Quote:
Originally Posted by BonzaiCelica
why did you go with a 3" exhaust?
is 3" exhausts for turbo engines only??
|
Depends, depends..... race car? Do whatever is allowed by rules AND adhere to noise restrictions of the track and/or regulations.
Street car? Well....depends where you want the "power" to be, unrestricted exhaust (or HUGE diameter exhaust pipe) will usually mean high top-end power & lose some torque + hp during the rest of the RPM range.
Want the scavenging/cavitation to "help" your engine to move things along? Go smaller diameter pipe....then again adding a Cat/Resonator/Muffler to the mix greatly affects what the diameter of exhaust pipe is doing for you.
My experience:
2.5" pipe from the 4-2-1 collector on back to a "straight-thru-fart-can" was retarded in the low end...the thing would just not get going untill the VVTi "kicked in". Added some crap resonator fixed this a bit, gained some low end torque. Removed the fart-can & added a Vibrant straight-thru muffler, slighly better results but the noise was tamed very nicely. Popped out the crap resonator & replaced it with a quality Vibrant resonator, lowered the noise down to a nice rumble and no real big power improvements.....then I added a high-flow cat also from Vibrant. Now here something happened, rumble got even deeper and much more evil sounding, some power improvements, which I have no idea if they are *just* from adding the cat or from adding this little fanagle I made while bored at the machine shop....basically made this piece of pipe that consists out of 3 sections of 2.5" pipe that has been reduced at one end by about 0.25" and put into the tail end of the next piece of 2.5" pipe.....basically like welding 3 reducing pieces of pipe into each other....I did this just on a hunch & sort of a "whatever lets try something" idea....I figured it might help the cavitation and/or scavenging....
But yeah, my ramble aside...it all depends on what you wanna use the engine/car for. Generally, anything with a turbo is best to allow as much unrestricted flow as possible, be that either from a lack of muffler/cat/resonator or from using huge diameter pipe.