Isuzu torque.. Off the line.

**AK83** · 14th April 2020, 12:33 PM

Interesting to read these old threads, then place them into context with personal experience.

Originally Posted by shack

... my question was aimed at proving this .....

Obviously hard to do without dyno graphs, and how many of us have easy access to those.

Seat of the pants experience still can count as proof tho.

Back in the day(30+ years ago), dad had an Isuzu truck, can't recall the exact model, all I remember it had the 3.9 4 banger.
Tons of low down torque, first gear(of 5) useless unless fully loaded to 4+ ton and uphill take off.
I do remember tho it did run out of steam at 2500RPM. That is, it'd rev beyond 2500, and 2700 was the 100k/h cruise revs, but it felt strained and losing a lot of it's initial torque that was so obvious from idle to about 2000ish RPM.
We used to do a weekly run to Ballarat(from Melb), and that meant doing the Pentand Hills climb. Not very steep, but just a fairly long climb, so getting momentum doesn't really help.
The Suzi, with about 3-ish ton load, would scream along at 2700 RPM at 100k/h, and then early on up the climb would drop down to about 70 at about 2000 RPM(maybe 1900, can't recall exactly), no need to drop a gear, as all that did was rev the motor with zero gain.
The other truck I used to regularly drive at that time too, was some (totally unknown model) Ford trader.
Similar style std 5 sp to the Suzi, I don't know engine size tho. That truck had to be moved off the line in 1st, loaded or not. Didn't have a rev counter so couldn't compare revs at 100 with the Suzi, but both trucks maxed 100 on a flat, Suzi just got there quicker too.

The other truck I had a lot of experience with was a very old International C1300. 280 ci six. No idea on revs, but faster(70MPH) on flats, but couldn't hold 4th up Pentlands, had to drop to 3rd, and max up the climb was never more than about 60k/m(or 40MPH).
Inter was far easier to stall than the Suzi, especially uphill. Had to use throttle on the Inter, where sometimes just letting clutch out and no throttle would see the Suzi creep uphill.
Inter motor finally died and dad had a 5.8Lt UD NA diesel fitted to it. What a monster that was! .. by comparison to the old 280 petrol donk.
5 speed came with the UD motor, but what the conversion really needed was a high speed diff ratio.
1st and 2nd were totally useless. Easily take off in 3rd uphill, and 4th take off on a flat was no problem. When I used to drive it, I always thought about the wasted effort in not having sped up the diffs to max out the ability.
Up Pentlands in this new setup always maintained 60MPH(5th), I remember about 2500-ish RPM and you had to feather throttle as well, unlike the petrol Inter or Suzi where you just held it hard to the floor.

I can't confirm Red's reply that the Isuzu motor compared to the Tdi has more power overall or not, and likely that the Isuzu truck motor was tuned/cammed for a more truck like environment(ie. all low down grunt with no thought to any higher than about 2500 RPMs), compared to what was best for a Landrover existence.
Or maybe, dads Isuzu was just badly tuned. But my experience with the Isuzu 3.9 was that it had nothing of value in terms of power/torque beyond about 2500RPM.

**Blknight.aus** · 14th April 2020, 02:41 PM

Originally Posted by shack

Pretty sure none of the ones here will.

And one is very low km, completely stock/original.

flat ground a 2.25D will idle off towing an empty 8t trailer in 1 high and those things weigh the better part of 4t empty.

Pretty sure I posted a vid of it when I did it...

key things to remember, the request was for on flat ground with a warmed up engine. You could do it with nearly anything, hell a quad bike would do it.

**Slunnie** · 14th April 2020, 06:30 PM

Originally Posted by AK83

Obviously hard to do without dyno graphs, and how many of us have easy access to those.

Seat of the pants experience still can count as proof tho.

I'd add to that, I recall driving a Ford Td ute I think it was, and it was near impossible to get on boost for a hill start with load. The dyno wont show that either.

**rar110** · 14th April 2020, 08:43 PM

We have a D1 300tdi empty and a perentie 110 with a GT28R. My 15 year old learner driver son can pick the torque difference by a mile. The D1 300 Tdi is a great all rounder, but the 110 with a fan a nice motor.

