[hayasa]

Anyone have any data about hp/tq gains on an otherwise stock exhaust when a catted bellmouth downpipe is dropped in? Looking for better efficiency than the 90degree wg exhaust route. I was planning on Cobb's, but don't know it it is worth it if you keep the rest of the exhaust stock. Additionally, with a UTEC or reflash, how much more hp do you all think could be squeaked out?

[hayasa]

No responses. I guess there are very few people who have done this; going cat-less seems to be much more common, even if you keep the stock exhaust. Just sending out the beacon one more time for anyone to chime in...

[mindchatter]

Hayasa - as you stated, I think the problem is most owners are running catless. I am about to install a catted PDE downpipe, and was told the cat will reduce power output by 5 or so HP, not much more. Apparently the race cats are not a terrible hindrance in terms of flow...granted, a race pipe will give better gains, but nothing Earth shattering IMO.

I'll have the catted DP run to a catless midpipe and finished off with the STi sport muffler. Should be good for 20 or so horse at the wheels, which is maybe 10-15 off what I'd gain with a catless straight pipe setup. (but I won't set off car alarms, either).

Stu

[Genya]

I have a cat, but got a 3" catted midpipe, didnt keep one in the downpipe. Seems to run strong, but not exactly what you are looking for. Any reason you want the cat in the DP?


Jason

[hayasa]

Why keep the cat? Legality (big a$$ fines), ethics (pro-environment), sound (hate fart-can sound), big nasty exhaust stink, less chance of boost creep, and I don't want problems every 2 years when I get my emissions tested. If you are asking why the dp as opposed to the midpipe, then I guess I should rephrase the question as "anyone just have a bellmouth dp with high-flow cat in dp or midpipe, and have a stock cat back?"

With the catted midpipe and catless dp, are you throwing any CELs?

[SUBINAM1110]

here is what i have , stock downpipe with cat of course, midpipe with no cat, blitz nur spec touring
no cels great gains for stock downpipe..also running cobb stage 1 93 and 91 as well. nice and clean
sman

[staticx313]

Dont forget... it isnt legal to modify the cats... so putting in a highflow cat is no less illegal then going straight pipes (in most states from what im told). So the only reasons I can see is for the environment and smell (although I think it would still smell with just one high flow cat). as for sound... i think they sound great catless. But thats very opinionated as well. Good luck!

Robert~

[SUBINAM1110]

ehem we would never do anything against the rules
and my name is jimmy hoffa and i live in new york state
and my wife is sharon soto yea thats it thats the ticket
jimbo

[trevor456]

the Sti has a cat in the stock downpipe?

[mindchatter]

Just got my catted PDE d/p and XX Tuning headers installed. Still running the stock midpipe and catback. Have done a few late night runs WOT in 4th thru 6th at temps of 50-60 with low humidity. Yes, my boost is creeping ever so slightly, as my Defi control unit says that my peak boost is a hair under 1.1 bar, and I reset the control unit just prior to the install. Highest boost recorded during the Winter months (when I was stock) was a smidge over 1 bar. The sound is DAMN close to stock, which I'm very pleased with. The plan right now is to keep the stock midpipe (to keep the exhaust note volume at an acceptable level for me) and I have an STi Sport Muffler en route. And I have a cat in the d/p and will keep the cat/resonator in the midpipe for noise 1st and emissions 2nd. I'd rather leave 10-15hp on the table and have my car sound stock.

Stu