Compound Boosting

frdlvr30

Registered User
I know that this has been talked about several times, but I like many people find this quite interesting. I went back and read the MM&FF article from the Hellion set-up they did over a year or so ago. I remembered Neibert talking about it when the article came out, and never did read it till a few minutes ago. Really is amazing what they got out of it without pullying the blower. 1200rwhp!! That is nuts. They did not say if it was a stock longblock. I assumed it was. How long could the headgaskets last with 44-75psi of manifold pressure? Let alone the ringlands?? I realize we could never dream of that kind of power out of a 90 degree pushrod V6, but the gain would have to be considerable. Another question is if the turbo pressure is readding 27psi and the manifold pressure is mid-40's psi. Isnt that restriction hard on the blower? Would it hold up to that kind of pressure difference?? That restriction would be directly on the rotor pack, right??http://www.musclemustangfastfords.c..._compound_boost_2003_mustang_cobra/index.html
 
I remember this article. Very informative, and insane. I like how they mentioned the cv axles bowing on the dyno becuase of the power. I've thought about this idea many times. I want to do this to my honda, not the sc, mainly to get a solid 12 psi at 2k rpm and hold it to redline 7.5kish. Use the blower to spool a turbo that would normally be too big. If I didn't have so much tied up in the SC, wouldn't be a bad idea, but the thought of spending another 2-4k on turbos, piping, misc parts, etc, can't justify it. Would be nuts to see it pulled off though.
 
quiet, thats my secret project

Twin turbos liquid cooled by acetone and dry ice feeding a mpx bower.:cool:
 
The latest issue of Hot Rod also has an article on the Hellion Hell Raiser kit that uses a pair of low mounted turbos feeding the supercharger on an 03/04 Cobra and a GT500.

David
 
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compounding your air movers is definatly a way to huge numbers( as seen in that article). i mean when factory engines like VW (k, slap my hand for saying a bad word!) are useing them, it's just a trickle down effect. the idea becomes main stream-ish and folks beleive it can be done, not just well" i heard of some guy that had a brother" thing.

food for thought, i drove the hmmtt( pronounced hemit) back in the gulf war and it was a compounded V8 diesel. a monster of a truck with somthin like a 14-71 roots style blower with a turbo the size of your torso!
 

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Can I run the twin turbos wide open without any throttles, then through 2 water IC's to a MAF then a throttle and normal sc setup? I was thinking I would need a blowoff vavle somewhere so that when the throttle snaps shut the boost will have somewhere to go, or maybe one the opens on a certain vac # and at high boost limits as well?
 
Compound boost happens a lot in commercial applications as well as quad turbo and whatnot. I used to build off-shore skids with Cat engines with a blower and twin turbos. I'm sure there are reasons this doesn't happen much in the civilian world, but I'm not sure what those reasons are. Some things that come to mind is complexity, maintenance, reliability, and probably expense.
 
Can I run the twin turbos wide open without any throttles, then through 2 water IC's to a MAF then a throttle and normal sc setup? I was thinking I would need a blowoff vavle somewhere so that when the throttle snaps shut the boost will have somewhere to go, or maybe one the opens on a certain vac # and at high boost limits as well?

yes this set up is relatively easy to do. the turbo you use will dictate the airflow you will have. the turbine housings for your turbos WILL have to have internal wastegates. when you look at the turbine outlet it'll have some sort of flappy valve and a rod connecting to a pressured bypass valve from the compressor. not the cheap ones you see for 200 bucks.

first you need to find your airflow by using this formula;

horsepower(hp)Xair fuel ratio(afr)X (BSFC.55for turbos /60 reducing hours to min)
lets say 450HPX12X(.55/60)= 49.5 lbs per min of air.
this isn't peak power flow but just that much air to get to that power number regardless of engine size or rpm.

i would expect that to get the most out of our engines is to use something like two 2.2L turbos placed somewhere like where the cats currently reside. the combined flow won't be great at low RPM, but that's what a positive displacement blower is for, right? then when you get to let's say 3grand RPM they'll come on and get things going. both these turbos are boost referenced by an internal wastegate to bypass exhaust past the turbine at say 8LBS. so combined at full steam a combined 16LBS would be getting to your I/Cs.

after doing some math that's quite a bit more complicated, i came up with for the 450HP figure you'll need 35PSIA pounds per square inch actual for the 3.8L engine. now subtract ambient of 14.7 from that figure and you have about 20 lbs of boost needed. now subtract all your bends in your pressured tract and intercoolers for 3 I/Cs and all the twists and bends to the order of about 6LBS of restriction. sooooo, 26LBS from the turbo at your boost guage to be in the ball park.

in a nutshell yes you can. twin internal wastegated turbos mounted as close to the heads as possible, but oversized a little to allow them to flow lots of air.
 
