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Educate me on the TDI

34K views 31 replies 13 participants last post by  bherde 
#1 ·
Ignore my Username as it was a prospect long gone and forgotten.

I have a '91 Jeep Cherokee XJ that I am seriously considering a diesel re-power for. Currently it has the stock 209k mile 4.0/AW4/NP231 drive-train getting 19-20 highway if it's happy, 14 town. My wife and I keep my Jeep for blizzard duty as it does the job well, and I want to try and boost the low end grunt while getting a few more MPG's.

If I do a diesel swap, I have it narrowed down to three engines: the Mercedes-Benz OM617, the Isuzu 4BD1T, or the VW 1.9 TDI.

The OM617 has been extensively swapped into Cherokee's, but it's gutless with a max tuned output of about 140hp and maybe 240 lb.ft of torque unless you spend $2k on a Finnish modified IP. The Isuzu 4BD1T is a monster and would fit my torque requirements and shear grunt well, but it is a large motor with a safe max rpm of 3600 that would require a serious lift and mod to fit.

I like the more I read on the 1.9 because they can be tuned for good power, can be tuned to rev up to 5k rpm (which is my stock 4.0's limit), and can be adapted to Yota tranny's which means I can retain my AW4 (rebuilt of course with a tuned VB and solenoids for higher line pressures, firmer truck-like shifts, and higher torque capacity). Plus, it is a little engine compared to the 4BD1T, and I think I could easily get away with my planned 2-3" of lift.

SOO, I need edumacated. I see there are various types of TDI's and I need to know which one's have what attributes. From research, 2002+ is ECU controlled with a dedicated engine management harness that would transplanted and modified. I'd like to see close to 200hp if possible, but slightly less will be fine if these engine's hit max HP and TQ at lower RPM's (the stock 4.0 gasser hits max HP at 4800 or thereabouts). With 170-200 hp, where would that put me at torque? With the AW4 mods listed, the trans could handle 450lb.ft IMHO.

Also, I understand the VW's are timing belt driven. Are these notorious to break? I am all about maintenance, but I know some TB setups can break before their maintenance schedule calls for replacement. Are they hard to replace? Are these engines interference types?

With my power goals, what fuel economy can be expected? I know that I won't see anything near their 40+ mpg car setups being in a box on wheels, but I have seen Toyota Pickup swaps claiming 30mpg highway.

I appreciate any and all help everyone. I am open to all recommendations and feedback!!
 
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#2 ·
I welcome you to check out tdiclub.com for information on the Volkswagen TDI.

If you are looking at a Volkswagen TDI there are a few variants in the 1.9L variety. The first of which is the AHU code. This can be had from a 1996 to 1999 Jetta or Passat. They make 90 hp and 149 torque in stock form. The AHU is computer controlled, without an immobilizer. The second is the ALH. Found in USA Golfs, Beetles, and Jettas from 1998 to 2004. They make 90 hp and 155 torque. The ALH has a VNT turbo and the engine management to deal with that control. They however have immobilizers from 2000 and up. The immobilizer can be deleted with a simple tune from most any TDI performance shop or supplier. There are more Volkswagen TDI models but they are not as common and fairly expensive. But they are the BRM, and so on.

All Volkswagen TDI's are interference engines as far as I know. The AHU and ALH and BRM are belt driven. As long as the belt is changed in a timely manner, there usually is no problem with keeping them running. Also, the timing belt job is fairly easy, if you can swap the TDI into the Jeep... you can do the timing belt.

As far as horsepower and torque go, it all costs money. But the 200 range for horsepower is easily obtainable. Turbo, cam, injectors, intake, tune, and an 11mm injection pump can get you there or above.

From what I have heard 30 to 35 in Toyotas is not unreasonable. I am currently swapping an mTdi AHU into a first gen Toyota 4x4 pickup.

The biggest thing with the Cherokee will be the automatic and the weight. I wouldn't expect over 30 with that setup.

Out of the three engines that you called out, the Volkswagen TDI is going to be the best as far as reliability, ease of finding parts, and ease of up grading. Also, there is more information out there about the VW TDI it is ridiculous.

Honestly, do as much research as you can before you start your project, so that you know what you are getting yourself into. Visit tdiclub.com and spend at least a month reading about all the things you can regarding the VW TDI.

I probably missed something, but I need to stop rambling now.


-Dan
 
#3 ·
I welcome you to check out tdiclub.com for information on the Volkswagen TDI.

