Couldn't think of a better title. I am new to Vettes and to modernhigh-performance cars as a whole. The only performace vehicles I ever had were 60's and 70's Mopars, none of the Fuel injected modern stuff.

Ok, I fixed my exhaust and I got it how I want it, but several changes have occured in the way the vehicle runs and I was wondering why.
Let me explain the differences so you understand what I am talking about.

Ever since I opened my exhaust up, it seems as if the car accelerates much more smoothly. I can understand that this would be the effect of a system that breaths better, with less back pressure etc.

Before: The car would pull hard to 3500K no problem. After 3500K, I could feel the acceleration start to level off as it approached 4k and I would have to shift by 4300 or 4400. In fact, the acceleration is "smoother" through the whole spectrum. It doesn't have that feeling that the car is working hard like it did before.

Now: The car pulls smoothly all the way through 4K and doesn't start to level off until almost redline.

It doesn't sound like a big diff, but you can definitely feel the difference. I am driving along, I glance down and I am at 4300 or 4400 without any real effort.

Was the exhaust system just starving the motor? Was the backpressure too much? How does that work?

Thanks in advance from the technically challenged. :cheers:


[Modified by Preacher, 8:09 AM 4/12/2003]

 

There are many arguments on this subject, you will find many that disagree with me.

First off all my results are track tested, the only way to really see a difference.

Any change in power whether it be an increase or decrease can not be felt by your butt. Seat of the Pants as they say is all in your head. You make a change that theoretically should increase power and you notice a difference because you expect one. The change may be there, but you can't feel 10 HP.

Now for my results.

In my completely bone stock '95 coupe, I used to run 108-109 mph in the 1/4.
I cut the mufflers off in an effort to reduce back pressure and save some weight. I succeeded at both, but,now I could only manage to reach 107 mph in the 1/4. So even though I cut weight and made it more freeflowing, I lost some power.

Now one argument behind this is that the stock cam was designed to work with a certain amount of backpressure. Whether this is true I don't know, but it makes sense to me.

OK, so now I install a Corsa Catback, mainly because my muff elims were falling apart due to excessive twisting of the car(all those hard launches).
So now with the Corsa on, I can hit 108 mph again. SO it appears that the lost power is back.

One more thing to add, with my current setup-Corsa catback and K&N filter(No cut lid anymore) I dynoed at 285 hp and 309 lb/ft.

That's higher than stock, but I never dynoed completely factory stock so I don't know.
It has been noted in the past that my car was a factory freak, a Wednesday car if you will and not like everyone elses since I was able to acheive some very unbelievable 1/4 mile times, but the time slips and eyewitinesses don't lie.

Bottom line, if you are happy with your exhaust that's all that counts.

 

Thanks for the reply, Mr.Mojo..

My situation was a bit different. A previous owner installed a Power Effects cat-back 2system and then he, or another owner, put another muffler inline between the cats and the PE mufflers, I assume to quiet the system down as it was barely louder than stock.

I cut the inline muffler out of the system and brought it back to true dual.

It seemed obvious tome that this would increase the flow and decrease backpressure, but the suprise was the dramatic change in the way the car pulls.

I am not saying that it pulls harder, just that it seems to pull LONGER if you get my meaning. It seems that I can get higher in the RPM range before the car starts to top out.

I was just curious why a change in the exahust would do that.