prechambers mods?
prechambers mods?
yes, i have done this mod in steps:
1st : engine wich is a 605.911 original was changed to TD using original parts from a 605.960, IP was left stock fuel.
2nd: engine was rebuilt with new rings and some minor mods inside, head runners were polished , small porting job . (MB head is very good from stock) engine was assembled with a 605.960 stock turbo, intercooler from c270cdi, IP stock fuel, injectors at 150BAR precups from 605.960 (they have a small dif from 605.911) (911 are marked 604 at the lip, and the 960 are marked 606) at the time i did increase the holes from 2.25mm to 2.50mm, engine become with a diff noise and rather alive response.
3rd: no mod´s from above except IP was assembled with a set of 6mm Bosch original elements, Gov tweaked to 70cc with boost 90cc, injectors were changed to orinal 605.960 set at 150BAR (injectors are the same despite on turbo they are set at 135bar instead of 115). huge increase in power , at time become possible to "eat" some serie´s 3 BMW. expecially in hills power was increase was amasing.
4th: somewhere along the way , turbo was changed to a GT2359V, boost become possible to be 2BAR continuosly from 2.5 k on till 6k, wich really improved power a bit more, response and RPM range.
5th: changed pre cups to a set with 3mm holes and the center hole 2mm. engine was tested and small diff at noise level, engine lost some live , become slugish, no noticeable power increase.
6th : engine was fitted wit a 7.5mm (dieselmeken) element IP with gov set at 80cc with boost 110cc , boost is set at 2bar . no noticeable gain in power.
conclusions: increasing the holes from 2.25 to 2.5 did resulted in an increase in power and engine live, oposite to 3mm wich did not result in any gain.
regards.
FD,
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Hy MTU,
yes, i have done this mod in steps:
1st : engine wich is a 605.911 original was changed to TD using original parts from a 605.960, IP was left stock fuel.
2nd: engine was rebuilt with new rings and some minor mods inside, head runners were polished , small porting job . (MB head is very good from stock) engine was assembled with a 605.960 stock turbo, intercooler from c270cdi, IP stock fuel, injectors at 150BAR precups from 605.960 (they have a small dif from 605.911) (911 are marked 604 at the lip, and the 960 are marked 606) at the time i did increase the holes from 2.25mm to 2.50mm, engine become with a diff noise and rather alive response.
3rd: no mod´s from above except IP was assembled with a set of 6mm Bosch original elements, Gov tweaked to 70cc with boost 90cc, injectors were changed to orinal 605.960 set at 150BAR (injectors are the same despite on turbo they are set at 135bar instead of 115). huge increase in power , at time become possible to "eat" some serie´s 3 BMW. expecially in hills power was increase was amasing.
4th: somewhere along the way , turbo was changed to a GT2359V, boost become possible to be 2BAR continuosly from 2.5 k on till 6k, wich really improved power a bit more, response and RPM range.
5th: changed pre cups to a set with 3mm holes and the center hole 2mm. engine was tested and small diff at noise level, engine lost some live , become slugish, no noticeable power increase.
6th : engine was fitted wit a 7.5mm (dieselmeken) element IP with gov set at 80cc with boost 110cc , boost is set at 2bar . no noticeable gain in power.
conclusions: increasing the holes from 2.25 to 2.5 did resulted in an increase in power and engine live, oposite to 3mm wich did not result in any gain.
regards.
FD,
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i have a friend wich has a small device with a cable conected to a nr1 injector line and a stroboscopic light. so the machine reads injection pulse, and lights at the same time rendering posible to read the crankshaft numbers
. if u´re familiar with this device disconsider my explanation.
in the papers for that machine , a multivalve MB type engine is said to be from 16 to 17.5 degrees, i understand 14º by the RIV method.
when i changed the pre cups, i left the engine at 21º(too much advance to make it easier to tune) , then reduced to 19º, now i have it at 18.5º i belive is the place where it works better, same as the previous precups at 2.5mm holes. the thing is the engine has a stange idle, and looks a bit dead untill high revs.
but lets wait a wile , u know that MB engines like to settle, maybe in a few days , this noises and behaviour changes. will see.
FD,
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that is dificult to say, well i do know till where i´ve been , i´ll try to explain.
i have a friend wich has a small device with a cable conected to a nr1 injector line and a stroboscopic light. so the machine reads injection pulse, and lights at the same time rendering posible to read the crankshaft numbers . if u´re familiar with this device disconsider my explanation.
in the papers for that machine , a multivalve MB type engine is said to be from 16 to 17.5 degrees, i understand 14º by the RIV method.
when i changed the pre cups, i left the engine at 21º(too much advance to make it easier to tune) , then reduced to 19º, now i have it at 18.5º i belive is the place where it works better, same as the previous precups at 2.5mm holes. the thing is the engine has a stange idle, and looks a bit dead untill high revs.
but lets wait a wile , u know that MB engines like to settle, maybe in a few days , this noises and behaviour changes. will see.
FD,
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Did the smoke and EGTs increase with the drop in "liveleness"?
