[urq] "Doesn't Need Distributor Signal"

[urq]

Craig wrote:

 


Good point, however the urq doesn't need the distriubutor signal after start
up.


 

. and you say this because you know that you can pull the cable off the Hall
Sender while the engine is running (on an urq, 5kT, v8q, ???) and the engine
doesn't stop running, correct?  Yes, I have done that test too, and have
been tending to agree . 

 

. but it is also well known that should the distributor timing get too far
out relative to the crankshaft the engine will cut out and die . in fact
this was one of my first findings when I got my urq way back when.  Ned
Ritchie printed this info in a QQ issue when I asked about a 4k RPM cut out
I had many, many years ago . 

 

Both these statements can't be true . and I now realize what is missing in
the first statement.  The Hall Sender has two states, and in some ways you
can think of it just like a set of points in an older car.  When you remove
the connector from the Hall Sender it is as though the "points" are open all
the time, and I agree that in this condition the engine will continue to run
(I too have run this experiment).  The thing is, if you then simulated the
points being closed by grounding the Hall sender signal to the ECU the
engine will stop running.  I have not yet run this experiment, but since I
know the circuitry on the ECU gates the reference pin signal with the Hall
Sender signal, the "closed points" will stop the reference mark signal .
this also explains the second fact.  If the crank to cam timing gets to the
point where the Hall Window no longer matches up with the reference pulse,
the "closed points" prevent the reference pulse from getting to the
computer.  

 

This mechanism was intended to ensure the ignition was synched to the proper
TDC mark (which is more important on an engine with an odd number of
cylinders), but it also provides some protection in cases where the timing
belt jumps teeth.  Of course it won't help much if the timing belt breaks . 

 

Steve Buchholz