I just got a line on an 82 two door Rabbit turbo-diesel. It only has a 4 speed, although I have a 1.7 gas wide ratio 5 speed available. Aside from the usual A1 chassis improvements, how do these early turbo diesels respond to tuning tricks? What is available, besides exhausts, and what kind of results will I be seeing? Thanks!
suggestions for A1 TD?
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Re: suggestions for A1 TD? (venturaII)
look propane injection. it is supposed to be for diesel what nos is for gas motors. you might beable to bore out the motor. I dont know if there is a more radical cam for a diesel. rig up a ram-air system, and check out tdiclub.com
look propane injection. it is supposed to be for diesel what nos is for gas motors. you might beable to bore out the motor. I dont know if there is a more radical cam for a diesel. rig up a ram-air system, and check out tdiclub.com
Re: suggestions for A1 TD? (busted-ass-jetta)
Good pump timing is about as far as you can go other than propane. Propane does give you a shot like NOS, but like NOS, it's hard on the engine, and only good for a short dose. You want to make sure the injection pump is timed well, and slightly advanced, but finding somebody who knows pump timing on the old diesels is hard to do.
The pump is entirely mechanical, so there are no computers to help you improve the fuel mapping curve. Added air doesn't really do much either other than improve the cloud of soot coming out the back end. It's not gonna give you much in the way of horsepower, because you already have a turbo forcing more air in, even a ram isn't gonna improve on that. Since a cam is essentially trying to do the same thing (get more air in the chamber) you're not gonna see much out of that either.
Also on the exhaust, because it is a turbo, you don't see much help from a better exhaust, other than a possible slight improvement in turbo lag.
I'm afraid you're kinda stuck with a sub 75hp engine. They get great mileage, and are essentially bullet proof if you make sure the timing belt stays in good condition. You may get even better mileage from the 5speed, but with a wide ratio, I doubt you're gonna get any better accelleration.
Good pump timing is about as far as you can go other than propane. Propane does give you a shot like NOS, but like NOS, it's hard on the engine, and only good for a short dose. You want to make sure the injection pump is timed well, and slightly advanced, but finding somebody who knows pump timing on the old diesels is hard to do.
The pump is entirely mechanical, so there are no computers to help you improve the fuel mapping curve. Added air doesn't really do much either other than improve the cloud of soot coming out the back end. It's not gonna give you much in the way of horsepower, because you already have a turbo forcing more air in, even a ram isn't gonna improve on that. Since a cam is essentially trying to do the same thing (get more air in the chamber) you're not gonna see much out of that either.
Also on the exhaust, because it is a turbo, you don't see much help from a better exhaust, other than a possible slight improvement in turbo lag.
I'm afraid you're kinda stuck with a sub 75hp engine. They get great mileage, and are essentially bullet proof if you make sure the timing belt stays in good condition. You may get even better mileage from the 5speed, but with a wide ratio, I doubt you're gonna get any better accelleration.
Re: suggestions for A1 TD? (BookerDog)
Propane is like NOS in only one way...more power. Other then that they are totally different. Check the posts at www.TDICLUB.com where a couple members are running it.
It lowers engine temps...makes the desiel burn more cleanly which lowers soot buildup. They said that the first time they took a run with propane they notice lots of soot coming out of the exhaust...it was as if it was cleaning out the system. Most of the guys running propane run it 24/7 unlike NOS where its just for a short boost.
If you have the $$$ and setup it up responsibly you can still enjoy engine reliability and more power.
[Modified by ST33LR4T, 3:44 PM 12-3-2001]
[Modified by ST33LR4T, 3:45 PM 12-3-2001]
Propane is like NOS in only one way...more power. Other then that they are totally different. Check the posts at www.TDICLUB.com where a couple members are running it.
It lowers engine temps...makes the desiel burn more cleanly which lowers soot buildup. They said that the first time they took a run with propane they notice lots of soot coming out of the exhaust...it was as if it was cleaning out the system. Most of the guys running propane run it 24/7 unlike NOS where its just for a short boost.
If you have the $$$ and setup it up responsibly you can still enjoy engine reliability and more power.
[Modified by ST33LR4T, 3:44 PM 12-3-2001]
[Modified by ST33LR4T, 3:45 PM 12-3-2001]
Re: suggestions for A1 TD? (venturaII)
I have some links below:
http://4crawler.cruiserpages.com/Diesel/index.shtml#TechInfo
Turn the injector pump up to the performance range, get an exhaust gas pyrometer and you can turn up the fuel and/or boost pressure until you start hitting the EGT limits for the engine.
I have some links below:
http://4crawler.cruiserpages.com/Diesel/index.shtml#TechInfo
Turn the injector pump up to the performance range, get an exhaust gas pyrometer and you can turn up the fuel and/or boost pressure until you start hitting the EGT limits for the engine.
Re: suggestions for A1 TD? (BookerDog)
Actually, I was wanting the wide ratio 5sp for performance reasons. On gas motors, turbo's like larger ratio jumps than naturally aspirated motors do, and I'm assuming diesels are the same way. Gives the turbo a little more time to develop max pressure(provided the rpm drop isn't TOO dramatic). Turbo's develop much more torque at lower rpms than N/A motors do, so why not take advantage of it?