If the only thing you changed is the prehambers, not the pump or injectors, and you played with the timing to try to find a better result and it is still flat, and, then if you only put the smaller holed Prechambers back in with no pump or injector changes, and put the timing back where it was before with the smaller holes and it comes to life, then it has to be the chambers. If you changed pumps then everything is out because the governors will be set differently, the torque control really determines how lively the engine is IMOP (at least in a MW pump) and it sounds line the M pump is not that tuneable beyond stock.
Did the smoke and EGTs increase with the drop in "liveleness"?
does not matter what , it might be like this results show.
RSF governor has nothing to do with the RSV. M pumps dont work like that. once u kick the pedal almost all the fuel is available, except ALDA increase, wich comes with boost.
regards.
FD,
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i see your point, as i said before lets wait a wile to see .
does not matter what , it might be like this results show.
RSF governor has nothing to do with the RSV. M pumps dont work like that. once u kick the pedal almost all the fuel is available, except ALDA increase, wich comes with boost.
regards.
FD,
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(02-17-2015, 12:35 PM)OM616 How much did you advance the timing after the PC mod?
So in an OM617 as such mine, what would you set pump timing to with the huge chambers that I have? I have the timing max advanced but have not re-clocked the pump yet, but sounds like that is something I should do? I can get to 1250 but not urgently quick on the street. A lot of off road hill climbing, second gear foot to floor, 2600-3000 RPM full load 16lbs boost and EGT will sit at right about 1200 degrees
1982 300D Turbo ... 3,6xxlbs, No fan, No AC, Hood Stack, No ALDA, No rear bumper and stuffed front, A/W Intercooled, Injectors by Greezer and HUGE Pre-Chambers with help from OM616 & Simpler=Better, Fuel Cranked up, 60 Trim Compressor wheel, EGT, EMP, Boost 50" Rigid Radius bar on roof Aux tank for a total of 48 Gal Of Diesel! Odyssey PC-1750 Battery in trunk, 27"x8.5"/R14 Maxxis BigHorn Mud Terrains, In June '14 issue of Off Road Mag
AX15 Jeep Trans swap in progress....
Captain America
02-24-2015, 01:35 AM #107(02-17-2015, 12:35 PM)OM616 How much did you advance the timing after the PC mod?
So in an OM617 as such mine, what would you set pump timing to with the huge chambers that I have? I have the timing max advanced but have not re-clocked the pump yet, but sounds like that is something I should do? I can get to 1250 but not urgently quick on the street. A lot of off road hill climbing, second gear foot to floor, 2600-3000 RPM full load 16lbs boost and EGT will sit at right about 1200 degrees
1982 300D Turbo ... 3,6xxlbs, No fan, No AC, Hood Stack, No ALDA, No rear bumper and stuffed front, A/W Intercooled, Injectors by Greezer and HUGE Pre-Chambers with help from OM616 & Simpler=Better, Fuel Cranked up, 60 Trim Compressor wheel, EGT, EMP, Boost 50" Rigid Radius bar on roof Aux tank for a total of 48 Gal Of Diesel! Odyssey PC-1750 Battery in trunk, 27"x8.5"/R14 Maxxis BigHorn Mud Terrains, In June '14 issue of Off Road Mag
AX15 Jeep Trans swap in progress....
Baldur Gislason
Of course the purpose of these small holes is to restrict the flow out of the prechamber to decelerate the combustion. That means any power gains from making them larger are going to present themselves with only small increases in hole diameter and past that going even bigger is going to make no difference whatsoever.
Baldur Gislason
(02-24-2015, 06:47 AM)baldur Of course the purpose of these small holes is to restrict the flow out of the prechamber to decelerate the combustion.
That's why I'd like to hear the reasoning behind enlarging the holes AND advancing the timing.
raysorenson
02-24-2015, 09:13 AM #109(02-24-2015, 06:47 AM)baldur Of course the purpose of these small holes is to restrict the flow out of the prechamber to decelerate the combustion.
That's why I'd like to hear the reasoning behind enlarging the holes AND advancing the timing.
(02-24-2015, 01:35 AM)Captain America(02-17-2015, 12:35 PM)OM616 How much did you advance the timing after the PC mod?
So in an OM617 as such mine, what would you set pump timing to with the huge chambers that I have? I have the timing max advanced but have not re-clocked the pump yet, but sounds like that is something I should do? I can get to 1250 but not urgently quick on the street. A lot of off road hill climbing, second gear foot to floor, 2600-3000 RPM full load 16lbs boost and EGT will sit at right about 1200 degrees
I was lazy and did not re-clock the pump, so I am at the stops as well, (how many other people can say that lol). When I pull the engine down I will measure what the start of injection is at the stops. I am going to be installing 10mm elements in the pump and reworking the advance mechanism, so my new timing demands will be much different.
Timing is specific to every engine according to how worn it is, the quality of fuel, the quality of the injection, altitude etc... The only "speck" that is worth anything for any engine tuning is the static timing so that the engine will start. Once running a tuner will find what the engine wants, (runs best at). This will no doubt have the engineers screaming at their monitors that you must be with in X degrees regardless of all the variables that affect combustion.
If you are happy with how it runs now, then leave it. If you want to see if the engine will take a little more advance, then recenter the pump and find out. Even at the stops, we are way more advanced than the general public lol...
