Robert56 - BMN timing pull diagram
Robert56 - BMN timing pull diagram I found this diagram below while visiting your web site. Is this a reliable way of pulling timing? I have read this method will pull 4 degrees of timing when nitrous is activated.
According to GM service manual: Wire A in diagram is the "TAN" IAT sensor signal wire, Wire B is the "PURPLE" IAT ground wire.
Wire C would connect to the positive wire (GREEN wire in NX diagram) of main nitrous/fuel solenoid wouldn't it?
THANKS
According to GM service manual: Wire A in diagram is the "TAN" IAT sensor signal wire, Wire B is the "PURPLE" IAT ground wire.
Wire C would connect to the positive wire (GREEN wire in NX diagram) of main nitrous/fuel solenoid wouldn't it?
THANKS
Last edited by gollum; Aug 4, 2005 at 09:18 PM.
The way I make out the GM resistance / temperature
tables (Helm book, pg 6-1377 for you book mechanics)
you will be indicating a higher temperature by this
(reducing resistance by paralleling the 750 ohms).
However I think this is not the right way to go. The
-actual- air stream is cold. High IAT pulls spark but
also figures into the speed density airflow calcs and
possibly fueling by the IAT adder.
Now, fooling it cold is pretty much the flip side of
this drawing. You want a 100Kohm resistor and a
relay with a normally-closed (NC) contact. If you
put this inline with the IAT (tan?) wire you will
jack the read IAT to -40F.
Now you are at a "special place" and you can use the
OLFA, PE adder vs IAT, spark adder vs IAT to mess
the fuel and spark around without having to worry
about stepping on your hot-day, NA performance.
This all supposes you are able to tune these tables.
If you just want to pull spark the drawing posted
will do it (some). But for the most part the IAT
spark adder only pulls -3; -4 is only in spots and
at lower throttle. So if you want more than -3
it's just too bad; see big shot guys running -8 to
the normal NA advance.
I favor pushing the IAT in the direction of more
realism so the speed density side feels like it's
at the party. And that (where I live) it's bloody
unlikely to see that temp except when I mean it.
tables (Helm book, pg 6-1377 for you book mechanics)
you will be indicating a higher temperature by this
(reducing resistance by paralleling the 750 ohms).
However I think this is not the right way to go. The
-actual- air stream is cold. High IAT pulls spark but
also figures into the speed density airflow calcs and
possibly fueling by the IAT adder.
Now, fooling it cold is pretty much the flip side of
this drawing. You want a 100Kohm resistor and a
relay with a normally-closed (NC) contact. If you
put this inline with the IAT (tan?) wire you will
jack the read IAT to -40F.
Now you are at a "special place" and you can use the
OLFA, PE adder vs IAT, spark adder vs IAT to mess
the fuel and spark around without having to worry
about stepping on your hot-day, NA performance.
This all supposes you are able to tune these tables.
If you just want to pull spark the drawing posted
will do it (some). But for the most part the IAT
spark adder only pulls -3; -4 is only in spots and
at lower throttle. So if you want more than -3
it's just too bad; see big shot guys running -8 to
the normal NA advance.
I favor pushing the IAT in the direction of more
realism so the speed density side feels like it's
at the party. And that (where I live) it's bloody
unlikely to see that temp except when I mean it.
You can also replace the known value resistor with pointometer. Then using a ohm meter or logging you can dial in a set amount of timing pull. There is a wiring diagram (I think) for this on my web also. It's late and i have been real busy lately so my brain is half shut down. I will try to get back later and ellaborate on the schematics and tuning effects. Probably Saturday, going ta the races tomorrow.
Robert
Robert
Originally Posted by Robert56
You can also replace the known value resistor with pointometer. Then using a ohm meter or logging you can dial in a set amount of timing pull. There is a wiring diagram (I think) for this on my web also. It's late and i have been real busy lately so my brain is half shut down. I will try to get back later and ellaborate on the schematics and tuning effects. Probably Saturday, going ta the races tomorrow.
Robert
Robert
-3 degrees at WOT (stock config). There is more pullout
at part throttle but that doesn't help us here. If you
want less pullout than this you can play with it by
adjusting the (faked) temp reading but more, needs
tune editing.
Figure NA cars see 0.76-0.8 g/cyl and a heavy shot
might be as high as the 1.2g/cyl table limit. But that
whole region has a pretty limited pullback.
If you made the pullout, at these higher CylAir ranges,
temperature-linear though (rather than a -3 plateau)
then the potentiometer would indeed give you some
manual adjustability on-the-fly.
Maybe -3 degrees @WOT is all that is needed with a Wet 150hp or less jet setting ? Seat of the pants and good old fashion plug reading will tell.
Last edited by gollum; Aug 5, 2005 at 02:49 PM.
Originally Posted by jimmyblue
Thing is that the IAT timing adder table only goes to
-3 degrees at WOT (stock config). There is more pullout
at part throttle but that doesn't help us here. If you
want less pullout than this you can play with it by
adjusting the (faked) temp reading but more, needs
tune editing.
Figure NA cars see 0.76-0.8 g/cyl and a heavy shot
might be as high as the 1.2g/cyl table limit. But that
whole region has a pretty limited pullback.
If you made the pullout, at these higher CylAir ranges,
temperature-linear though (rather than a -3 plateau)
then the potentiometer would indeed give you some
manual adjustability on-the-fly.
-3 degrees at WOT (stock config). There is more pullout
at part throttle but that doesn't help us here. If you
want less pullout than this you can play with it by
adjusting the (faked) temp reading but more, needs
tune editing.
Figure NA cars see 0.76-0.8 g/cyl and a heavy shot
might be as high as the 1.2g/cyl table limit. But that
whole region has a pretty limited pullback.
If you made the pullout, at these higher CylAir ranges,
temperature-linear though (rather than a -3 plateau)
then the potentiometer would indeed give you some
manual adjustability on-the-fly.
Robert
