landyboots · Dec 8, 2015

Hi all. Just looking for opinions. I am going to undertake a diesel conversion on my classic as the crappy VM has well and truly expired and I fancy an upgrade. I have a choice of these 3 engines which have become available local to me so I was just wondering what you guys would choose and why....

1. Mazda SL35TI with conversion kit.

2. Isuzu 2.8 4JB1T with conversion kit

3. BMW M51 with conversion kit and Mechanical injector pump.

My choice would be based on reliability. Fuel economy. Availability of parts and cost of same.
What in all your opinions, would be the pluses and minuses for each?

Thank you all in anticipation.....

jamesmartin · Dec 8, 2015

200 or 300tdi

landyboots · Dec 8, 2015

jamesmartin said:
200 or 300tdi

Not on the options list.....

kds · Dec 9, 2015

jamesmartin got a point, find yourself a disco with the body falling off and you`ve got all the bits you need plus it will make things easier in the future, I put a 200tdi into my 89 classic when the vm went west but if you must either the mazda or the isuzu.

wil2813 · Dec 9, 2015

jamesmartin said:
200 or 300tdi

+1

wil2813 · Dec 9, 2015

kds said:
but if you must either the mazda or the isuzu.

done the 2.8 td Isuzu conv years ago in a 92 v8 auto on air. tbh the engine was nice but mated to a autobox it was terrible imo. I ended up selling it

norseman · Dec 9, 2015

wil2813 said:
done the 2.8 td Isuzu conv years ago in a 92 v8 auto on air. tbh the engine was nice but mated to a autobox it was terrible imo. I ended up selling it

Because the slush-box was set up to suit the original spec. V8
I'm reasonably sure that the shift speeds/revs will be different for a diesel's torque curve.

spencer1885 · Dec 9, 2015

Mazda 35slt engine in my range rover classic with zf hp4 is the best sounding and performing diesel in my experience
Owned this range rover with this combination for over 9 years.

rangie1998 · Dec 9, 2015

I'd have to say you'd be better off with a 200 or 300 TDI. Fitted a 200 TDI in my 92 classic to replace the v8. Very happy with it and 30 mpg.

landyboots · Dec 9, 2015

Thanks all. I know the TDI's are great engines but I've only ever had them (and the VM that's expired) I want to try something different. Something quieter, and just as simple to work on, and is good on fuel. That is why I have picked those three. Whatever one I choose will be bolted to a manual gearbox for fuel economy. I appreciate all the inputs guys and would ask that those of you with experience of those three engines to keep the opinions coming....

Thanks all.

wil2813 · Dec 10, 2015

tbh I was impressed how the Isuzu started instantly regardless of any conditions/temperatures, no/zero winding over at all

landyboots · Dec 10, 2015

I always heard great things about the Isuzu's.....Okay, got a drive today in a classic with the Mazda SLT engine. Manual Gearbox. Bin the tdi's everyone. Power and Torque was astonishing compared to the tdi, and as for performance and fuel economy, 3rd gear, 30mph @ 1400rpm..... 4th gear, 40mph @ 1400rpm.... 5th gear, 50mph at 1400rpm. Drove approximately 40 miles, some of it in gridlock traffic. I was 1 hour negotiating this traffic, with engine idling then moving a few metres then back to Idling again. The rest of the journey was open roads and winding lanes with a few hills thrown in for good measure. The fuel gage was working perfectly and never moved from just below the halfway mark......Impressive

The conversion on this Rangie was done some years ago by Motor&Diesel and the Transferbox gear ratio's were changed to suit. The owner says he gets 50mpg no problem and after this test, I don't doubt him.

spencer1885 · Dec 11, 2015

30 MPG is more like it and that's on a good day.

landyboots · Dec 12, 2015

spencer1885 said:
30 MPG is more like it and that's on a good day.

I suppose it's like any other engine. If they are looked after throughout their lifetime, they will function better and be more frugal than if they're not....Did you run one yourself?.....I have to say that this particular engine was returning a far better fuel mileage than 30mpg. I do believe he gets close to 50 because he drives very casually most of the time and with the manual box and uprated gearing, this particular Mazda engine was never unduly stressed so that would help I suppose. I was blown away with the speed/rpm gains. 1400rpm has you at all the desired speed points in the correct gear. That has to return good mpg figures. I suppose it comes down to the way it is driven among everything else. I remember the record set on a 200tdi years ago was around 53mpg in a classic Rangie. That was a deliberate effort for a publicity campaign where the guy drove it from Land's end to John O' Groats and back and attained this figure doing a brim to brim measurement so, this figure of 50 from the Mazda makes perfect sense.....

kds · Dec 12, 2015

Use to get 27/28 mpg round town with the 200 tdi in mine and thats with my very heavy right foot, over 30 mpg on the run up to Leeds to see the grand kids as long as stuck to 70 mph, start pushing it over that (illegal of course) and its back down in the mid twenty`s.

Yoyodyne · Dec 12, 2015

My RRC had a 2.8 Diahatsu (Fourtrak) engine and that was excellent. Converted by Milners so the job was done right. Still a few rusty Fourtraks around so could be really cheap.

spencer1885 · Dec 12, 2015

A tdi is 2.5 and a mazda 35slt is a 3.5 and if a 2.5tdi is going to do 30mpg a 3.5 is not going to be more economical.
If you read the reply I made earlier on you would see I own one of these engines in a range rover for over 9 years.

landyboots · Dec 12, 2015

spencer1885 said:
A tdi is 2.5 and a mazda 35slt is a 3.5 and if a 2.5tdi is going to do 30mpg a 3.5 is not going to be more economical.
If you read the reply I made earlier on you would see I own one of these engines in a range rover for over 9 years.

I agree with you about the CC's having a determining factor in fuel economy but I can only report that which
I have seen for myself. The fact that all normal road speeds for all conditions are available at such low rpm's are going to cancel out the fuel usage benefits of a smaller engine versus the bigger lump. 1400 rpm will require less fuel into the cylinders in the 3.5 than 2200 rpm in the 2.5 unit. Was your Mazda powered Range Rover classic Auto...and did it have the correct Transfer box gear ratio's for the engine? ....... Thanks for your input

spencer1885 · Dec 13, 2015

I think the mazda engine is about 130 hp so not a massive amount so over gearing it will only help on motorways.
My engine conversion was done by M&D many years ago.
The only way to get more speed with less engine rpm is to fit a transfer box from a early 3 speed auto range rover and that would sap the hp making towing hard work
If your mate can get 50 mpg out of a 3.5 mazda slt engine it's a world record.

norseman · Dec 14, 2015

I can never understand this quest for fuel savings from vehicles that were never designed with economy in mind. I've owned four RRC V8's, enjoyed them for their original design & knew what they would cost to run when I bought them. Tearing the heart out of these classics is surely taking away the vehicle's very character.
Just an old fart's opinion

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