If the engine does not like the additional timing, it will get hard to start cold, be naily, and not run as well as the previous timing setting. In that case you have found the limit and go back to the previous timing setting where it ran the best.
(02-24-2015, 01:35 AM)Captain America(02-17-2015, 12:35 PM)OM616 How much did you advance the timing after the PC mod?
So in an OM617 as such mine, what would you set pump timing to with the huge chambers that I have? I have the timing max advanced but have not re-clocked the pump yet, but sounds like that is something I should do? I can get to 1250 but not urgently quick on the street. A lot of off road hill climbing, second gear foot to floor, 2600-3000 RPM full load 16lbs boost and EGT will sit at right about 1200 degrees
I was lazy and did not re-clock the pump, so I am at the stops as well, (how many other people can say that lol). When I pull the engine down I will measure what the start of injection is at the stops. I am going to be installing 10mm elements in the pump and reworking the advance mechanism, so my new timing demands will be much different.
Timing is specific to every engine according to how worn it is, the quality of fuel, the quality of the injection, altitude etc... The only "speck" that is worth anything for any engine tuning is the static timing so that the engine will start. Once running a tuner will find what the engine wants, (runs best at). This will no doubt have the engineers screaming at their monitors that you must be with in X degrees regardless of all the variables that affect combustion.
If you are happy with how it runs now, then leave it. If you want to see if the engine will take a little more advance, then recenter the pump and find out. Even at the stops, we are way more advanced than the general public lol...
If the engine does not like the additional timing, it will get hard to start cold, be naily, and not run as well as the previous timing setting. In that case you have found the limit and go back to the previous timing setting where it ran the best.
raysorenson
02-25-2015, 07:11 PM #113I think the N/A precups are flat on the bottom to make room for the piston.
(02-17-2015, 12:35 PM)OM616 I was lazy and did not re-clock the pump, so I am at the stops as well, (how many other people can say that lol). When I pull the engine down I will measure what the start of injection is at the stops. I am going to be installing 10mm elements in the pump and reworking the advance mechanism, so my new timing demands will be much different.
Timing is specific to every engine according to how worn it is, the quality of fuel, the quality of the injection, altitude etc... The only "speck" that is worth anything for any engine tuning is the static timing so that the engine will start. Once running a tuner will find what the engine wants, (runs best at). This will no doubt have the engineers screaming at their monitors that you must be with in X degrees regardless of all the variables that affect combustion.
If you are happy with how it runs now, then leave it. If you want to see if the engine will take a little more advance, then recenter the pump and find out. Even at the stops, we are way more advanced than the general public lol...
If the engine does not like the additional timing, it will get hard to start cold, be naily, and not run as well as the previous timing setting. In that case you have found the limit and go back to the previous timing setting where it ran the best.
Understood! I think I will re-clock to see how it likes it, because the "what if it can run better" will always bug me if I dont, lol.
Most noticeable about the pump being max advanced (whatever it is now, coming from 28 degrees) is that I noticed a bit of a powerband develop. Like over 3k it loves it, or that's where it makes most HP. Also on the highway 3k< it pulled like a mofo, but trans wouldn't hold the power so I never could see the most out of it. I still is hungry for more fuel for sure.
1982 300D Turbo ... 3,6xxlbs, No fan, No AC, Hood Stack, No ALDA, No rear bumper and stuffed front, A/W Intercooled, Injectors by Greezer and HUGE Pre-Chambers with help from OM616 & Simpler=Better, Fuel Cranked up, 60 Trim Compressor wheel, EGT, EMP, Boost 50" Rigid Radius bar on roof Aux tank for a total of 48 Gal Of Diesel! Odyssey PC-1750 Battery in trunk, 27"x8.5"/R14 Maxxis BigHorn Mud Terrains, In June '14 issue of Off Road Mag
AX15 Jeep Trans swap in progress....
Captain America
02-25-2015, 10:07 PM #114(02-17-2015, 12:35 PM)OM616 I was lazy and did not re-clock the pump, so I am at the stops as well, (how many other people can say that lol). When I pull the engine down I will measure what the start of injection is at the stops. I am going to be installing 10mm elements in the pump and reworking the advance mechanism, so my new timing demands will be much different.
Timing is specific to every engine according to how worn it is, the quality of fuel, the quality of the injection, altitude etc... The only "speck" that is worth anything for any engine tuning is the static timing so that the engine will start. Once running a tuner will find what the engine wants, (runs best at). This will no doubt have the engineers screaming at their monitors that you must be with in X degrees regardless of all the variables that affect combustion.
If you are happy with how it runs now, then leave it. If you want to see if the engine will take a little more advance, then recenter the pump and find out. Even at the stops, we are way more advanced than the general public lol...
If the engine does not like the additional timing, it will get hard to start cold, be naily, and not run as well as the previous timing setting. In that case you have found the limit and go back to the previous timing setting where it ran the best.
Understood! I think I will re-clock to see how it likes it, because the "what if it can run better" will always bug me if I dont, lol.
Most noticeable about the pump being max advanced (whatever it is now, coming from 28 degrees) is that I noticed a bit of a powerband develop. Like over 3k it loves it, or that's where it makes most HP. Also on the highway 3k< it pulled like a mofo, but trans wouldn't hold the power so I never could see the most out of it. I still is hungry for more fuel for sure.
