Paul I have a new RX-7 friend that used to race p-ports, he said he
could get them to idle just as good as a carb by retarding the timing
20 + degrees then would reset it for racing after he got his carbs
tuned. Is that something that Trace's system could be set up to do
only advance it so it would have a normal idle to WOT range. He did
this years ago when all he had was a stock Mazda electronic ignition.
With an electronic ignition like Tracy's this should be a peace of
cake.

Allen Ervin


Paul what do you think about this?

Allen Ervin


Sounds like it would work. Talking Tracy into it might be another
matter.

Paul Lamar

Hay just opens up more market for him. lol

Allen Ervin

Yes but it idles pretty good without retarding the ignition.

Paul Lamar

I talked to John this weekend and he also mentioned it stopped the
fuel blow back that p-ports have a problem with. John also showed me
how he did his p-ports using a stock intake manifold, I'll take some
pic's next time i get over there.
Allen Ervin

What does he mean by fuel blow back?

Paul Lamar

Paul,
He may be alluding to back pressure from commencement of the
compression stroke, as the compression over powers the incoming gases
as and when the inlet is still open.
I believe your opinion is that the close ( to the housing) butterfly
or slide control reduces that problem.
I would be interested in other possibilities.
George ( down under)

I don't see how ignition timing would change that.

Paul Lamar

A delayed shot at the charge gives it more time to get in the chamber ?
How's that for a reason ?
jofarr, soddy tn

Nope! Still does not make sense.

Paul Lamar

How about this?   Retarding the spark is another way to cause the engine
RPM to be reduced.  The countering effect is to open the throttle plate
more than with the advanced (normal) timing.  Now that the throttle plate
is further open, there's less vacuum (higher pressure) in the runner.
This changes the gas flow dynamics associated with the intake opening and
closing, reducing the stumbling effect.


Matt-

Most logical explanation I have heard do far.


Paul Lamar