**AK83** · 15th April 2020, 07:38 AM

110 would obviously trounce the D1, not just in terms of torque, but isn't gearing much lower in a 110 anyhow 1.2 high range as opposed to 1.4 or something.

When I got my license dad was just getting the old 2a converted from the LR 6cyl into a diesel.
He'd got some massively heavy Toyota 3lt, 6cyl lump, turned out to be out of a forklift or something like that.

I remember the old petrol motor felt fine. relatively smooth and as a learner easy not to stall(although by this stage I'd been driving for many years anyhow!

)
Diesel conversion tho ruined it in terms of overall driving, lots of low down grunt.
I remember the routines in driving it efficiently.

Petrol 6 1st/2nd always quickly. 2-3 a few seconds, maybe 5 or 10, 3-4 much longer. 4th possibly at about 40Mph or so.

With the diesel, start in 2nd, 3rd pretty much immediately 4th by about 20MPH(old 2a, had MPH speedo).

2a was my favourite car(and why I became a Landy(or more accurately RRC) nut case and Rover nutcase too.
As young petrol heads, all my mates were going to Lygon St in their V8 XCs and VBs and whatnot, one mate with a really clean Scorpion(all others v8s) .. and here's me in the crappy, banged up smokey frankenmonster 2a! with it's crappy roofrack, gas bottle in a holder on rear, spare on bonnet, etc. Never stalled in on the very slow cruise down the strip tho. Idling in 4th at whatever crawl speed it did was never a problem.

**Slunnie** · 15th April 2020, 11:16 AM

Originally Posted by AK83

110 would obviously trounce the D1, not just in terms of torque, but isn't gearing much lower in a 110 anyhow 1.2 high range as opposed to 1.4 or something.

That compares the Defender and Discovery high range with the LT230, it's because of the different tyre sizes.. and probably aerodynamics. The low range is the same though.

I'm not sure what the overall gearing differences are between those and the LT95 in the 110, but I think you are right in that it has lower gearing at least for low range.

**mark2** · 16th April 2020, 07:10 AM

4th in a LT95 (Perentie 4BD1) is appx the same rpm for a given speed as 5th in R380 300 TDi (Defender). Disco is geared taller but sill 20% lower transfer ratio than 4BD1, but also smaller wheels, so similar overall to Defender.
300 TDi would struggle big time with the 4BD1 ratios.

**INter674** · 16th April 2020, 07:25 AM

I recently sold an Isuzu NPR truck with the 4.7 (?) intercooled turbo motor. First gear very low...so empty simply use 2nd. It had an anazing ability to hang on in any gear... even when overloaded eg on the farm🙄 Reverse could have been lower tho as it struggled to back up steep roads loaded. Very good fuel economy too even when flogged.

Truckie who bought it loved them saying they have the best gearing of any truck and gave very few mechanical problems.

Interestingly a relative drives the current version albeit 4x4 with DPF burner etc and reckons they are a POS😞

**Rick Fischer** · 16th April 2020, 10:36 AM

Recall when I had D1 TDi 300 auto. On club runs on long climbs or creek climb outs etc, Could watch the manuals spin rear wheels and lose traction as the turbo came on at around 1800rpm; alternatively if behind me would gripe about having to change gears up and down all the time (me using torque converter) and in a different gear, autos had different diff ratio too.

With torque converter didn't need to go to low range as soon either. Turbo diesel and torque converter a marriage made in heaven

.
Cheers
RF

**whitedisco** · 16th April 2020, 12:36 PM

Just a thought about this.
One factor effecting the "grunt" when easing out the clutch at zero throttle is the fuel pump/governor characteristic. The governor may be mechanical or in ECU software.

Some diesels (and some electronic petrol engines) have very fierce idle speed governors. As the clutch is eased the governor will crank on the fuel attempting to maintain the set idle speed.

Detroit diesels eg 6V92 used in coaches had this type of governor. The standard way to move off was zero throttle, ease out the clutch and when fully engaged squeeze down on the throttle. This even worked up hill. Good for the clutch also.

My Barina SRI was similar but the fly by wire throttle was a bit too slow.

I have no idea about the diesels you are comparing but the way the governor works may be at play.

Love those Detroit 2 strokes!!

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