1982 300D Turbo ... 3,6xxlbs, No fan, No AC, Hood Stack, No ALDA, No rear bumper and stuffed front, A/W Intercooled, Injectors by Greezer and HUGE Pre-Chambers with help from OM616 & Simpler=Better, Fuel Cranked up, 60 Trim Compressor wheel, EGT, EMP, Boost 50" Rigid Radius bar on roof Aux tank for a total of 48 Gal Of Diesel! Odyssey PC-1750 Battery in trunk, 27"x8.5"/R14 Maxxis BigHorn Mud Terrains, In June '14 issue of Off Road Mag
AX15 Jeep Trans swap in progress....
(02-25-2015, 07:11 PM)raysorenson I think the N/A precups are flat on the bottom to make room for the piston.
From what little I know, only the older pre Sept-79 NA engines had those flat bottomed prechamber tips.
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
(02-25-2015, 07:11 PM)raysorenson I think the N/A precups are flat on the bottom to make room for the piston.
From what little I know, only the older pre Sept-79 NA engines had those flat bottomed prechamber tips.
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
(02-26-2015, 02:29 PM)barrote yep , the fellow´s with the 617´s dont know about pre cups
pitty looks like we have to disassemble them out
thanks anyway
the "up-rated" (roundish bottomed) 617.91 (NA) Prechambers are identical to the "up-Rated" Prechambers in the 616.
The 617.95 (Turbo) prechambers have a larger burn tube diameter inside and out, and will not fit in a NA head unless the head is machined for the lager tube. Also the holes on a turbo Prechamber are also larger than the Up Rated NA prechambers.
The up rated prechambers (roundish bottom) from a NA will fit in a turbo head, but do not use them as the burn tube OD is smaller than the bore in the head, and I think there could be a heat transfer (cooling) problem, but I do not know for sure. At the very least without the burn tube being snug in the head, it might sing and tend to brake, but again I am only guessing.
So to recap, turbo prechambers have larger burn tubes and holes than the NA versions do.
(02-26-2015, 02:29 PM)barrote yep , the fellow´s with the 617´s dont know about pre cups
pitty looks like we have to disassemble them out
thanks anyway
the "up-rated" (roundish bottomed) 617.91 (NA) Prechambers are identical to the "up-Rated" Prechambers in the 616.
The 617.95 (Turbo) prechambers have a larger burn tube diameter inside and out, and will not fit in a NA head unless the head is machined for the lager tube. Also the holes on a turbo Prechamber are also larger than the Up Rated NA prechambers.
The up rated prechambers (roundish bottom) from a NA will fit in a turbo head, but do not use them as the burn tube OD is smaller than the bore in the head, and I think there could be a heat transfer (cooling) problem, but I do not know for sure. At the very least without the burn tube being snug in the head, it might sing and tend to brake, but again I am only guessing.
So to recap, turbo prechambers have larger burn tubes and holes than the NA versions do.
(02-26-2015, 06:11 PM)OM616 So to recap, turbo prechambers have larger burn tubes and holes than the NA versions do.
That rules out using those 1990s OM616 angled injector prechambers then in a 617.95x
However I was always under the impression the NA and turbo heads were the same casting. Must just be the machining that makes the difference
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
(02-26-2015, 06:11 PM)OM616 So to recap, turbo prechambers have larger burn tubes and holes than the NA versions do.
That rules out using those 1990s OM616 angled injector prechambers then in a 617.95x
However I was always under the impression the NA and turbo heads were the same casting. Must just be the machining that makes the difference
1978 300D, 373,000km... OM617.912 with a Holset HX30W, 7.5mm IP, 711.113 5 speed (project car, 7 years off the road and counting ;/)
1977 250 270,000km (parts car)
1977 300D (ex 280) 500,000km
1981 240D 498,000
1975 HJ45 ???,000
2001 2.8TD Rodeo 4x2 - 456,000 - DD
(02-26-2015, 10:38 PM)NZScott(02-26-2015, 06:11 PM)OM616 So to recap, turbo prechambers have larger burn tubes and holes than the NA versions do.
That rules out using those 1990s OM616 angled injector prechambers then in a 617.95x
However I was always under the impression the NA and turbo heads were the same casting. Must just be the machining that makes the difference
If you can get them that is lol.. Aren't they very expencive?
To my knowledge, (which is sketchy) the heads are basically the same in regards to valve size, Precahmber pockets and glow plugs. Perhaps you could sleeve down the hole in the head for the smaller burn tubes? I would recommend a collar that would prevent the sleeve from being able to slide down into the cylinder though. There is always a way if you want it had enough lol...
(02-26-2015, 10:38 PM)NZScott(02-26-2015, 06:11 PM)OM616 So to recap, turbo prechambers have larger burn tubes and holes than the NA versions do.
That rules out using those 1990s OM616 angled injector prechambers then in a 617.95x
However I was always under the impression the NA and turbo heads were the same casting. Must just be the machining that makes the difference
If you can get them that is lol.. Aren't they very expencive?
