Exhaust mod lost power?

[DOUGLASMELTER]

I CUT THE CAT, U, AND RESINATOR OUT OF MY 2000 GTP AND NOW IM SUFFERING POWER LOSS AT FULL THROTTLE DO THESE CARS NEED THE CATS BACKPRESSURE TO MAINTAIN PERFORMANCE SHOULD I PUT IT BACK ON MINUS THE U OR LEAVE IT OFF

[Bio248]

backpressure doesnt matter for a roots blower car. something else is wrong.

also, wanna back off on the caps lock? that is all kinds of annoying.

[2000GTP]

backpressure doesnt matter for a roots blower car. something else is wrong.

also, wanna back off on the caps lock? that is all kinds of annoying.

yes, you are right bio... on both accounts!

[DOUGLASMELTER]

so if i got a guy to inspect my car regardless of what may or may not be on the car should i keep the cat off

[Ragefear]

the whole idea of back pressure is ridiculous. When you ask about back pressure it really shows that you don't have the necessary knowledge to be properly tinkering with your vehicle, and before you get all annoyed, this is a common problem that people do not understand. They throw a bunch of parts at a car and then get upset when they don't get the results they were expecting, but that's an entirely different thread.

The idea of exhaust back pressure is really the idea of exhaust gas velocity. I would imagine that you are complaining that your butt dyno is showing lack of acceleration, am I correct, thought so. :-D This is because a larger/less restrictive exhaust pipe will cause the loss of the lower end power. What properly tuned exhaust needs is the ability to suck the exhaust gasses from the engine, how is this done? Exhaust velocity. More restrictive exhaust systems, much like that of your stock system, give better low end performance because they can maintain a good exhaust gas velocity at lower RPMs.

OK, so we have talked about a larger/less restrictive exhaust pipe and an smaller/more restrictive exhaust pipe, we have discussed that the smaller/more restrictive the pipe the better it performs at lower RPMs, which makes your butt dyno happy. We also touched upon the idea that a larger/less restrictive exhaust won't perform as well at lower RPMs. We also spoke of velocity and how back pressure is an ignorant term. So what does this tell us?

smaller/stock/more restrictive exhaust performs better at lower RPMs. Why? Because it has the ability to suck the exhaust gases out. What does this do to your top end? It chokes the hell out of it.

larger/aftermarket/less restrictive exhaust perfroms better, when? Very good, at higher RPMs. Why is that? Exactly, because there isn't enough velocity for the larger/less restrictive exhaust pipe to pull the gases from the engine. This makes for a dumping ground at lower RPMs. Basically the engine is pushing exhaust gases which are usually being pulled from it at lower RPM range. Once the RPM range comes to a more affective level for the size/restriction of your exhaust pipes, the exhaust system will begin to scavenge the gases pulling them from the car once again.

So, what does this tell us?

If you and another GTP line up, all the same mods EXCEPT you have a modified exhaust which is less restrictive than the other GTP. In the perfect conditions (both cars are running exactly the same and the drivers are perfectly matched in response time and accuracy), the other GTP will get you off the line but you will catch up and more than likely pass. As long as you didn't take this literally and put a 4" exhaust on the car, being that is well out of the normal operating range of most any 6 cylinder (cummins asside). lol

[Ragefear]

your welcome! glad I could help!