i use to drive a bluebird sss with a stock n/a sr20de...the factory exhaust was a tapered square tube that got smaller at the end, then went into regular round pipe into the muffler...

i sold that car but was thinking, how effective it would be to use a 2.5" pipe, then have it go down to a 2" pipe using a connector that is tapered...

the bluebird exhaust was really good, and performed better than a straight round pipe...

anyone ever try using 2 different sized pipes? maybe i'll be the first. :tongue:

A lot of turbo guys go from smaller to bigger (2.5" downpipe to 3.0" exhaust) in some combination. But...going bigger to smaller would probably lead to a bottleneck of some type, IMHO.

I'd be curious what the results would look like on a dyno, however. Especially on a NA engine. You never know...

My HS gen 6 header came with a 3" dp that reduced to 2.5" at the flange :rolleyes: and I was using a full 3" exhaust. After I got the downpipe modified to 3" as well, the car performed better, and it was noticible. It also got a little quieter if you can believe that.

serban's car is the loudest vvl ive ever heard///i envy that noise

think going to a smaller pipe, say half way to a quarter of the length of the whole assembly, would give better back pressure for more low end punch...

i always forget what back presure is more useful for, low,mid,top end ? i want something with a broad powerband..heck i guess it couldnt hurt to try, and i could just change the 2" back to a 2.5" if it doesnt work good

where i live it only cost $40 for the entire piping excluding muffler... ;)

the farther down the exhaust the bottleneck occures, the more restriction it creates. Bigger is better.