To my knowledge, (which is sketchy) the heads are basically the same in regards to valve size, Precahmber pockets and glow plugs. Perhaps you could sleeve down the hole in the head for the smaller burn tubes? I would recommend a collar that would prevent the sleeve from being able to slide down into the cylinder though. There is always a way if you want it had enough lol...
raysorenson
02-27-2015, 12:39 PM #121While we're talking about this, does anyone know how to get parts for a Force Motors Trax Ghurka with the turbo OM616? I wonder if it got angled prechambers.
Ninth Year Anniversary with STD on 1-9-2020
visit: www.dieselfuelinjector.guru
Project 2018: Really get the car finished -- Turbo OM617 greater than 175 MPH goal.
RED W123 - left Germany as 240D in 1982. Full AMG body kit less rear apron, 2:65LSD, five speed Getrag 717.400, manual steering, read leather interior, manual brake conversion, electric water pump (EWP), and a bunch of other goodies ...
Good luck getting a response. I pestered them for a few months and never got a response.
Ninth Year Anniversary with STD on 1-9-2020
visit: www.dieselfuelinjector.guru
Project 2018: Really get the car finished -- Turbo OM617 greater than 175 MPH goal.
RED W123 - left Germany as 240D in 1982. Full AMG body kit less rear apron, 2:65LSD, five speed Getrag 717.400, manual steering, read leather interior, manual brake conversion, electric water pump (EWP), and a bunch of other goodies ...
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
sassparilla_kid
03-02-2015, 03:11 AM #123FWIW, I don't have reamed pre-chambers (yet) and my pump timing is maxxed, no real issues starting (although there are definitely more vibrations when starting it in the cold until it warms up), although I haven't played with any of the pump settings yet either.
-1982 300D Turbo, 280k miles, ALDA apparently maxxed, fram 8038, 12 lbs boost, non-egr manifolds, W/M injection, 4 brake light mod, Gen II w126 front rotors/calipers, 4-speed swap
In the works: A/W IC, adjust pump, turbo rebuild (w/60 trim comp wheel)
-1980 300SD, 110k, project car. Goal is to get it lookin' like it did on the showroom floor (body and interior wise, not necessarily under the hood )
-1974 240D, FRESH PAINT!!!!!!
I think it's "cold" when it's below 0F haha
'82 300D -3" straight pipe, ALDA deleted, 3in1 glowshift gauge, HX30, egr-less manifold, A/W intercooler
'14 Ram 6.7l cummins -G56 handshaker, wishing it was deleted
You also live in California Sass, it doesn't really get "cold" there :p
I think it's "cold" when it's below 0F haha
'82 300D -3" straight pipe, ALDA deleted, 3in1 glowshift gauge, HX30, egr-less manifold, A/W intercooler
'14 Ram 6.7l cummins -G56 handshaker, wishing it was deleted
About the pre cups, looks like i had a snag in my engine, and i didn´t knew it, the thing was with the advance mechanism, somehow the f#$"% device was too tight and did not returned to the idle advance quantity.
I just find it out after tweaking the pump to reach 5500 RPM at full load, after i went to try the car and when it went through the 5000 range a metalic and strange noise come about and from that on a huge nailing noise come about. After some thinking, measured the timing and found it at 35º.
removed the device, corected it and set the timing at 18º and the nailing and rough idle disapeared along with the smoth and clean acceleration.
i have to agree that increasing the holes on a 4 Valve engine has some benefits over stock.
my mod was , the eight holes to 3mm, the center to 2mm, the pre cup neck 8mm.
happy with the result.
regards
FD,
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Hello fine people,
About the pre cups, looks like i had a snag in my engine, and i didn´t knew it, the thing was with the advance mechanism, somehow the f#$"% device was too tight and did not returned to the idle advance quantity.
I just find it out after tweaking the pump to reach 5500 RPM at full load, after i went to try the car and when it went through the 5000 range a metalic and strange noise come about and from that on a huge nailing noise come about. After some thinking, measured the timing and found it at 35º.
removed the device, corected it and set the timing at 18º and the nailing and rough idle disapeared along with the smoth and clean acceleration.
i have to agree that increasing the holes on a 4 Valve engine has some benefits over stock.
my mod was , the eight holes to 3mm, the center to 2mm, the pre cup neck 8mm.
happy with the result.
regards
FD,
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I have to add, could be wrong here, but if anyone has ever paid attention to the carbon buildup on the piston in relation to pc holes, it seems pretty clear that the different diameters are there to control the pressure expansion in relation to the pc's location in the combustion chamber. As it is off center in the cylinder, the holes get progressively larger relative to distance from the cylinder walls. Look at the score marks. Smallest at the points where the prechamber is closest to the wall. Makes sense, consider how you'd like a pressure wave to behave in an environment where it originates off center, yet uniform expansion is desirable. Want all that extra pressure bouncing of cylinder walls and hammering down on one side of the piston significantly more than the other? Maybe splitting hairs here, but assuming we've more or less accepted that more pc flow is desirable, stands to reason that ideally you'd like to introduce more holes on a spacing and sizing gradient consistent with the existing trends and conically port them on a very slight negative axis (10-15 degrees?). Nice even expansion that way with the added bonus of a little extra downward encouragement. I'd imagine a decent egt drop over just increasing bore because of the theoretical possibility of less work being wasted and mayyyybe even some more love on the low end. I've got my 617a torn up for a rebuild, heads currently on my coffee table(yeehaw) receiving a fairly aggressive port/polish job, and, along with other goodies , I'm gonna go ahead and screw up my pc's while I'm at it. Granted, I have no intention on a dyno run unless both free and unrealistically convenient, who cares lol, but some loud obnoxious videos are guaranteed. Also though, I'd be curious to the idea of adding significantly smaller holes between the others and maybe even a little bit closer to the tip creating something of a "crown" pattern, again sized in gradient but tiny, in an attempt to create a pressure wave that is more centrally energetic/downwardly cuncussive without getting too crazy over the latter one that distributes energy, ideally, pretty much uniformly. Hopefully I get an eyebrow or two lifted with this.
