Noisy truck

I am seeking some intelligent advice or dumb ideas... I had the pleasure of taking my Acco for a run to Melbourne the other week with a light but large load, all went well (except the two speed curcuit breaker) we got along nicely at 100 kph no trouble, (its down hill into Melbourne... bit slower going home) and the trip time was very satisfactory....

Just one thing bothered me... the noise, no longer 20, wearing a bluey with my head out the window, I find the drumming from the exhaust quite wearing.

I think I have got the engine noise under control, the cab has insulation in places that .... you know. It is at lower speeds say cruising at around 60 with half throttle the exhaust particularly seems to set up a harmonic hum... not a vibration.Its just a roar...

The muffler is under the chassis and has a very long tail pipe, its seems well mounted and does not vibrate or touch the body/chassis...

is there a Best size for exhaust pipes, their length, the muffler size etc. and no its not a GM... its a 6.354 perkins.

what did you say :question

Sarge in ear muffs :-X

... no longer 20...

not alone there ...

... ... has a very long tail pipe,

there's ya most likely culprit.
Bung another muffler on closer to the end of the pipe. Could even go to the extent of replacing the muffler ya got with a couple smaller ones.
Stick one close to the engine as ya can, and t'other as close to the tail as ya can

Hi Sarge, it sounds about right with what your describing, EVERY International truck did it, they all made lots of noise, some more so than others.
Sound proofing was VERY expensive way back then and the " indoors boffins " NEVER EVER went for a ride in a finished one and NO ONE ever told them, that they were bloody noisey.
There was a good cure for it, even back then, turn the bleedin' radio up full bore, now what noise were you worried about.

You forgot to add that that whilst driving, the heat and noise from the motor is unbearable as well, cold day it's OK, but wait till the weather gets stinkin' HOT, then ya gunna really enjoy a cold beer, you need to keep the fluids up, eh.

Think you been spoiled TOO MUCH, what with drivin' around in them brand new air conditioned cars all the time :

If you're really worried about it, go get some off-cuts of that soft backed lino, cut to shape and stick it down on any surface that makes a drumming noise, that's everywhere you can see in an Inter, it does work, lowers the decibals quite a bit and softens the hard heavy rattles to audible tinkles.
The other thing that might help with the exhaust note resonating, pull the muffler off, shove a crow bar straight up into the mufflers guts and make it a straight flow thru.

Joking aside, try adding a false cover over the top of the muffler, about a couple of inches over the top of it, this will deflect the noise down and will really quieten it down. Just a sheet of tin shaped correctly and screwed down will do the job.

regards greenie [smiley=vrolijk_1.gif]

Sarge,

Your problem is one we spend millions of dollars on each year here.
If you find the noise seems worse at mid range it doesnt surprise me.
If your muffler is a straight through type you will only achieve a small reduction in db at the top of the noise ( Hz ) spectrum and it can actually make it worse mid range.
Noise travels in waves. The length of the wave is measured in Hz. If you want to kill noise in an exhaust you need to cancel out the waves.
The way to do this is bounce the waves against each other and this is what a segmented or baffled muffler does. You know the ones that are in at the top and out at the bottom type.
The problem is you have to weigh up against back pressure and noise reduction.
See if you can find a second hand muffler that is not straight though type and bung it on your Perk and try it. I will be very surprised if it doesnt fix your problem. If it does buy a new one.
If it has already got this type of muffler drop the tail pipe off and go for a run. You notice a change in where (rpm ) the noise is now. It may get quieter.
Try these things and if no good let me know the length and diam of pipe, how many bends and what muff you have and I will run it through our CFD program and work out whats up with it. The pipe diam could be doing it also.
And the other thing to consider also is it is a Perkins ! ...noisy sods
What Greenie says about the tin cover over the muff is what im going on about cancelling out the waves.

Basil

Gentlemen, I thank you... I can see a few busy days ahead, its a pity that going to work is going to interfere with my private life, it may be a week or so before I get to play with the hacksaw.

Your help is much appreciated.

Sarge [smiley=vrolijk_26.gif] :-X

No worries Sarge,

Lets us know how you get on.

Barry

Sound advice Basil as always.

Could the noise be coming from the air intake, under the engine cover?

maybe make sure the inspection flaps(for radiator top up tank etc)are closed properly also the rubber seal around the gearshift is sealing ... ive had a few accos they are inherantly noisey but not to bad ..the last one (neuss D358 powered)i hand made a 3" exhaust the muffler was close to the spare wheel carrier & the tailpipe was pointed downwards to the road (bad move!) after that i made a exhaust stack pointing upwards (good move!) and as far as i know a neuss make more noise than a perkins

I find the drumming from the exhaust quite wearing.

Oh to be so lucky My exhaust is about a foot away from my ear and I cannot hear it. And no, I'm not deaf.

There was a good cure for it, even back then, turn the bleedin' radio up full bore

Tried that. Could not hear the radio so removed it from the truck.

Sound advice

Now that's funny

I think I will invest in ANR headset :-[