If you are looking at a Volkswagen TDI there are a few variants in the 1.9L variety. The first of which is the AHU code. This can be had from a 1996 to 1999 Jetta or Passat. They make 90 hp and 149 torque in stock form. The AHU is computer controlled, without an immobilizer. The second is the ALH. Found in USA Golfs, Beetles, and Jettas from 1998 to 2004. They make 90 hp and 155 torque. The ALH has a VNT turbo and the engine management to deal with that control. They however have immobilizers from 2000 and up. The immobilizer can be deleted with a simple tune from most any TDI performance shop or supplier. There are more Volkswagen TDI models but they are not as common and fairly expensive. But they are the BRM, and so on.

All Volkswagen TDI's are interference engines as far as I know. The AHU and ALH and BRM are belt driven. As long as the belt is changed in a timely manner, there usually is no problem with keeping them running. Also, the timing belt job is fairly easy, if you can swap the TDI into the Jeep... you can do the timing belt.

As far as horsepower and torque go, it all costs money. But the 200 range for horsepower is easily obtainable. Turbo, cam, injectors, intake, tune, and an 11mm injection pump can get you there or above.

From what I have heard 30 to 35 in Toyotas is not unreasonable. I am currently swapping an mTdi AHU into a first gen Toyota 4x4 pickup.

The biggest thing with the Cherokee will be the automatic and the weight. I wouldn't expect over 30 with that setup.

Out of the three engines that you called out, the Volkswagen TDI is going to be the best as far as reliability, ease of finding parts, and ease of up grading. Also, there is more information out there about the VW TDI it is ridiculous.

Honestly, do as much research as you can before you start your project, so that you know what you are getting yourself into. Visit tdiclub.com and spend at least a month reading about all the things you can regarding the VW TDI.

I probably missed something, but I need to stop rambling now.


-Dan
 
#4 ·
VW Timing belts:
Are these notorious to break?
Nope, more likely to jump a tooth...or loose a tooth and skip one ahead each time it goes around.

Are they hard to replace?
Nope; I just did mine for the first time. It took about 10-12 hours. I'm sure I could do it faster now.

Are these engines interference types?
Yep, so you don't want it to jump even one tooth. If I remember right the 96-99 factory timing belt is a 65,000 mile belt. The 2000-04 is an 85,000 mile belt. The 2005 forward is a 100,000 mile belt. There are belt kits available to upgrade all years to the brand new design 100,000 mile belt, which is what I just put on my Jetta.
 
#5 ·
I have a TDI, and am not a big fan. The mileage is great, it starts well in the cold, and hasn't broken down on me. However, VW did a lot of dumb things, in my opinion, with the design of this engine and the car in general (of course you don't care about the car). There are lots of sensors and whatnot that like to go bad a lot. The engine is an interference engine, and the timing belt must be attended to at the proper time. I did it myself, it was a bit difficult, not too bad. Depending on your skills fabricating and thinking ahead, a timing belt change might necessitate pulling the engine if you don't have the right clearance or access. Turbos and whatnot are expensive. The timing belt and all the electronics would steer me away from this engine for a swap. Of course it may be the best option for you - but it has some limitations and drawbacks.
 
#6 ·
I have a 2009 4wd car with the BMM engine. This is the 2.0 variant of the 1.9tdi. Still 8 valves, still reverse-flow head but the highest factory power rating in that configuration. Injection is PD (pumpe deuse) and electronically controlled.
Stock it runs 22psi max boost, car has a big factory front mount intercooler (same size as the radiator), it delivers 320Nm from 1750-2500rpm and 103kw at 4000rpm. The turbo from this engine (I think it's a GT1646V) is often used to upgrade the 1.9 tdi's.

But that is limited by the ECU's torque limiters. Simply raising those torque limiters in the ECU without changing the boost or fuelling gives you maybe 20% more.
I am a big fan of the electronic controls in diesel engines. Easy starting and smooth running at pretty much all temperatures (timing maps change with engine temp), smoke free and plenty of power and torque without the safety risks. Not to mention keeping the VNT turbo working as it should.

Mileage wise, best I can do in this 4wd car is 6 litres/100km. That's 37 USMPG and I averaged that over the 1900km driving last week. I'd expect 30mpg in a Jeep depending on how and where you drive it.
Those guys claiming 50-60-70mpg are on crack. Just because you saw it once on the readout, doesn't make it real.
 
#8 · (Edited)
Mileage wise, best I can do in this 4wd car is 6 litres/100km. That's 37 USMPG and I averaged that over the 1900km driving last week. I'd expect 30mpg in a Jeep depending on how and where you drive it.
Those guys claiming 50-60-70mpg are on crack. Just because you saw it once on the readout, doesn't make it real.
Oh you can get 70mpg from a 1.9 TDI. Just not in a modern off-road vehicle.

