odarabla

iTrader: (1)

I have a 2002 Camaro Z28 A4. My mods consist of SLP lid, baffels cut out of the air box, screen removed from the MAF, exhaust and a tune. I dynoed 306 whp. I thought I had a clogged cat so I removed them and knocked the ceramic out and reinstalled them (after removeing them I found that the cat was not clogged). Could I lose HP by doing this? The car felt like it pulled harder in the mid range and upper rpms before I gutted the cats. But it feels like it leaves harder off the line now?? If anyone knows anything about exhaust on a LS1 and can answer this for me. Please respond. Thanks

5_02ls1

iTrader: (20)

no you gained a few ponies theres a thread somwhere here this guy done back to back dyno pulls and gained 10rwhp......

boola1341

iTrader: (1)

when you gutted the cats did that trigger any engine codes. Im thinking about doing that also but there isn't a tune shop where i live for miles.

teke184

iTrader: (5)

YES it will trip the SES codes for the cats

NO it will not have any affect on the function of the car

for $100 you can install some o2 simulators on the rear sensor plugs and the SES will go away.

or tune it....in person or mail order

ChocoTaco369

Cats cause backpressure. Backpressure causes your car to feel much more powerful down low in the RPM range. You definitely gained peak rwhp, but too many people on this site confuse peak rwhp with a gain in power. For instance, I GAINED 2 tenths on my ET by opening my cutout. I ran back to back 13.60's with just a Corsa catback, but after adding an FTRA, an aluminum driveshaft and a cutout, plus running on a COOLER night, after 5 runs (2 consecutive trips to the track), I COULD NOT run better than 13.79 even though I gained MPH. I definitely gained peak power by having my cutout open, but overall, I lost power throughout the rpm range because my low end power took a serious hit. Peak rwhp is a TERRIBLE way of gauging performance, as I lost serious rwhp on average throughout my curve by opening a cutout. Gutting cats will likely have a similar effect.

What I'm trying to say is that backpressure helps a naturally aspirated engine to an extent, especially a stock one. Don't expect gutting your cats to do a thing for you performance wise. It's more of a "sound mod" than a performance mod, and probably won't help your ET much at all. If anything, you may run slower because you're not pushing nearly enough air to make the loss of backpressure worthwhile.

That's my $0.02.

5_02ls1

iTrader: (20)

choco you are so amusing.....**** im glad you are here to steer folks back in the right direction.......

your car will run better at the track without the cats.........the stock y pipe is a crimped up piece of **** anything you can do to free up flow on that bitch will net you some power.......the stock converters are restrictive as hell......im about to install a cutout behind each header to open at the track and I have a 3"x td setup
Oh wellls I guess opening those cutouts will slow me down I wont be gettin any suction from my x merge....lol.........

OP go to the track look under a few "FAST" cars and see if they are runnin cats.......By fas I mean faster than 13s

ChocoTaco369

Crimped up piece of **** or not, I ran substantially slower at the track, even in better conditions, with my cutout open due to the low end power loss. I wouldn't expect gutting the cats to help that much. I would expect a little loss in low end.

odarabla

iTrader: (1)

No, my car didn't throw any codes because I have the rear o2 sencors turned off when I had the car tuned.

odarabla

iTrader: (1)

I think this might be true because the low and mid range feel like I lost power. Although it feels like it might be makeing a little more torqe down low. I ran a friend yesterday that has a 2001 Formula with all the same mods I have except he has headers with full exhaust. I pulled about a car on him off the line but when I topped out 2nd gear he started to pull past me pretty good. He would have beat me by about 2 1/2 lengths in the 1/4. His car is running mid 12's @ 116mph on the track. So although I haven't run my car on the track yet we figure it should run low 13's high 12's.

boola1341

iTrader: (1)

my cats are getting gutted and i'm getting a tune!!

odarabla

iTrader: (1)

I did mine myself. It's really not that hard. All you need is a 1/2 drive rachet, 1/2 extention, 14mm socket and a little *** to put behind that wrench. Then the cats just pull right out. I didn't even have to take the Y-pipe lose. Once you get the cats out find a hammer and something long to stick in the cats to bust out the ceramic. Make sure to rinse them out after because you wouldn't want any of those little particals to get sucked back into your engine.

boola1341

iTrader: (1)

thanks for the info.

