+- STD (https://www.superturbodiesel.com/std)
+-- Forum: Tuning (https://www.superturbodiesel.com/std/forumdisplay.php?fid=6)
+--- Forum: Engine (https://www.superturbodiesel.com/std/forumdisplay.php?fid=7)
+--- Thread: Parallel twin turbo... Think with me.. (/showthread.php?tid=6378)
Parallel twin turbo... Think with me.. - Tito - 03-25-2015
Hey guys,
So i've been thinking about this for a while now, I definably going to do this. But i reckon I could use your guys opinion.
I'm building a OM606 8mm dieselmeken pump and HX40s in a w114/115. I've been thinking about different dual charge setups.
I have some choices i'm already owning:
HX40s
HX35w
stock KKK turbo
Eaton M65
Some throttle body's and a 3.5" special exhaust valve.
I don't like just using the HX40s because I think it will be laggy.
I don't like the HX35w + HX40s compound charge setup because you're limited to your LP turbo.
I don't like the M65 + HX40s compound because it's just too much work figuring out how to turn off the charger for fast boost + valve piping and so on. + noisy
So i'm trying the stock turbo, with the HX40s. But not together but side by side.
Pro's:
Fast spool
Barely any influence for both turbo's
Looks quiet easy to me (can image it being complicated but I thought about this like a 100 times when I trying to fall asleep
)Not much less space than other setups, but more movable placement.
Cons:
First time?
Complicated activating (playing with multiple wastegates and pressures)
.....
.....
So here's the story, I'm using the stock turbo for early spool, and completely by-passing this at high boost. Looking at the design, it just like any other HX40s turbo build. But, after the turbo in the downpipe, there's a valve which blocks the exhaust flow completely. So when spooling the valve is shut and gas is forced to go trough the small turbo, making it fast spooling. At high RPM and a certain intake pressure (quiet low, like 0.8 ~ 1.0 bar, so it gets the valve to completely open up at <3.0 or so making the big turbo breathe easily) the valve is open.
Looking at intake side, It's about the same. The common big turbo setup is used again and there's another valve completely shutting off the big turbo's pressure side so pressure can build up against the valve. After the valve, the small stock turbo can build boost directly into the engine without restriction. When the big turbo is starting to build boost (0.8~1.0 bar) before the throttle valve, the same pressure is gently opening up both valve's (also in the exhaust!) making the big turbo come alive and eventually reaching a boost pressure making both valve's completely opened up, so big turbo fully active. So the small turbo's boost is feeding the big turbo.
Looking at the exhaust again, but with the valve fully opened the small turbo looses back pressure. Therefore it can not make any boost and a one-way valve shuts so no big turbo boost gets lost.
Here's a simple paint diagram to show the setup:
![[Image: Untitled_2.jpg]](http://s2.postimg.org/v7psj7ujt/Untitled_2.jpg)
The reason I don't let the small turbo blow in the big turbo (would help spool) and using a diverter flap is because the flap is hard to control mechanically because boost get to 0 before the big turbo 2 times in a full rev range. So it would bug and just use the big turbo.
Also I like to keep thing mechanical. That's the iconic thing about this engine.
RE: Parallel twin turbo... Think with me.. - TurboTim - 03-25-2015
I gotta be honest there is no way you will fit any of that under the hood of a W115. I just did a motor swap on one and so much stuff had to be fabbed to make anything work. That engine bay is tiny! I wish you the best of luck and if you got any questions let me know. On the setup you have it will force the big turbo past the surge point and it will stall out the air flow and be pretty hard on the turbo. I also know in my experience with compound setups your small turbo will not spool as good as it would without another turbo behind it. I say try a little bit bigger small turbo and that should be able to get the big boy online quicker since there wont be so much restriction on the exhaust side.
RE: Parallel twin turbo... Think with me.. - barrote - 03-25-2015
have u considered a Variable vane turbine and a Kompressor, conected in series...... da da da
VNT turbines come alive pretty soon at 2500 the are at peak boost, so u can fit a compressor fitted with a electroactuated pulley , just before the inlet, such a way that when the turbo takes over u just need a means of actuate the compressor puley to release and a buterfly valve to redirection boost the right path
so , VNT turbo, intercooler, split the air path in two ways , one to compressor, other to the intake plenum . the passage wich is paralel to the compressor takes the buterfly valve.
low revs , compressor on, buterfly closed. high revs compressor off , buterfly opened ..... pretty simple
dreamed of that the other day.....
RE: Parallel twin turbo... Think with me.. - TurboTim - 03-25-2015
I gotta be honest there is no way you will fit any of that under the hood of a W115. I just did a motor swap on one and so much stuff had to be fabbed to make anything work. That engine bay is tiny! I wish you the best of luck and if you got any questions let me know. On the setup you have it will force the big turbo past the surge point and it will stall out the air flow and be pretty hard on the turbo. I also know in my experience with compound setups your small turbo will not spool as good as it would without another turbo behind it. I say try a little bit bigger small turbo and that should be able to get the big boy online quicker since there wont be so much restriction on the exhaust side.
RE: Parallel twin turbo... Think with me.. - Tito - 03-26-2015
(03-25-2015, 06:21 PM)barrote have u considered a Variable vane turbine and a Kompressor, conected in series...... da da daBeen thinking about this too. But having some problems with this.
