RE: IML: Auto Pilot vs. speed control

["Dick Benjamin" <dickb@xxxxxxxxx>]

A minor correction to Ernie's post, (or perhaps a difference from other
years):  at least on my car (the Gold 68) the system automatically
re-engages at the set speed without having to push the off-on-auto control
again after using the brake pedal.  

However, you do have to push it to "auto" again if you turn off the key. 

Once the desired speed is set on the dial, it holds that speed setting until
you manually change it, as the "memory" is purely mechanical (AKA known as
"static friction"!)

Ernie is right in that you have to bring it up to the set speed yourself,
after tapping the brake - it doesn't accelerate back up by itself, the way a
modern one does.

One other difference, while I have your ear, is that the auto-pilot is an
electro-mechanical device as has been well discussed, which as we know makes
it immune to poor vacuum conditions (cause by a weak or poorly tuned engine,
or high altitude, or a heavy load).  

That's all to the good, but because it depends on a lot of mechanical moving
parts, there is wear, and wear produces sloppy operation.  As a practical
matter, this isn't a factor until the car gets up to well over 100,000
miles, but I have had them wear to the point where I had to take all the
rotating parts apart and re-bush the bearings, and tighten up the ball
socket where the actuating rod fastens to the accelerator pedal linkage
under the floor.  If the linkage is sloppy enough, the actuating rod can rub
on the exhaust manifold near cylinder #7, this will cause erratic operation
as the engine rocks over during heavy acceleration, and could conceivably
lead to a locked wide open throttle condition - so take care of all those
joints and rotating parts for good operation and safety.

When everything is hunky-dory, it will hold to about +/- 2 MPH, in my
experience.  The modern type which uses the VSS sensor on the wheels, and is
computer operated, is much more precise - but those are only on the really
recent cars.  The ones on the 69 and later Imperials are sort of in between,
but they are of course vulnerable to low vacuum problems.  As for speeding
up on the downhill, all of the older designs will do that, as they are not
designed to apply the brakes.  Very modern cars will also apply the brakes,
but that is not an Imperial related remark!

Dick Benjamin

-----Original Message-----
From: mailing-list-owner@xxxxxxxxxxxxxxxx
[mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Ernie Stepney
Sent: Friday, March 17, 2006 3:08 PM
To: mailing-list@xxxxxxxxxxxxxxxx
Subject: RE: IML: Auto Pilot vs. speed control

The major feature differences between the two systems are:

1) The modern system will resume, tap up and tap down; auto pilot does
not, touch the brake and you are done until you go through the set
procedure all over again.
2) Cruise remembers whatever speed you push the set button at, AutoPilot
needs to be preprogrammed for the desired speed, then the car needs to
be brought up to that speed (at which point you feel feedback through
the pedal) then you set the set button to maintain that speed.
3) AutoPilot works as a speed warning device when not engaged, dial in
the desired maximum speed and when you reach that speed the throttle
effort increases substantially. Cruise control does not do this.

Best regards:
Ernie and The Black Bitc_!!





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