I know this may seem like a stupid question, but how should we determine the plug gap to use with the megajolt setup?
Is the stock plug gap the way to go, or should we be adjusting it since I should have a much stronger spark with the EDIS/coil setup compared to stock.
What plug gap to use?
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Broke4speed
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Spockie-Tech
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*Theoretically*, it would depend on how you go about tuning it..
I saw a graph of combustion pressure vs time in an ignition book once - Like most fireballs, spark-initiated flame growth rate is exponential... It takes much longer for the fireball to go from 0.02" dia to 0.04" diameter, than it does for it go from 1" to 2"..
So, if you can hurry that initial tiny fireballs growth along by starting it off at a bigger diameter with a wider gap, then you can significantly reduce the time required to reach peak combustion pressure, which means less advance required, and more of the combustion wave buildup time is on the right side of top-dead-center (making power by pushing down, not fighting the pistons pushing up compression)
So, the widest gap you can get away with without mis-fires is the best, *provided* you adjust the timing in a knock-sensitive fashion whilst testing for peak torque (acceleration) and tweaking to find the best timing settings without knock.
If you are following a factory timing curve, or just using someone elses map who runs small plug gaps then you should stick to the same gaps they (factory or friend) used. If you widen out the gaps significantly (which you can probably do with a EDIS), then you will need to pull some timing back out of to compensate.
This is a *good* thing (less advance needed for peak torque = more efficiency) *if* you are tuning it carefully and measuring reponse and knock and not just following a narrow-gap curve.
I saw a graph of combustion pressure vs time in an ignition book once - Like most fireballs, spark-initiated flame growth rate is exponential... It takes much longer for the fireball to go from 0.02" dia to 0.04" diameter, than it does for it go from 1" to 2"..
So, if you can hurry that initial tiny fireballs growth along by starting it off at a bigger diameter with a wider gap, then you can significantly reduce the time required to reach peak combustion pressure, which means less advance required, and more of the combustion wave buildup time is on the right side of top-dead-center (making power by pushing down, not fighting the pistons pushing up compression)
So, the widest gap you can get away with without mis-fires is the best, *provided* you adjust the timing in a knock-sensitive fashion whilst testing for peak torque (acceleration) and tweaking to find the best timing settings without knock.
If you are following a factory timing curve, or just using someone elses map who runs small plug gaps then you should stick to the same gaps they (factory or friend) used. If you widen out the gaps significantly (which you can probably do with a EDIS), then you will need to pull some timing back out of to compensate.
This is a *good* thing (less advance needed for peak torque = more efficiency) *if* you are tuning it carefully and measuring reponse and knock and not just following a narrow-gap curve.