swaping in a diesel engine into a gas VW - Page 2 - Fuelly Forums

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Old 07-28-2006, 09:14 AM   #11
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Give it a search, there's tons of info on it. I actually saw it on the news in MO where someone set up a company building stills (is that how it's spelled) for people to make ethanol for their business.
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Old 07-28-2006, 09:22 AM   #12
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Those power numbers only require remap on a 2.0PDI four banger. VW builds some durable engines.... When they first released to TDI it only had 90hp, but as injection technology progressed and they found the 1.9L internals to be pretty solid, they increased hp and bore a little bit and ended up with the 2.0PDI pumping out ~170hp stock. Old 1.6NA's can easily be pushed to ~70-100hp with no problems and an increase in fuel economy provided it's done right. From what I've gathered, the limiting factor with diesel power is not the engine bottom end, but EGTs. So if a manufacturer can push fuel in faster, then it should combust as well as it did before and they can get more power out of an engine at the same temperatures. Of course you can always remap and toss more fuel in there regardless, but unless your fuel pressure has increased or you have more air, you'll run hight EGTs and can melt your engine.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 07-28-2006, 11:34 AM   #13
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I'm just deflating on him, because I think most of the power/fe numbers he cites as easily attainable are way out there.
The numbers might seem way out there, but such figures have been done before.

Google search "Opel Eco Speedster". 97 mpg, 112 horsepower diesel, 160 mph top speed, .20 drag coefficient, 15.06 square foot frontal area.


The Rabbit is an unaerodynamic brick, .36 Cd and 18 square foot frontal area. Yet it can still get over 40 mpg combined EPA, approaching up to 50 mpg highway attainable at about 65 mph. There's numerous reports of individuals attaining 55-60 mpg at a steady 55 mph, which is about the speed this person drives.

Imagine what happens with extensive aeromods, to get Cd to around .25, along with LRR tires, synthetic transmission oil, drag free brakes, and other simple modifications that this person is planning. Highway fuel economy would no-doubt increase more than 20% from the aeromods alone(evidenced by many examples on this site and elsewhere of extensive aeromods having this impact), 10% or more from the other things.

80 mpg is well within grasp at the speed this guy drives, keeping the original engine unmodified but adopting extensive mods for the car itself.

An updated higher horsepower turbo diesel could actualy increase fuel efficiency even more if this mod along with the ones above were pursued, given that the 80s diesel is nowhere near as efficient as a modern one.

A stock 1980s Rabbit gets slightly over 40 mpg EPA, while a Prius gets around 55 mpg EPA. Take the 80s diesel out of the Rabbit and replace with something modern, even with a performance chip and added turbo boost, mpg in the 50s is probably obtainable. This is before aeromods and such are considered.
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Old 07-28-2006, 12:35 PM   #14
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Where'd you see .36 for the rabbit? I always saw that mk1 vws range from .42-.46 depending on whether the car's a jetta, rabbit, or rabbit pickup.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 07-28-2006, 12:36 PM   #15
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A stock 1980s Rabbit gets slightly over 40 mpg EPA, while a Prius gets around 55 mpg EPA. Take the 80s diesel out of the Rabbit and replace with something modern, even with a performance chip and added turbo boost, mpg in the 50s is probably obtainable. This is before aeromods and such are considered.
I had to borrow my brother's mid '80's diesel Rabbit 4-speed once when my car was being worked on about 10 years ago. My trip to work was 25+ one direction and it was around 75-80% highway. After 2 days of driving to work and driving into the town where my car was being worked on(twice), I refilled it when I gave it back to my brother and the mileage checked out at just over 52 mpg. This was before I was really big into driving techniques.
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Old 07-28-2006, 03:05 PM   #16
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The Rabbit is an unaerodynamic brick, .36 Cd and 18 square foot frontal area. Yet it can still get over 40 mpg combined EPA, approaching up to 50 mpg highway attainable at about 65 mph. There's numerous reports of individuals attaining 55-60 mpg at a steady 55 mph, which is about the speed this person drives.
Before you quote the epa on the rabbit you should note it was evaluated before the epa redid their testing and dropped ~20% off their estimates. The same year that the Diesel L got 48 mpg highway the CRX HF was rated for 67...

