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View Full Version : An interesting EVO thread about high flow cats

EVILUTION
03-05-2008, 10:47 AM
http://forums.evolutionm.net/showthread.php?t=329753
VPT
03-05-2008, 10:59 AM
Thats just common knowledge.
Dizmm, (Old Account)
03-05-2008, 11:18 AM
So they are proving the already known "test pipe > High-Flow Cat"
EVILUTION
03-05-2008, 12:26 PM
I found it interesting that even a very high flow cat is restrictive on a stock turbo. The boost changes due to back pressure was an eye opener as well.
Dizmm, (Old Account)
03-05-2008, 12:43 PM
I found it interesting that even a very high flow cat is restrictive on a stock turbo. The boost changes due to back pressure was an eye opener as well.

Why waste a time by replacing a factory cat with a hi-flow cat unless you are required to have your car emission tested
SgtRauksauff
03-05-2008, 01:30 PM
The best exhaust for a turbocharged engine is none. However, since we can't really afford to melt and burn things behind the turbo, we've got to have a bit to move that hot gas and flame away.

I've read Maximum Boost by Corky Bell, and a few other articles here and there, one of them being from an engineer at Garrett, and this is really no suprise for me at all.

Interesting to see the graphs of it, via a real dyno, but the readouts were the same on my butt-dyno, with my Escort, and especially with my Volvo.


--sarge
EVILUTION
03-05-2008, 01:49 PM
The subject is old news..... But..... The numbers and graphs are interesting to me. I never though spool would be unaffected and yet topend would be ganked 20whp.
VPT
03-06-2008, 10:52 AM
Thats just common knowledge.
TSi_II
03-06-2008, 11:26 AM
Everyone can take off their cats, give them to me, then replace them with a testpipe from JJM or VPT. Sounds good.
EVILUTION
03-06-2008, 11:59 AM
The guy just did another test with the stock cat and lost another 15WHP. Holy shit.
03-07-2008, 09:13 PM
I can vouch for the exact same results on my car also. Last spring I had to throw my stock dp with a cat back on the car to make good on a "fix it ticket". No other changes, spool felt great, but my good did the top end suffer. lt like it ran out of power in the upper rpms. It normally only takes 1 mile to reach 160 mph in my car.. I think it took more like 2.5 miles to reach those speeds with the cat on!! I have video footage of this run actually, but it's a large file, 26 megs so I have no way to host it.
Dizmm, (Old Account)
03-07-2008, 09:20 PM
try breathing through a straw, ok....


.....now, try blowing through the straw as much as you can.


See the difference???