A question of GIRTH!!!

[Monk BANzai]

ive been reading on other forums of the balance between a 3 inch exhaust and a 4 inch exhaust...with most ppl saying that the the 4 inch exhaust is really too much unlessur car making like 600HP plus....

theres also a school of thought that the 3 inch exhaust makes yu lose low end power in exchange for more ommph up on top...

TRuths? Lies? Myths?

[Mini]

well i assume you talking about a turbo'ed car.. since IMHO unless you have a V16 truck... 3" is too much

when you get into fluid dynamics and cross sectional flows and friction on the inside of a pipe and thing... even them calculations is too much... plus they'd hold only for a specfic RPM (i.e. volume flow rate through the exhaust)

having said that... I personally feel that you can go too big... and going too big would cause you to lose some low down power....

[seanf3000]

I guess the real truth lies is if you look at your dynochart before the install and then after the install. But then we know you cah doh that right now.

[Dave]

generally 3" would suffice for what you are doing
only 3.5" - 4" would become useful when talking about 500hp+

[cdx2k1]

So wider = greater effect @ higher RPM..

[Monk BANzai]

^^^ seems so...but wher does the balance lie?....if yu want the high end performance but at the same time maintain the low end "grunt"

is 3.75 a popular diameter?...i see HKS marketing that......

[Big Z]

Everyone says that a friend of a friend said that a friend said that a bigger exhaust diameter gives more power up high and less power down low (as compared to a smaller diameter).

Anybody got dyno chart proof? Or everyone regurgitating?

[seanf3000]

I've seen dyno charts with changes from 2 to 2.25 and 2.5" give a few hp and some give no hp. Actually i think it was a DC5, a celica and an eclipse. SCC I think was the mag. But from 3' to 4'?? i dunno bout that one.

Looks like its application dependent.

[Rainman]

IMO high flow exhausts and larger diameter down pipes only serve their correct functions on appropriate applications. for instance if you have a relatively small engine 1500-1800 (non-turbo of course) increasing the diameter of our exhaust piping can result in compression loss and it can take a dramatic toll on your low end torque.