Apologies if this is a repost, I coudn't find much in a search as "stock" pulls up pretty much everything.

As the title says, anyone making significant power on the OEM 2.5" cat? What's your set-up and tune like? is there a known cut off point/ ceiling for hp/tq with the stock cat?

Thanks

 

hmm , I traped 109 mph with the stock DP/CAT/CatBack but no dyno #'s

 

I might be able to provide some numbers like Matt, but I am not on a quest to make the most hp with the stock cat or anything. I'm just trying to go as fast as I can without voiding the warranty and without being illegal. This is my current set of mods:

S-AFC
3" Cat-Back
Hallman Pro MBC
JDM MR BOV

With just the S-AFC, I did the 12.83@106.3 in my sig...
Now with the Exhaust/MBC/BOV, I _expect_ to trap 110 on 93oct, but I won't know until this Friday. I also won't know my exact same whp until I hit the dyno in late July, but I ran almost the exact mph in the 1/8th last week as another MR who went with me, and he just dyno'd 297whp on Saturday. We also did a 3rd gear pull from 30-80 while side by side, and it was dead even with me pulling ahead ever so slightly, so one would assume that I am right around 300whp.

With cams, obviously, I could get another 20-30whp, but I don't plan on that or cam gears. The only other mods I plan to sneak in undetected are a Walbro 255 and some 680 or 720cc injectors. With these 2, I can do some serious tuning with the S-AFC without them being detected/noticed/seen.

 

Here are all my mods...

Helix Intake
Helix 3" DP
RNR Ver2 3" Catback
Hallman MBC set @ 21psi
Walbro Fuel Pump
ACT Clutch with Fidanza Flywheel
with Stock Cat I dynoed ~270whp and after DynoFlash still with Stock Cat see below...

 

Just get rid of it.

 

Thanks for the replys! It's an elusive bit of information because removing the cat is one of the easiest and least expensive ways to make your car go faster. It's obviously rare to see built cars with a stock cat.

My rules are simple: stock/ish turbo, stock ECU and cat. Every thing else is open season. With alky and a trick tune I'd love to see what's possible.

All EVO and too legit!

 

If keeping the cat isn't an option, perhaps a high flow cat is up your alley.

GHL Motorsports will sell any custom pieces of exhaust including the cat. Cantact me if you'd like more info.

 

See that's the the thing. Even the Works cats have trouble passing smog. With cams, forget it. There's a reason the OEM cats are more expensive than the aftermarket hi-flo cats, unless I'm mistaken I've heard 7-800$!!.

 

Take THAT POS off ya car!

 

IIRC, the reason is the high flow cats need more heat to do the job. Also it all depends on how many cells it is too.

As for price, the reason why OEM is so expensive, is because it's OEM

 

One of the reasons I got a high flow cat is to keep my stocker in good shape come smog time. The extra performance is also an added bonus too.

I've failed smog twice in my DSMs due to old high flow cats. They don't seem to last too long on boosted cars perhaps. The stock cats weigh a lot more, so I'm pretty sure its' cell count is more dense.

 

389whp / 420wtq

I still have my stock cat-back exhaust on the car... ^.^