Choice of scilencer?

Doing stuff with air...

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Mouse
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Choice of scilencer?

Post by Mouse » Mon Mar 15, 2010 6:01 pm

Do diesels need more or less silencing than petrol engines?

I have a pair of 'shorties' I used to use on a XS250 until the police stopped me and suggested I change them, but after looking at a lot of diesel bikes many don't appear to have much in the way of silencers compared to the original engines / exhaust them I'm wondering if they will do.
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Re: Choice of scilencer?

Post by Sphere » Mon Mar 15, 2010 6:56 pm

This is worrying me as well. According to what I hear at Nanko's, the air cooled diesels sure produce their share of noise. But even with stuffed exhaust the knock will still be significant. I will try to secure a dB meter, and report back if I get readings.

In Holland noise regulations depend on engine size and year of first registration.
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Re: Choice of scilencer?

Post by andrewaust » Tue Mar 16, 2010 4:09 am

The less restrictive a diesel exhaust is the better, the reason for back pressure on a petrol engine is to stop some of the fuel/air charge from escaping the savaging processes when the inlet and exhaust valve is open.

Diesels are a totally different state of affairs as only an air charge is drawn into the cylinder and the valve timing is usually very different to a petrol engine meaning less chances of the air charge escaping through the exhaust valve.

I'm running a straight through pipe on my Enfield, it's the long muffler which isn't all that loud and allows the engine to breath well.


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Re: Choice of scilencer?

Post by Nanko » Tue Mar 16, 2010 7:29 am

Mouse wrote:Do diesels need more or less silencing than petrol engines?
Less....
Compared to the dieselbike my BSA B33 produces a lot more noise with the same (absorption)silencer
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Re: Choice of scilencer?

Post by Dan J » Tue Mar 16, 2010 9:05 am

You also don't want anything that will get bunged up with soot. I seem to recall although my Enfield has a "silencer" it has no baffles in it for that very reason. It's no more noisy than any of the other diesel bikes I've seen and certainly not at levels that would attract bored Policemen...
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Re: Choice of scilencer?

Post by Sphere » Tue Mar 16, 2010 9:06 am

I think I will take a chance and fit the short silencer for the test run. Mainly because the long one I had is badly rusted. :mrgreen:
'92 Enfield + Hatz 1B40: street legal, weld up stainless exhaust, check engine rpm and change final drive sprocket.

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Re: Choice of scilencer?

Post by buckles » Tue Mar 16, 2010 8:01 pm

Hi mouse, my daihatsu is fitted with just under a metre of straight pipe no baffles or owt, its not too noisy. I did think throughout the build that it was going to be too loud, you just associate diesel with noise i know i did.

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