Forcedvert

What causes this.... car lost power after only a few thousand miles, they were brand new lg high flow cats, motor is 383 9.5/1,cam, headers, a&av3 base kit with 3.6 pulley. Is it the rich tune or would it happen anyway with a sc motor?





Tell me if you have lost yours, and was your tune was the problem.

JT FRC 00

I'm going to say they melted from running rich

pewter99

curiosity...its what kills all cats


seriously though

neutron82

that would be my guess... I would never run cats on a boosted motor... punch them out, reinstall, have the tune adjusted, and let it roll

realcanuk

Same thing happened to my ARH high flows, and it wasn't running rich. Cats just don't like boost.

robert miller

This is the reason every one knocks out the insides of these cats & just put back into the car. Running way to rich..

Patches

Nobody here runs cats???

reactor2

I'm running cats w/ heads,cam,intake,exhaust, and supercharger (6-7psi). I'm also running on the rich side under boost. I didn't know this was such an issue.

If I'm not throwing any codes (post cat O2s) and the other vitals (AFR, etc.) look good, should I still worry about plugged cats?

momo20

i have the high flow cat's that came with my lg long tube header's this has me curious as to what mine look like..and if i should maybe put my test pipes in..hmmmm

Rob Petyo

I ruined a set from spraying N20 - high flow cats on the heads / cam

Rkreigh

put some fuel on the fire, now blow really hard on it!

temps go through the roof and they melt. I knocked the centers out of a set of random flows on my LT5 95 ZR-1 with nothing more than lots of high rpm driving.

cats need a bit more fuel to keep them in a narrow range of efficiency.

it's why alot of cars run rich at WOT even though they are reaching for economy. it's to save the cats and keep them in the right operating range.

put a thermocouple before and after the cat and you'll soon find out what is killing them.

heat and flow!

PEETYZ

I melted my stock cats.... Boost and Cats are not the best combo. They melted then cracked apart and blew particles out the exhaust

madmatt9471

What were your symptoms that led you to pull them and find them looking like this?

I actually run cats, C6 ZR1 manifolds, cats, xpipe, etc. on my setup! 347 15.5 psi of B@@ST and Meth (I have always run cats, even my Kooks cats previously before the ZR1 exhaust setup)

Either way that was "HOT" to melt them

Thanks,Matt

schpenxel

My opinion, is people misunderstand this topic.

I don't believe extra fuel making it to the cats is what kills them. Take a look at a stock ZR1 tune sometime. They go extremely rich from the factory and the cats (generally) hold up fine. They command as rich as 10.5 AFR. They also run very high ignition timing. Anywhere from 5 to 13 degrees HIGHER than a STOCK LS2.

Something else to consider along this line of thinking.. cat over temp protection. What it this used for you might ask? It turns on when the cats get too hot to try to cool them down. What does it do? IT ADDS MORE FUEL! Up to about 20% more on a stock ZR1. GM implemented this to COOL the cats down. If adding more fuel were going to fry them, it sure doesn't sound very smart to implement a feature for adding more fuel to already hot cats on a vehicle they have to warranty for 100K miles. i.e. it cools them down, not the other way around.

I believe the death of cats comes from over retarded ignition timing along with extra fuel. Not because the extra fuel makes it to the cats, though. Extra fuel will slow down the flame travel speed, and delaying the ignition timing obviously delays the whole combustion process. Combine these two things and you create conditions where a lot more heat is going out the exhaust ports which ends up right on the cats.

Ever seen headers glow red at idle? Lower your ignition timing at idle sometime and you probably will...

Here's a pretty good article on flame travel speed, ignition timing, AFR, etc.
http://www.innovatemotorsports.com/resources/rich.php

Of course, there's a point where power wise the cats are just going to get too hot no matter what, which ends in them melting.. but the factory ZR1 type ones should at least last up to ZR1 power levels and a little more.

BLOWNBLUEZ06

heat and pressure

A lot of the problem that I see is people running what they call a "conservative" tune and that tune having ridiculously retartded timing. When that happens, you end up with an incomplete burn in the chamber, burning fuel in the exhaust and running your EGT's too high. Run the engine rich as hell and then add a point of resistance in the exhaust flow to capture all that heat and you end up with a runaway-freight-train effect, like you have here.

BLOWNBLUEZ06

schpenxel, I might should've scrolled down and read your reply before mine since we seem to somewhat agree, but I presented mine a little differently, so I'll leave it.

schpenxel

I was glad to see you said pretty much the same thing. The article by the Innovate engineer I thought was pretty good too

Forcedvert

I believe the last couple of answers, simply because the tune was supposed to be "conservitive", if some of you may recall this car has been tuned via email and data logging. This was all done as a temporary solution until the tuner my mechanic likes is in Florida. Fast forward... to, car fouling plugs, running like crap with no *****! Car was strong when first done, then I took out trans so I had to get that installed so it missed the first chance at the dyno tune, (bad timing and bad planning). I have been trying to get the cats pulled for some time because that was the only thing that I could figure would change to make car run this bad. Cats are cleaned out and back in car, plugs and oil getting changed and a slightly less conservitive tune is being loaded, car will be on dyno in October. I will share this info with mechanic and tuner but hopefully tuner already knows it.

Thanks for you help as usual, you guys know your stuff.

Forcedvert

I've been trying to figure out for months why my car went from pulling like crazy to running like crap with no tune change(all new motor and trans) first I thought it was the heat of summer but it kept getting worse, I don't have a local tuner as you may recall from other posts. The answers from blown blue and schpenxel seem right on, as I know this tune was conservitive by design.

There was no doubt about something killing major power, but car idled fine and didn't seem to have any noises at all, that's why I was hung up on tune..... but that didn't change so it made no sense to me that it was that off that much!

Hope this helps someone else

realcanuk

I don't know enough about cats to know the "why" but I can tell you my stock cats fell apart under mild boost, and then the ARH cats didn't last much longer, although at that point it was with more boost and more power. I had a similar situation where the car just seemed to not be making the power it was before. I guess a fully blocked exhaust would explain that.

Stock.....



ARH....