gutting the cat???

[radsonic08]

has anyone gutted there cat? I had a chevy Colorado and someone did a dyno before and after gutting the cat and gained 10hp with a stock exhaust. I know what your thinking what about the cel. well a spark fouler fixed that. then smog well mine was an 08 sold it like 2 months ago and I never had to smog it I think for 08 its like 7 years before smog. and some truckes were smogged and passed with the cat deleted. just incase others ask why we gutted the cat because there was only one company that made headers for our trucks and the fitment was aweful. some other companys started to make headers but they were all stainless steel tig welded like were driving zr1's they were 700$ and only made you 5hp over the gutted cat mod. so not too many people bought them. id rather not get a header if I can gut the cat for some free hp.
thanks in advanced

 

[Italianjoe1]

Gains will probably not be as good as the Colorado, those trucks had a horrible cat design close-coupled and they tended to melt under any abuse. These engines are much smaller and probably aren't seeing as much backpressure from the cat. There will always be a gain when removing it though. I just wouldn't get your hopes up for 10hp or anything like that. 3-5 probably on an otherwise stock 1.8L.

 

[sx sonic]

Which engine do you have? 1.8? If so go for it I suppose. You'd probably gain a decent bit.

With the 1.4 the whole downpipe is restrictive plus the cat. The replacement for it is cheap

 

[radsonic08]

yes 1.8 ok so dumb request does anyone have a header with a high flow cat with a stock muffler? how does it sound. my Colorado was no cats to a tiny muffler best time in the 1/8th was a 9.3 I went to the sonic and I feel like I have to put the pedal down just to get it to go. I don't want to straight pipe the sonic my truck basically was and was loud and I never got pulled over for 5 years probably cause its a truck. but for the sonic I want it to stay comfortable but a bit more umpth. I know cops really care about little car exhaust like Hondas acuras neons etc. when it comes to noise

 

[mitdr774]

Header, ZZP secondary cat, Magnaflow resonator, to super turbo muffler makes for one LOUD ASS car. I have been tempted to try throwing the stock cat back on to see what happens. My guess is that the gains from the header will be just about wiped out though.

 

[AustinK]

Would removing the cat add more crack/pop on deceleration from the exhaust?

 

[Italianjoe1]

Would removing the cat add more crack/pop on deceleration from the exhaust?

Yes, the converter's job is to remove unburnt fuel and that popping in the exhaust is just extra fuel lighting off outside of the engine. If your tune is setup in a way that produces over-run popping it will be much more prevalent with no cats. My cars with cat's removed have always shot flames from the exhaust on shifting and such.

 

[radsonic08]

also being an automatic the decel popping is hardly there my colorado was auto and never popped unless i reved it

 

[Quinton Exler]

That's how I run my car... the downpipe to me was pointless because where the cat mounts to the turbo has the same diameter as the aftermarket downpipe. when you get to the exit of the first cat you can just cut a little higher than where the pipe was exiting so it can accept larger pipe than stock... I gauged mine up to 3" and had a very nice difference... I don't think downpipes are worth the $ if you have a guy who is willing to get a little custom for you.

 

[Italianjoe1]

also being an automatic the decel popping is hardly there my colorado was auto and never popped unless i reved it

This is also true. There are settings you can adjust to produce more of that decel popping if you want via HP Tuners, but it's strictly for noise :banana: