Compound Turbos in a different perspective

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Bigrednightmare

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So being Sunday I haven't done very much lol and was having some out of the box thoughts on a compound setup. But before I get into it, let me start off by saying I am aware of how compounds work and have built multiple sets in the past. But I had an idea and was just curious if it would work or not.

Generally in a compound setup you have the smaller charger(primary) on the manifold and the larger charger(secondary) fed off of the exhaust gasses coming out of the primary charger. And the air sucked in from the secondary and pushed into the inlet of the primary and then into the intercooler/intake of the engine. But....

What if one was to build a compound setup the opposite way. By that i mean secondary on the manifold and primary downstream. And what i was thinking is that there would be a wastegate on the manifold that would divert exhaust to the smaller charger under low boost situations and close at a desired boost level (so basically its working the opposite way of a normal wastegate) keeping all the exhaust in the larger charger. This would also require a wastegate between the large charger and the small charger on the exhaust side to bypass the small charger and direct into the downpipe to keep from over spinning and high drive pressure.

And in doing so I would think one would be able to get the most out of the larger secondary charger and no have near the issues with drive pressure, and possibly be able to make more hp due to the fact there is not such a restriction on the manifold and you would be able to drive the secondary harder...

Im not sure if something like this has ever been done or tried, it could be a dumb idea lol but I guess it never hurts to try to think outside of the box.

But feel free to leave an explanation if you would like id be curious to what everyone thinks about this idea, good or bad and why it wouldnt work.

Thanks.
 
Standard setup is secondary on the manifold and primary as the atmo. I don't see what the gain would be running it opposite, plus it wouldn't compound. You're describing more of a sequential setup

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I've always wondered the same thing. I could see one of the benefits being the larger turbo capable of more flow wouldn't be choked up by our secondary and the heat would be closer to the larger charger helping with spool on the unit that needs the most help. Could possibly utilize the divided aspect of many primary exhaust housings a little better as well. Only negative is you're still limited by the exhaust side of the secondary. That is an issue in a conventional compound setup anyway though. I suppose you could hate it interstage and dump it or route it to the downpipe though.


Only thought I've always had is if it is such a grand idea peoole would be doing it so I've always pushed it out of my mind LOL
 
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yeah you can't argue with that fact at all lol, but it doesn't hurt to try and think outside the box every now and again
 
I wonder if the secondary gets to be too much of a restriction at higher boost levels. I always wanted to try a moderately larger secondary (say a 466 or 467 as opposed to a typical 363) with a TDV so you still get it lit before the primary starts to build boost. I just thought it would be less restrictive on both turbine and compressor sides. But it's all theory until somebody picks up a welder and builds a set.
 
Yeah i am really thinking about doing it just to try it, I mean I have all sorts of piping and turbos laying around even if I halfassed a set together just for testing and the learning experience of it, I'm always up for building things even if it's a terrible failure lol I would atleast have real feed back for others wondering the same
 
Build it! Pics too lol. Some crazy Canadians were messing around with it awhile back but I never heard the outcome.
 
Horrible idea really. And primary=First stage. Secondary = second stage. Kinda like trying to make **** run up hill. It would be no less silly having your second stage compressor before your first stage compressor.
 
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Care to elaborate on why you feel that wAy? I'm not disagreeing either I would just be interested in hearing a reason
 
Bigrednightmare said:
Care to elaborate on why you feel that wAy? I'm not disagreeing either I would just be interested in hearing a reason
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Feeding an 80mm turbo air discharged from say a 63mm turbo will not work...if the primary ever lit, it would be trying to PULL air throught the smaller turbo....kinda like a VERY restricted air filter...

The big turbo moves more air than the smaller one...the small one will never be able to feed the primary to it's full potential.

Think of it this way:
stand on top of a pumper fire truck, and fill it with a garden hose while the pump is in use...the pump is using more than the garden hose can supply, and it will not work.
 
Sounds like you may not actually understand how compounds work after all.
 
Some of you guys need the read the whole post
He was talking about plumbing the exhaust different, not the intake side.
 
