Thread: Torque Impulse

The Isuzu 4BG1T is an industrial engine using the same block, it's flywheel in the sectioned drawings is a monster but I haven't gone to the trouble of calculating the weight of it. It would bolt up to the engine, but you may not have room for a clutch.[/QUOTE]

FWIW

The 4BG1T is an industrial engine meant for stationary use such as driving a generator. They have been installed unsuccesfully in vehicles - broken crank shafts - broken valve gear. Reason: these engines are designed for constant rev applications. I suspect that the heavy flywheel has contributed to the crank breakages in automotive applications.


The 4BD1T has a light flywhee:l for a reason - to do with harmonics and crankshaft vibration.

Torque pulses are always at the same interval in any 4cyl engine at any given engine speed. The intensity of the pulse will vary but not the frequency, (a more powerful engine will produce a more intense pulse).

The old 2 1/4 4cyl petrol motors run very harshly when fitted with a forged steel Diesel crankshaft - because the shaft is stiffer than the cast iron Petrol item. I think that fitting a heavier flywheel to a 4BD1 will have consequences that are not immediately apparent.

FWIW

C H T

Originally Posted by C H T

FWIW

The 4BG1T is an industrial engine meant for stationary use such as driving a generator. They have been installed unsuccesfully in vehicles - broken crank shafts - broken valve gear. Reason: these engines are designed for constant rev applications. I suspect that the heavy flywheel has contributed to the crank breakages in automotive applications.

Have you got any more information on this, it seems very strange. These engines aren't designed for constant rev applications, it's just another application of what was originally a truck motor. The 4BD1T was sold as truck, industrial and marine, the landrover 4BD1 engines are industrial variants and they don't break cranks or valve gear. The 4BG1T wasn't fitted to an Isuzu truck (replaced by 4H series) but it saw both marine and industrial use.

The 4BG1T was fitted into many other industrial applications where rpms continually rise and fall. Like excavators which reduce the engine rpm when load drops, pick it up again when the load increases. The 6BG1T is used extensively in buses here.

Originally Posted by C H T

The 4BD1T has a light flywhee:l for a reason - to do with harmonics and crankshaft vibration.

Torque pulses are always at the same interval in any 4cyl engine at any given engine speed. The intensity of the pulse will vary but not the frequency, (a more powerful engine will produce a more intense pulse).

The old 2 1/4 4cyl petrol motors run very harshly when fitted with a forged steel Diesel crankshaft - because the shaft is stiffer than the cast iron Petrol item. I think that fitting a heavier flywheel to a 4BD1 will have consequences that are not immediately apparent.

FWIW

C H T

The frequency of vibration varies continuously with engine rpm. Hence while the maximum torque pulse is the same the engine running at higher rpm has less torsional vibration than the same engine running at lower rpm. It's simply less time for the flywheel to decellerate before the next pulse. The rotational space remains constant, but the frequency does not.

The US 4BD1T owners who run a dual flywheel setup aren't having the low speed impulse problem those of us with the light factory flywheel are having.

Originally Posted by Dougal

Have you got pictures or model codes?
The MSA series boxes were 5 speed overdrive without anything hanging off the back. I'm wondering if it's a splitter or low ratio in the rear housing.

I currently run a MSA-5G. I have an ugly gearlever which consists of austin allegro parts grafted into the top of it. It works but I intend to replace it with a linkage or cable system at some stage.

I'll try and get some better pics if needed......this is all I could manage without breaking my balls lifting it out. The only obvious numbers were on the L/H side, should I look somewhere else on the box for other identifying marks/numbers.
The overdrive/splitter ???? was operated by a lever on the steering column. The spedo drive is on it too, which suggests it's a pretty standard setup.
When I get a chance I'll take pics of the gearstick, cables etc.

Murray

Up until the rear housing that looks identical to mine.
From there my one finishes essentially with a cast cap (which is removed to fit the LT230 adapter) where your one has the extension housing.

I'm still suspecting hi/lo ratio/splitter.

Model codes on mine are by the level plug on the RHS.

Originally Posted by C H T

The old 2 1/4 4cyl petrol motors run very harshly when fitted with a forged steel Diesel crankshaft - because the shaft is stiffer than the cast iron Petrol item. I think that fitting a heavier flywheel to a 4BD1 will have consequences that are not immediately apparent.

FWIW

C H T

Also FWIW,

2.25Ds have a flywheel that is MUCH heavier than a 2.25P.

I have heard of many people who have increased flywheel mass in both petrols and diesels. I haven't ever heard of any adverse effects (apart from acceleration...)

Here is my setup.

Originally Posted by Dougal

Here is my setup.

Hey Dougal who made the adaptor for you and what are the ratios like???

Justin

Nice. If the box in my 120 gives up I'd consider this set up as likely be cheaper and far more robust in the long run.

Tony