3.1 vs 2.8 Diesel

[tellicorick]

Gentlemen (and ladies, if any),

Starting the process of changing from petrol to diesel in my 97 LR Discovery. I've settled on the Isuzu diesel for the power even though it was never imported into the states for highway use, but is widely used for gensets and construction equipment. This makes getting parts a lot easier than trying to import LR diesel engine parts. With all that said, how about weighing in on which engine would be the best for my application. Vehicle weighs 4500 lbs, automatic transmission, 3.54 gears, and cruises at about 1750 rmp at 55 mph. I don't do a lot of off roading but mostly travel hard surfaces with the occassional trip off-road. Now, in your opinion would you go the 2.8 4JB1-T or 3.1 4JG2-T? I'm mainly interested in reliability and economy.

Thanks,
Richard
Southeastern U.S.

PS- Forgot to mention, but I hate electronics and would prefer the choice to be as mechanical as possible.

[geeves]

3.1 is more powerfull and smoother but uses slightly more fuel and is only found in isuzu 4wds Later ones have electronic control. Its better at low revs
2.8 can be tweeked to give very good power and still be very ecconomical. It is found in all manner of isuzu products. In the disco 30mpg would be easily achievable but it likes to rev and might struggle with those gears.
You could also look at the bigger isuzu engines eg the 4.3 or 3.6 in turbo or non turbo that are also good engines but lower revers. Look for direct injection for ecconomy.
Did the disco have a separate computer for the auto? If it was a v8 the change points will be wrong for any diesel

[tellicorick]

Geeves,

I'm somewhat lucky that my year Disco has an auto tranny that shifts non-electrically, I think. I believe that the Discovery II's had electronically controlled auto trannys. I'm sure I'll have to do some re-programming of the valve body and possibly a gearing change in the axles. I've gone to larger tires and mine cruises at about 1750 rmp @ 55 mph, so I might just be able to get away without a gearing change.

Thanks for you response; I've just about concluded that the 2.8 was the way to go but wanted to hear from some folks that actually run the engine.

Regards,
Richard

[geeves]

I heard of a truck the other week that hit 1000000km without major work on this engine but also know of several troopers with the 4jb1 with well over 400000km. They are fussy regaurding maintenance though and if the ist owner neglected them the second owner might have it blow up at 150000km.
make sure your new engine is well checked

[tellicorick]

Geeves,
Thanks for the input; once I get an engine, I'll most likely tear it down for inspection and replace anything worn or do a total rebuild on it. It's the anal tendencies in me since I'm an engineer and I like things to run correctly the first time instead of constant work.

Regards,
Richard