VNT turbines come alive pretty soon at 2500 the are at peak boost, so u can fit a compressor fitted with a electroactuated pulley , just before the inlet, such a way that when the turbo takes over u just need a means of actuate the compressor puley to release and a buterfly valve to redirection boost the right path
so , VNT turbo, intercooler, split the air path in two ways , one to compressor, other to the intake plenum . the passage wich is paralel to the compressor takes the butterfly valve
low revs , compressor on, buterfly closed. high revs compressor off , buterfly opened ..... pretty simple
dreamed of that the other day.....
Space: the 606 fits exactly in the w114 bay. For a electronic sc clutch I need a bigger pulley diameter. In this case a double crank pulley. This isn't going to fit.
Second: vw TSI engines use the same principles. The have a very noticeable power drop when switching from sc to turbo.
(03-25-2015, 06:35 PM)TurboTim I gotta be honest there is no way you will fit any of that under the hood of a W115. I just did a motor swap on one and so much stuff had to be fabbed to make anything work. That engine bay is tiny! I wish you the best of luck and if you got any questions let me know. On the setup you have it will force the big turbo past the surge point and it will stall out the air flow and be pretty hard on the turbo. I also know in my experience with compound setups your small turbo will not spool as good as it would without another turbo behind it. I say try a little bit bigger small turbo and that should be able to get the big boy online quicker since there wont be so much restriction on the exhaust side.
The stock turbo is going to spool slower indeed. There's some energie lost in the big turbo and it's basically operating just by gas flow (remote mounted turbos use extra small exhaust turbines, I don't think I need a bigger one). Surge point is something I didn't think about.
The bay is indeed tiny. But I'll get it done
Do you have some pictures or a build thread?
Btw I noticed another design flaw. The valves are never going to open because the big turbo can't even build up pressure because the small stock exhaust housing is limiting.
So next thing I'm looking into is just the small turbo feeding the big one. Way more logical but I need to sort out valve opening pressure.
RE: Parallel twin turbo... Think with me.. - anths - 03-26-2015
why not feed the larger turbo into the smaller with external waste gates when the small one spools up the wastgate opens and bypass into the bigger ones...?
RE: Parallel twin turbo... Think with me.. - barrote - 03-26-2015
i have to say , and sorry for that, exotic ideas wont go far!!! wether u copy whatever engine manufactures have done and it works with anyother snag , or it is just wasted trouble.
good luck ,
regards.
RE: Parallel twin turbo... Think with me.. - Hario' - 03-26-2015
Why not just compound them normally? You will need a big wastegate to bypass the KKK turbine, that wastegate should be exhaust manifold referenced. Thats all, simple.
RE: Parallel twin turbo... Think with me.. - Hario' - 03-26-2015
Like so:
![[Image: CompoundDiagram.jpg]](http://s1250.photobucket.com/user/Mercedes_Power/media/CompoundDiagram.jpg.html)
RE: Parallel twin turbo... Think with me.. - anths - 03-26-2015
I built a similar system for a small 1.2ltr engine not a diesel but same idea work very well,It was the only way to reduce lag of a larger turbo with a Automatic transmission and no convertor mods, the small turbo becomes a choke restriction later , but for ease of operation and all the extra work in control gates was far easier to do it this way. I would consider doing this again on my diesel if I had the choice
I think you will find that the drawing from Hario is sequential (the same design I built) and may not compound as the waste gate opens on the smaller turbo the gases bypass, so the smaller one freewheels as the energy pushing it is reduced and the the larger turbo takes over, If you remove the wastegate or reduce the size on the smaller turbo it would compound.
Cheers Anthony
RE: Parallel twin turbo... Think with me.. - Tito - 03-26-2015
That's indeed a more common setup. But however, the turbo i'm using is really small (i also have the hx35w though). And I just like the idea of a big free flowing turbo for power and a small one for lag. Ideally they would not have any influence on each other. And I think I can almost achieve this with my dreams
But my old drawing isn't going to work.... So i tried something new. Still both turbo's separate but no crazy inlet side. Just the small turbo feeding the big one and a diverter flap. This setup basically looks like Hario's drawing, just a little different on the inlet side. and there's no wastegate but a valve. Looking at flow I think mine ideas look a little better to me than a wastage feeding the big turbo.Another horrible drawing
:![[Image: Untitled_2.jpg]](http://s2.postimg.org/n9ijehb6x/Untitled_2.jpg)
Just ignore the green boost lines as they make no sense.
RE: Parallel twin turbo... Think with me.. - Jetmugg - 03-27-2015
I'm having a tough time getting my mind around it, but hope that you proceed with this experiment. The path to learning has to include some experimentation.
My initial thoughts are that the small turbo, while being quick to respond, will not be able to supply the volume of air on the cold side in order to give effective boost. Just because it has very little turbo lag does not mean that it will be able to provide a usable amount of boost for the entire engine. (at least that's my thinking).
Steve.
RE: Parallel twin turbo... Think with me.. - Hario' - 03-30-2015
To clarify the wastegate in my drawing is a 'diverter' and not a 'bypass'.
It diverts excess exhaust gas past the small turbine as engine rpm's & gasflow become too great and start to overspeed the small turbine, hence the wastegate should be exhaust manifold referenced to avoid the above situation.
I have yet to see a turbo compound system which does not employ a wastegate to divert some exhaust around the smaller high pressure turbine.
Utilising the series compound method willl also allow you to produce drastically greater manifold pressures..
RE: Parallel twin turbo... Think with me.. - MFSuper90 - 03-30-2015
I agree with hario. The compound turbo system works like a two stage air compressor, which allows for greater efficiency, and great spool up and top end.