If I can pick some brains...
How much of the power improvement from the exhaust is due to the chambers, and how much due to the cans?
I have a set of race cans I wanna put on, but standard chambers still. Just wondering what I can expect..
MC 21R with PoshFirm derestrictor
I have
K&N Pod filters, Race cans,HRC jet kit to add...
(plus the SP forks Off ebay last night!)

Also.. Pre-mix or not? my oil pump has the 'leak into the gearbox', and what with the jet kit I'm wondering if it's worth changing..


cheers for any help

Chris

Matt is obviously the expert here, but as my understanding goes, the chambers determine the "shape" of the power delivery ( in conjunction with the porting) and such things as how steep the cut off of power is.

The cans determine the total amount of power available, since to silence the noises for road use means stifling gas flow for the most part. Straight through race cans don't have much slowing effect, but the length and bore size do have a power effect I believe.

Saying this, chambers will obviously affect power since a bad shape will work against the power pulses and end up stuffing burnt exhaust gases back into the cylinder. The best shape will work with the power pulses and scavenge properly at the same revs the ports operate at. With power valves you get a better spread of power, and having these correctly adjusted will help too.

The shape of both cones of the expansion chamber is critical to the way the power is delivered. As is the length between them - hence equal length pipes on a V means one exhaust looks longer.

I think the colour is quite important too.

It's all very complicated really...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

A little contribution about cans...

I've got about 4 different types of can for the Abbey made spannies on the Yam twin. on the dyno, the can on the end of the spannies made no difference at all to anything except noise.

I tried similar runs but using different chambers and agan - no measurable difference.

All the cans vary in length, internal bore size of the perforated tubing and the exit hole.

Draw your own conclusions.


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These aren't the droids you're looking for.

Were they all straight through?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Ohhhh yes-sir !
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These aren't the droids you're looking for.

Interesting. So the only thing that changed was the noise level? Don't suppose any of them were road legal then?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Pertty much so - none carry a BS AU stamp naturally and all would draw unwanted attention at any engine speed other than idle or almost stalled out.

I found the info strange hence why I popped a reply in - maybe some good info would come out ?


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These aren't the droids you're looking for.

Wow! Does the MAN bother you guys for noisy exhaust across the ocean? I know alot of cops over here who ride( not to mention lawyers, the sheriff, and the DA ) with drag pipes and skull caps! if they bothered us for noise, you guys could hear the whining over there. It's bad enough already
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To much HP is barely adequate!

Oh yes. We have small towns, twisty roads and old ladies. Add a race pipe to the mix and there's trouble.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Oh yeah - for sure.



It's down to common sense though - knowing the shift patters for the politzi helps and also time of day ie... if you got out at 10.30pm with a set of spannies, pod filters, lotsa revs etc.. you will get stopped and trouble comes your way.

Same bike but mid day or early morning and you tend to be ok. How aggressive you ride also makes a big difference but we all know this stuff already.

Just get out there and enjoy !
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These aren't the droids you're looking for.