Melted my Cat! - Hyundai Performance Forums

SpeeDemoN · 02-16-2003, 03:06 PM

Well for the past 2.5 months I have been driving around with my OBX Header and 2.5" hiflow cat. I was very happy with it until earlier last week when I noticed a strange rattle underneath the car at low rpm. I kind of pin pointed it to my cat. So I took it back to the shop that originally installed the header/cat and said that I think something had come lose. So they checked it out, and it turns out that the front of my cat had melted after only 2.5 months. They replaced it with a different brand cat, but they think the same thing will happen to the new one. The exhaust guy thinks there is something wrong with my engine, ie... running to rich, backfired or something. My car runs fine... idles fine... never have had a CEL. Anyway I am taking the car to the dealer next weekend to get them to do diagnostics checks and see if they can find the cause. My car only has 67000 km on it as well. Has anyone else experienced this? Anyone have any suggestions on what the problems could be?

bretton · 02-16-2003, 06:00 PM

Hi SpeeDemon,

Something doesn't sound right. Cat's need to get pretty hit before they melt and fuse the matix inside, and this is usually something is more likely to happen to a turbo car than N/A.

Two things come to mind..
1. Are you running any kind of heat wrap tape on the extractors? This will keep the heat in the exhaust gas and can lead to Cat's dying, however you would have to be flogging your car pretty hard for quite a while for this to happen.

2. Do you run any kind of octane booster in your fuel? I have heard that these can lead to cat's dying, as they generate much higher exhaust gas temperatures.

Cheers

Bretton
www.PerformanceStylingCentre.com.au

SpeeDemoN · 02-16-2003, 08:19 PM

No heat wrap... even though I was considering it. And no octane booster. The exhaust guy said that the problem wasn't caused by the cat's location after the header. He said the distance was fine. Hmmm... He also said the cat most likely wasn't faulty either.

BV1 · 02-17-2003, 01:54 AM

I have the same setup and the same symptoms. Change the cat it went away. Guess its normal...

-Steve

SpeeDemoN · 02-17-2003, 10:45 AM

you changed the cat and then that one didn't melt? Do you think that its the header then? Is my cat maybe too close to the header?

91cavgt · 02-17-2003, 06:21 PM

Having a cat close to the outlet of the header does not adversly effect it's lifespan. One thing that everyone has to keep in mind is that our cars are designed form the factory to run EXTREMELY rich at high rpms. When I dynoed my 2002 Accent, it was at a nice 13:1 air/fuel ratio at 5,000 rpms, but by 5,300 rpms it was running 11:1 air/fuel ratio!! Then by 6,000 rpms it was runnning 10:1 air/fuel ratio!!!! The extra fuel in you exhaust heats up your cat to temps WAY above what it normally experiances. However, this alone typicly will not cause a cat to go bad. I've put 300 track miles(i.e. constant high rpms) on my car and it has not had any side effects as of yet.

However, it could also be because of your mods. IF(I don't know exactly what your mods are) you have an IAT(intake air temp) sensor mod and/or relocation then your car will run richer than normal. A faulty fuel pressure regulator(on the older cars) will also make a car run richer. If I were you, I'd look at differant things that might be causing your car to run on the rich side at lower rpms.

SpeeDemoN · 02-18-2003, 02:02 AM

my mods are AEM CAI, obx 421 header, 2.5" hiflow cat, 2.5" press bent custom exhaust and 2.5" bomb muffler. Hmmm what are the best ways for getting your engine to run less rich? Will the dealer's diagnostics show that my car is running rich?

Dragonsys · 02-18-2003, 09:57 AM

I had the same problem on one of my older cars, it was cuased by running too rich. The cat get fouled and clogged, then it just over heats and melts. Check your O2 sensors and make sure they are still good.

Voiddweller · 02-18-2003, 10:14 AM

Probably not as it is normal for them to run that way. You can get a SAFC or use a laptop with the ODBII software or some other for of a/f monitoring/adjusting hardware or software.

SpeeDemoN · 02-18-2003, 10:57 AM

So there is no direct way to check and say... "yup she's running rich".

hmmm SAFC is so expensive. Should I remove the cat all together until I have to pass emissions testing, and then by a cat just for the test?

if my car is running really rich, will this effect my emissions?