Randall0093

I recently rushed myself into buying an exhaust system and now I'm thinking I made a big mistake? Maybe someone with more knowledge on this topic can please help me out. I have a 2001 S2k and I got the Apex'i GT Spec single exhaust system with Rick's 6plus headers and an Invidia test pipe. I'm worried that the piping diameter on the exhaust I got is to big? It runs 3.75" from the cat. A friend was telling me that the piping diameter is to big and it creates backpressure thus losing horsepower on low end? Is this true and if it is I was thinking about switching to the Spugen single pipe system. Which system will give me the most power out of those two and If I put a supercharger on will it make any difference between running 2.5" or 3.75?? Thanks all

Ape_X

Generally the exhaust needs to match the output of the engine. The stock S2k exhaust is very efficient and its rare that an aftermarket exhaust provides a large power improvement. Most see results with testpipe and a single exhaust, though beit a small one. I think your friend ment to say... "The exhaust is TOO big and DOES NOT create enough backpressure in the low end" The engine likes a tad bit of restriction in the low portion of the revrange but then likes it nice and open for the 9K redline... its basic laws of fluid dynamics. SOO.... If you're going to supercharge, you might see a benifit from the super large exhaust diameter because of all that extra air being forced in and out of the engine... but for a stock F20c It probably won't help and could be hurting you.... but thats nothing a DYNO can't solve!!!

did that make any sense?

D

MugenRioS2k

great here we go again with the backpressure mith.

Back pressure is allways bad when it comes to extracting power form an engine.

However there is a inversely proportional relationship between induced backpressure due to pipe diameters and exhaust velocity.


Exhaust velocity is what you are looking for when trying to maximize exhaust gas scavenging.
However to get an increase in exhaust velocity (with a fixed amount of mass flow) one must decrease the pipe diameter to get more speed (ignoring the effects of increases mass due to gas cooling as it travels down the pipe) mass flow in must = mass flow out

Randall0093

That is the best info anybodys ever giving me? Wow you guys know your shit! I just created my account and I'm glad I did cause I couldn't find anwseres anywhere! Hey thank you both so much for the help and yes it made clear sense!! I'm leaning towards keeping it for fact that I am getting a supercharger.

Thanks again

Randall0093

Hey would you guys know where I can find torque specifications for the headers?

MugenRioS2k

https://www.s2ki.com/forums/index.ph...f=148&t=445570

Randall0093

Sorry.....I meant torque down ft lbs for the headers?

MugenRioS2k

you mean the torque that needs to be applied to the header bolts??

If so ask here

https://www.s2ki.com/forums/index.ph...f=118&t=419790

marknconnie

i hda the apex gt spec exhaust before and its only 60mm.. 2.5 may the 3.75 part is just the tip.