Okay maybe I can help with this one.
Forced Induction is forced induction. 1,2,3.... turbos, supercharger. All creates an artificial volumetric efficiency.

Okay so I guess why can you buy a car with no turbo, add a turbo and get more power, and why does a person buy a twin turbo Supra or RX7 and convert to a single turbo for more power? That seems to be the question.

Well its an engineering problem. There is no perfect answer and there is no perfect solution. Only trade offs. Personally I would prefer a turbo car over a supercharged car because I like the lag. Makes the endorphines rush a little harder.

With a single turbo the mapping of the of the turbo is limited. You either have a smaller turbo or a bigger turbo. A bigger turbo might produce more boost and a stronger top end, but you´ll get lag. With a smaller turbo you get less lag but you can actually "overspin" the turbine. You´ll reach a point where the car is spinning the turbo as fast as it can go...and you might have rev range left to go.

Twin turbos you can solve alot of those problems. Most twin turbo setups are sequential turbo´s...one small turbo spools a larger turbo. This lessens the lag and allows a decent top end. Another benefit of twin turbo´s, usually used in sandrail applications, is heat dispersion. Turbo turbo´s can bleed excessive heat better then one turbo. That´s why most aircooled boosted applications use twin turbos and run on methanol.

Im beggining to think cars with twin turbos go to a single because they like the feeling when other cars get a jump on them at the line before they go flying by at near mach speeds (there´s a guy I know with a T88 turbo pushing 30psi on a 96 Supra pushing over 800HP. He lives down in Phx and loves screwing with Mustang GT´s because they get a jump on him before he can spool the turbo..sucks to be in a stang then.)

Anyhow, specifically can you twin turbo an Escort? Yeah I definately think it can be done, but let me tell you one turbo is enough cramming under the hood of an EGT. Two would be mastery of a welder and reconfiguring alot of stuff. And with all that work, you wont be gaining a whole lot, because remember you still only have 4cyl to produce exhaust to spool them. Really if you want alot of power...just build the BPD Lower your compression ratio to like 7.5:1 or something insane like that, and run 28psi on a ball bearing turbo.

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Jason Blade
93´ Escort GT (Special SLO model)

[ Edited by TheBlade On Date 11-07-2002 ]

 

I think it´d be pretty sweet to twin turbo an EGT, but theres a few problems that i can see. 1. how the hell you gonna fit that under the hood? cause i don´t think you´d wanna put your second turbo in the passenger seat

and 2. twin turbos are sequential turbos, meaning there´s a small and a large turbo, the small for low rpms and the large for high rpms. Aren´t you going to need a computer from say a twin turbo Supra or something to make that work? I dunno maybe it´s my own ignorance on this subject but i´m just really trying to figure out how that would work.

 

James, twin turbo´s dont always have to be sequential. However I do agree with you, cramming it in would be hard. Take a look at my pictures in my showcase...you can see how much room one (small) turbo took up sitting up front.

As far as the computer aspect goes...one or two turbos isnt the hard part for the computer. Boost is boost....to the computer its just getting boost, or in the case of our nonturbo computers its more like "Error: Engine Running Lean" simply because it doesn´t "see" boost, it interprets it as not enough fuel for full throttle.

 

well, the only way I want to get a twin turbo would be if they were sequential, that way I can still be putting 127 hp to the ground from start to 3500 rpms, then let the bigger turbo take over to 7000 rpms. I´m going to try to get into a dyno jet tomorrow, if they have openings to see what exactly my car is putting to the ground. When I get this done, might not be this weekend, I´ll post it up with the rpms to hp.

 

Well one of the big limitations is that the turbo´s have to be mated, you can just put on a really small turbo, then a really huge one. And you´ll still run into the prob of overspinning the smaller one. If the smaller one was a ballbearing turbo you´d be set, but that´s usually unlikely.

Personally I want a big V8, twin turbo´d. One turbo per 4 cylinders. Oh yeah...