Why are Stage 1 Isuzu's so noisy ??

A couple of differences that I can see.

First is the application, these early engines appear to be the industrial type with no acoustic kits.
Second the industrial engines may run more advanced timing out of the box than the automotive (truck) engines.
Third, Isuzu went to "close clearance" at some stage which takes out all the piston slap noise. I won't forget how quiet one of these can be with the piston/liner clearance as tight as it should be.

However last time I rebuilt my engine I used aftermarket liners which were only available in one clearance grade (but they were virtually free), the genuine liners come in about 4 different sizes which are matched up through bore measurements.
As a result my engine is louder than it could/should be and the ring gap is slightly bigger.

Quote:

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Originally Posted by justinc

...... My ex 1988110 engine at 100km'h is almost as quiet as when I had the V8, as I can hear the M/T's over the noise of the 4bd1:)

JC

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Yes, well some V8s can be noisy!

Seriously though, with my 110, the engine itself is not particularly noisy (although it is more so since the under bonnet insulation disintegrated - need to replace that). What is noisy when idling is the chattering of the gearbox, and the rattle of body bits, tools, the change in the parcel tray, and your teeth. When pulling, the noisiest part is the exhaust - always has been, even with a new muffler.

John

Quote:

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Originally Posted by JDNSW

When pulling, the noisiest part is the exhaust - always has been, even with a new muffler.

John

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There's a well documented fix for that.
Five letter word beginning with "T".;)

Mine is LOUD, my 120" is LOUD and the other wreck I have is ever so SHHHHH in comparison:eek:

Mine is definately MUCH louder than JC's:)

I've been meaning to check pump timings on all the above to try find a reason, they all have the rocker cover cover, one day I'll check:D

I did fiddle with the timing on the blokes Isuzu that I rebuilt, and yes it did make a small differance however the throttle response was a little slower on the road. He felt that the small amount of differance that it did make didin't justify it.
I can dig up the different Pt no's for you if you want, I'll PM them to you just let me know. From memory a replacement cam was around the $680 mark:o

I did not know that about the different piston/liner sizes, this dose make alot of sense, as it dose sound exactly like piston slap in the older race engines that had forged pistons.
I'm not sure if the different sizes are still available though, as I put a new liner/pison/ring set into one of the bores and the set Isuzu themselves gave me was an aftermarket set. Their excuse was that Isuzu stopped making the replacement parts years ago as they had such a low turn over it wasn't economicly viable for them to make them anymore.

Looking at this thread I must have a quiet 4BD1. Although is an 89 model. The turbo wine and Tyres are louder than engine noise.

For me, my '82 Stage 1, you can hear each tappet at idle.

It is the low frequency drum that comes from the large metal cylindrical air cleaner element bolted to the firewall that gives me a headache after about an hour. The wagon seems to amplify the sound. There is no acoustic rocker cover, nor much in the way of sound deadening on the firewall.

I pull the door tops off for extended runs and the wind noise seems to make it more bearable. The windows rattle(need to change the bailey channel) as well as the metal dress panel above the windscreen. Not much has rattled off, although I do have the cracks in the guards between the headlights and the radiator.

This is a major reason I never looked at buying a County, but now I know they are not as bad I may have to revisit that thought. This car was and has returned to being my daily driver as my 130 is prepared to take up it's role as the purpose built tourer.

CC

The turbo reduced the noise coming from my 4BD1.

My LT95 probably makes more noise than the motor.

Most of my cabin noise comes from the transmission tunnel cover.

All other things being equal, an exhaust of a turbo engine will be approximately 4.5 dB(A) quieter than the exhaust of its non-turbo equivalent (at the outlet).

In comparison, a well muffled exhaust will be up to 25 dB(A) quieter than its non muffled equivalent.

Problem with Land rovers (especially defenders and counties) is that floor construction has very poor noise transmission loss, so much of the muffler noise breaking out of the exhaust pipe will find its way into the cabin.

This can be minimised by:

1.) fitting the muffler as close to the engine as possible
2.) lagging the exhaust pipe (using a thicker walled exhaust pipe will do the same)
3.) increasing the mass of the floor panels.

Not necessarily in that order.