Thread: 4BD1 performance

firstly, welcome to the forum! consider an intro thread in the introductions area and please also update your location in the User CP so we know where you are

onto the questions...

how big is the 'large boat'?

it's either a case of you are expecting too much, or something is NQR as the 4BD1 has great pulling power, even among current models it's torque is quite aceptable and should be ok pulling up hills at 80+ km/hr.

given it has a 5 speed, could you advise what model transmission? AFAIK, the 85 model didn't have an option for the 5 speed, so you might find a previous owner has also altered transfer/diff ratios etc etc which might not suit towing...

lastly, what's the tyre size? this too could 'assist' in underperforming while towing...

Turbo

make sure all the filters are micky mouse for starters and have a decent diesel mech check the timing. the pump can be tweaked a little but its not really worth it without some kind of induction assistance.

as previosly mentioned making sure all of the gearing and tyres are stock should be high on the list.

Thanks for the help EchiDna. I think you might be on to something with the diff and gear ratios. Someone once told me that the diffs were "highway geared" or something like that. I run 235,85,16 tyres whereas when I bought the car it had 15 inch tyres and rims. The motor has only done about 10000 klms since a full rebuild so I am guessing it is not the motor.
The boat I tow is about 2 ton in weight so you would think the car should be able to handle it fairly well.
As it is though I have to drop back to 2nd gear on most hills on the highway,dropping my speed back to about 50kph.

Originally Posted by O SEA D

Thanks for the help EchiDna. I think you might be on to something with the diff and gear ratios. Someone once told me that the diffs were "highway geared" or something like that. I run 235,85,16 tyres whereas when I bought the car it had 15 inch tyres and rims. The motor has only done about 10000 klms since a full rebuild so I am guessing it is not the motor.
The boat I tow is about 2 ton in weight so you would think the car should be able to handle it fairly well.
As it is though I have to drop back to 2nd gear on most hills on the highway,dropping my speed back to about 50kph.

The diff ratio's will be 3.54:1

I've driven a few and even my own is slow as a wet weak, I've had *cough*approx3.5ton*cough* on mine though and **** you know it, christ can even feel the 9x5 tandem empty

Turbo is the fix

well I guess another thing is how fast/far do you want to tow the boat? if it's 20km once a week, then shouldn't be a huge deal to have to gear down for hills, but 200km once a month is a whole 'nother story... a 4BD1 powered 110 should pull 2 tonne of boat quite well, so second gear on hills @ 50km/hr would mean it's working at the very high end of the rev range!

how does it go offroad climbing hills? as good as others? if not, as Dave said it could be filters, timing, fuel... lotsa stuff... I'd do a complete filter swap as a first step (including the sedimeter - might have been missed since new)... timing might not have been put back right since the re-build too...

those tyres are not extremely big, I'd have thought they would be fine in terms of reduced performance, but if you really want it as a tow vehicle, factory sized 31's are the go!

Hi mate, I know this is a bit late but just thought you might like to hear my input into this one.I have run a 1986 Isuzu 110 for about 15 yrs now and wouldnt be without it. Without a turbo they are slow on the hills. They are like an elephant-slow but strong. I also run 235/85r16 tyres on mine with 130 rims ( bit wider at 6.5in) and these make no difference to the gearing-they are the same height as 7.50r16. I have a turbo motor and tow a 3.5tonne Sharkcat to the boatramp every couple of months.Even with the turbo its a bit slow towing the boat but I can live with that.Where the Isuzu really shines is off road especially in low range-there is nothing that comes near to it.Best thing I can suggest is fit a turbo to it-might cost a few grand but you will be impressed with the difference-even feel confident overtaking.Regards....Brian

Only recently got mine (85 model 4 speed) but I am very impressed with the performance. Admitedly it isn't a TD5 speed wise but then again the TD5 isn't a 4BD1 in bottom end torque. Still learning to drive mine properly but feel comfy cruising at 90 - 100 kph unloaded on the freeway (need new shocks and springs) I'm dropping to 80 up hills, one even 60kph, again I'm only starting off at 90 - 100kph. I never got as low as 2nd gear on freeway hill climbs though. Offroad it's a monster, I was only stopped by my tyres lack of traction. 1st gear LR the GPS read 0.4kph at idle, (who needs Hill descent control or anti stall features? I have yet to stall it and haven't driven a manual regularly in years never before in real off road situations) up on the beach the first steep dune I hit I was in 3rd, revs bottomed out, dropped to 2nd , again the revs died, I dropped to 1st thinking I was about to get bogged, again the revs died to idle yet the car just kept climbing, slowly and steadily it climbed the dune, I could not do that in my TD5 disco. Keeping up with other cars on the beach the gearing was an issue but once I managed to get it into 3rd and even 4th idling over the beach it was awesome. Bumpy, very bumpy we were only stopped by my youngest chucking up (again suspension issues)

Overall I am very, very impressed with it.