I Personally know someone who is getting 70mpg consistently out of an ALH engine that is not even tuned, no water injection or anything. The secret is that his vehicle weighs about 1700lbs including himself and a full tank of diesel. He's got it in an old Rabbit Sportruck. Awesome build.

If you wanted to get 70mpg out of an ostensibly off-road vehicle with an ALH in it, you'd have to have something like an old Suzuki LJ10 with road tires.
 
#10 ·
I just sold my 2000 beetle with 1.9 TDI had it for almost 3 years and drove it 54 miles one way to work everyday. I checked the mileage very carefully, would fill it to the top where I could see the fuel each time. I averaged 48 mpg, that's driving 65mph the whole way. I could put over 700 miles on each tank. great little engine! the car was junky but the engine good. I did change the timing belt myself and it was time consuming but doable, especially if you had more room to work with. The only downside is parts are a little more expensive, and to get over 200 hp would probably cost a good bit.
 
#11 ·
2000 beetle with 1.9 TDI
I have the same car, nearly, Jetta, not Beetle. It doesn't seem to hardly matter how I drive it, it gets 47.5 to 48.5mpg all the time.

The only time it got less was on a long trip Wisconsin to Kansas hauling 500lbs of guys, a 60lb dog, and a week's worth of luggage and dog gear. Then it got 46mpg.
 
#17 ·
I can take a box truck, throw a thousand pounds of steel in the back, go for a flat drive and not have any significant difference in fuel consumption.

Weight mainly affects fuel consumption when you are on the accelerator and brakes the whole time (i.e. city driving). Your mate certainly isn't city driving.
 
#16 ·
Increases in air resistance increase as a square (both a larger frontal section and also with speed). Increases in weight increase drag linearly, but really only affect fuel burned during acceleration. You can actually get some of the fuel back by having more momentum and coasting further.

So if you are talking about a lot of highway driving where you reach a speed and hold it there; better aerodynamics rule increasing your MPG.

If you are talking about stop-and-go, low speed; decreasing weight will dominate increasing your MPG.
 
#18 ·
Here's what I would do for your cherokee;

2000-2003 ALH from automatic car (or swap on 11mm pump from auto car if you start with a stick motor)
ARP head studs
Bosio race 520 nozzles
Garrett GTB1756VK turbo
4 bar map sensor
Standalone tune from TDTuning. Removes immobilizer, MAF, and all non essential modules from ECU programming. Hook 12v to ecu, crank starter and it fires up.
Big of an FMIC as you can fit
5-15psi lift pump

That will give you ~225hp at the crank with 350lb/ft. Motor will rev to 5500 happily, peak hp will be at ~4300rpm, peak torque 2100-2400rpm.

Timing belts are every 100Kmi. It's quite rare for them to break. Not saying it never happens, but I've only ever seen 2 in 8 years of working on what has to be over 1000 TDI's by now. The timing belt job isn't a big deal to do in a longitudinal setup at all.

With the standalone tune in ecu, all you need to wire up to make it run are gas pedal, obd port, map sensor, and a handful of powers and grounds. The injection pump, 3rd injector, coolant temp, and crank sensor are all in the engine harness. The wiring is extremely simple when stripped for use outside a VW.

For mileage, I'd expect high 20's to low 30's depending on your right foot. It will hands down be the best power/weight ratio of any of the motors you listed. Any IDI merc is going to be a dog compared to a mildly built TDI (unless you spend $2k on a Myna pump and do compounds on it). Dressed ALHweighs 365lbs.
 
#20 ·
You don't need a superstructure mount of any kind for an ALH. You can use OEM mount brackets from a 04-05 Passat TDI to give you side mounts. You'll have to notch about 1/4" on the main accessory bracket for the driver side Passat mount, but nothing major that'll affect strength. There's plenty of m10 and m8 empty bosses on both sides of the block to make you own like any other motor.
 
#28 ·
All depends on what you are trying to express. :)

I could say that my 1995 Ram truck, when I am running on 100% biodiesel, gets a cost-based mileage of about 51mpg.

It gets the same real mileage as it does on diesel (about 17mpg), but the fuel is 1/3 the cost, so it triples my cost-based mileage.

Put another way; I spend no more on fuel than a guy running a 51mpg car only on regular diesel. So it can be an effective comparison, in a specific situation. :)
 
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