Catalytic Converter As Part of Exhaust Collector

[jrg77]

Hello,

It would seem that if the converter is minimally restrictive that it could be incorporated into the tuned length of the collector.
The second thought would be what proportion of restriction would require a change in the collector length?
Could the converter be created in similar fashion to straight through mufflers coordinated to work along the length of the header?

Thanks,
Jason

 

[magnograil]

Most catalytic converters are a honeycomb structure sitting in the exhaust flow to maximize the exposed area. Motorcycles tend to use an annular ring type but do not have to conform to the same polution requirements. Putting the converter in the header will most likely burn it up from the high temperatures. The closest one I have seen is on the Mitubishi 2.6l four used in the pick-ups, located just downstream of the collector about 4 inches. That is the first of two.

 

[bobqzzi04]

I can't comment on the effect on exhaust tuning, but the Audi A4 with turbocharged 4 cylinder has the convertor attached directly to the turbine discharge. So, with proper materials I don't think the cat would be in danger.

 

[MikeHalloran]

I'd expect the converter to damp the pressure waves that you try to manipulate with tuned pipes.

Not that you couldn't do something interesting with them, but the results may not be what you expect.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[jrg77]

I recognize that the performance would not be on par with an unrestricted collector. I am just wondering if it could be a step above the shorty style headers.

 

[NickE]

On the current subaru WRX (2.0L H-4 turbo) there is a cat in the pipe leading from the collector to the inlet of the hot side of the turbo. Cars that are running factory ECU with other non-factory parts that create a rich condition during up-shifts (atomospheric bypass valve)will tend to dump much fuel into this cat causing it to melt down, fragment, and destroy the turbo.

 

[schmidtj86]

There are many close mounted cats in production now. Usually supplimented with another, unless the engine is so clean or so small that it's not needed. If supplimented, the first cat usually has less everything and is mainly used to light the second cat quicker, but also do a small bit of work itself.
The main problem I see with the idea of putting it in a header is that the substrate requires shock and vibe insulation that takes up some of the available space, and also is easiest to do with a two-half welded assembly. That can just be a bolt on thing, rather than incorporating it.
The back pressure associated with it would have to go into the calculations for tuned length, and there may be some reflection at the interface, but honestly, I don't think many header manufacturers care much about actual performance, as long as it's better than stock (which isn't always the case). As long as people buy it, they'll sell it. I'm sure there's a few exceptions.

 

[jrg77]

That is my point. I think more people would buy headers is they could still pass emissions with them.

I know I would.

 

[NickE]

jrg77- actually the people I know that are modifing their cars tend not to care one bit about having kittys in the exaust.

also I think tha ta high flow metal substrate cat in the pipe after the headers (midpipe?) would be more effective and have longer life.

 

[jrg77]

The guys I know that put on shorty headers vs. long tubes for this very reason would differ with the guys you know.

I agree putting them after the headers would be better, except I don't think they would be close enough to the "stock" location for the inspectors. I also think they may have lost enough heat at that point to not be effective enough (purely speculation).

At any rate Mercedes Benz has the ability to put 700+ lb-ft of torque through their exhaust system. They must have some sort of solution that has some applications outside their programs...

 

[schmidtj86]

A kit that includes long tube header(s) and cat(s) and a heated O2 (or 2) could probably pass the emissions requirements, but it's expensive to take the official test for an EO#. It's also illegal to remove a functioning catalyst that is under a certain age and still functioning. That's probably why you don't see too much effort in this area.