Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Catalytic converter removal

Not sure why there are Cats on the M3W in the first place, other than US spec models needing to meet The Republic of California's regulations for import, so I'm taking the plunge and removing mine. Fairly quick job with a rubber mallet and a long flat screw driver. I drove the screw driver blade all around the outer edge of the honeycomb material until if felt loose within the chamber. From there, it is a simple, but slightly tedious job of fishing the honey comb plug out. A few more minutes of scraping the inside wall free of left over bits, and bobs your uncle.

I'm at work today, so I'll have to report back tomorrow how it sounds and feels back on the car. I'm hoping for a gain of a more horses and at least a few decibels. Fingers crossed

A cat is required for European homologation on all cars and bikes.

This should be interesting ... I don't think you'll see much in the way of an HP increase, I don't the cats are that restrictive. Might be a slight TQ decrease. As a rule of thumb, Harley's like a straight pipe with a 1 7/8" ID with a length of 42-44", for the street. You need a little restriction or TQ fall off the map. Actually, given piston diameter and stroke, a (single) Harley cylinder is very similar to a (single) SB chevy cylinder. The S&S has a bit more displacement and the M3W pipes are definitely longer ... did you check what the ID of the pipes is ? From the pictures, the pipes look 'chambered'. S$S designed the exhaust, the mufflers are basically straight through 'glasspacks'. It's designed for max performance, as is. I think S&S R&D rewrote the book ... unless they share some of their secrets, it's going to be trial and error.
Got a dyno handy ?

Yeah, I'm not expecting too much in HP gain if any, and I definitely hope to not see any decrease in HP or torque. My feeling is, yes the restriction, at lease while still new, isn't much at all, and because of this I don't see much if any back pressure created by the 3" long cat (there is only half the length of medium of the cat chamber with in it).
If anything, I'm hoping for a bit more sound out the tail pipe with out having to modifying the muffler.
I don't believe there is any chambering with in the pipe, i think what you are seeing inside are welds, otherwise it's smooth in there. The ID at the end of the cat chamber is 2.25" and from the header from the engine back to the beginning of the cat chamber appears to be darn close to 1 7/8" like you mentioned. The rest of the exhaust is not with me at the moment, so I can't comment on that.
I'll get it back on in the morning when I get home from work and go for a spin and see what I've got.

Have you tried it?

You'll have to speak up. He's deaf now. HAVE YOU TRIED IT?

Great that you are trying it, but I suspect it will be a lot of work for nothing. When I had my old 260bhp Caterham, I removed the rather large Cat, and replaced it with a section of straight through pipe, and have to say, that apart from looking much better, there was no discernable change in exhasut note or noise, nor did I notice any HP gain in day to day driving.

I probably won't bother, I quite like the volume and quality of the exhaust noise just as it is. That's at least one thing I'm happy with!

Haha, still at work! (Firefighter on 24/48 shifts). I'll get them on there this morning when I get home.

Good work chap - really looking forward to hearing about the results. I actually think this WILL make a difference, but perhaps only when the horribly restrictive baffles are removed from the exhausts (or the Sport/Semi-Sport pipes are fitted, when the factory finally get round to releasing them again). Sports Cats on performance cars are huge and need a big surface area to work - both in terms of ceramic media and cross-sectional area. I had a 'sports 200cell' cat on my Spider (2 litre)and it was too restrictive overall, despite being way bigger than the M3W cats. But as we need them for the MoT test, I will be having a cat-replacement pipe made up for each side I think, so that it's not a one-way trip.

The 2 baffles in the exhaust are really very restrictive, with about 5 small holes drilled around the outer edge of each. The straight through Sports pipes will lose these for good, the semi-sports will retain baffles, but have bigger holes in them. I read into this as meaning the noise of straight-through might be too much for some, but I am sure performance will come with it. It is well known - and already said - that Harley engines like open pipes and a non-restrictive exhaust, but the stock M3W has just the opposite in my view, likely contributing to the glowing headers as the hot gases struggle to get out.

It will be very interesting to hear what the infamous Stage-1 tune brings - if it every materialises - but I bet that majors on exhaust revisions in one form or another. But in the absence of that, my preference right now would be for a pair of decat pipes and the semi-sports exhaust tailend....