent and modern metallurgy and machining techniques have reduced weight, but the basic design hasn't changed. Turbos are still working in the 60-78% efficiency range as they have for decades.
Quote:Achieving a curve shape at 80kw and acheiving the same shape at 180kw are two massively different outcomes.No kidding, my numbers are much smaller. Give me more fuel, a bigger VNT and a stronger drivetrain and I could easily exceed BMW's power figures. Fuel economy, that would be a different story.
Quote:let me know what single turbo can do that.That occurred in post #3 of this thread.
PSI is merely flow against a restriction. 42psi is meaningless. To get the same flow as BMW on a 2-valve OM617 would require far higher pressure.
So in other words, to get the same power at 1400RPM, all thats needed is a reduction of flow resistance. After porting, removing the cats, etc, a single turbo could produce the same figures AND more power at the top end from the increased flow across the range.
Don't forget that the VNT equipped BMW also didn't have a DPF or SCR cat, it only had to push through an OxCat. A DPF alone causes significant exhaust obstruction.
International's (ford) 6.4L compared to the 6.0L is another great example.
It has 0.4L more displacement, compound turbos and 15psi more boost. Yet, it only makes 25hp and 80lb/ft more torque. Why is that? The displacement increase alone should produce that much difference. Why is a 7% increase in displacement and 50% increase in boost needed for a 10-15% increase in power?
The exact same is true of BMW. They need that 50% increase in boost to overcome restrictions and limits added by the 2009+ emissions standards. Simple as that.
11-17-2009, 01:22 PM
#37
(11-17-2009, 12:07 PM)Tymbrymi Going from a T3 to a GT series turbo, even at the same boost/flow levels will result in less backpressure and less heating of the intake air... AKA better efficiency.Thats mainly from rotating mass. A GT turbo can be physically sized smaller than a T. Having a GT with 56mm compressor and 49.4mm turbine vs a T3-45 with 60mm and 62.5mm alone is a big reduction in mass.
ForcedInduction
11-17-2009, 01:22 PM
#37
(11-17-2009, 12:07 PM)Tymbrymi Going from a T3 to a GT series turbo, even at the same boost/flow levels will result in less backpressure and less heating of the intake air... AKA better efficiency.Thats mainly from rotating mass. A GT turbo can be physically sized smaller than a T. Having a GT with 56mm compressor and 49.4mm turbine vs a T3-45 with 60mm and 62.5mm alone is a big reduction in mass.
11-17-2009, 03:29 PM
#38
(11-17-2009, 11:58 AM)lars I`d rather take a less complicated approach..
I would probably start with a single VNT then... If you look around on the forum there are some mechanical VNT controls that work, but they do require a good bit of tuning. Once you get comfortable with that then you can start to work on compounding.
Yes sir! That is the shortterm plan. put there a vnt with a tuned-up stock pump. -But finally, within not too long time, I want to install 7mm.
FI: see your point that a vnt is good enough. Eventhough, I testdrove a friends 120d and a dealer`s 535d. Both had decent torque below 2000, but the 535 felt more responsive. I think that is due to higher inertia turbo on the 120d..
(11-17-2009, 11:58 AM)lars I`d rather take a less complicated approach..
I would probably start with a single VNT then... If you look around on the forum there are some mechanical VNT controls that work, but they do require a good bit of tuning. Once you get comfortable with that then you can start to work on compounding.
Yes sir! That is the shortterm plan. put there a vnt with a tuned-up stock pump. -But finally, within not too long time, I want to install 7mm.
FI: see your point that a vnt is good enough. Eventhough, I testdrove a friends 120d and a dealer`s 535d. Both had decent torque below 2000, but the 535 felt more responsive. I think that is due to higher inertia turbo on the 120d..
11-17-2009, 04:16 PM
#39
(11-17-2009, 12:07 PM)Tymbrymi With a typical mechanical wastegate the turbo will generate boost regardless of the need for it. The efficiency for a given boost may be better, but, if you are spending the energy to create boost you don't need, the system is less efficient.
Actually no. Besides the backpressure pumping loss, the turbo is feeding itself off normally wasted exhaust heat. Therefore the only energy lost is the difference between boost and backpressure.
If you've got 3psi backpressure and no boost (i.e. no exhaust energy recovery), you're considerably worse off than having 3psi boost for 6psi backpressure.
My 4wd runs 8-9psi on cruise (12-13psi total backpressure) with a wastegated turbo and my fuel economy averages 10km/l (extremely good for a 2.3t constant 4wd brick). I have a bigger A/R turbine housing which I'll fit soon and keep tabs on the results.
I know I'll get hotter EGT's, less boost and less backpressure, but I don't know what the fuel economy will do.
The big question is:
"Will the loss of efficiency from losing boost be greater or less than the loss of pumping losses?"
The backpressure from an open vane VNT is much higher than from an open wastegate.
