Rev limiting

[Craig Pugsley]

> 
> > 
> > On Fri, 12 May 1995, Craig Pugsley wrote:
> > 
> > > 
> > > Hi,
> > > I'm currently designing a rev limiter that works by cutting out the
> > > spark when the revs exceed a certain limit. I was thinking of
> > > progressively cutting out more sparks as the revs go over a certain
> > > level to reduce power (eg at 7000 rpm) then all the sparks (eg
> > > 7500 rpm) IE:
> > > 
> > > 
> > I would cut fuel instead of spark (or at least both) if your going to be 
> 
> I second this.  We recently had a bug with our research engine which cut
> the spark under partial load conditions and subsequently blew a double skin 
> stainless steel muffler inside out.

While cutting fuel is preferable, the box I am making is for a carb fed
application. I had intended to make a spark at a semi-regular interval
to avoid exhaust blow up problems. I made one several years ago (with a
simple tachometer/comparator curcuit), which seemed to work quite well
in it's limiting role, some medium size pops from the exhaust, however it's
calibration varied wildly with temperature so I want to use a micro.

I'll re-ask the question, Is having sparks cut out 'randomly' likely to
be capable of causing mechanical damage to the engine, especially when
it's happening at/near maximum power RPM range?

Cheers,
Craig. 
pugsley at trl.oz.au