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[Modified by venturaII, 9:34 AM 12-4-2001]
Actually, I was wanting the wide ratio 5sp for performance reasons. On gas motors, turbo's like larger ratio jumps than naturally aspirated motors do, and I'm assuming diesels are the same way. Gives the turbo a little more time to develop max pressure(provided the rpm drop isn't TOO dramatic). Turbo's develop much more torque at lower rpms than N/A motors do, so why not take advantage of it?
[Modified by venturaII, 9:34 AM 12-4-2001]
Re: suggestions for A1 TD? (venturaII)
quote:[HR][/HR]Actually, I was wanting the wide ratio 5sp for performance reasons. On gas motors, turbo's like larger ratio jumps than naturally aspirated motors do, and I'm assuming diesels are the same way. Gives the turbo a little more time to develop max pressure(provided the rpm drop isn't TOO dramatic). Turbo's develop much more torque at lower rpms than N/A motors do, so why not take advantage of it?
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[HR][/HR]
You also want the wide ratio because of the diesel's somewhat limited RPM range. I'll have a wide ratio FN 5-speed (0.71 5th gear) for sale shortly. It was professionally rebuilt about 2-3 years ago and is in great shape.
Re: suggestions for A1 TD? (VWCaddy)
Actually, wouldn't limited rpms and rpm range be an argument for a close-ratio tranny? 50% of 6000rpm only brings you down to 3000, but 50% of 3500rpms is only 1750, which is getting pretty low, and that's using an engine's hypothetical redline. Isn't that why OTR semi's use ultra-close ratio 13 speed gearboxes?
What about input shafts for gas versus diesel VW's? Are they the same size? I know the cluches are different, but that's easy. How about final drive ratio's? I have tons of gas motor and tranny stuff, but not much practical experience with VW diesels....
Actually, wouldn't limited rpms and rpm range be an argument for a close-ratio tranny? 50% of 6000rpm only brings you down to 3000, but 50% of 3500rpms is only 1750, which is getting pretty low, and that's using an engine's hypothetical redline. Isn't that why OTR semi's use ultra-close ratio 13 speed gearboxes?
What about input shafts for gas versus diesel VW's? Are they the same size? I know the cluches are different, but that's easy. How about final drive ratio's? I have tons of gas motor and tranny stuff, but not much practical experience with VW diesels....
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Re: suggestions for A1 TD? (venturaII)
Slap on an intercooler, a better air filter and a 2" or 2 1/4" exhaust system on it.
Cams don't do much with a diesel, but improving the turbo efficiency (with an I/C and exhaust) definitely does. There's actually a VW intercooler you can order from europe that came on European GTDs, but it would probably be cheaper to scrounge your own from a Talon or a Daytona or something.
After that, propane (where it's legal) is the way to go.
Slap on an intercooler, a better air filter and a 2" or 2 1/4" exhaust system on it.
Cams don't do much with a diesel, but improving the turbo efficiency (with an I/C and exhaust) definitely does. There's actually a VW intercooler you can order from europe that came on European GTDs, but it would probably be cheaper to scrounge your own from a Talon or a Daytona or something.
After that, propane (where it's legal) is the way to go.
Re: suggestions for A1 TD? (venturaII)
With only 5 gears, you need to spread them over a wider range. VW diesels tend to have lower final drive ratios, ~3.9 is common, while the gas engines use ~3.6, probably to give the diesel engine a bit of help getting started. Then they'll end up with a 5th gear of 0.71 or so. I would love to get a 6-speed with that same range but finer steps in the middle. I find the jumps from 2-3 and 3-4 are a bit too large.
http://4crawler.cruiserpages.com/Diesel/VW_020_transmission.shtml
quote:[HR][/HR]Actually, wouldn't limited rpms and rpm range be an argument for a close-ratio tranny? 50% of 6000rpm only brings you down to 3000, but 50% of 3500rpms is only 1750, which is getting pretty low, and that's using an engine's hypothetical redline. Isn't that why OTR semi's use ultra-close ratio 13 speed gearboxes?
What about input shafts for gas versus diesel VW's? Are they the same size? I know the cluches are different, but that's easy. How about final drive ratio's? I have tons of gas motor and tranny stuff, but not much practical experience with VW diesels....[HR][/HR]
Ideally yes, as you mention, look at the big rigs. Great to have a close ratio tranny, given you have enough gears to get up to speed. They usually have 10-20 forward speeds.What about input shafts for gas versus diesel VW's? Are they the same size? I know the cluches are different, but that's easy. How about final drive ratio's? I have tons of gas motor and tranny stuff, but not much practical experience with VW diesels....[HR][/HR]
With only 5 gears, you need to spread them over a wider range. VW diesels tend to have lower final drive ratios, ~3.9 is common, while the gas engines use ~3.6, probably to give the diesel engine a bit of help getting started. Then they'll end up with a 5th gear of 0.71 or so. I would love to get a 6-speed with that same range but finer steps in the middle. I find the jumps from 2-3 and 3-4 are a bit too large.
http://4crawler.cruiserpages.com/Diesel/VW_020_transmission.shtml
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