The wastegate bypasses the turbine scroll, where to exit a VNT turbo the gas must be accelerated through the vortex created in the scroll before being redirected by vanes and finally through the turbine wheel. A tortuous path if no boost is the goal.
(11-17-2009, 12:07 PM)Tymbrymi I spent all day yesterday working on a compound turbo calculator. It is essentially the Not2Fast calculator in Excel and supports compound turbos, Intercooler, and Aftercooler. It has resulted in some pretty interesting numbers and interactions. Suffice to say the "LP" designation is very misleading as far as what pressure ratios you need to use on it so the "HP" turbo doesn't choke. I'm still not quite finished with it. I'll post it in another thread when I'm done.
I've had turbo calculators (including compound variations, BSFC, AF Ratio etc) running since last year. But I'm still a long way from releasing one for public consumption.
Let me know how you get on with between stage intercooling. I ended up with a pretty crazy mathematical function to mimick that, I'm interested to see what you come up with independently.
It seems we're on the same page with the rest of this debate. I'm also planning to turbocharge my NA work car (2.2 diesel, direct injection 4 valve) which will be another study in the fuel economy benefits of turbo vs none.
(11-17-2009, 01:08 PM)ForcedInduction No. Because the VNT runs the engine only at the pressure needed, excessive boost is not produced and backpressure is minimized. A VNT can run 0-3psi on the highway while a WG turbo will typically be in the 5psi area.
See my reply above to Tymbrymi. Zero boost with 3psi backpressure is worse than 5psi boost with 8psi backpressure.
(11-17-2009, 01:08 PM)ForcedInduction Not really. The GT overhaul increased efficiency by a few percent and modern metallurgy and machining techniques have reduced weight, but the basic design hasn't changed. Turbos are still working in the 60-78% efficiency range as they have for decades.
A thousand times, no.
I'm talking about turbines, you're talking about compressors.
(11-17-2009, 01:08 PM)ForcedInduction Give me more fuel, a bigger VNT and a stronger drivetrain and I could easily exceed BMW's power figures.
Hurry up then.
BTW, by my calculations the BMW's run about 23:1 AFR at max torque. That's not 50% from where anyone used to be. Their BSFC has been published at 205 g/kwh. Proving that efficiency hasn't been lost.
This post was last modified: 11-17-2009, 04:23 PM by Kiwibacon.
(11-17-2009, 12:07 PM)Tymbrymi With a typical mechanical wastegate the turbo will generate boost regardless of the need for it. The efficiency for a given boost may be better, but, if you are spending the energy to create boost you don't need, the system is less efficient.
Actually no. Besides the backpressure pumping loss, the turbo is feeding itself off normally wasted exhaust heat. Therefore the only energy lost is the difference between boost and backpressure.
If you've got 3psi backpressure and no boost (i.e. no exhaust energy recovery), you're considerably worse off than having 3psi boost for 6psi backpressure.
My 4wd runs 8-9psi on cruise (12-13psi total backpressure) with a wastegated turbo and my fuel economy averages 10km/l (extremely good for a 2.3t constant 4wd brick). I have a bigger A/R turbine housing which I'll fit soon and keep tabs on the results.
I know I'll get hotter EGT's, less boost and less backpressure, but I don't know what the fuel economy will do.
The big question is:
"Will the loss of efficiency from losing boost be greater or less than the loss of pumping losses?"
The backpressure from an open vane VNT is much higher than from an open wastegate.
The wastegate bypasses the turbine scroll, where to exit a VNT turbo the gas must be accelerated through the vortex created in the scroll before being redirected by vanes and finally through the turbine wheel. A tortuous path if no boost is the goal.
(11-17-2009, 12:07 PM)Tymbrymi I spent all day yesterday working on a compound turbo calculator. It is essentially the Not2Fast calculator in Excel and supports compound turbos, Intercooler, and Aftercooler. It has resulted in some pretty interesting numbers and interactions. Suffice to say the "LP" designation is very misleading as far as what pressure ratios you need to use on it so the "HP" turbo doesn't choke. I'm still not quite finished with it. I'll post it in another thread when I'm done.
I've had turbo calculators (including compound variations, BSFC, AF Ratio etc) running since last year. But I'm still a long way from releasing one for public consumption.
Let me know how you get on with between stage intercooling. I ended up with a pretty crazy mathematical function to mimick that, I'm interested to see what you come up with independently.
It seems we're on the same page with the rest of this debate. I'm also planning to turbocharge my NA work car (2.2 diesel, direct injection 4 valve) which will be another study in the fuel economy benefits of turbo vs none.
(11-17-2009, 01:08 PM)ForcedInduction No. Because the VNT runs the engine only at the pressure needed, excessive boost is not produced and backpressure is minimized. A VNT can run 0-3psi on the highway while a WG turbo will typically be in the 5psi area.
See my reply above to Tymbrymi. Zero boost with 3psi backpressure is worse than 5psi boost with 8psi backpressure.
