Right.

the long and the short of it is that neither of my timing guns like my waisted spark coil ign system.

anyone sugest a suitable gun thats readilly available that is known to work with a waisted spark system

Many thanks

Agriv8

Used my Snap On digital timing light today with wasted spark , yes you do get double the rpm as it reads the number of times the plug is fired , simple to halve the reading . The timing is not altered with wasted spark . If funds will run to a Snap On light then I would recommend them . PS How often will you use one?

quote:

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Originally posted by rusty nuts
Used my Snap On digital timing light today with wasted spark , yes you do get double the rpm as it reads the number of times the plug is fired , simple to halve the reading . The timing is not altered with wasted spark . If funds will run to a Snap On light then I would recommend them . PS How often will you use one?

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The timing value show double with the snap-on lights that read double rpm on wasted spark.

What does a timing gun do???

quote:

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Originally posted by chriscook
The timing value show double with the snap-on lights that read double rpm on wasted spark.

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But the flashing every rev instead of every other it thinks that 360degrees is actually 720degrees so it doubles the timing readout too.

Rob - The main man behind VEMS suggests one without the Dwel device as can cause problems ( I suspect that the Snapon one is EXPENSIVe enough to deal with this )

so the drapper one is a possible any others. So as its waisted spark assume I am going to get two flashes ( first at 0 and another at 180 )

Further sugestions welcolm

Regards

Agriv8

Wasted spark fires plug EVERY 360 degrees so would show the same advance. It would NOT show double the advance BUT would show double the rpm. Read David Walkers book on engine management !

Rusty's right. All that happens is you get 2 flashes per 720 rather than 1. As long as you double or half the number of flashes, then no change will be seen. If it went to 3 per 720 degrees, then you'd have issues. As it is, the light falls on the same mark twice, rather than just once.

I'm sorry but I disagree from experience and also if you work it out.

I'm talking about the type of light that has button on it which advances/retards the flash to align the timing marks and it displays an advance figure for the amount of advance it is using. The light I was using was quite an old snap-on light - the newer ones understand wasted spark and work properly.

However, for the older type If say you are running at 10degrees advance on a NON wasted spark ignition at 3600rpm (to make the numbers a bit easier). Then the advance in terms of time to delay the flash is:

3600rpm = 60rps = 21600degrees/sec

10degress => 0.46ms

Now with wasted spark the light does not know it is wasted spark so reports 7200rpm or 43200deg/sec.

The time delay is still the same to align the timing marks which is manually set by the user at 0.46ms. Now 0.46ms at 43200deg/sec means:

(0.46/1000)*43200=20degrees

The time delay is the same but because the engine speed is read as twice as fast it calculates the advance wrong also.

FWIW I have read Dave Walker book on Engine management

[Edited on 10/4/07 by chriscook]

If you set the advance on the gun to zero and physically mark a pulley at 0,5,10 deg etc and read the marks you should be OK either way i'd have thought.

My digital Snap-on advance timing light works very well with my MJLJ install but you do have to half the advance and rpm readings.

Got my light off ebay for about £35, twas a good investment.

I have a locost DIY version - uses a xenon bulb with power supplied by a 12 V transformer wired in reverse bulb housed is in an old bicycle lamp