custom exhuast

[AutoXFC3S]

i made a custom exuast after my racing beat headers for my n/a 87 i made it out of 3.5 inch tube for home depot and bent it my self and it sounds so mean and it flows like crazy ive had it on for about a week,... am i gunna hurt any thing????

[AusTexRex]

What material did you use for the piping? What mufflers did you use? Does it have a cat, if so is it connected to the split air pipe/air pump?
3.5 Inch is probably too much for an N/A, you'll lose most of your backpressure and your low end torque. Rev it high to launch and keep it in high rpms if you don't want it to bog down.

[AutoXFC3S]

ok thanks so what size do u think i should go down to???
2.5 or just 2
and theres no cat just a n1 muffler but besides that its a straight pipe

[AusTexRex]

What is the straight pipe made out of. Some metals can't handle the high exhaust temps from a rotary engine and will melt. The N1 can handle it though. As for back pressure with a single exhaust setup you should be fine, I'd measure the backpressure though. Or at least try launching and see if it feels slow

[AutoXFC3S]

will do
thanks for the help

[7Tim]

S4 (86-88 ) N/A's use exhaust backpressure to open the 5 and 6th ports.

3 inch pipes almost for sure arent going to have enough backpressure for your otherwise stock(?) S4, unless you find another way to open your 5 and 6th ports. You must be losing at least 20-25 hp top end because of this.

There are ways you can set up your ports with pretty much the same system the S5 cars do, using your own air pumps, but i cant remember where ive seen some nice articles on it, try a search or ask someone else?

[AusTexRex]

You can also wire open the actuators. I'd just get a turbo though.

[7Tim]

i would never wire them open, and i dont recomend it to anyone, unless you are using it as a track only car, way too much lost low end power...

[AusTexRex]

From the guys I've talked to as long as you keep it a little higher than normal in the power band it's just fine. To each his own, I wouldn't wire them open either.