The Silent BJ40? (1 Viewer)

[AF Road]

We all know diesels are loud but is it even possible to insulate the noisy, but much loved rattle of the 1981 BJ40 2B engine?

I'm thinking of trading my 2B engine in but if there's a chance, I'd like to keep it but lower the decibels it creates during those long, leisure drives.

Just wondering folks if any of you have ideas on how to muffle the sound of a 2B engine. Insulations? but where do I fit them and who do I get them from? Will they even work? Thanks guys for your input and photos are most welcome

AL

 

[SteveH]

I would look into insulating the underside of the hood, sealing all firewall holes, and then putting Dynamat (or any sound attenuating mat) on the firewall and floor. That'd be a good start.

 

[MoCoNative]

I was running a Bobcat mini excavator last week that I rented for some work at home. It was very quiet, I wore my earmuffs with a radio in them just for the music, but it would have been comfortable without them. This was an open cab model.

I looked in the back where the engine was because I was curious how the sound was deadened so well. The back cover and side cover over the hydrualics are sealed with weatherstripping to start, at least in the areas around the operator. But most of the interior surfaves were covered with thick foam with the egg carton shape to it. Very dense stuff, probably 2.5 to 3 inches thick from the tops of the peaks to the back. These units like the Bobcat skidsteers have a Kubota diesel engine in the back. The muffler was decent sized also and inside the engine area. But with the covers open, I listened to it at idle and full throttle and then shut the cover. While not the noisest diesel engine, the covers make a huge difference.

I was interested because I built a tractor cab for my compact tractor and I get alot of engine noise in the cab. It also has some foam and sealing employed under its hood, but not nearly as much as the Bobcat unit did. I have also been looking for ways to quiet my 40 a bit too.

It seems that hood insulation is a key component, as is the firewall. A 60 series is much quiter and employs those two techniques.

The Bobcat unit is actually quiet enough you can talk loudly over it at full throttle, that is pretty good I thought, you can't do that around my small deisel tractor, it is pretty loud at full power.

The egg carton foam would get pretty dirty though on a vehicle, not sure if it would be practical under the hood, but I bet it would quiet down a 40 a lot.

 

[lostmarbles]

Hi Al

In my view ......

Layers of insulation tend to trap moisture thereby promoting rust. Furthermore, they obscure your view of bodywork so that when rust develops you may not notice it till large areas are rotted out.

As well as this, an insulated engine-bay or footwell-area can look rather unattractive compared to bare paint or plastic mats (OEM).

(Even OEM under-hood insulation on LX 40-series models is rather unattractive to me!)

And furthermore engine-bay insulation can soak up oil and diesel in the event of leaks as well as promoting fire in the event of electrical shortcircuits.

So, with all these negatives, I've simply developed a policy of wearing ear muffs for long journeys.

But I wear them only on open-roads sections when my speed exceeds 80kph and the noise is greatest.

This suits me because I can take them off (and "let my ears breathe" or whatever it is that makes me feel more comfortable) whenever I'm passing through towns or other areas where I can't (or am not allowed to) maintain speed.

With ear muff use I find I can arrive at my destination still able to hold conversations with people rather than having been deafened. And I don't feel at all worn out either..

Of course muffs are good for "marital bliss" too.



Sorry... I know I'm not answering your question about "how to best apply sound-insulation".

To own a 40-series diesel I think you really have to appreciate the sound of a tractor.

So this post is really just suggesting a rethink about whether you really want to install insulation, or heaven-forbid, whether you really want to ditch your 2B tractor-engine.

 

[cult45]

Twelve months ago I finished restoring a 1969 Aussie Fairlane. The heat was incredible so I insulated the floors and firewall. When you get down to brass tacks there is very little difference between thermal and acoustic insulation - so my input still applies to you. The reduction in heat was probably 40% and there was a significant reduction in noise, although it was a 302W so I wasn't too happy about that! The noise came down maybe 30%. But damn that motor sounded great. Unless you're constantly wading I'd insulate the floors and firewall. Not all insulation is going to be fibrous and therefore soak up oil/fuel and be a fire danger. You can get recycled plastics bonded into a bubbly type layer 8mm thick with foil on both sides and attach it to your floors and firewall. Down here we call it E-Therm. For best results I'd do both sides of the firewall and under the bonnet. It will reduce a lot of fatigue whilst driving your 40.

How do I know? Used to work in insulation..

 

[DSRTRDR]

Dynamat and sound deadening material (foil on one side, fabric on the other) from Summit - cheap rubber mat and carpet mats on top

I am not so concerned about humidity - my 40 lives in dry heat

 

[AF Road]

Thanks guys for the tips. All great ideas and very interesting. I will have to see whats available in my side of the world but if I can't find it, I guess I'll have to have it couriered over if it comes to that.

I do love the sound that the 2B makes, but the long drives tend to be draining.

A local mechanic mentioned that the perhaps changing my OEM muffler (which is in a pretty tired state) would be good by making it slightly larger in diameter and to use Stainless steel material. Not sure if it's worth the money but thought you guys might have some thoughts on that too.

Thanks again for your time.