My cat converted.....| Grassroots Motorsports forum |

AquaHusky Reader
6/21/11 8:02 p.m.

Now, what would cause this to happen? I have been noticing the truck getting slower over time, but in the past few days, I'd drive a few miles and it would get slower and slower, to the point that it would struggle to get up to 35 MPH. Fuel filter swapped, no change. So, I thought I'd take the cat off and have a peek inside...

This is what I saw when I looked inside. I poured it out since I couldn't get a good pic of it still in the cat case.

These are a few of the bigger pieces. Dang thing had a meltdown!

Mind, this truck has 145K on the clock too and this is the factory piece. I figured age had a role in this.

BoxheadTim GRM+ Memberand SuperDork
6/21/11 8:09 p.m.

It probably started breaking apart and due to the increased back pressure the exhaust gases got hotter under load and started melting parts of the cat. I've seen a partially collapsed cat glowing red...

Capt Slow Dork
6/21/11 8:10 p.m.

I have heard that old cats are worth a quite a bit of money due to all the platinum in the matrix material.

AquaHusky Reader
6/21/11 8:25 p.m.

Well, this one got gutted as the second matrix was starting to melt as well. Hollowed out shell now, but it accelerates pretty good now.

The funny thing about this is the short ram intake sounds quieter now since I had done this.

mndsm SuperDork
6/21/11 8:47 p.m.

I expected to see a tabby holding a bible.

mad_machine GRM+ Memberand SuperDork
6/21/11 8:50 p.m.

repent!

seriously, I saw what with my father's old 300zx.. black chunks came out.. but the car still passed emissions testing with just a gutted cat

Toyman01 GRM+ Memberand SuperDork
6/21/11 8:56 p.m.

I have had two of the do that. One on the RX-7, and both of them on one of my work trucks. I can just imagine the brightly glowing color of a cat when the ceramic matrix is melting down inside it. Don't park in tall grass.

erohslc Reader
6/21/11 9:23 p.m.

I had one break apart in a Volare SW with slant6. Intermittently at cruising speed, would start to make this strange horrible 'whistling' kind of noise, and I had to floor it to keep going. Thought the tranny was going bad and slipping. Tried everything else until I discovered all the broken chunks in the cat body (light bulb over my head).

AquaHusky Reader
6/21/11 10:19 p.m.

mndsm wrote: I expected to see a tabby holding a bible.

Not holding a bible, I know... But, close enough.

alfadriver SuperDork
6/22/11 6:46 a.m.

that's usually caused by air and fuel ending up in the catalyst, unburnt.

Do you have a misfire? even a small one? If you are running hard, already, it doesn't take much to melt it, especially with pre-OBDII cars that do not have the best cat temp control + misfire detection.

iceracer Dork
6/22/11 8:09 a.m.

My nephew started losing power in his Yugo. If that is possible. Anyway, plugged cat.

alfadriver SuperDork
6/22/11 9:26 a.m.

In reply to Datsun1500:

I'm still trying to figure out how it could have been better....

DaveEstey HalfDork
6/22/11 1:04 p.m.

In reply to Datsun1500: It wouldn't even roll downhill.

AquaHusky Reader
6/22/11 1:13 p.m.

In reply to alfadriver:

I haven't felt a miss in it yet. Truck actually runs quite good. And, no ith the cat gutted, I don't smell any unburned fuel from the tail. That's hy I think it happened just from age. But, it's nice to see the different reasons this happens. I'm looking it all over to make sure it wasn't something else that caused it.

alfadriver SuperDork
6/22/11 1:37 p.m.

In reply to AquaHusky:

Age by itself won't melt a cat. It takes well over 2000F to do that kind of damage (and most cars are tuned to keep the cats below 1600-1700F all the time, under all conditions, etc). Age will do other things- sinter the coating, cover it with poison- things like that. But that doesn't generally generate that much heat.

hmm.

jrw1621 SuperDork
6/22/11 1:44 p.m.

AquaHusky wrote:

Is there an illusion here or are you missing a finger?

AquaHusky Reader
6/22/11 4:56 p.m.

In reply to alfadriver:

I figured age caused it to break up, causing the plug, in turn, causing the heat actually.

AquaHusky Reader
6/22/11 4:58 p.m.

In reply to jrw1621:

No, no illusions. I only have 4 digits on my left hand. Old injury from about 20 years ago.

iceracer Dork
6/22/11 5:09 p.m.

Datsun1500 wrote:
iceracer wrote: My nephew started losing power in his Yugo.
How did he know?

He couldn't get it up to 45 mph

alfadriver SuperDork
6/22/11 8:06 p.m.

iceracer wrote:
Datsun1500 wrote:
iceracer wrote: My nephew started losing power in his Yugo.
How did he know?
He couldn't get it up to 45 mph

THat's not a design feature?

foxtrapper SuperDork
6/23/11 5:18 a.m.

Backpressure and age won't melt a cat. You need heat for that. Excessive richness is probably the most common means of accidentally getting that heat. Between the simple combustion and the increased catalytic action, you start melting cats.

DrBoost SuperDork
6/23/11 7:40 a.m.

AquaHusky wrote:

Dude, where'd your other finger go?

pinchvalve GRM+ Memberand SuperDork
6/23/11 7:49 a.m.

AquaHusky wrote: In reply to jrw1621: No, no illusions. I only have 4 digits on my left hand. Old injury from about 20 years ago.

A college friend had a similar digit count, and every time someone asked him how he lost the finger he told a different story. Seriously, every single time. Funniest thing ever.