A few points on this one.
I have run VW/Audi 1.9 Tdis for the last ten years or so, I can honestly say they are the best small diesel engine I have ever had. Two Audi 80 estates with 1Z 90ps engine and currently a VW Passat estate AFN 110ps. They do about 20,000 miles a year, and in all that time, apart from regular service items, I've never had to put a spanner on the engine itsef, I've done starters, alternators, PAS pumps etc, the two Audis both had well over 200,000 on them, when I'd finished with them and the only reason I changed them was because a younger lower mileage vehicle turned up very cheap, I'm talking £600
. They don't need topping up with oil inbetween services, are plenty powerfull enough and ridiculously economical, our current Passat does 54 mpg, long term, according to the trip computer and that's with Mrs pdq doing an eighty mile commute every day, I get more out of it, she is not a particularly light driver.
, so overall an excellent choice for you van.
Gearboxes, My dad has Volvo 940 with the 2.4 idi straight six, as per LT, I have a stripped engine, so I can take a pattern off the backplate for you, I am 99% sure it is the same as the four pot version, so the Volvo box from the 760/940 would be an option too.
All the 1.9 tdis I've had have had the VP37 electronic injector pump, the first generation electronic pump derived from the VE, it has a stepper motor which turns the throttle spindle, controled by the ecu and an electronic timing solenoid, otherwise it's a VE. They have all been completely reliable. The 98 Passat I have now has been in the family since new, all it has ever had is one MAF sensor, it now has 206,000 miles. One of the Audis had 290,000.
VP30 anybody?
Either you drop in the engine with ecu, all the electronics, immobiliser etc, bit of a nightmare really, or you go MTDI. There have been lots of succesful MTDI conversions on the 1.9, mostly bolting them in to T4 Transporters etc and older Golfs, which had the old idi engine. The simple recipe is to fit the VP37 camplate to the idi pump, with the VP37 delivery valves, not a particularly good option, because the tdis have a higher lift camplate and the control levers in the idi pump have too small a range of movement to cover this, they need pivot points shifting to compensate, so you need control levers from a big cam di pump, also the idi pumps have a smaller diameter pump shaft. Direct injection pumps tend to have higher lift camplates with a steeper ramp, as they have to get the fuel in faster than idi, they have a shorter time to inject the same amount of fuel, than with indirect injection, they have a higher load on the shaft, so using the large shaft pumps is desirable.
I have spent hundreds of hours researching MTDI conversions and have learned a lot about what works and what doesn't. Most of the development has been done by privateers of the VW brigade, mostly in the US and Canada, despite fuel prices being half what they are here, they seem to have much more of a "can do" attitude than we Europeans
.
Turbos, the later turbos are VNT, controled by the ecu, so earlier wategate ones would be easier, for MTDI. Someone (Canada or US, of course
) has developed a mechanical control system for VNT which would seem to work really well, much more boost at lower revs than a wastegate. I'm going to adapt this system to the Duratorq when I have time, I've spent all my van fiddling time, for the last year or so, improving the pumps.
I'll get some links up later, to the relavent stuff, if you have a few hundred hours.
Andy.