I don't seldom give up on a problem, but I came awfully close this time.
Mark
OK; Mark; (or anybody).
Since we both have 20Bs, and both use the EC2 controller, maybe you have
a clue for this one. I’ve brought this up here before, but no solution.
I have all the latest updates on the
EC2, and I have double checked the static timing set at 35o BTDC.
From that point on the EC2 is handling the timing curve with rpm and MAP.
At lower power levels, disabling the
leading ignition clearly has a larger effect than disabling the trailing –
as one would expect. At somewhere around 18” MAP, (don’t know
right now what rpm that is, maybe close to 4000) the effect is about equal when
disabling either set. At higher power levels, there is a larger effect of
disabling the trailing than the leading. That troubles me. I think
the leading should always have a greater effect. It makes me wonder about
the timing; or if something else is wrong.
I have in the past tried varying the
timing 2 or 3 steps while at power, but couldn’t discern a change in rpm greater
than the normal variation in the readout. Tracy sent me the XL
spreadsheet with the timing curve data, but I haven’t yet figured a safe
way of checking it with that prop spinning close by.
Does your installation exhibit the same behavior? Is
there some explanation for this? What test should I perform?
One thing that occurs to me is that Tracy measures MAP out
before the runners. I measure MAP at the manifold, downstream from intake
plenum and three short runners and the 3-barrel TWM throttle body. At WOT
my MAP is not atmospheric pressure – it is maybe 2-3” HG less. I
can’t quite see how that is an issue; but maybe someone else with a TWM
TB setup with the MAP port downstream would know.
Other than that I’m very pleased with
the new mixture correction table setup for the 20B. Much less tuning and
seamless transistion between tables and through the stage point. Probably
the pulse clamping and injector isolation diodes are part of that.