Howdy,

Have a question about exhaust systems. Keep in mind I know next to nothing about how my truck runs (which is why I am here).

I kinda understand why velocity is important, however it seems to me that velocity will be created by the engine as it pushes the exhaust out, no matter the size of the pipe. But why is back pressure important? How does it affect low end torque?

I just put a flowmaster on my truck that I got from my brother-in-law. It's got 2 1/2" pipes, and I know for sure that diameter won't be an issue, so now I want to learn what I just did to my truck! LOL!

 

Back pressure isn't required, but it does give the truck that nice rumble. The exhaust you went with is perfect. The faster you get the exhuast out of the truck the better. Anyone else wanna list what i might of forgot.

 

You need a certain amount of backpressure. Without backpressure you're right it will affect performance.

 

Some backpressure is good to have. It aids in creating low end for take off. I have very little back pressure but I also have a blower, and even though alot of people seem to think that low end is comprimised with flowmaster, I tend to disagree as mine makes full tq at 2800 rpm and rides within 10#'s of max all the way to 4000.

 

Thanks for the responses guys. One of the reasons I ask is that my brother-in-law has a '99 V6 and wants to remove the cats and muffler and just run a pipe that exits behind the doors. However he was told by a mechanic that he would lose all backpressure, and that would be bad for the motor. I'm just curious as to why.

I'm trying to learn how all of this works. If any knows a "Engines for Dummies" website I'd like to check it out!

 

ok, here is my .02 cents.

an engine is an air pump. Air in through intake, exhaust out through muffler. By drastically reducing the back pressure (ie no muffler/cats) you create an imbalance in the normal operation of the engine. An engine CANNOT exhaust more air than it takes in!!!!!

Now with todays computers and air/fuel management tools, this is not as big an issue as it used to be. Keeping that in mind, the O2 sensors that are installed near the catalytic converters require a certain amount of heat for optimum function. so, as you make changes to the exhaust, you are changing the characteristics of the engine. Your computer program now has to compensate for these changes.

So, a less restrictive muffler allows the exhaust to exit with less backpressure and normally a better sound. But I BELIEVE that drastically reducing exhaust backpressure alone = a bad thing.

however reducing backpressure and increasing the intake flow (and reprogramming the computer) can yield amazing gains..

I hope this helps and good luck with whatever you choose to do!


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