I put up a comparison to the compressor side thinking it would make it obvious why it wouldn't work on the hot side but I guess not.

The hot side is no different, it works on gas expanding through the smaller 1st stage turbine and loosing heat, expanding through the 2nd stage and again loosing heat.

When you crap up down stream the large turbine you cut its nuts as you loose that massive expansion you had across that turbine with restriction on the backside.
 
Joesixpack said:
I put up a comparison to the compressor side thinking it would make it obvious why it wouldn't work on the hot side but I guess not.

The hot side is no different, it works on gas expanding through the smaller 1st stage turbine and loosing heat, expanding through the 2nd stage and again loosing heat.

When you crap up down stream the large turbine you cut its nuts as you loose that massive expansion you had across that turbine with restriction on the backside.
Click to expand...

How'd your quest for a better high pressure pump go?
 
You would be better off gating completely around the secondary turbine, and using a BPV to gate completely around the secondary compressor for a full sequential setup... The whole idea of compounds though is for a more usable airflow range, not less, you would be shooting yourself in the foot. A properly sized, gated and tuned compound setup cant be beat.
 
Bigrednightmare said:
Yeah i am really thinking about doing it just to try it, I mean I have all sorts of piping and turbos laying around even if I halfassed a set together just for testing and the learning experience of it, I'm always up for building things even if it's a terrible failure lol I would atleast have real feed back for others wondering the same
Click to expand...

There was a thread on this a while back...don't know if the dude ever got it running...

http://www.competitiondiesel.com/forums/showthread.php?t=170493
 
A little more detail about what I'm thing now this is just an example because my OP was kinda confusing.
For example sake were gunna use a s363 and a s475

You would put the 475 on the manifold exhaust out of the 75 feeds the 63. Exhaust from the 63 goes to the downpipe. The air filter will be connected to the inlet of the 75. The discharge from the 75 will feed the inlet of the 63 (to be compounded). Discharge on the 63 to the intercooler. This system would utilize a WG on the manifold which stays open under low boost/drive situations driving the 63 harder for quick spool, and would close at desired boost/drive to drive the 75 harder. This system will also use a waste gage between the 75 and 63 on the interstate exhaust Pipe to prevent overspooling and high drive caused by the restriction downstream of the 75.

And my thinking in all this i guess would be it would still be a compound setup but also act like a sequential setup in its own aspect.
I don't know if this clarified my thoughts to anyone, but like i stated before it might be a god awful idea but Im always for a good technical discussion about out of the box ideas
 
I guess what I'm ultimately trying to get at is, in my eyes it seem like either way you go with conventional style of compounds you fight through the small charger to get exhaust gases to the larger charger which ends up with quick initial spool, but in my theoretical setup I'm assuming you would still have good spool up characteristics because it wouldn't take much to light the smAller charger even being downstream but overall your going to have quicker spool up on the larger charger and overall more power.
My thinking is this regardless of where the secondary and primary are located in the setup your either going to have a restriction before or after the large turbo which I would think either way as long as you had good waste gates it would take care of the problem
 
Bigrednightmare said:
I guess what I'm ultimately trying to get at is, in my eyes it seem like either way you go with conventional style of compounds you fight through the small charger to get exhaust gases to the larger charger which ends up with quick initial spool, but in my theoretical setup I'm assuming you would still have good spool up characteristics because it wouldn't take much to light the smAller charger even being downstream but overall your going to have quicker spool up on the larger charger and overall more power.
My thinking is this regardless of where the secondary and primary are located in the setup your either going to have a restriction before or after the large turbo which I would think either way as long as you had good waste gates it would take care of the problem
Click to expand...

I see your thinking, but when it comes in term to spool up on compounds, having a quick-spooling large charger actually hurts performance in terms of spool-up on the small charger, because the larger turbo is sending over-atmosphere pressure into the small turbo, which requires it to move a larger volume of air, making it spool slower. Having a large charger that is attatched to the manifold I think would make this problem worse, which would make me think you'd be better off just running a big single.
 
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