5_02ls1

iTrader: (20)

ok so what is the ******* point of opening up the exheaust if it slows us down???????these are 10.0;1 compression engine they love to breathe......have you had a tune?????maybe thats your problem cause an open cutout on an ls1 should make it a lil faster at the track.....never heard of a car loosin power with freer flowin exhaust......
put a stall in that thing and forget bottom end power...........

ChocoTaco369

Umm, more flow isn't always good. Why do you think stock or light bolt-on cars lose power with a FAST 90/90 setup? Why do you think stock or lightly modded cars run slower times with open headers? These are naturally aspirated cars putting out unimpressive amounts of horsepower. They NEED backpressure to a certain extent. More flow is not always a good thing. Put on a set of 1 7/8" or 2" headers on a bone stock car and see how much power you'd lose vs. a set of 1 3/4" headers. Again, some backpressure is a GOOD THING. If you had 700 rwhp or if you were running a turbo, then you don't want want any backpressure, but at the power level we're at, we need some.

Again, an open cutout seriously hurt my times. I had more mods, better conditions and I was significantly slower because of it. I've said it a million times, FLOW IS OVERRATED. More flow can hurt you if you're not set up for this.

I don't know why you're bringing up the tune argument. I didn't even have headers at the time. I had a lid, a catback and an FTRA. That's it, and I ran a lot worse with the cutout open. I couldn't come close to my lid/catback time. If you have a good catback like I have, a cutout is nothing but an invitation to running a slower time at the track. They disrupt the flow when the cap is closed and they kill your low end when the cap is open. That's just the way it is. It's a "fun mod," not a performance mod. Don't let people bragging about a 5 rwhp gain with it open mislead you. They never mention the 10 rwhp loss down low.

RoDan

back pressure is a myth, you want the least amount of back pressure you can get. what you WANT is proper exhaust scavenging. By this I mean you want the exhaust flow to pull itself out. This is accomplished with HVMC's on headers, velocity spikes and the proper merging at y's etc. Anytime you can reduce back pressure, you will gain power. That is unless you severely degrade the scavenging effect in the process.

odarabla

iTrader: (1)

I once asked myself that same question. If more flow isn't always good, than how could putting headers on a car help it make more power? The answer is what this guy above me was talking about, proper exhaust scavenging!!! I totally understand how headers and such work. My base line question is, with stock manifolds, stock y-pipe, and Magnaflow exhaust. If I gut my cats is it possible to lose hp in the power band? I really don't think the stock manifolds work that well in exhaust scavenging (but I'm really not sure). The fear that I have is actually reducing the exhaust turbulence through the voided area of the cats, causing less scavenging and losing HP through the mid range. I was not looking for opinions on this matter. What I was looking for was a professional that could explain what might be happening here. That way it doesn't happen to someone else in the future. There are a few free mods that people are doing and actually losing HP. Pulling the screen out of the MAF is one of them. I read a huge write up on this mod. About how it fools the computer into thinking it is drawing more air. This is BS. It does fool the computer but into running lean in the upper rpm range. I know this is BS because I dynode my car with and without the screen in it. It made more power with the screen. After 4500 rpm the knock sensor pulled some timing out to prevent detonation. There for losing peak HP. If anyone that has experience in anything like this, or could explain what might be happening here and would like to comment. Please do!! But please people lets try to keep the B.S. to a minimum. I am trying to get facts here!! Thanks

5_02ls1

iTrader: (20)

this argument is stupid guess i need to take my true dual longtube setup off and put a catted ypipe on so i can be faster...............


"lots of ******* sarcasm"

5_02ls1

iTrader: (20)

look ive been building/racing cars for the last 12 years....I will promise you that your not gonna lose any power by guttin your cats.....Im pretty sure choco is still in school and pays someone to work on his car.......believe who ever you want.....racers and hot rodders have been guttin cats for years.........hold a straw up to your mouth blow through it....then remove the straw breathe through your mouth....which way is easier.....the internal combustion engine is like a big air pump,,,,the easier itr breathes ibn and out the more power its gonna make.....

khaos288

iTrader: (9)

odarabla

iTrader: (1)

Calm down *****!! No one is saying that long tubes don't make more power!! All I am saying is there is a science to it.