Thread: 6BD1T in Land Rover?

Thanks Chief, I'll read through your build thread for driveline ideas, I'm about half way through the MXA thread and that has answered some of my questions.

I read somewhere that Ashcrofts estimated the limit for the LT230 to be about 440Nm (engine), a turbo 6 could start eating the strongest component LR made.

Dan

Originally Posted by zkdaz

Thanks Chief, I'll read through your build thread for driveline ideas, I'm about half way through the MXA thread and that has answered some of my questions.

I read somewhere that Ashcrofts estimated the limit for the LT230 to be about 440Nm (engine), a turbo 6 could start eating the strongest component LR made.

Dan

My threads are terrible and I struggle stringing 2 words together but you may see something useful...The more I look at other diesels the more I like the Isuzu range...
I am not at the stage where I am worrying about the lt230 yet and that's with I'd say over 450Nm easy.
Gearbox is mxa,front diff is a mix of Nissan patrol,rear is soon to be Dana60 35spline.

Originally Posted by zkdaz

I read somewhere that Ashcrofts estimated the limit for the LT230 to be about 440Nm (engine), a turbo 6 could start eating the strongest component LR made.

Dan

There is at least one guy in the UK with a 6BT powered 6x6 landrover based camper running an LT230 with 3.54 ratio salisbury's.

Engine torque doesn't worry transfer boxes. It's more vehicle weight and gearing. I've been well past 440Nm for ever.

In a vehicle, the torque that the engine produces is not what the engine is capable of producing, but the resistance that the torque is apposed to.

Similarly with power, except power is a function of the aforementioned resistance multiplied by the velocity/speed.

So question where does the resistance change when you swap engines or add a turbo.

If the weight is increased, that will add some resistance. A little through rolling resistance of the wheel bearings, and a greater amount going up slopes.

However most will undoubtedly come from inertia. Inertia is mass x acceleration. The driver, has pretty good control over acceleration with the right foot, and brain. Accelerating harder at every opportunity, won't make much difference to trip times. Overtaking is another matter, and having more torque available will open up more opportunities for safe overtaking.

The 4BD1 has a deserved reputation for treating weak gearboxes harshly, or put another way, finding the weaknesses. This comes from the torque delivery at low engine speeds, where it is a series of pulses. As engine rpm's increase, the time between pulses reduce and the delivery is much smoother. With a 6 cylinder engine, the pulses from the extra cylinders smooth it at much lower rpm's.

The weaknesses with the LT95 that are exposed by a 4BD1 are; the thrust bearings in the transfer case, and the centre diff. Both can be upgraded.

Well said John.

Torque ratings for gearboxes and t-cases are somewhat of a misnomer.

When I was getting engine dyno quotes recently for work, all the suppliers wanted to know if I wanted to run 4cyl or 6/8cyl engines. They said they had to up-spec the dyno for 4cyl engines!

Originally Posted by isuzurover

When I was getting engine dyno quotes recently for work, all the suppliers wanted to know if I wanted to run 4cyl or 6/8cyl engines. They said they had to up-spec the dyno for 4cyl engines!

I'm hoping that story leads somewhere. Somewhere like BSFC plots for 4BD1's.

Thinking about it, I would expect Ashcroft to rate the LT230 very conservatively as they offer some warranty on their rebuilds. Good to know others have pushed it further without problems, full time 4wd and coils are kind of the soul of a Land Rover.

Fully agree, drive line stress is limited by traction providing back torque (rather than engines available torque), which is a function of weight and grip. Bigger tyres, even if you adjust the diff ratio for gearing, have more grip therefore you can apply more torque before they let go.

Bush65, inertia is mass by velocity not acceleration, torque is mass by acceleration, but your logic still holds. Highest loads will be impact loading when traction suddenly increases back torque, ie the tyre grabs something. These impact loads will be lower if there is less momentum in the system to dissipate, so best practice is to drive as slowly (linear inertia) at low revs (angular momentum) as possible when traction could suddenly increase. There are however times when we need high inertia/momentum to carry us past a patch of low traction, this is when we have the highest risk of damage.

To my mind, a well designed vehicle should stall when traction exceeds engine torque, rather than break something. And if this is not possible the weakest part should be the easiest to change, ie the spline caps on a full float axle hub. This logic of weak engines and soft metal was classic british post war vehicle design.

Now if I run 35" tyres with chunky grip, an engine with gobs of low down torque that won't stall and load her up with a few weeks of supplies, have I exceeded the strength of the drive line? Anecdotal evidence in these forums suggests this sort of combination will eat any gearbox weaker than an LT95, followed by cv joints, half shafts and flex rover crown wheels.

I am nearly ready to buy a vehicle and start slowly doing it up but I want to be absolutely clear in my mind what I am aiming for at the end. Just to make my decision more difficult, there is a high potential I will move to NZ at some point during or after the build, so I need to meet australian and NZ rules.

I am currently leaning towards buying a factory isuzu 110, sorting out the axles, diffs, suspension, body, etc. Then hunting down a complete truck turbo motor and gearbox, rebuilding the original block using the truck and new parts (thus keeping the factory engine and chassis numbers in case NZ makes it harder to import modified vehicles) and use the truck clutch and gearbox with the LT230 adaptor.

Undecided are the axles, dana 60 sound about right but I need to do more reading, and the flywheel housing / starter motor depending on what the heaviest available flywheel is compatible with, preference for 24v and don't want to notch the chassis.

I have no problem sinking lots of time and money in to this project, I am hoping it will last forever, but I do want to avoid costly mistakes.

Thank you all so much for your input, it is really helpful being able to bounce ideas around with people who have actually done similar stuff already. I promise when I do decide and find a good base vehicle to take lots of photos as I go.

Cheers
Dan

Originally Posted by zkdaz

...

Bush65, inertia is mass by velocity not acceleration, torque is mass by acceleration, but your logic still holds. Highest loads will be impact loading when traction suddenly increases back torque, ie the tyre grabs something. These impact loads will be lower if there is less momentum in the system to dissipate, so best practice is to drive as slowly (linear inertia) at low revs (angular momentum) as possible when traction could suddenly increase. There are however times when we need high inertia/momentum to carry us past a patch of low traction, this is when we have the highest risk of damage.

....

I think it is funny that someone thinks they can teach John Physics...

While waiting for John to reply, here are some vids of 6BT powered land rovers...

There are a few out there...

[ame=http://www.youtube.com/watch?v=LPyy2BSn1vc]The Big Purple One Land Rover 90 Cummins 6BT conversion driving - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=DxKFu_wb0Gg]Cummins Land Rover - YouTube[/ame]

[ame=http://www.youtube.com/watch?v=ocNoI8XAuiI]6BT 109 Land-Rover - YouTube[/ame]