Spark timing vs timing light
Spark timing vs timing light
(OP)
The question came up at work: Does the timing light flash as the current passes through the inductive pick up or does it flash as the current jumps to ground via the spark plug? We set timing at WOT at 6000 rpm fully loaded on the dyno. We set individual cylinders to read the same as cylinder #1. We adjust this timing by bending the reluctor inside the distributor for any cylinders that are differant. The question arises because as the cylinder pressure increases the resistance across the spark plug increases, thus slowing the actual ignition timing and perhaps delaying the signal to the timing light? Any thoughts?





RE: Spark timing vs timing light
Mike Halloran
Pembroke Pines, FL, USA
RE: Spark timing vs timing light
RE: Spark timing vs timing light
RE: Spark timing vs timing light
Conversely, if there's an ECU in the circuit between the reluctor and the spark coil, then all sorts of strange behaviors are possible, including retard of an individual cylinder in response to ... well, anything that the ECU can sense or infer.
Mike Halloran
Pembroke Pines, FL, USA
RE: Spark timing vs timing light
RE: Spark timing vs timing light
First, since electricity travels at near the speed of light there is virtually no delay as it travels down the wire and jumps the spark plug gap. If there was a measurable delay all spark plug wires would need to be the same length, just like diesel injection lines. And your timing light would show a slightly different timing depending on where you placed the pick-up along the spark plug wire.
Second, there is likely a very small delay in the timing light itself. The inductive coil needs a finite amount of time to build up enough energy to trigger the strobe circuit. It would be interesting to test two different timing lights on the same engine at the same time to see if there is a perceptible difference.
Third, I agree with Bribyk. You are worrying about something that doesn't really make a difference. Just be consistent.
ISZ
RE: Spark timing vs timing light
RE: Spark timing vs timing light
If there is a measurable difference in reality, I do not know.
Dan
RE: Spark timing vs timing light
RE: Spark timing vs timing light
That would set the maximum timing difference related to pressure, then. (?)
Dan
RE: Spark timing vs timing light
Cheers
Greg Locock
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RE: Spark timing vs timing light
http://www.fs.isy.liu.se/~larer/Projects/main.html
Spark-Advance Control by Ion-Sensing and Interpretation
...The development is based on new sensors or improved interpretation of available sensor signals. One example is ionization current sensing which is obtained by applying a sense voltage on the spark plug when it is not used for firing. The sensed current depends on the ions created, on their relative concentration and recombination, on pressure, and on temperature to mention some of the more important factors. The signal is very rich in information but also complex to analyze.
RE: Spark timing vs timing light
RE: Spark timing vs timing light
RE: Spark timing vs timing light
Regards
Pat
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RE: Spark timing vs timing light