Just to clarify, I noted on every piston head that the carbon buildup was very heavily concentrated in areas where the prechamber was closest to the cylinder wall, and especially in the areas around the smallest prechamber holes exhaust and were subject to the most turbulence. Now, in a perfect world one would think that a properly distributed combustion event would be unlikely to leave consistently localized deposits.
Juuuuust sayin...
PanicButton
08-15-2015, 04:48 AM #126Copied from flame front thread seeing as this seems more current
I have to add, could be wrong here, but if anyone has ever paid attention to the carbon buildup on the piston in relation to pc holes, it seems pretty clear that the different diameters are there to control the pressure expansion in relation to the pc's location in the combustion chamber. As it is off center in the cylinder, the holes get progressively larger relative to distance from the cylinder walls. Look at the score marks. Smallest at the points where the prechamber is closest to the wall. Makes sense, consider how you'd like a pressure wave to behave in an environment where it originates off center, yet uniform expansion is desirable. Want all that extra pressure bouncing of cylinder walls and hammering down on one side of the piston significantly more than the other? Maybe splitting hairs here, but assuming we've more or less accepted that more pc flow is desirable, stands to reason that ideally you'd like to introduce more holes on a spacing and sizing gradient consistent with the existing trends and conically port them on a very slight negative axis (10-15 degrees?). Nice even expansion that way with the added bonus of a little extra downward encouragement. I'd imagine a decent egt drop over just increasing bore because of the theoretical possibility of less work being wasted and mayyyybe even some more love on the low end. I've got my 617a torn up for a rebuild, heads currently on my coffee table(yeehaw) receiving a fairly aggressive port/polish job, and, along with other goodies , I'm gonna go ahead and screw up my pc's while I'm at it. Granted, I have no intention on a dyno run unless both free and unrealistically convenient, who cares lol, but some loud obnoxious videos are guaranteed. Also though, I'd be curious to the idea of adding significantly smaller holes between the others and maybe even a little bit closer to the tip creating something of a "crown" pattern, again sized in gradient but tiny, in an attempt to create a pressure wave that is more centrally energetic/downwardly cuncussive without getting too crazy over the latter one that distributes energy, ideally, pretty much uniformly. Hopefully I get an eyebrow or two lifted with this.
Just to clarify, I noted on every piston head that the carbon buildup was very heavily concentrated in areas where the prechamber was closest to the cylinder wall, and especially in the areas around the smallest prechamber holes exhaust and were subject to the most turbulence. Now, in a perfect world one would think that a properly distributed combustion event would be unlikely to leave consistently localized deposits.
Juuuuust sayin...
I would suggest not tapering all the exit holes,did this,ended up having to advance timing 3 degrees. A straight hole has a faster flow rate
than a outside taper. The flame front will take longer to transverse the cylinder. Advancing the timing will be needed.
Now a small taper on the bottom and rear exit holes will call for no advance,plus the engine feels more balanced,smoother,quicker rpm.
Have noticed that carbon build-up. Incomplete burn,most likely caused by lack of oxygen. Most of the oxygen being consumed front side.
I would suggest not tapering all the exit holes,did this,ended up having to advance timing 3 degrees. A straight hole has a faster flow rate
than a outside taper. The flame front will take longer to transverse the cylinder. Advancing the timing will be needed.
Now a small taper on the bottom and rear exit holes will call for no advance,plus the engine feels more balanced,smoother,quicker rpm.
(02-19-2018, 06:51 AM)Hercules Have noticed that carbon build-up. Incomplete burn,most likely caused by lack of oxygen. Most of the oxygen being consumed front side.
I would suggest not tapering all the exit holes,did this,ended up having to advance timing 3 degrees. A straight hole has a faster flow rate
than a outside taper. The flame front will take longer to transverse the cylinder. Advancing the timing will be needed.
Now a small taper on the bottom and rear exit holes will call for no advance,plus the engine feels more balanced,smoother,quicker rpm.
I never tried tapering the burn holes as it would help get air in, but act as a defuser.. Your observation is interesting.
Whey you say you had to advance 3 degrees, where were you before? What method did you use to determine start of injection? (different methods have different levels of accuracy and consistency).
(02-19-2018, 06:51 AM)Hercules Have noticed that carbon build-up. Incomplete burn,most likely caused by lack of oxygen. Most of the oxygen being consumed front side.
