Should you run a 4 inch exhaust?

[Gjkrisa]

So who's going to be first to run a three or four inch?

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[bpd1151]

I'd like to see someone, anyone, double down and run 6".

Lol.

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[FoMoCoSHO]

What is the impact of transitioning from 2.5 to 4 on exhaust velocity?

Exhaust pulses, pressure wave timing, etc, Exhaust theory is very complex....

http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm

[FearlessAZ]

I'd like to see someone, anyone, double down and run 6".

Lol.

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Go big or GTFO!

[AJP turbo]

I do know that there is an incredible amount of back pressure that would be more than you ever need in the exhaust pre turbine between the heads and turbine due to the size of the tiny turbo....So even if the exhaust was wide open after the turbo and you didn't run any down pipes there is still a lot of back pressure because all the exhaust is exiting a 38mm turbo!

[MiWiAu]

This Firechicken was at the shop while I was getting dynoed. Looked like a 3.5 or 4" exhaust dumped straight out the side. Looks like the turbo would suck in an albatross and keep on going.





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[Bmckee40]

Can


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[J-Will]

Is that firebird a v6? Engine seems pretty far back to be an 8. The 3800 series II v6 engine is a beast, and came stock with a supercharger on several GM vehicles.

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[MiWiAu]

Is that firebird a v6? Engine seems pretty far back to be an 8. The 3800 series II v6 engine is a beast, and came stock with a supercharger on several GM vehicles.

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Some sort of V6. I was just poking around the shop and didn't ask many questions. I was on the clock @ $100/hr, so I was trying not to distract anyone. LOL The car was a T/A, so surely it was some sort of swap, as I didn't think you could get a 4th gen T/A with a V6?


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[jbrown9999]

The layout reminds of the Buick Regal GN engine layout, but the alternator and turbos were on opposite sides.

[NITSOOB]

From my understanding,

Exhaust out of the turbine is never laminar. Its turbulent, until a few feet after..

Big downpipes help spool by keeping the least amount of restriction off the turbine. But if you run a full exhaust, you neck down gradually to aid velocity and laminar flow. Too big of an exhaust after the downpipe actually creates turbulence and slows the exhaust.

Which is why you see some set ups with bigger downpipes - necking down to a smalller pipe depending on the power output. Typically 3" for up to 400hp 3.5" to 600, and 4" 700 and up