Cleaning a Griff500 catalytic converter

[lancelin]

Hi Folks, my Griff500 is coming up for an MOT and I’m concerned the emissions will fail. The Wideband lambda sensor is covered in black carbon deposits and I suspect the car may have been running rich for a while when there was a problem with the fuelling. There are also small deposits of black carbon on the paint at the rear of the car near the exhaust pipes. I think the system could do with a complete clean.

I’m pondering removing the y section with the cat and giving it a good clean. There are some petrol cleaning additives but I suspect they are not that effective. Has anyone else done this and what products will clean the cat. Apparently paint thinners will work or is there something else more suitable. Cheers

[blitzracing]

You can get catalyst cleaning liquid to add to your fuel. The basic game is to get some extra heating in the catalyst to burn off the excess carbon, so you combine the fuel additive with a good Italian tune type thrashing to get everything nice and hot and the carbon will disappear. I would not bother messing around with trying to clean it cold with any solvents.

[ridds]

"Cleaners" are a waste of time.

Sounds like you've fixed the fueling issue, you now need to get the whole system hot and run at high engine speed and load to burn off the carbon.

If the cat isn't poisoned it'll work fine. Just make sure you get the cat nice and hot before the MoT and get it tested as soon as you arrive.

Petrol emissions tests don't look for Particulates (yet) they look for Air Fuel Ratio, CO and O2 levels. This is all combustion and chemical byproducts from within the combustion chamber and catalyst.

Limits for a Griff are quite wide so I'm sure you'll be OK.

[GreenV8S]

I'm skeptical that any of the solvent/soap based cleaners will do any good and I think there's a very high risk they will simply poison the cat. I'm sure that the vast majority of people trying these things out will be applying them to cats which are already screwed so hardly anyone would notice if they actually make things worse. Lambda sensors are similarly notoriously fussy about contamination andI wouldn't bother trying to clean them.

[GTRene]

I use a fuel pressure thing on mine, instead of say the 5.2-6 pressure I set it on 3.5 max, so it runs just and they can drive it slowly in the garage for that sniffelthing in the exhaust, it then 'just' passes.

So a adjustable pressure valve could be a handy thing.

I do not have a TVR but a V8 which does not have the original things on it, and even with 4 new race kats on it, I still need it that way and a friendly tester .

[B'stard Child]

I cleaned some cats out with hot water and washing powder (good soak and then rinsed)

Not sure I'd try that with ceramic ones but it worked with the metalic honeycomb type

[GTRene]

B'stard Child said:

I cleaned some cats out with hot water and washing powder (good soak and then rinsed)

Not sure I'd try that with ceramic ones but it worked with the metalic honeycomb type

I also cleaned some cats out about 20 years ago, from a Nissan Sunny GTI-R (you know as Pulsar there)

but I used different tools, I used a big pipe and a hammer and cleaned all black iron rubbish out, after that the car sounded more rally GTI-R with some pufs and small bangs when going of throttle, and ow, was also faster :-) by the first puff/bang out the exhaust some carbon/blackish dust came out I saw in the mirror hahah, then no more, the car runs way better after that, but not for all cars good for TUV, but the Nissan still came through back then :-)

[lancelin]

Thanks everyone for replying. If only there was a relatively cheap analyser one could put up the exhaust to check pre MOT. I’ll give it a good blast today and check the AFR again. Fingers crossed. Cheers

[Jon39]

We do wonder how sophisticated the testing really is.
One of my cars (now only on garden rubbish to the dump duties) is a 1995 repmobile.
Some of the emissions figures are better now than 20 years ago. How can that be possible?
You can sometimes see a slight worsening of figures though, if the car was not given a hot run immediately before the test.

If you know it was OK last year, I would not worry. Trying to save you work.

Should it fail, just tell me to keep quiet next time. -

Edited by Jon39 on Sunday 8th January 15:03

[lancelin]

I’ll know on Wednesday. It’s a black art this cat stuff. I suspected the cat might be bad but it looks ok after inspection BUT I do get a rotten egg smell if I give it a real blast for a wile then the smell goes away after a sensible cruise. Perhaps this is expected?