Just FYI

For those running boost with stock cats, Danger.

After 5,000miles, the stock cats blew into chunks inside causing the exhaust to clog. The pressure had to go somewhere. It resulted in a lifted head only. It could have been much worse. We cut the cats and welded pipe through them and installed ARP bolts and new gaskets. Everthing is well now.

If you have stock cats, PLEASE replace them or modify accordingly. They can not take the heat and pressure. If you have gotten by longer than this, you are driving a time bomb.
PEACE,
Shane

 

Shane do you think us guys using high flow cats from LG or other header manufacturers are ok?

Glad to hear the damage wasnt too extensive for you.

 

I am not intelligent on how the internals are made. Sorry, I can't answer that but I assume that they had major heat potential in the design of aftermarket performance cats. Maybe someone else can chime in on that.

 

Well that answered my Question I just bought an ATI Procharger HO Intercooled with it I bought an offroad pipe (no cats) I guess that was a good move??
My question was do I need the offroad pipe? It was a bit pricey
450.00$

 

no but its sort of winky winky cat mod for people. I can't tell you that I do it for people. I can tell you that you if you were to do it, You cut at the factory weld and cut a section of 2.5" pipe (5$ at the local exhaust place)
to fit nicely inside. Weld up the new pipe so there is no leaks. Grind welds so that there is optimum flow. Weld factory weld back. Tune out rear 02s.
That is how to do it if I was to (wink wink) do it for someone.
Cheers!

 

My Dynatech Headers are great... but the highflow cats blew out on them as well.
Jeremy

 

I have to be honest... If you're going to spend 5k+ for a supercharger (and more if you have it professionally installed), why would you then turn around and skimp on the exhaust? The headers and pipes cost a whole $1600.

Not only that, but what since does it make to improve the breathing on the front side if you're not also going to increase the breathing on the back side?

A bit of a silly rant, I guess... But in the over all scheme of performance corvette mods, it just seems to me to be a cheap corner to cut.

Also, just to throw a vote in there... There isn't any real gain in going with the non-catted over performance catted pipes. There is a lot more smog and smell with the non-catted pipes, though. Do your fellow travellers a favour and choose the cats whenever you can.

 

problem is zeno, the cats blow out over time... several of us have experienced this... It can cause problems, including blown head gaskets...
Jeremy

 

I notice no smell difference and I wanted a quiet exhaust. I am putting down over 500 and that was my goal. There is a gain to be had but that is not what is important. What is important is that my motor will not nuke because of a part that can be improved or removed. I'm not a cheap ***. You should see what else is in my garage. I can build my car however I please. I posted as a FYI for anyone that has cats and FI. It seems that the person that just posted before this had a problem with aftermarket cats. If this was not helpful for you or has nothing to do with your application, I recommend that you **** OF BIG NOSE!

 

Im picking my vette back up tomorrow from having a procharger d1 put in, and previously had full exhaust done to it with no cats(dynatech lt's with magnaflow 3" catback). during the time of just exhaust/intake my exhaust didnt smell, like people make to believe catless cars stink. its the people in catless cars using cheap gas is what stinks.

Where are you finding a full set of LT's with exhaust for 1600? Dont forget to include the price of midpipes bout another 500-700 bucks.

 

Wow.. Ok, well first off I wasn't trying to cause an argument... just putting in my $.02 on the cats issue.

For the record, I used the stock cat-back and did not gain a lot of noise with the headers.. almost none with normal driving.

And your right, how you build your car is your prerogative, I was simply stating that it's a cheap corner to cut...

And about the smell... there most certainly is one. If you cam, it gets even worse. YOU may not smell it because it's behind you, but others do. And if the wind is at your back and your windows are open, you may as well.

I got my Kooks headers and X-pipe from Jeff at Total Performance. He was running a special and I got them for cheaper than that. Maryland Speed will even ship them with ceramic coating for under $1700 for the set last I checked... and that includes the catted x-pipe.

 

There are 1000s of FI vettes running around with stock cats with no issues. Some of the longevity of the cats is directly related to the tune.

Phil

 

I totally agree. I've done hundreds myself. I've seen very few.
The ones that I did see were not on stock applications..
It's certainly nothing to be concerned about for the average customer.

 

what tuning characteristics would relate to the breakdown?
Also what construction differences from stock to aftermarket cats would affect longevity?
Thanks

 

We're running stock headers and exhaust for stealth with the Vortech SQ - you can't see or hear that its not stock unless you know what the (distant) whining is.

I understand all the pros of the headers - they will be a likely addition down the road - and I understand they don't add much noise now (just had to hear some stock exhaust vs. headers w/ stock cat-back to compare).

But if the tuner is installing the SC and Headers...not to mention requisite drivetrain modifications to harness 500+ rwhp safely and you're talking about 12k+ .... not 5k + 1600...

Your error in logic is common. Many people perceive the difference between 1,000 and 3,000 to be larger than the difference between 48,000 and 50,000 when it is (obviously) the same. This principle applies here. 2 grand is 2 grand. It might not seem like a big difference on paper (or to you), but it is still a significant sum of money for the marginal utility provided by whatever the 2k is buying (for the more financially conservative of us out there).

Headers will primarily bolster the (relative) lack of torque in SC applications, but what is the point in adding torque if the first 2 gears are limited by the tires already? Shouldn't wheels/tires come first? How much does a quality set of those cost ya? Another 3k? Things are adding up fast here....

I know you didn't mean any offense - but I still don't think what you said was appropriate.

The cat blowing out thing happened to us as well, though it didn't cause any ill-effects, just smoke out of the exhaust until we could have the tuner look at it.

Why does the tune affect the longevity of the cats? What causes them to burn out like that?

 

Lets think of who is using superchargers with stock manifolds......most people in california. Last time i checked Callaway is using stock manifolds......

How do cats get ruined...????

Too much cyl pressures not allowing exhaust gas to flow through the cats fast enough......most likely not.

OR.....

Too much fuel in the exhaust....this will cause the cats to get too hot which makes them melt....therefore causing them not to allow air to pass through them. The answer is in the tune my friend. There are plenty of oem cars with FI that have cats in the manifold (ie Mini Cooper type S).

Or if you previously had a cam that had a huge overlap I could see that doing the same thing (basically dumping raw fuel into the exhaust)

 

interesting theory. I'll get the car back on the dyno in a week or two and post up some sheets. Thanks

 

Why take a chance???
Just get the offroad pipe and be done with it!!
You can always change it back If you need inspection or want to go back to stock! Bolts on and off!
You have a 60,000$ car or more (ZO6 ZR1)why chance it???

 

stock cats are gutted now. It is a clean pass through. I don't have a problem with running cats, I just don't want to have a meltdown because of something that really does nothing for the car in the first place. Some years ago in denver, I got sent away from emmisions check because of no cats. After installing cats and going back, Both sheets (before and after) were nearly identical. I think it is a racket. With that being said, I am not breaking the law on purpose.

Another thought on the tuning:

Tuning was done at WOT where fuel looked good.
There is a lot of tables to be addressed to really get into the fuel issue during normal driving. It could be the case that it is rich during normal driving. It would be a shame to mess with all that just to keep something from not breaking that you run better without anyways.

 

Because in California they have emission check points like DUI check points. You drive by while a 5 gas sniffs your tail pipe and tape records you license plate.