Date: Sat, 8 Aug 1998 16:54:48 -0400
Reply-To: Martin Jagersand <jag@CS.YALE.EDU>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Martin Jagersand <jag@CS.YALE.EDU>
Subject: Re: Westy Engine Swap and A/C Installation
In-Reply-To: <199808051954_MC2-5538-6F71@compuserve.com> (message from Jan
Eggspuehler on Wed, 5 Aug 1998 19:53:54 -0400)
> Thank you for your continued help. I will try to work out the A/C
> according to your instructions but first I want to get the drivetrain up
> and running. I think I will put the A/C on hold for awhile. In the
> meantime I will pull the appropriate parts from the Quantum.
This sounds like a good plan.
> My new 1.6TD
> arrived today courtesy of VW. I used the Quantum as a core.
Just curious, how much was the exchange? Did you get a long block
or a complete engine? I understand the VW exchanges are a pretty
good deal since you also get a good warranty with the rebuilt engine.
> Now comes the
> transmission. I have the old 4 speed tranny from the Westfalia which I
> suspect does not work (it was lying in a field next to the van when I
> bought it). I called German Transaxle of America today and they
> recommended I use a 4 speed from an early 80's gas Vanagon. They said it
> is geared higher and will help acheive the smae things I was trying to when
> I wanted to put a 5 speed in. Do you have any comments or suggestions
> regarding this? I.e. a little more top end speed. Thank you again for you
> help.
The difference between the two 4sp trannys is the final ratio.
It's 4.57 for the gas and 5.43 (or possibly 5.86 if you have
the "mountain" gearing) for the diesel. Designing gear ratios
for a particular vehicle engine combination is a bit tricky.
Among things you want good accereration, but also reasonably
low cruising rpm, and the shift points should be conveniently
placed (so you don't have to shift more than necesary during
city or highway driving).
On rule of thumb when installing a more powerful engine is that
you can decrease the final drive ratio up to as much as the
new engine has more torque (or power). In reality it gets
a bit more complicated, since torque and power varies with
rpm, and ideally one must check that the torque at the
wheel for each wheel rpm is no less with the new combination
than with the old. Equivalently one can check for each
driving speed what rpm the engine turns, and then look in
the power curve for that rpm. Power for the new engine at the new,
lower rpm must then be higher than the power availible at
for the corresponding higher rpm the old engine turned.
To do this requires access to the torque and power curves
for the engine. Jake had a jpg or gif scan of those for both the
1.6 nat aspirated and turbo diesel. Maybe he can send that to
you as an attachment. Jake, are you there? Did you subscribe to the
temporary diesel list? (I'm also cc:ing this to you in case you didn't)
For your reference, I'm going with the 4.57 final for my 1.9 TD
swap, but the 1.9 is a longer stroke engine than the 1.6, and
has more low end torque. With the 1.6l TD's that VW sold in
Europe, they used a 5.5 final drive for quick startups, but
changed 3rd and 4th gear (.78 4th in the TD compared to .85 4th
in the earlier D). This makes sense, since the turbo doesn't
really help at startup. It only gives substantial boost
around 2000rpm and above)
Let us know how the swap goes.
Good luck,
Martin
82 Diesel Westy
85 Quantum TD
--
Martin Jagersand email: jag@cs.yale.edu
Computer Science Department jag@cs.rochester.edu
Yale University
Slow down and visit the VW diesel Westy page:
WWW: http://www.cs.rochester.edu/u/jag/vw
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