Thread: c.h.i.e.f 's 110 Isuzu county

Originally Posted by c.h.i.e.f

Thanks for this...any help or info you can provide on anything is always welcome....
So in regards to stiffness would it only be applicable to the engine mounts or all the mounts (gearbox and transfer)... So engine mounts can reduce the vibration but how much compared to extra inertia on the flywheel I wonder...

It would be all the mounts, there is no isolation between the engine/gear box/transfer so you would treat it as a lump mass.
The primary job of the engine mounts (other than attaching the engine to the chassis) is to minimise/control vibration transfer to the chassis, as far as i was a aware the primary function of the flywheel is to 'iron out' the pulses of power you get from an IC engine, however i THINK the engine inertia is also used to absorb vibrations from the suspension/road conditions.

Modern car manufacturers go to great lengths to tune their engine mounts, i came accross all kinds of high-tech desigins when i was researching it at the time.

It might be worth sitting with the car in neutral and slowly going up throught the rev range to see what rpm you are getting resonance (high vibrations) and even trying to see what the vibration mode is (up and down, side to side, back and forth, (x,y,z) or role, pitch or yaw). Most likely it will be up and down, or pitch (front of engine/gb assembly goes up at the same time as back goes down). If you can hold the rpm at the point it vibrates you might be able to place you hand at different points on the chassis and narrow it to a particular mount or pair of mounts that are the ones not doing their job and transfering all the vibration to the chassis!

I have quite a bit of resonance through my mounts, factory Isuzu ones. When I was entertaining the original conversion in the Rangie, I purchased a pair of Td5 hydraulic mounts including their relevant chassis bits, but decided the Td5 engine was quite a bit lighter than the Isuzu, so went with the OE ones. I am convinced that some research into marine engine mountings for 350KG engines would yield some useful results, but at the time I had no time so in went to OE mountings


JC

When I did my conversion, I found that there was a lot of difference between aftermarket mounts (I think from Don Kyatt) and genuine LR sourced ones. The Landy ones were much a much softer rubber compound, and I could flex the rubber slightly by pushing my thumb into it. No way I could do it on the aftermarket ones.
I didn't have access to any genuine Isuzu ones to compare.

Steve

Originally Posted by Jitterbug

It might be worth sitting with the car in neutral and slowly going up throught the rev range to see what rpm you are getting resonance (high vibrations) and even trying to see what the vibration mode is (up and down, side to side, back and forth, (x,y,z) or role, pitch or yaw). Most likely it will be up and down, or pitch (front of engine/gb assembly goes up at the same time as back goes down). If you can hold the rpm at the point it vibrates you might be able to place you hand at different points on the chassis and narrow it to a particular mount or pair of mounts that are the ones not doing their job and transfering all the vibration to the chassis!

In my case, I have no unloaded vibration problems. I've got vibration at high torque at low engine speeds and I also have a vertical secondary effect from the engine bouncing up and down after a running through a G-out onroad.

I'm planning to flatten out the V of my engine mounts to give more vertical stiffness to stop the second problem. The first I'm still banking on an inertia ring.

I never had problems with the R380/LT230 combo. It's only since fitting the MSA/LT230 combo. I had to modify my trans mounts and notch my crossmember to make it fit. I have double checked the distance that the brake drum needs to be from the R/H chassis rail etc.

I am running brand new Isuzu engine mounts with rover trans mounts. Yet I have a bad vibration on static acceleration around 2000 - 2500.

I truly think it must be the lighter truck flywheel and possibly a lighter clutch. I was going to modify the trans mounts to run horizontal truck engine mounts, but frankly I a bit over the whole thing.

J

LR changed the mounts from what Isuzu use. the RH side is longer (further from block) and the LH side is angled steeper and closer to the block.

I like the hydrolastic mounts like those used on for the TD5. Lord is one manufacturer, but they are expensive. I would be tempted to try TD5 mounts.

Originally Posted by DRanged

I was going to modify the trans mounts to run horizontal truck engine mounts, but frankly I a bit over the whole thing.

J

The truck mounts aren't horizontal, they are also angled on a V. I have access to an NPR here, but the engine gets in the way of measuring the included angle.
One of the Isuzu industrial drawings shows a V angle on the engine mounts of 100 deg internal (40deg from horizontal each side). Picture attached.


In comparison the V8 mounts which I am using are 60deg internal V (60 deg from horizontal each side). I would flatten my mounts out by 20deg each.

I have mixed experience with liquid filled mounts. I had major axle tramp issues on my work car which were caused by a liquid filled mount being too soft. After much agonising last week I removed it, drilled drain holes through, preloaded it and pumped it full of 3M fast curing black urethane. All axle tramp is now gone.
Another nissan I have which runs a similar engine has active engine mounts front and rear. Being a used japanese import I can find no information on them. I am not curious enough to cut one open.

Originally Posted by Dougal

The truck mounts aren't horizontal, they are also angled on a V. I have access to an NPR here, but the engine gets in the way of measuring the included angle.
One of the Isuzu industrial drawings shows a V angle on the engine mounts of 100 deg internal (40deg from horizontal each side). Picture attached.


In comparison the V8 mounts which I am using are 60deg internal V (60 deg from horizontal each side). I would flatten my mounts out by 20deg each.

I have mixed experience with liquid filled mounts. I had major axle tramp issues on my work car which were caused by a liquid filled mount being too soft. After much agonising last week I removed it, drilled drain holes through, preloaded it and pumped it full of 3M fast curing black urethane. All axle tramp is now gone.
Another nissan I have which runs a similar engine has active engine mounts front and rear. Being a used japanese import I can find no information on them. I am not curious enough to cut one open.

Isuzu mount the tranmission on horizontal mounts, I thought that was what Justin was thinking of - using truck engine mounts, in a horizontal position for the transmission.