ChrisG

I have a 98 Z28. I just recently put on Hooker L/Ts, off road pipe, and have a loud mouth exhaust system. Is it true that our cars need 12 psi of backpressure to run properly? I was told I am probably losing power with my current setup. Any info would be good.

Speedfreaks101

The idea that backpressure is a good thing was probably started by Flowmaster, and is complete BS. You do not need xxx amount of backpressure for "proper perfomance." When you upgrade the exhaust you are trying to increase velocity while increasing volume at the same time. Also you are trying to keep air turbulance at a very minimum. Now to prove that backpressure is a bad thing. A set of headers that are designed a specific application will be tuned to work over a broad rpm range. These headers will do what is called scavenging. This means that as Number 1 cylinder fires the exhaust creates a pulse (or gas pressure wave) in the exhaust and will create a vacuum that will help pull the intake charge into the nimber 8 cylinder before the engine even starts on the intake stroke.
People aregue that this would mean that open pipes should be best, but when they do run open pipes they find that the car can actually be slower . This is because they use pipes that are to large to be run as an open pipe and loose velocity and the scavenging effect. I hope this helps.

Later,
Bart

soonerZ28

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">The idea that backpressure is a good thing was probably started by Flowmaster, and is complete BS
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"><img border="0" alt="[Camaro]" title="" src="graemlins/camaro.gif" />
I am also looking at exhaust systems...Does this quote mean that Flowmasters are more restrictive than others...

I need something not as loud as a Loudmouth <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> but not quiet while also getting some HP gains... <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />
A little feedback <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

ratio411

Flowmasters are very restrictive.
Needing backpressure is a myth.
If you needed backpressure to make power, folks wouldn't run open headers when racing.
Good luck
Dave

ChrisG

I think I understand what your saying. So do you think my exhaust is ok the way it is. It has the 3 inch intermediate pipe and then the 2 1/2 where it y's back to the duals.

Thanks for the replies.

BYBYC5

Chris, your fine just replace that "resonator" with a borla XR-1 and youll be alot happier <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

ChrisG

Cool, ill look into it
thanks kevin