ajmccarrel

Well then..... I had quite a placebo effect from the cruise control delete. Lol!

kponti

Bolded part do not apply here! This is NOT a 1970s carburated car

laxdude362

iTrader: (1)

Ok for god's sake. Some SC400's come with traction control and some don't. If you do have it you will have a button next to the shifter and it will say TRAC in your engine bay. If you don't have a button then you DON'T have it! No one tried to remove it or whatever dumb idea the guy earlier posted. The 2.5 inch piping is hurting your performance, especially down low. You need to keep it at 2.25 inches. Use TCS for traction control system and TC for torque converter, so you stop confusing everybody. This is all pretty simple stuff that has been discussed NUMEROUS times. You are a new member and need to learn to use the search feature. A majority of your questions can be answered by researching them.

GSteg

iTrader: (15)

You never ever ever ever want back pressure. Back pressure is bad in any case and it hinders your engine to breathe. The larger the pipe, the larger the backpressure. You only need the pipe as large as the engine needs. 2-1/4" seems to be a good compromise on an N/A motor.

ajmccarrel

What do you mean? Is what he said wrong, or those parts are causing the issue? Im not sure what you really mean.

ajmccarrel

I am usually searching first then asking. There is a lot of conflicting information, unhelpful information, outright wrong information and incomplete threads.

ajmccarrel

On the piping, does it make any difference what size my piping is considering that i am using the stock headers and that there is still a foot or two of stock piping after the cat? All of the 2.5" pipe is right before the x pipe and between the x pipe and the mufflers. My understanding after reading more is that if the pipe at any point post cat is 2.25" then the piping is in effect 2.25"? Is this correct?

INTIMAZY

iTrader: (5)

I literally cringe everytime someone still spews the words "motor needs backpressure."

I'm gonna leave this here.

http://www.gomog.com/allmorgan/exhaustbackpressure.html

Dual 2.25" piping will choke off a 4.0L motor in the top end. It's cutting it too close as far as CFM requirements go (assuming ~400cfm flow on a 4L motor spinning 6500rpm at VE of 85%). Dual 2.5" is just fine.

And yes, the minimum diameter of your exhaust is the bottleneck that limits CFM. However, transitions screw with velocity and are not a good idea unless you make them go larger the further back you go.

ajmccarrel

OK, so based on this article, I'd say my exhaust is just fine, until I build some headers. It starts out through high flow cats goes into 2.25" piping, transitions to 2.5" to an x-pipe and through straight through mufflers. It doesn't sound like I need to change anything.

CANDYAPPLE

iTrader: (1)

piping all depends on your set up, the most important thing is restriction, not reall 2.25 vs 2.5 very little difference unless your boosted. i have a 450whp 3.0 liter motor with 2.5 in piping, vs my 2.25 stock piping and it did fine. people kept telling m3 you need 3.0 cause it will run better but my car ran just fine with 2.5 in. i ran a car with the exact same mods as me except he had 3 in piping, i ran a 12.0 @ 121mph and he ran 13.2 @ 109mph. at higher speeds his car seem to run a little better than mine, but in the money making 1/4 runs i killed him,lol. rkyat a member on here knows me very well. im about to do the same to my awd is.

ajmccarrel

Not sure what happened, but I can smoke tires on demand now.