<all> home dyno kit??

[Mike]

>
>I would guess that the trigger point or the center of a given spark
>(measured in the audio-domain) is probably centered pretty
>consistantly at the same point, and since you don't have to do things
>real time you can take some time to analyze and determine exactly were
>each pulse was centered.  And even if they varied a  bit, the average
>should be pretty good.  I did some quick calcs, and 3000 rpm the pulse
>spacing is 20 ms, and 3025 rpm is 19.83 ms (DIS), so if you have .1 ms
>resolution you would be able to get better than 25 rpm accuracy at
>this point.   And ao long as you have enough bandwidth to be able to
>determine each pulse you should be able to do it.  My guess is that a
>basic cheap take recorder should give you enough data to do the job.
>A 6000 rpm pulse is 100 pps (DIS) or 50 pps (fire every other rpm), so
>to get accurate and distinct centers you would not require that much
>bandwidth (ie 1-2khz looks to be adequate)
>
>				Roger
>

If resolution is what you want (and we all do :), how about picking up the
peaks from the alternator output? Maybe they can be of some use other than
pissing-off stereo installers. 

I figure 6 peaks per alternator revolution (3-phases, full-wave rectified,
complete in one revolution). Since the alternator is "geared" to turn quite
a bit faster than the crank, you'd get much better resolution. All you'd
need to know is the alternator to crank speed ratio (pulley diameters would
suffice).




--
 Mike