Thread: Torque Impulse

My 4BD1T came out of an Isuzu truck and has a harmonic balancer. I don't know about the version of the engine used by Land Rover - they seem to have a few differences to mine.

If the rubber element looks the slightest bit suspect (protruding, cracked or perished) I would replace the balancer.

Edit: The harmonic balancer does not and can not, reduce torque impulses. What they are for is to reduce the torsional vibration problems that result.

harmonic balancer?? umm, could everyone take a pic, thinking of the othere thread compairing older and newer isuzu donks, maybe there is something in the harmonic balancer, as well as the cam ??

Originally Posted by garryseries3

Hi all
So has or does anyone have any opinions or experience with hormonic balancers on isuzus to reduce torque impulse?
Kindest regards
Garry

Same as Bush65, my 4BD1T is from an 86 truck and has a two piece harmonic damper front pulley.
I also agree that it does nothing to reduce torque impulses (it doesn't have enough inertia to do that), it's role is to prevent torsional vibration issues. From harmonics.

Originally Posted by Dougal

Same as Bush65, my 4BD1T is from an 86 truck and has a two piece harmonic damper front pulley.
I also agree that it does nothing to reduce torque impulses (it doesn't have enough inertia to do that), it's role is to prevent torsional vibration issues. From harmonics.

So is it the torsional vibrations that destruct gearboxs etc. in Landys or the torque impulse? Perhaps someone could explain torsional vibrations as I though they where much the same. Also does the dampener lead to a quieting motor noise levels?
Kindest regards
Garry

Originally Posted by garryseries3

So is it the torsional vibrations that destruct gearboxs etc. in Landys or the torque impulse? Perhaps someone could explain torsional vibrations as I though they where much the same. Also does the dampener lead to a quieting motor noise levels?
Kindest regards
Garry

Chicken-egg.
The torque impulses (coupled with a flywheel that IMO is lighter than it should be) cause the torsional vibrations.
A flywheel with more inertia reduces the size of the torsional vibrations. "Uprating" your engine (i.e. more fuel and boost) increases the size of the torsional vibrations.

Originally Posted by Dougal

Chicken-egg.
The torque impulses (coupled with a flywheel that IMO is lighter than it should be) cause the torsional vibrations.
A flywheel with more inertia reduces the size of the torsional vibrations. "Uprating" your engine (i.e. more fuel and boost) increases the size of the torsional vibrations.

So Dougal
when you fitted you isuzu box behind your motor did you stick to the isuzu flywheel and hence reduce if I understand it correctly your torsional vibrations compared to a standard landrover isuzu setup. So does more torsional vibrations lead to noisier motors?
Kindest regards Garry

Originally Posted by garryseries3

So Dougal
when you fitted you isuzu box behind your motor did you stick to the isuzu flywheel and hence reduce if I understand it correctly your torsional vibrations compared to a standard landrover isuzu setup. So does more torsional vibrations lead to noisier motors?
Kindest regards Garry

I don't know exactly which flywheel the landrovers use, but it appears to be similar to my 86 model flywheel and clutch. This is the 275mm clutch compared to the 300mm clutch used in the later (88+) Isuzu NPR's.

More torsional vibration does lead to more noise, especially that low rumble I get when I ask for more than 10psi at 1400rpm.

Originally Posted by Dougal

I don't know exactly which flywheel the landrovers use, but it appears to be similar to my 86 model flywheel and clutch. This is the 275mm clutch compared to the 300mm clutch used in the later (88+) Isuzu NPR's.

More torsional vibration does lead to more noise, especially that low rumble I get when I ask for more than 10psi at 1400rpm.

Would there be any reason why you could not use a isuzu flywheel clutch setup in between a 4BD1 and an isuzu gearbox in a landrover defender?
Kindest regards
Garry