Guys,

Got my car dyno tuned + 42# injector install at Norris Motorsports last Thursday. The power curve looks a little better, and the car has MUCH better manners since the tune, but I'm still hitting about the same peak RWHP (430 RWHP/400RWTQ) as I was before. Right now I am running 6PSI.

Because of the low power I am lead to believe that there may in fact be a restriction in my exhaust somewhere (my pulley is large enough to make 4-5PSI on many setups but it makes 6PSI on mine). I am thinking the cats are the easiest place to start. Any visible way to tell if they are clogged? Can any old exhaust shop look at the Random Tech cats and know what they are seeing? How much should I expect labor to be for a cat swap?


Has anyone else had a clogged cat problem? I only have about 20K miles on these cats, but I also had a super-rich tune and a bad O2 sensor for god knows how long, which could have easily dumped all kinds of nasty stuff into the cats. Plus, if you recall, my setup was running so poorly that cranking the car would spatter a nice pattern of black stuff all over my garage floor.

BTW, I can't say enough good things about Mike Norris. He knows his stuff and is very customer service oriented. His tune really did give my car its street manners back -- the Breathless Performance tune that was on it before continuously fired fuel trim rich codes, had a rough idle, and just made the car all-around annoying due to various other small issues. :cheers: to Norris!

 

Tony, when you get a chance to get back to Norris, unbolt the exhaust in front of the cats and dyno. If you pick up 10-12 rwhp cats are OK. If you pick up more than that then it is time for a cat change. Others should chime in with maybe a better way to check cats. Good Luck

:smash: :smash:

 

I had my cats take a dump on me at 29,000 miles (dont ask me how because I dont know) anyway, the insides were loose chunks of honeycomb metal when I saw them. Andy at A&A said we should get the aftermarket High flow cats ($120 each) compared to the factory ($700) each. On the other hand, the dealership would have replaced them under warranty... but at that killer price, and the bennys I would get from the high flows... I decided to go with those instead. :smash:

VR :cheers:

 

Thanks Rick,

That sounds like a good idea. Any ideas how much my boost should drop? I guess if I see 4-5PSI like my pulley should see, AND I get a small bump in HP, I will have isolated the problem to the cats and back... which will be miles from where I am now.

 

Cats!?!? We don't need no stinking cats!! :jester

I wouldn't be at all surprised if your cats had tanked. Running rich does some interesting things to them. I'm not sure how to tell, other than the idea above which sounded pretty good. :cheers:

 

I beleive I have a similar problem with my car. I have ordered the 3" kooks x-pipe with cats from LAPD and will have them installed and dyno'd very soon.

Here is a link to a thread that I created describing my specific problem and dyno results.
http://forums.corvetteforum.com/zerothread?id=697157

 

A bad 02 sensor could explain why your cats would be shot. Running open headers is the only way I can think of to test it. BTW, better get some earplugs first :lol: It is really really loud, you can't imagine how loud it will be.

 

Hey guys, just curious -- won't running open headers cause the rear O2 sensors to mess with the car's tuning? I know when people run open cats the rear O2s can really throw things off, but will they be OK with all the exhaust gas coming out of the headers?

 

The rear 02s have nothing to do with the tune. They are used for odbII emission purposes (to verify the cats are working). The car will run just fine without them. It will set the SES light, but it won't cause it to run any different.

 

:iagree: The installer who put on my exhaust got some bad O2 sims sent to him. There was no difference in the car running, but the SES light came on. Swapped out with good sims and light went away. Car ran the same throughout. :thumbs: