EST Distributor

[Shannen Durphey]

Isn't this abbreviation in the FAQ?  It should be.

EST stands for Electronic Spark Timing.  This is a control mode.  The ECM is in
control of spark timing (and dwell in distributor applications), with input from
and output to the distributor.  The ecm also uses inputs from the other engine
sensors to determine spark timing.  This is one of two basic spark modes, the other
being Bypass mode.

I don't know what you mean by "the 8 eng coded 91".  The only distributor which I
can think of with something close to EST, in addition to mechanical and vacuum
advance units, is the 81 vintage 305 used in Chevy/GMC pickups.  This was an ESC
system, which would retard spark when knock was detected.  I do not know of any CCC
or later generation ecm/pcm controlled engine management systems which used
mechanical and vacuum advance in addition to ecm controlled timing. 

You would be a wise man indeed to trade your Chilton's reference manual for a real,
true GM service manual.  You should also consider finding the address for the
company that supplies GM with its training materials, MSX.  The manual titled "fuel
injection" will supply some very good reading material. Much of what you are saying
is backward or misinterpreted, which could easily be attributed to a good mind
learning from a poor source of information.

Shannen

Bob Wooten wrote:
> 
> Questions #2, I think also another simple question.
> 
> what is meant by EST?  I have a 91 Camaro that has an EST distributor (so
> says Mr. Chilton).  what I have noticed, & I am guessing but want to clear
> it up is that EST is more a scheme than anything.  this means that the
> Distributor controls the spark duties w/the small input from the ECM for
> retard & LHM.  this means that the distributor conditions the PU coil, has
> the driver in it for the HV coil & outputs a signal that is used to
> determine RPM.
> 
> another guess is that all the EST setups do not have any Vac or Mech advance
> to them, but?????  I noticed that the 8 eng coded 91 has the "standard" HEI
> setup & I think (I don't have it so....) that it does have both Mech & Vac
> advance on it still.
> 
> thanks for clearing that up.  here comes #3.
> 
> Bob Wooten
> r71chevy at earthlink.net
> www.r71camaro.homestead.com
> 
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