Major Back Pressure Problem off New Exhaust System

[00blackzx3]

Ok I just had my new cat back exhaust system put on my SL in place of stock back in february. My problem is after i put the exhaust on i noticed a horrible low end loss of torque. The loss is very evident on the car. It takes off horribly slow. Now I am trying to find out the problem of the system. The system includes 2.5 inch piping from the pre cat all the way back with a resonator in place of the cat to quiet things down. After the resonator it runs into a 2.5 single in dual out FLOWMASTER 50 series muffler. Out the outlets it runs into a dual setup. Now is my back pressure problem probably:

1. 2.5 is too big, should get new piping (2 1/4)

2. the new resonator i had put on to quiet it down, very baffled.

3.the FLOWMASTER 50 series muffler itself.

4.runnign dual exhaust

[talskinyguy]

Sounds to me like you are just experiencing what happens when you upgrade your exhaust. Your powerband shifts to a higher RPM giving you more HP up top.

[Stealthee]

2.5 inch is not too big. In fact for a NA its about optimal. Is your car ATX?? If so then thats the culprit.

[xXxRocker5150]

^ I've heard that some people notice a loss in difference, and that others don't when they switch to larger exhaust systems, I know Musashi had the same problem

[Twizted_3KGT]

Yeah i'm with talskinyguy, increasing the size of your exhaust decreases low end torque and puts it up top, so you probably have a higher top speed, but your acceleration is worse.

[00blackzx3]

well guys is really doesnt matter anymore, out of fucking nowhere my automatic tranny went out on me...... i have to get a new tranny now, im thinking of manual conversion

[Stealthee]

Originally Posted by 00blackzx3

well guys is really doesnt matter anymore, out of fucking nowhere my automatic tranny went out on me...... i have to get a new tranny now, im thinking of manual conversion

BINGO, thats the answer. It had nothing to do with the exhaust size.

[talskinyguy]

Originally Posted by Twizted_3KGT

Yeah i'm with talskinyguy, increasing the size of your exhaust decreases low end torque and puts it up top, so you probably have a higher top speed, but your acceleration is worse.

you missunderstood what I said. Acceleration will not be slower. What I said was that you will have less torque in the lower RPM's, and more power in the upper RPM's.

[sLADe781]

Is there anything that we could do to fix this problem? Top end power is great but if it reduces your torque at lower RPMs then that sucks....especially for us NAs. Would it be a bad idea to just stay stock? I know stock is restrictive but just how restrictive are we talking about?

[00blackzx3]

my vote: stay stock, add testpipe only, or go aftermarket SINGLE exhaust, dont loose torque low just so you can accelerate faster at 100 mph, just not worth the loss

[Stealthee]

A custom 2.5 inch exhaust will not make you lose power. I know someone who has a ATX 92 base 3k with a custom 2.5 Magnaflow exhaust. He said power was gained in all ranges and he lost no low end. You just wont lose low end because most of the stock NA exhaust is near 2.5" anyway.

And its kinda funny, soon after you get a custom exhaust your tranny goes out. Well a week after I added my TT catback my clutch went out. Maybe it was all that extra power.

[sLADe781]

What's the difference between a "custom" 2.5 setup versus a 2.5 piping from say Borla? I thought 2.5 is 2.5 and will all be the same... What's the stock setup? 2"?

00blackzx3, testpipes....are those CARB certified? Because I live in CA and have to worry about emissions. DOH!!!

[Wischmaster]

Testpipes are anti-emissions. I don't think you would pass emissions in CA with a testpipe... you would with a cat though. Just a tad more performance to your ride, but just a tad more destructive to the environment.

[talskinyguy]

Originally Posted by 00blackzx3

my vote: stay stock, add testpipe only, or go aftermarket SINGLE exhaust, dont loose torque low just so you can accelerate faster at 100 mph, just not worth the loss

Does no one listen to what I say? Higher RPM not higher speed.

[sLADe781]

Originally Posted by talskinyguy

Does no one listen to what I say? Higher RPM not higher speed.

Maybe I don't get it....care to explain?