Not to mention that it has 48 hp, the cars fall apart like nothing else, and I have been told by more than a few people that cruise control was leaving a brick on the pedal because it couldn't break 75 mph and that in hilly areas it takes everything it has to keep it going.

And then I stopped wanting to buy one and ended up with a crx and couldn't be happier...
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Old 07-28-2006, 03:26 PM   #17
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Hehe, that's all true in some cases! But it depends on the car/tranny you get... On the postivie side the drivetrain is just about as durable as it gets, and roughly doubling the horsepower while leaving efficiency unchanged can be done for maybe $250-500 depending on how you thrifty you are. The disparity in highway mileage comes from the CRX having a CdA of ~6 square feet, while a Rabbit is ~9 square feet. You have any sources for the EPA estimates?
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Old 07-28-2006, 03:41 PM   #18
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http://fueleconomy.gov/feg/how_tested.shtml

At the bottom is a little blurb about how they changed them, this is also the reason you can't find EPA estimates older than 85 on the website.
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Old 07-28-2006, 04:04 PM   #19
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That explains a lot. I figured they would've left the older data there with a big fat disclaimer, but I guess they don't want people getting the wrong idea? Shoot, I dunno...
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Old 07-29-2006, 02:24 PM   #20
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Where'd you see .36 for the rabbit? I always saw that mk1 vws range from .42-.46 depending on whether the car's a jetta, rabbit, or rabbit pickup.
Crap, you're right.

I had confused the Rabbit Mk I's drag coefficient with that of the Scirrocco.

Although, Uve's EV Calculator does list the Rabbit as .36(a number that's been floating around some groups for the Mk II determined by coast down method).

Even still, cutting from .42 down to the high .2 region would have even a larger impact than doing it from .36 down to the high .2 region.

Mk II VWs had a bit of a drag reduction over their ancestors though. The Mayfield Companion quotes the Mk II Jetta at .32, for instance.

Here is a Rabbit Mk II photo, for those interested in how it looked being run through the wind tunnel:



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After 2 days of driving to work and driving into the town where my car was being worked on(twice), I refilled it when I gave it back to my brother and the mileage checked out at just over 52 mpg. This was before I was really big into driving techniques.
Not bad at all. Reflects what others have gotten with the cars.

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Before you quote the epa on the rabbit you should note it was evaluated before the epa redid their testing and dropped ~20% off their estimates. The same year that the Diesel L got 48 mpg highway the CRX HF was rated for 67...
Indeed. The EPA estimates are notorously inaccurate. Little known secret: the EPA doesn't measure fuel consumed, but estimates it from emissions.

But people are achieving and exceeding these estimates with proper driving technique. The figures were convenient and available, so that's what I used as a basis for comparison. Just as there are people getting 50 mpg in Toyota Priuses, there are people doing the same in old Rabbits with inefficient engines.

Replace the old inefficient engine with a more effiicient, high-power diesel engine, and you get the same or better fuel economy, with much more performance.

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Not to mention that it has 48 hp, the cars fall apart like nothing else, and I have been told by more than a few people that cruise control was leaving a brick on the pedal because it couldn't break 75 mph and that in hilly areas it takes everything it has to keep it going.
With all this I can agree.

But many love these cars. The person I am referring to that is aiming to make his own fuel goes by the name "Pilferage" on peakoil.com and on the maxmpg boards. He's keeping the oroginal engine.

If I had a Rabbit, I'd do a swap to something modern. I like to go fast.

Also of note, my Triumph falls apart faster than any Rabbit. But I love the **** out of it.

Converting these Rabbits to a slow EV on flooded batteries and low-power Curtis controller is widely considered a performance upgrade.

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And then I stopped wanting to buy one and ended up with a crx and couldn't be happier...
Aside from needing gas and not being able to be run on biodiesel, the CRX is a good choice. The HF has a .29 Cd, which is pretty damned good. I considered using a CRX as a base for the electric car I wanted to build, but there were already many of them converted, I don't like the looks much, they are expensive as hell in my area, and I found the Triumph.
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