Re: Top speed limiter... a definitive answer sought/Landshark

[Jim Conforti <lndshrk@xxxxxxxxxxxx>]

Michael Greto wrote:
> 
> I would like to hear from Jim C. or anyone else who can give a definitive
> answer as to what limits the top speed.  I thought the ECU was programmed to
> recognize full throttle in top gear and then limited the max speed through a
> RPM limit.  Am I wrong?

  OK.. let's look at OBD-I and OBD-II...

  First, in BOTH of them, Vehicle Speed is measured by receiving the "A" signal
  from the vehicle speedometer. and once a preset limit is reached, speed
limiting
  goes into effect..

  How that happens differs..

  In OBD-I generally two banks of cylinders are disabled.. first one.. then if
the
  vehicle speed continues to increase, the other..

  In OBD-II (specifically Siemens MS41 and MS42) the system cuts ONE cylinder at
a time
  until the speed increase stops.. up to ALL cylinders.. it does so in a pattern
that
  makes the speed (and rev) limiters much smoother on the engine and you.

  Note.. that the REV limiter is basically the same function, only that the
current RPM
  is compared with a pre-programmed limit to activate the same FUEL CUT
functions.

  Jim

------------------------------