One note, you don't see many solutions that use one turbo to feed another turbo in the aftermarket. The combination is fairly complex and the balancing of the two turbos can be a challenge.

Hellion is using twin turbos in a parallel config (each one powered by either side of the head) dumping their output into the intake of a positive displacement blower. This tends to be a simpler configuration than running two turbos in series, and the design is easier. A positive displacement supercharger makes it easier to dial in the compressor maps and housings.

While multiple turbos in series look crazy, the reality is, for most automotive engines a single turbo can cover the power band pretty well if sized correctly without any of the complexity of another turbo or a supercharger.
 
staged turbos can put out TREMENDOUS ammounts of air. continue stacking turbos and you end up getting turbojet typs of power! how's 200+psi??

but back to the point just get the second turbo's inlet flows as much as the first ones outlet, minus the resriction of the I/C.

you want 40LBS of boost? well stage 2 turbos, first kinda small like a t3, then put one after that one like a super 60 or 70 and your off and running!

ofcourse, you gotta work backwards from the engine, thru the second I/C to the second turbo. then to the 1st I/C to the 1st turbo with your flow rates. then the other way to check you work and flow rates. not simple math, but doable.
 
. the turbine housings for your turbos WILL have to have internal wastegates. when you look at the turbine outlet it'll have some sort of flappy valve and a rod connecting to a pressured bypass valve from the compressor. not the cheap ones you see for 200 bucks.

The turbos don't need to have internal wastegates.

David
 
ya, but is sure does simplify things :D

besides that, BOVs are for ricers and sheep shaggers!!!
 
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My plan uncovered

I was plannin on hiding the twin turbos inside the bumper cavities. Plumb the exhaust along the "framerails" and dump into the bumper cavities, then route the exhaust a bit lower to where it would usually tie into the cats. I would buy a xenon front airdam and use the fog light holes as a ram air setup. The worry is clearances and having all the heat inside the bumper area, or atleast venting the cavity. At least when I work on my 94 there seems to be alot of space in there, even more with the airbox stuff removed too.
 
ya, but is sure does simplify things :D

besides that, BOVs are for ricers and sheep shaggers!!!


A Blow Off Valve or Bypass valve is a necessary turbo system component to protect the compressor wheel and throttle body from being damaged from pressure spikes when quickly letting off the throttle.

Not sure what that has to do with using an internal wastegate. The wastegate (internal or external) regulates the turbine/compressor wheel speed by bypassing a portion of the exhaust gasses around the turbine. BOV has a completly differnt function and is needed with either style of wastegate.

David
 
OK, this is what I have been working on for 6 months now. stock 90 sc motor, exhust like supper reds turbo kit( grand national style), holset H1C 12cm wastegated rated at 65# per min of air, 60# injectors, 80mm c&l, bypass vavle insted of bov, 3" down tube, 255 pump, ported 90 blower with stock pully, amd large FMIC. :D:cool:
 
I too was amazed at the Hellion project. I originally wanted a remote turbo to compound boost my SC. I completed the rebuild on the car only to have the engine and tranny stolen.:mad: I have the original block which I will start to rebuild in the up coming months. I still love the idea of that setup. I have been thinking of a couple options for the car. Since the blower was taken and I will need to buy one I am considering a remote setup from STS to boost the 3.8 and bypassing the purchase of a SC.

Next option is to use a TVS 1900 w/no turbo

Next option would be a MP 2, as it is derived from the original 94/95 blower(since my SC is a 95) and down the road add a remote turbo.

I am in no rush and will build this one right.:D

Stephen
 
Ive been experimenting wit hcompound boost on my 4.0 exploder. Im just working on the drivability problems as im using the stock ecu with a Vortec super adjustable FMU
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