Twin compound turbo (2 turbo paired in series ) are the big rage on diesels . Faster to spool up , higher boost and lower boost intake charges due to both turbo sharing the load . What is stopping us from running this type of set up on a gas motor with space not being a option?
And how would you size the turbos?
Last edited by bakes; 03-30-2009 at 02:15 PM.
I found this on another site.
You have to look at boost as a function of atmospheres (bar) to make it easy to understand. If the first turbo is working under atmospheric pressure at a pressure rate of 2:1, then it is pushing 2 atmospheres or 29.4psi. Now where it gets interesting is that the second compressor(first turbo from the engine) is running at 2bar or 29.4psi from the first compressor(second from the engine) at a pressure ratio of 2:1, so you would multiply 2 x 29.4 for 58.8psi.
Alot of compressers are comfortable and fairly efficient up to 3 bar so you would get 14.7 x 3 = 44.1psi x 3 = 132 psi to the manifold.
The other thing to keep in mind that I have not seen mentioned is that the compressor efficiency doubles in the opposite direction. So, if you are 65% effcient on the first and you add X amount of heat, then you mulitply times X for the second compressor which gets you up pretty good in the heat department. All of this is of couse dependent on ambient.
I would not run a compound setup without water injection. You will need a high pressure pump or a good way to pressure reference the tank to make it work at 120+ psi.
The formula for adiabatic compression (natural temp rise of air when compressed) is T2/T1 = Rp^((1.4-1)/1.4)
The 1.4 is for air, different gases have different coefficients, the Rp is your pressure ratio, temps T2 and T1 are absolute (kelvin scale).
Compressor inefficiency increases this temp. So work out the temp difference caused by compressing the air, then if your compressor is 70% efficient, divide that temp rise by 0.7
Intercooling between stages can help a lot, but it results in a massive amount of plumbing.
Run a mitsu off 1 and 4 and another off 2 and and 3 and then run 7-10psi out of each. Should spool like a garrett or better and be right in the efficiency zone and have low backpressure in the exhaust. Good luck cramming it back there.
Was thinking 2 mitsu or garrets in series over the gear box in front of the master cyl running 15-18 psi each to a total 30 psi or more. running a 4 into 1 equal length header into them .
My poor L body is already cramped for space.
Haven't they been doing this years ago in tractor pulls?
It's a good way to use up my spare stock turbos...
later Dick Westerhof
I think it would great add on to you new ride Dick
I saw where someone was making one of these and it was a parallel system and that was years ago.
Didn't the 4th Gen Supra come with twin turbos?
Edit: found the post, the link to the page is in there:
http://www.turbo-mopar.com/forums/sh...ght=twin+turbo
Were they compound turbos ?Originally Posted by chilort
I wouldn't compound the exhaust side of a mitsu turbo. It's already restrictive enough to run off 2 cylinder's easy. So get the exhaust flow and the benifits of compounding them. Yes tractor pulls and desiels have been doing this for years. I've seen setups with an intercooler between each stage.
What about a super 60&70 paired together with a external waste gate?
Last edited by bakes; 03-30-2009 at 10:55 PM.
also you could run a turbo into blower as well
Unlimited Hydroplan allows turbo charged, super charged, Allison V12s.
I'm thinking of doing the same thing to my 16V Hybrid Spirit I'm building. I'm building the car for drag racing. I have a large turbo from a 2000 7.3 Powerstroke a buddy gave me. I want to try it first by itself and see how it does, but if it is still to laggy off the line I will compound it with my Turbonetics super 60 to help with spool up. I am still a long ways away from getting it going. I have all the parts I need but I need to get the block ready for the machine shop. I have alot being done to the block and kind of scared to see what the machine work is going to cost. But with all I'm doing to the bottom end it should handle the compund setup well.
From what i have found so far the primary turbo (one that attached to the exhaust manifold ) is to be the smaller turbo and the secondary turbo is to be the larger one compressing into the smaller turbo intake.
That sounds right. Primary on manifold, exhaust from primary feeds the turbine wheel of the smaller turbo. The air filter goes on the small turbo, the compressor outlet from the small turbo goes to the compressor inlet of the primary (large) turbo and the compressor outlet of the primary goes to the intercooler.
Rotary's and some Jap imports, IE Skylines are twin turbo'd, and MR2's I believe had a turbo and SC.
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There was a kit back in the early days of imports that had a supercharger and a turbo charger. I think the one I saw was on a acura integra. Of course Detroit deisel big rig motors have done that for decades.
Pretty sure you got this backward. The primary is the smaller turbo. Exhaust mani feeds it on the hot side ... larger secondary turbo feeds it on the cold side.
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