Ignition cuts for rev limits / traction control

[Bruce Plecan]

> Does anyone have any cunning ideas for implementing ignition cut
strategies
> for rev limits and traction control purposes?

I tried the retarded timing idea, but to make it progressive was a PITA.
Took lots of timing change to make a little rpm change.  Remember you might
be wanting to slow down 3-4K rpm per sec rate change.  *Alot* of traction
problems happen at peak torque, and WOT trying to slow the engine down at
that situation takes alot of drastic measures.  OEMs have it easy the engine
(well other then make 4-6 of them) are slugs any way, but with peak torque
at say 3.5K and max HP at 5.5K, toss in an overall gearing of like 10:1
possible 15:1 and well, I hope you see my point.
   What did work in my experimenting, was an ignition cut.  At the first
sign of very sudden wheel movement, I dropped every 7th cylinder in the
firings, (oh v-8), if ther was still *wheel spin*, then every 5th, and then
every 3.  I took water on the street, and truely dumb as driving to get it
to hit the 3rd stage, but there was just a tad of spin (not enough to lose
any contol) for it ramp up to that stage. The rest of the time ie was just
noticeable as an engine miss when working.
   The reason the oem use both fuel and timing, IMHO, is so that doesn't
scare anyone so once activated it comes back very slowly.  Just look at all
the *problems* there are with ABS braking, my goodness, I feel it in the
pedal somethings wrong, oh my,  quick take it to the shop!, scared me I
almost 1. smeared my makeup, 2. spilled my coffe, 3. interupted my cell
phone convo.

> I'm struggling with the following concern: You detect an over-rev (or
> wheelspin) event and want to cut spark ASAP, but the coil driver(s) are
> already charging the coil(s) for the next combustion event (or 2, or 3,
> depending on your system). Do you wait until the next available 'slot'
when
> you can avoid charging a coil up (and therefore possibly risk over-reving
> further) or can you 'bleed down' the charging coils somehow without
causing
> a spark to fire?

Just don't supply an *off* signal to the coil.  It will sit there just fine
waiting for an off signal to fire.

> The only other solution that springs to mind is retarding the already
> charging coils to limit torque output while waiting for the cut to be
> available.

> Another thing that bothers me is engine stalling: If you stall an engine,
> and have a charging coil, what do you do with the spark? If you just fire
it
> off after the maximum safe dwell for your coil, the engine could be in any
> position and you could blow up your inlet manifold, or push the engine
> backwards...
> Any thoughts?

That really hasn't been an issue.  Engines been stalling for years and
years.  Just the cheap crap plastic intakes might have a problem with that,
and it seems they are doing OK now.  There is no strategy I know where they
worry enough about the last engine fire signal enough to try and bleed it
off, only a couple pcms look at engine accleration rates, and that's just
for fiinding a misfire as I understand things
Grumpy
>
> Ian
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