(11-17-2009, 01:08 PM)ForcedInduction Not really. The GT overhaul increased efficiency by a few percent and modern metallurgy and machining techniques have reduced weight, but the basic design hasn't changed. Turbos are still working in the 60-78% efficiency range as they have for decades.
A thousand times, no.
I'm talking about turbines, you're talking about compressors.
(11-17-2009, 01:08 PM)ForcedInduction Give me more fuel, a bigger VNT and a stronger drivetrain and I could easily exceed BMW's power figures.
Hurry up then.
BTW, by my calculations the BMW's run about 23:1 AFR at max torque. That's not 50% from where anyone used to be. Their BSFC has been published at 205 g/kwh. Proving that efficiency hasn't been lost.
11-17-2009, 04:39 PM
#40
(11-17-2009, 04:16 PM)Kiwibacon The backpressure from an open vane VNT is much higher than from an open wastegate.Not quite. A VNT has a far larger turbine A/R than even a non-wastegated turbo and a larger throat than any fixed A/R turbine. Velocity through the turbine is very low with the vanes open.
The wastegate bypasses the turbine scroll, where to exit a VNT turbo the gas must be accelerated through the vortex created in the scroll before being redirected by vanes and finally through the turbine wheel. A tortuous path if no boost is the goal.
http://www.youtube.com/watch?v=tGehI4WcNd8
Quote:Zero boost with 3psi backpressure is worse than 5psi boost with 8psi backpressure.Only from a combustion thermal efficiency point.
Quote:I'm talking about turbines, you're talking about compressors.Thats even worse, turbine efficiency is in the mid 60's to low 70's. There is no map for a T3 so knowing its actual efficiency is difficult.
Quote:Hurry up then.Loan me about $10,000.
This post was last modified: 11-17-2009, 04:40 PM by ForcedInduction.
ForcedInduction
11-17-2009, 04:39 PM
#40
(11-17-2009, 04:16 PM)Kiwibacon The backpressure from an open vane VNT is much higher than from an open wastegate.Not quite. A VNT has a far larger turbine A/R than even a non-wastegated turbo and a larger throat than any fixed A/R turbine. Velocity through the turbine is very low with the vanes open.
The wastegate bypasses the turbine scroll, where to exit a VNT turbo the gas must be accelerated through the vortex created in the scroll before being redirected by vanes and finally through the turbine wheel. A tortuous path if no boost is the goal.
http://www.youtube.com/watch?v=tGehI4WcNd8
Quote:Zero boost with 3psi backpressure is worse than 5psi boost with 8psi backpressure.Only from a combustion thermal efficiency point.
Quote:I'm talking about turbines, you're talking about compressors.Thats even worse, turbine efficiency is in the mid 60's to low 70's. There is no map for a T3 so knowing its actual efficiency is difficult.
Quote:Hurry up then.Loan me about $10,000.
11-17-2009, 04:59 PM
#41
(11-17-2009, 04:39 PM)ForcedInduction Not quite. A VNT has a far larger turbine A/R than even a non-wastegated turbo and a larger throat than any fixed A/R turbine. Velocity through the turbine is very low with the vanes open.
Do you know how to calculate velocities in a free vortex?
Put simply, the gas speed at the outer rim of the turbine is roughly twice the tip speed. That will give you some idea of the velocities produced. They are very high and they come at a cost, that cost is backpressure. Bernoulli has all the reasons why.
The wastegate bypasses the scroll.
Not that I see the point in dumping all the boost at cruise, unless you're trying to burn a DPF clean.
(11-17-2009, 04:39 PM)ForcedInduction Only from a combustion thermal efficiency point.
Also from pumping losses, cylinder fill and pretty much every other viewpoint.
Sorry, my toy budget is full from sometime in the past to some unknown point in the future.
(11-17-2009, 04:39 PM)ForcedInduction Not quite. A VNT has a far larger turbine A/R than even a non-wastegated turbo and a larger throat than any fixed A/R turbine. Velocity through the turbine is very low with the vanes open.
Do you know how to calculate velocities in a free vortex?
Put simply, the gas speed at the outer rim of the turbine is roughly twice the tip speed. That will give you some idea of the velocities produced. They are very high and they come at a cost, that cost is backpressure. Bernoulli has all the reasons why.
The wastegate bypasses the scroll.
Not that I see the point in dumping all the boost at cruise, unless you're trying to burn a DPF clean.
(11-17-2009, 04:39 PM)ForcedInduction Only from a combustion thermal efficiency point.
Also from pumping losses, cylinder fill and pretty much every other viewpoint.
Sorry, my toy budget is full from sometime in the past to some unknown point in the future.
11-18-2009, 12:48 AM
#42
*Note VNT+Mech. Compressor producing more low-end power.
**Also note its Mean Pressure, not boost.
This post was last modified: 11-18-2009, 12:51 AM by ForcedInduction.
ForcedInduction
11-18-2009, 12:48 AM
#42
*Note VNT+Mech. Compressor producing more low-end power.
**Also note its Mean Pressure, not boost.
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