[jason8225]

I don't have any intentions of buying this, but what does everyone think of this:

*link removed until auction is over in case somebody wants to bid - this way nobody is at a disadvantage over the find, it's on ebay in case you didn't guess*

 

[pimpin90GL]

the high flow cat will hurt you off the line, but give you a bit more power up top

 

[sixfofalcon]

You need backpressure for low-end grunt ("off the line.") Take two identical cars, make one straight pipe exhaust (no backpressure) and leave the other one stock. Now race them. The stocker will pull ahead off the line, but the straight pipe vehicle will pull ahead when you start building RPMs. Depending on the characteristics of the car and what your goals are, either one can be desirable. If your engine revs out to 7500rpm or higher, and you are running a long, high-speed race, you'd probably want something with less restriction than the stock system. If your engine never sees high-rpm situations, and you are running a short track or racing light-to-light in the city, you might actually benefit from stock restriction. Paul Nimz left the restrictive stock exhaust tips on his exhaust (they taper to like 1-7/8" at one point) and he runs one of the fastest 1/4miles of any n/a V8SHO.

 

[jason8225]

here's the link to it now that the auction is over, so you guys can see it:

http://cgi.ebay.com/ebaymotors/ws/eBayISAP...item=2447520124

 

[mikehawk]

http://www.magnaflow.com/05news/magazine/05sportc.htm

I thought this article from magnaflow explained the whole myth about back pressure. Back pressure is bad no matter what. What you really want is exhaust velocity to increase scavenging in the cynlinders. The way you get velocity is by using (somewhat) small pipe diameters with little to no restrictions. That way you don't lose low end torque. People often confuse relieving back pressure via bigger pipes with losing velocity through bigger pipes. You lose low-end torque with big pipes because the gas expands and slows down.


When I got my catback done, it didn't feel like I lost any torque. And I can still get my torque-less wonder duratec chirp off the line. But, I haven't been to the track to test it...yet.