Exhuast Pipe Sizing for Jdm Engine

Bluesr20 · Aug 11th, 2003, 04:49 PM

I have a 91 Nx 2000, with a JDM high compression engine, i have intake, advance timing,no cat, and im goin to be putting the jdm equal length exhaust manifold on very soon, What size of exhaust should i be gettin, 2.25 or 2.5?

bahearn · Aug 11th, 2003, 04:56 PM

The bigger the better as long as you don't have interference problems.

fugiot · Aug 11th, 2003, 05:57 PM

Bigger is NOT better for N/A applications. You will lose tons of low-end power if you have no backpressure. I'd suggest between 60mm and 70mm. For N/A SR20's I'm pretty sure that 60mm is ideal but I'm not completely sure. Only go as big as you can if you're also going turbo. Check HKS and Greddy exhaust systems. I'm not sure if they offer a bolt-on exhaust for the NX2000 but you might be able to get an SE-R one on there with some fabrications.

jdmser · Aug 11th, 2003, 08:53 PM

i have that engine and i am running 2.5 and it works great top and bottom end.

fugiot · Aug 11th, 2003, 09:11 PM

yeah, 2.36 and 2.5 would be your best bets. Don't go over 2.5 inches. You will notice considerable low-end lag with 3" piping.

Bluesr20 · Aug 11th, 2003, 11:49 PM

well i think ill go with 2.5, when i do go turbo, i plan on using a electronic dump valve, so exhaust does not really matter for the turbo. Just wanted to know a good n/a setup, thanks

OZMAN · Aug 12th, 2003, 12:14 AM

2.5 inches naturally aspirated,3.0 inches on turbo applications.3 inches is way 2 big for all motor applications u do need sum back pressure,but on a turbo application your turbo is your backpressure.

Nxtasy · Aug 12th, 2003, 02:28 AM

I have driven cars with both 2.5 and 2.25 both sr20s and stock except for I/H I felt that the 2.25 was optimal, it offered the perfect blend of low and top end gains, while the 2.5 lost some on the low end. A lot of this debate is preferance, same as in choosing a cam shaft...

bahearn · Aug 12th, 2003, 11:37 AM

Quote:

Bigger is NOT better for N/A applications

Cough cough Bullshit cough cough

Dyno a 2.5" over a 2.25" and you'll see improvements in torque and horsepower. Dyno a 3" over a 2.5" and you'll see the same thing. Even for N/A apps. Butt dynos need not apply.

fugiot · Aug 12th, 2003, 03:59 PM

You might have more gain on the top end with 3" but the huge low-end loss isn't worth it. 1/4 mi. times will suffer badly.

Bluesr20 · Aug 13th, 2003, 01:46 AM

Ill have to agree with fugiot on that one.

bahearn · Aug 13th, 2003, 11:44 AM

Show me the loss. Ignore conventional wisdom amoment and show me documentation.

Bluesr20 · Aug 13th, 2003, 01:21 PM

go visit se-r.net and read up on exhaust.

In a smaller pipe diameter the air velocity moves much quicker than in a larger pipe diameter, but smaller also limits the amount of exhaust that can flow through. So you need to find that in between,You want an exhaust that flows quickly,but also has the maximum amount of volume,don't just go out and get a truck exhaust or somethin, you'll experience "turbo lag" in a n/a car, no low end,heck why not go get the largest exhaust that'll fit, or run some side pipes?

Bluesr20 · Aug 13th, 2003, 01:23 PM

by the way, what size of exaust are you running in your car?

fugiot · Aug 13th, 2003, 03:41 PM

I think it's similar to the way you can siphon gas. The size of the tube sorta pulls it out, you know? If you tried it with a big fat-ass tube, you'd have to have an elephant siphon your gas for you.