I would suggest not tapering all the exit holes,did this,ended up having to advance timing 3 degrees. A straight hole has a faster flow rate
than a outside taper. The flame front will take longer to transverse the cylinder. Advancing the timing will be needed.
Now a small taper on the bottom and rear exit holes will call for no advance,plus the engine feels more balanced,smoother,quicker rpm.
I never tried tapering the burn holes as it would help get air in, but act as a defuser.. Your observation is interesting.
Whey you say you had to advance 3 degrees, where were you before? What method did you use to determine start of injection? (different methods have different levels of accuracy and consistency).
I am not opposed to advancing the timing if the results are the most positive. Little explanation, drilled the prechamber exit holes in steps,about 2 %
each time until high rpm performance fell off. Test ground,starting at 7,000 ft. 6% grade to about 8,500 ft. Nice long smooth road. Starting at 60 m.p.h.
noting how much time taken to achieve 70 m.p.h. Injectors checked for proper spray and pop pressures. Each increase in hole size netted a small but
noticeable over all performance increase. After 8% hole size increase this happened,engine was louder ,time to reach 70 m.p.h. almost doubled and
a delay in throttle response of 1sec. was noticed. Timing still set at 26 degrees.
More prechambers acquired drilled to max. 8% than tapered. Reassemble, engine very sluggish needed to advance timing to 29 degrees to regain
performance. The engine response not the same. Before a light touch of throttle at any speed,immediate increase in rpm,now a slight delay and
higher rpm a little slower.Did not want to advance more,nailing starting .
IMO this is what is occurring,a temp/pressure/time relation. Slow down the burn rate,increase timing will be needed. Increase the burn rate,decrease
the timing. This can be inside or outside the prechamber. Example,drill the flame tube very much larger,a increase in timing well be needed,a slowing
of the burn rate. How,larger voulmne to a lesser amount ,the fuel rich flame not coming in contact as much with the hot prechamber walls .
Slower temp. rise less pressure rise ,slower flame coming out prechamber,taking more time to travel across cyl. Advance the timing.
On the other hand tapering the burn tube a decrease in timing will be needed,increased velocity to a lesser extant ,pressing more of the fuel rich flame
onto the hot prechamber increases temp/pressure faster,more velocity out exit holes,less time to travel across cyl. raising working pressure.
Timing will needed to be decreased.
Great job on those prechambers 616 . Also thanks for sharing. All here to learn and enjoy.
Bit more info. Timing was at 26 degrees before tapering,after tapering 29 degrees. Thought this might happen. Bubble method used to time.
I am not opposed to advancing the timing if the results are the most positive. Little explanation, drilled the prechamber exit holes in steps,about 2 %
each time until high rpm performance fell off. Test ground,starting at 7,000 ft. 6% grade to about 8,500 ft. Nice long smooth road. Starting at 60 m.p.h.
noting how much time taken to achieve 70 m.p.h. Injectors checked for proper spray and pop pressures. Each increase in hole size netted a small but
noticeable over all performance increase. After 8% hole size increase this happened,engine was louder ,time to reach 70 m.p.h. almost doubled and
a delay in throttle response of 1sec. was noticed. Timing still set at 26 degrees.
More prechambers acquired drilled to max. 8% than tapered. Reassemble, engine very sluggish needed to advance timing to 29 degrees to regain
performance. The engine response not the same. Before a light touch of throttle at any speed,immediate increase in rpm,now a slight delay and
higher rpm a little slower.Did not want to advance more,nailing starting .
IMO this is what is occurring,a temp/pressure/time relation. Slow down the burn rate,increase timing will be needed. Increase the burn rate,decrease
the timing. This can be inside or outside the prechamber. Example,drill the flame tube very much larger,a increase in timing well be needed,a slowing
of the burn rate. How,larger voulmne to a lesser amount ,the fuel rich flame not coming in contact as much with the hot prechamber walls .
Slower temp. rise less pressure rise ,slower flame coming out prechamber,taking more time to travel across cyl. Advance the timing.
On the other hand tapering the burn tube a decrease in timing will be needed,increased velocity to a lesser extant ,pressing more of the fuel rich flame
onto the hot prechamber increases temp/pressure faster,more velocity out exit holes,less time to travel across cyl. raising working pressure.
Timing will needed to be decreased.
Great job on those prechambers 616 . Also thanks for sharing. All here to learn and enjoy.
Do I understand you correctly that you drilled out the inside diameter of the burn tube (you would have had to remove the impingement ball) the first time, and then tapered the inside diameter of the burn tube so the PC end was larger in diameter than the inside diameter at the tip?
Or are you saying you drilled out the smaller burn holes at the tip? Then tapered the burn holes?
For example, I removed the impingement ball and tapered the inside diameter of the burn tube, then eliminated the three burn holes lol... I did not touch the two small rear burn holes.
To help reduce confusion, lets standardize terms.. The burn tube is the stem that is between the PC and the cylinder. The Burn holes are the angled holes at the tip of the burn tube.
Do I understand you correctly that you drilled out the inside diameter of the burn tube (you would have had to remove the impingement ball) the first time, and then tapered the inside diameter of the burn tube so the PC end was larger in diameter than the inside diameter at the tip?
