Timing belt ?

[Richard J Lebens]

--- SJ <syljay at optonline.net> wrote:

> 
> > From: Kent McLean <kentmclean at mindspring.com>
> > Subject: Re: Timing belt ?
> >
> > Huw Powell wrote:
> >  > You could run the dizzy off the crankshaft, but then there'd be
> a
> >  > wasted spark at TDC on the exhaust stroke.  And coil charging
> time
> >  > would be halved...
> >
> > Some cars (the Miata comes to mind) have a wasted-spark by design.
> > I think 1 coil powers 2 spark plugs, so one spark gets wasted each
> > (every other?) cycle.
> 
> **** Yup, thats correct - no dizzy anymore. Each coil pack feeds 2
> spark
> plugs. Many newer cars (maybe all?) use this design.

Newer cars are going to a single coil per plug to get rid of the high
tension wires all together.

> I guess they use crank positioning sensors(hall effect) to tell the
> computer

The sensors for timing are typically variable reluctance off the
flywheel teeth with some other sensor to establish the original TDC
position at startup.

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