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"Noisy" exhausts

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Bush Tucker Man:

--- Quote from: "Bulli" ---squires has always been a biker haunt and quite often has a few hundered bikes and a police presence. I go loads and have never had any issues...
--- End quote ---



Didn't go out on bike yesterday, but might end up there this afternoon at some point (in passing)

glaggs:
2stroke and 4 stroke exhausts have slightly different jobs to do. Two strokes are much more dependant on back pressure for various reasons, but mainlt to stop the fresh charge making its way out of the exhaust ports too soon and by-passing the combustion cycle! Interestingly reading my'Four Stroke Performance Tuning' Manuel (by A. Graham Bell and published by Haynes) any back pressure will actually reduce bhp, the ideal set up being a tuned length of straight through pipe with as few bends as posible. For ultimat bhp diameter and pipe length are crucial, but back pressure will reduce power on a 4 stroke engin.

This is a simplified explanation of one of the black arts of engin tuning!

ps. I run a 1200bandit putting out 150bhp+ which I did all tuning work my self. The exhaust ia full race Akrapovic titanium system which is suprisingly quiet at every day speeds bu effing loud on full chat. I guess this is down to quality construction and it being a properly tuned system designed to release power not turn it into noise!

Range Rover Blues:
A lot of people are confusing back pressure with port velocity.  The exhaust gasses help scavenge the exhaust and if you look hard at most cylinder heads the exhaust port widens as it leaves the valve.

The flow of gasses is a very complex issue, partuclualry as it is not even a continuous flow, but pulsed.

A tuned sports pipe will almost certainly be focused on a narrow rev-band with the view to optomising the engine's performance at that speed whereas most road systems make compromises to get a fair performace over a wider band.  Driveability.

BTW anyone else noticed that performance often comes with an increase in the engine's top speed? so again the ability to breath is important.

Eeyore:
Gotta agree with above.

Also, good flow doesn't have to equal noise.

What it may indicate however, are the compromises needed to be taken to achieve that flow.

Cheers
 8)
Eeyore

Evilgoat:
What needs to be made clear is theres a difference between £700+ of tuned, professionaly built sports exhaust on a car (les son a bike but not much) which is loud because its doing its job...




And a Mahoosive backbox slapped on a 1.0 engine and the stock exhaust system. you know 1" in, 12" out. I've actually seen a standard 206 with 8 5" pipes before now.

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