Or are you saying you drilled out the smaller burn holes at the tip? Then tapered the burn holes?
For example, I removed the impingement ball and tapered the inside diameter of the burn tube, then eliminated the three burn holes lol... I did not touch the two small rear burn holes.
At 8% overage and than tapering outside of flame tube exit holes a 3 degree advance was needed .Started at 26 now 29.
At 8% no taper. opening flame tube to 10mm a loss of performance, 3 degrees advance was also needed. 29
At 8% tapering only inside of flame tube from approx.10mm down to 8mm a decrease in timing was needed,back to 26.
Now , tapering both inside and tip exit holes a increase in timing was again needed to 29.
Tapering the inside of flame tube and leaving tip exit holes to 8% netted the most gain,smoothest run.
Should be noted that if more oxygen is available,lower altitude,holes can be increased to approx. 10% without increasing timing,for a bit
more performance again leaving tip exit not tapered.
Tapering bottom and rear tip exit holes,no different timing was needed and engine seemed smoother and more balanced,a bit quicker rpm.
Hope this did not confuse even more.
Think I might have wore out the head taking these in and out soooo many times. lol. 11-12 sets history.
Modifying the prechamber,flame tube exit holes beyond 8% at 7,000 ft. netted a loss of high rpm performance.
At 8% overage and than tapering outside of flame tube exit holes a 3 degree advance was needed .Started at 26 now 29.
At 8% no taper. opening flame tube to 10mm a loss of performance, 3 degrees advance was also needed. 29
At 8% tapering only inside of flame tube from approx.10mm down to 8mm a decrease in timing was needed,back to 26.
Now , tapering both inside and tip exit holes a increase in timing was again needed to 29.
Tapering the inside of flame tube and leaving tip exit holes to 8% netted the most gain,smoothest run.
Should be noted that if more oxygen is available,lower altitude,holes can be increased to approx. 10% without increasing timing,for a bit
more performance again leaving tip exit not tapered.
Tapering bottom and rear tip exit holes,no different timing was needed and engine seemed smoother and more balanced,a bit quicker rpm.
Hope this did not confuse even more.
Think I might have wore out the head taking these in and out soooo many times. lol. 11-12 sets history.
Yes drilled out inside of pc. Yes removed impingement pin.
Yes,burn chamber end larger than burn hole end.
Drilled all burn holes same increase,than tapered.
Also turned impingement pin noted increase ?? Did drill a concave area in bottom of said pin,said to increase turbulence,
noted gain ??
ok,let me try this again. Burn tube and burn holes,will do.
Yes drilled out inside of pc. Yes removed impingement pin.
Yes,burn chamber end larger than burn hole end.
Drilled all burn holes same increase,than tapered.
Also turned impingement pin noted increase ?? Did drill a concave area in bottom of said pin,said to increase turbulence,
noted gain ??
(02-19-2018, 09:41 PM)Hercules ok,let me try this again. Burn tube and burn holes,will do.
Yes drilled out inside of pc. Yes removed impingement pin.
Yes,burn chamber end larger than burn hole end.
Drilled all burn holes same increase,than tapered.
Also turned impingement pin noted increase ?? Did drill a concave area in bottom of said pin,said to increase turbulence,
noted gain ??
Gotcha.. I gave my ball a slight angle as well but did not mod it. Your guess is as good as mine if it makes a hill of beans difference lol.. By tapering the ID of the burn tube, the incoming air has more room to flow around the ball so it may not make any difference.
I also back cut the inside of the chamber bellow the injector seat to help keep the nozzle area cleared out. This along with the tapering increased the volume of the chamber, how much who knows.
Have you tried raising the boost?
My set up does not like to be lugged for sure, but if I don't load it up when I take off and keep it above 1200 ish, it does ok, and starts to come to life around 2500 and is on the pipe by 3200 and pulls through to 4500 when I get out of it because i don't like to rev it that high. It pulls 3rd gear cumming out of a corner really nice and is fun to drive. I am very curious how it will run with 30* in it.
(02-19-2018, 09:41 PM)Hercules ok,let me try this again. Burn tube and burn holes,will do.
Yes drilled out inside of pc. Yes removed impingement pin.
Yes,burn chamber end larger than burn hole end.
Drilled all burn holes same increase,than tapered.
Also turned impingement pin noted increase ?? Did drill a concave area in bottom of said pin,said to increase turbulence,
noted gain ??
Gotcha.. I gave my ball a slight angle as well but did not mod it. Your guess is as good as mine if it makes a hill of beans difference lol.. By tapering the ID of the burn tube, the incoming air has more room to flow around the ball so it may not make any difference.
I also back cut the inside of the chamber bellow the injector seat to help keep the nozzle area cleared out. This along with the tapering increased the volume of the chamber, how much who knows.
Have you tried raising the boost?
My set up does not like to be lugged for sure, but if I don't load it up when I take off and keep it above 1200 ish, it does ok, and starts to come to life around 2500 and is on the pipe by 3200 and pulls through to 4500 when I get out of it because i don't like to rev it that high. It pulls 3rd gear cumming out of a corner really nice and is fun to drive. I am very curious how it will run with 30* in it.
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