Date:         Tue, 19 Dec 1995 15:05:00 -0800 (PST)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Maher, Steve (SD-MS)" <SMAHER@PO2.GI.COM>
Subject:      RE: Cruise control for '80-82 Vanagon


>Anybody put cruise control on your bus?  My right knee has never liked
>driving, but ever since the patellar cartilage was removed it
>has HATED it... I measure trips in aspirin and limit them by driving
>days I know the knee can survive (4, if I'm lucky).
>
>I'm hoping that the newly rebuilt engine will have enough
>additional power so that I won't have to break out the oars on
>every hill,

I put it on a '69 bus, but it didn't have enough power, as could be
expected. Your Vanagon might have enough, though. Two places cruises
and buses don't get along: (1.) Engine power, obviously, and (2.) Engine
vacuum to actuate the servo (most cruises have vacuum servos).

Roughly speaking, engine vacuum is a function of how far down you're
pushing the accelerator pedal. The farther you're pushing the pedal
down, the harder your engine is working, and the less vacuum you have.
Since many VWs spend large amounts of time with the accelerator flat
on the floor, they are poor candidates for vacuum-powered devices
such as cruise controls.

Anyone who has ever driven an old Jeep with its vacuum-powered windshield
wipers, which stop when you floor the pedal, knows what I'm talking about.

A cruise control opens a valve to let vacuum into a plunger that opens the
throttle. Perversely, when you open the throttle, you get less vacuum. 
Larger
engines have enough extra vacuum to work well anyway, but guess where a VW
falls on that scale.

JC Whitney sells many different kinds of cruise control, and they also sell 
a
little plastic can called a "vacuum reservoir", with some hose connections
and a one-way valve to save a bunch of vacuum from the last time your engine
had any. Not a bad idea for a small engine in a big car.

If you get one of these reservoirs, then a cruise control should work OK
in a vanagon, on mostly flat ground. If it ever has to go up a significant
hill,though (as you know), a cruise control won't help-- especially if it
couldn't maintain speed up that hill BEFORE you installed the cruise 
control,
obviously.

You'll probably need to buy a bunch of 18-ga stranded wire, and splice a
15-foot length into each wire of the harness that goes from the cruise
control body (in the engine compartment) to the control module that mounts
on or near the steering wheel. No big deal if you have a soldering iron.

Try to find a cruise control that has an adjustable "gain" control. The
manufacturer doesn't know in advance, how much to open the throttle to
get a certain amount of push from the engine-- the bigger the engine, the
more push you get from one inch of throttle movement, for example. Some
manufacturers try to strike a "happy medium" with their cruise controls,
which invariably shortchanges VWs. Others provide a hole you can stick a
screwdriver and adjust a screw inside there. Then, when it's time to
open the throttle to maintain speed up a hill, the cruise control knows
not to bother with subtlety, but just open it a LOT. Some "gain" adjustments
are done with a screw, while other manufacturers use banks of switches
that you set in various combinations for more powerful or less powerful
engines.

I'm going to put one sometime into the V6anagon, but that's a different
story-- plenty of vacuum to spare with that CHevy V6 engine.

BTW, JC Whitney used to sell a cruise control with an electric-motor servo
instead of a vacuum servo. No vacuum tap needed! But I think they no longer
distribute it-- haven't seen it in their catalog in a few years. Six years
ago I put one of those into an '80 Honda Accord, which was no great shakes
in the acceleration department. It worked beautifully for a few years, then
pooped out-- maybe due to my poor installation.

Good luck-- let me know how it goes.

Steve Maher   smaher@gi.com   '80 V6anagon
                              '71 VW Transporter