That Leading / Trailing ignition disable responce is still a mystery to me Al.  I finally got my 20B installation going well enough to test this and I got the same (expected) results as on my 13B and Renesis (more rpm drop on leading disable at any rpm).

OTOH, I could not get a smooth staging transition to save my life.  Investigation showed I was getting terrible electrical noise as the staging relay switched with much (normal) contact bounce.  Since I didn't have any diode clamps in the staging circuit, there was a lot of noise generated by switching the inductive injector load.  It was noisy enough to cause my EM2 (and possibly the EC2) to reset causing a lot of missing and occasional backfire during the staging process.  Made me wonder if this was the cause of the data corruptions you were having in you EC2 map table.  I also thought it might be the cause of Marks'  high rpm miss but his problem turned out to be that he made the CAS mounting bracket out of ferrous metal instead of aluminum  (he used the Renesis crank sensor).  Glad he stuck with it and found this problem because I never could have guessed what it was.

I don't know why Mark and Al are not having the staging problem that I am but this is the nature of alternative engines where there are no two installations alike. In the future I am changing the 20B staging relay to a solid state relay that has no contact bounce and adding some clamping diodes to suppress the inductive noise.  This should make the EC2 20B controller less installation dependant.

Still no  'Plug 'n Play' in the alternative engine game :>)

Tracy  (still recovering from 36 hr drive back from Colorado)


On 9/17/07, Al Gietzen <ALVentures@cox.net> wrote:

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.