GT Motorsports: 370Z Supercharger system development

RCZ

Alright so after reading a bit from reputable sources. AKA Garrett from the stuff that Silo showed us.

Bigger turbos make more power per the same psi for two main reasons:

1) Bigger turbo will put less heat into the air and therefore the air is denser. More air = more power

2) The actual CFM of the turbo is meaningless. What matters is how much of that air is actually going into the engine and being used. There are restrictions that keep all the air from getting to the combustion chamber, the main one being backpressure from the exhaust housing of the turbo. The smaller it is the more backpressure, the less air that can flow through the engine, the less air that can flow INTO it in the first place and therefore less power. So bigger exhaust housing means less backpressure, meaning more air in, meaning more power.

The logic seems to be that it doesnt matter if the turbo can flow an infinite cfm, if the engine can't make use of it. The less backpressure, the more the engine can use, the more power it can make.

So how does this all apply to the SC vs TC dilemma?

I would say its the same thing, more flow through the engine means more power. So why do manufacturers recommend sticking with 2.5" piping rather than 3" piping on an SC? Because the sc doesnt flow enough in the first place to cause a 2.5" exhaust to become an obstruction??

Zsteve

This makes sense, with my 4 cyl turbo, when we just upgraded theintake and Down Pipe we saw huge gains as more air was flowing in and out. When I chipped the ECU I also went 3 in TBE and with the small turbo on the car I hit full boost @ 2500 rpms and actually had more TQ than HP on the car. I had over 300 TQ and about 260 HP on a 4 cyl FWD car, it was fun to feel all that TQ. Since the turbo does create its own back pressure we could go larger on the exhaust (to a point of no return of course) but I guess NA cars use the exhaust to create the back pressure.

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2010 LS3 C6 Silver coupe corvette

Togo

If I had to take a guess, and yeah thats what I'm doing with this post, I'd say the SC doesn't make enough power to bog down a 2.5" exhaust. The turbo's turbine housing would be causing some back pressure relatively close to the engine so I'd suspect the 3" turbo back exhaust would help elevate the back pressure by creating a lower pressure area aft of the turbines. The low pressure area would help increase the flow over the turbines due to a relatively high pressure zone pre-turbine. I don't think that a 500RWHP TT setup produces more exhaust than a 500RWHP SC setup so the 3" exhaust might just help to lower the pressure pre-turbine by moving those gases over the turbine blades faster and more efficiently.

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