[DeTomaso] More cruise control issues

Charles McCall charlesmccall at gmail.com
Mon Aug 31 13:36:04 EDT 2009


On Mon, Aug 31, 2009 at 7:26 PM, <asajay at asajay.com> wrote:

> -That- brought back memories.
>
> I used an old CompuCruise computer in an older car of mine that had a
> manual transmission.  The Tach signal was only -one- source of input
> for the cruise control.  The others were the brake switch and the
> third was a set of magnets attached to the drive line and picked up by
> a nearby sensor.  -That- was the speed sensor.
>
> The tach adapter can NOT be used as a speed sensor.  After all, you'll
> get the same rpm in 1st gear, second gear, third, etc.  i.e. 2,000 rpm
> in first is one speed, while 2,000 rpm in 5th is totally different.
> You -can't- use the tach as a speed sensor.
>
*****Why not? The message you are sending to the cc brain is not "maintain
47 mph"... the message you are sending is "maintain the current speed,
whatever it may be". If you are in 3rd at 3000 rpm, it will maintain a
constant 30mph (for example). If you are in 5th at 3000 rpm it will maintain
a constant 70mph. If you press the clutch to change gears, all bets are off
and it shuts off.



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