Exhausts - options and compromises

[highlander]

I see an unusual range of cans used on this forum and many not explicitly designed for the TRX, mostly the two-into-ones. And no one really talks about performance hits/gains with cans on this forum (that I can find), it's mostly around the carbs and cams.

My understanding of the physics is that the cans and pipes are tuned to the bike to the optimise fuel burn, balance back pressure, etc. If you use other cans you are compromising this design and adversely affecting the balance, power, etc.

So what are the real compromises of using non specific trx cans, if any? Is it simply that free-breathing, less restrictive cans are an improvement as long as you tune the carbs/dyno to suit?

Wearing my ignorance on my sleeve here, but if you don't ask you don't learn....

[Killerwhale]

I see an unusual range of cans used on this forum and many not explicitly designed for the TRX, mostly the two-into-ones. And no one really talks about performance hits/gains with cans on this forum (that I can find), it's mostly around the carbs and cams.

My understanding of the physics is that the cans and pipes are tuned to the bike to the optimise fuel burn, balance back pressure, etc. If you use other cans you are compromising this design and adversely affecting the balance, power, etc.

So what are the real compromises of using non specific trx cans, if any? Is it simply that free-breathing, less restrictive cans are an improvement as long as you tune the carbs/dyno to suit?

Wearing my ignorance on my sleeve here, but if you don't ask you don't learn....

A German bike magazine did test on 8 aftermarket cans VS standard on TRX way back, standard beat most of them so one CAN say that it is mostly to let it sound right...and also huge weightsaving.
My experience is that the standard cans work better at lower revs and aftermarket gives more power on top...standard sounds crap though!!

[trixynut]

First off, you need to differentiate between cans and a full system.

Most manufacturers make generic cans and then just tailor the link pipes to fit the specific bikes original headers.

The TRX runs a bit rich as standard so a free-flowing set of cans evens this out and adds a few BHP without any carb fiddling. Plus the TRX motor is not as 'delicate' as some others.

Its only when you get into a full system that you need to think about back-pressures and bend diameters etc, but if you are fitting a full system it must be one thats been designed for the TRX anyway (otherwise it wouldnt fit!) and taken these maters intoconsideration, like an Akrapovic, Over or Renegade one.

[highlander]

I meant cans ... ok so as long as I get a good fitting can I am not likely to do something horrible to the performance. Even chopping for aesthestics isn't frowned upon. Certainly HP-bang for buck it looks like FCRs are a much better deal. I would not be looking for top end but fattening up mid-low range torque (even on a grunty big twin) and a can isn't normally the best the way to do that!

Bottom line is I can do pretty much what I want with cans for the looks/sound that I want.

What happened to Renegade, I found a couple of links to their site but they all seem dead, are they RIP?

Akrapovic don't list TRX even in their discontinued lines, just have TDM900 cans which should work if I can confirm link pipe diameter fits. Claim a hefty torque increase over 4000rpm but I suspect that is optimistic at best.

That leaves OVER in Germany for downpipes/full system

[Killerwhale]

I meant cans ... ok so as long as I get a good fitting can I am not likely to do something horrible to the performance. Even chopping for aesthestics isn't frowned upon. Certainly HP-bang for buck it looks like FCRs are a much better deal. I would not be looking for top end but fattening up mid-low range torque (even on a grunty big twin) and a can isn't normally the best the way to do that!

Bottom line is I can do pretty much what I want with cans for the looks/sound that I want.

What happened to Renegade, I found a couple of links to their site but they all seem dead, are they RIP?

Akrapovic don't list TRX even in their discontinued lines, just have TDM900 cans which should work if I can confirm link pipe diameter fits. Claim a hefty torque increase over 4000rpm but I suspect that is optimistic at best.

That leaves OVER in Germany for downpipes/full system

You also have MAB 2-1-2 system, i´ve tried Akra 2-1, Over cheat system (stainless instead of titanium) and MAB. The MAB is absolutely best in low/mid grunt. If going flatslides those who have tested both thinks the Mikuni TDMR´s are better for low/mid grunt, also have choke.

[Kayla]

I had my standard system modified to 2-1 and it made no appreciable difference (bum dyno) but I did chop a massive amount of weight off the bike by doing it It was well worth the £70 I paid, plus it meant I only had to buy one generic 50mm bore can

[Mincehead]

At the moment I have stock headers / front pipe assembly with some 300 mm long carbon race cans on custom link pipes. Even before the FRC`s were fitted the bike ran fine and dandy, TRX`s are not particularly `touchy` about exhaust systems unless you are after those elusive extra ponies that can be liberated with a tuned and tapered system.

[gregs656]

I bought a very cheap set of modified standard cans. Chopped down and gutted, for I think 15 quid on ebay.

They make noise, and are quite a lot lighter than the stock ones. I don't notice any substantive difference in performance, I just prefer them.

[highlander]

OK, so any "more open" exhaust that fits the link pipe will be OK and not kill performance.

I am thinking mainly for looks & sound here without kneecapping (or improving) the performance - any twin set designed for a 750cc to 1000cc bike that fits should be fine.

Thanks for responses.