Autosport Labs

How sharp or steady should the strobe image be?
With the EDIS alone I was checking for a good 10BTDC but the white mark is spread over about 10deg, from +10 to 0 and gets worse as RPM increases. So it starts in the right place but is not sharp.
I have tried 2 lights, both the very cheap in-line variety. I have also tried the whole lot set up in a drill and still the same. I guess if the spark event has duration then this is to be expected.
Are the newer ones with clip on HT and 12v supply better?
Or do I have an EDIS problem?

Fiddler wrote:How sharp or steady should the strobe image be?
With the EDIS alone I was checking for a good 10BTDC but the white mark is spread over about 10deg, from +10 to 0 and gets worse as RPM increases. So it starts in the right place but is not sharp.
I have tried 2 lights, both the very cheap in-line variety. I have also tried the whole lot set up in a drill and still the same. I guess if the spark event has duration then this is to be expected.
Are the newer ones with clip on HT and 12v supply better?
Or do I have an EDIS problem?

the image should be sharp and rock steady.


regards
alexander.

OK tried another EDIS and a new coil (very nice COP from volvo S40).

No change.
The only bit left is the VR and I just cant believe its that. Will try a more fancy timing light next. The trigger wheel is a standard 4.5 inch fron triggerwheels. Right nunber of teeth and one missing. By the way the enging runs fine.

I can confirm that this COP works well with a big fat spark. It sits on one plug and has a HT lead to the next one also (but not in my application)

http://www.ipdusa.com/version.asp?strPa ... V_ID=10956

part num 1275602.

Now going to use science to explain what Im seeing, based on the theory that my old simple light stays on during the whole spark duration. I don’t know if the new ones just give a sharp flash only.

Reading on many websites it seems that 12v Inductive discharge (I think that’s what we have here) should have a spark duration of between 100 and 1000 uS (micro sec 10 -6).
Lets go with 500 uS.
An engine running at 3000 RPM does 50 rev/sec or .02 sec per rev.
If the spark duration is 500 uS then .02/.0005 = a 40th of a revolution which is 360/40 =9

Spark lasts 9 deg of rotation and that’s exactly what I see.

Is that right? Need a beer now.