hi all, i have a mini digger and im looking into ways in which to reduce the sound level from it. i have surrounded the engine with sound absorbing material but would like to now reduce the exhaust noise. has anybody any ideas how to do this? i was thinking of adding an old small car back box or similar on to the existing system.
Steve
I suspect that most car mufflers are going to be designed for too high a gas flow to be useful - what's the capacity and working speed of the minidigger engine?
You could probably make it whisper quiet with a bodge-it-yourself muffler. Get a bit of metal tube the same size as the existing tailpipe, drill a load of small holes in it, block the middle, wrap it in wirewool or coarse fibreglass and stick it inside a larger tube. Close the ends of the outer tube.
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absorbing
anybody any
What ever you do, expect problems with the engine or it's performance, the design of exhausts are not just for reducing noise - they cause back pressure etc that is vital for the correct running / performance or the engine.
What might work and not cause to much of a problem is to extend the final exhaust pipe (that is after the silencer) with a larger diameter pipe so as to allow the spent gases to expand somewhat before leaving the pipe - this should reduce some of the 'pulse wave' caused by the expanding gas in a uncontrolled manor IYSWIM.
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absorbing
I'd go with the muffler box idea, adding it on the end of the existing exhaust, but dont block the main pipe, let it be a straight through job. Fibreglass or pref rockwool for the deadening.
Also consider adapting the old carpeted box idea. Tronic kit used to be quietened by fitting a carpet lined box over the fan outlet, with a box hole at 90 degs. All sound out thus was reflected off carpet, and significantly deadened. You could prolbly do with with more rockwool, held in place with metal netting.
Also I'd look at the engine mounts, check its mounted on rubber blocks, and that theyre not knackered.
And check the body panels are painted with underseal or rubber matetd to deaden resonance.
NT
This is much less of an issue with 4-stroke than 2-stroke engines, and more with an engine tuned for peak power than high torque at lower revs. Somehow I doubt that a mini digger will have a radical cam profile.
How is that going to reduce the pulse? A simple baffle system would probably do a lot more with no significant increase in back-pressure.
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bodge-it-yourself
performance,
cause
performance
So try running it without, exhaust design are important what ever the engine the original reply suggested all but blocking the system up - hence my reply.
diameter
leaving
Never hard of an expansion chamber, it the same principle of how a gun silencer works ?!
back-pressure.
Go back to playing with your Matchbox cars....
Nobody suggested that was a good idea.
But not to the extent that an increase in back-pressure is necessarily going to have a major effect.
That would depend very much on how it was implemented - flow required, size/number of holes, type and amount of packing ...
"What ever you do, expect problems with the engine or it's performance". That's just not true though, is it? A slight reduction in fuel efficiency or peak power isn't a problem, it's a trade-off against noise.
Expansion chamber - tuned resonant cavity to make 2-stroke engines produce greater peak power and lots of noise. Maybe that's not the sort you mean.
Which, of course, has baffles in it.
You mean the ones that you threw out of your pram?
engines,
radical
You simple can't say that.
You simple can't say that. What someone does to an exhaust system, certainly what was suggested originally, will have an effect.
extend
Yoy really are clueless....
Oh, right, so bullets go around corners do they, you utter plank !...
No, the ones you are throwing about because someone showed up your total ignorance by the looks of things.
I can. I did.
Try reading what I write - I didn't say it would have no effect, I said that it wasn't necessarily a problem.
This is the point at which you could explain to me why your notion of an expansion chamber is different to the one that I described, showing everyone how clever you are and how stupid I am.
Why would they have to? It's the expanding gases that make the noise, not the bullet (apart from a mini sonic boom).
Okay, if that's the way it works on your planet I guess it must be right.
Quite correct, you can, but that doesn't change the fact that you are sumizing about something that you don't don't - heck, we havn't even been told what the make digger is let alone what engine it has....
You can say that, so don't say that either suggest something that will either improve or be natural in it's effect...
system
engines
Because what you describe uses a restriction along with baffles to cause back pressure along with attempting to silence, you can have a gutless / quite / two-stroke just as you can have a gutless / noisy / two-stroke - exemplified by all the 'go-faster' kiddies on their de-baffled scooters, being overtaken by milk floats and un-modified scooters !
You said that a gun silencer uses baffles, either you don't know what a baffle is or you are just clueless !
So what planet are you on, it's certainly not Earth ?!
the engine is a Honda G300 general purpose motor....id estimate running at about 2000 rpm but can be used at a faster speed if you need more power or speed from the hyd. pump. this thing must be over 20 years old and the original exhaust has rotted through, I've filed the gaps with exhaust repair putty...but it aint gonna last long....and its still noisy!
steve
running at
exhaust repair
Ah!....
Why didn't you say all that in the FIRST place, have you checked to find out if the original exhaust box / pipes are still available ?
even if the oem exhaust was available, i doubt it will make a big diff in noise levels...i have fixed the original temporarily with exhaust putty...its quieter but not quiet enough.
Steve
It should do. As well as having holes in the outside, the internal stuffing of exhaust boxes fails with age too.
Anyway, you don't need the _right_ exhaust, just an exhaust. Go to the digger shop and get anything that fits. If it's a Honda, then somewhere fettling gennys will have suitable exhausts too. Some of the big genny exhauts are very quiet.
Another ill informed message from the groups 'know all', you're spouting total clap-trap, not all exhaust boxes are the same and fitting a inappropriate box could very likely effect the running of the engine adversely.
It's a four stroke, designed to be used by brickies. Now you might have a point for a '60s DKW motorbike, but this is not an engine that's sensitive to its exhaust.
Stop showing your total lack of knowledge, you said that the Op can fit any exhaust box to the engine, the simple fact is that he can. You are totally clueless about this, stick to advising about computer software...
Exactly ! Glad you agree.
Troll ! You are wrong and the above is nothing but a typo.
I've seen several samples of a certain vintage vehicle, and no 2 have had the same exhaust, or even anything close. One came out the rear end, one came out the side just behind the driver, and another had a truck style exhaust that ended over the roof. Not even remotely similar. All ran just the same.
Jerry has a point that one /could/ screw up, but I think the odds are you wont, as long as you dont stray too far from original sizes.
But I could well be wrong, I'm no engine expert, just a practical ex car diyer.
NT
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