Exhaust

[Don]

I am hoping that the Collective can help with a query I have relating to exhausts. My car after three years running failed the emission test for its MOT, further investigations have revealed that the Catts have died. Now my silencer that was built for me incorporates two Catalytic Converters, they are enclosed in a Stainless-Steel outer, that with them being together has caused them to overheat and it’s killed them. Because there is a very short space between the end of the bundle of snakes and the end of the car, my guy put the Catts at the top of the silencer, to get the extra space he made the gasses turn 180 degrees and go through three pipes with perforations under the Catts, then 180 degrees again and out of the back of the silencer. As the silencer was 20in/50cm long, the gasses went through three times, this in effect was a 5ft/152cm long silencer. But this was the problem, it was all contained and the heat generated was too much for the Catts.

So, I have been searching for a solution, I still have to have Catts, this restricts the space left for an effective silencer. I found the picture below on the net of a GT40 that on the face of it could solve my problem, but a few questions. First is heat management, how much more heat will this type emit. The picture shows four silencers; do I need all four, would two suffice. If anybody has got this type of set up, or have any knowledge I would be grateful for any feedback.

Don_A

 

[Bob Putnam]

Generally Cats overheat when the engine is running too rich.

 

[Walter]

Yes, heat is a problem when you have to run CATs. I have one setup which uses a total of 2 2" Magnaflow 599560910 CATs in line with 2 mufflers (and dB killers - not too loud but hot due to the loop exhaust fumes have to take - like a heater coil ). The other uses 2 HJS CATs enclosed in a muffler (somewhat cooler and louder ). Both will pass CAT emission tests no problem. Look for photographs in my log https://www.gt40s.com/threads/walters-rcr40-build.57015/page-2. - you see both versions.

I recommend using HJS (race) CATs - they are about the best you can get. In the past a Magnaflow CAT has failed on my car (after little use). Make sure you ceramic-coat your exhaust system. Most of the heat comes from the CATs (they need it to work) - high quality units should take it. It is more a question if their surrounding does. From a heat management standpoint you want the hot exhaust out of the engine bay as swiftly as possible (by convection rather than diffusion!).

 

[Don]

Thanks for the information, I will follow up on your information.

Don.