Hi all,
I have a MJLJ with the Motorcraft EDIS setup and was wondering if anyone can tell me the ideal plug gaps to run to suit the coil-pack etc, also I have had to get leads made up (Ford ones don't reach the VW plugs!) and have used 8.8mm Top Gun leads. Granted, the job's already done and I should've asked before, but these should be fine for the coil-pack, right?
Thanks in advance, MArc.
Leads and spark plug gaps...
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beachbuggy61
- Posts: 17
- Joined: Fri Feb 18, 2011 1:00 am
- Location: Central Coast, NSW, Australia
Hi Marc,
After a lot of web-reading, I'll stay with the standard gap as requested by the manufacturer. Some try to run with a bigger gap and argue a higher voltage should be able to pull a larger spark, thus leading to a better detonation. With that in mind and approaching somewhere the point where the spark tears off, you may find out what the ideal gap might be for your setup. No rocket-science there, more of trial and error I think.
Cheers.
Jos
PS: My car has really transformed, it pulls & pushes simultaneously, doesn't backfire anymore, runs like hell...
After a lot of web-reading, I'll stay with the standard gap as requested by the manufacturer. Some try to run with a bigger gap and argue a higher voltage should be able to pull a larger spark, thus leading to a better detonation. With that in mind and approaching somewhere the point where the spark tears off, you may find out what the ideal gap might be for your setup. No rocket-science there, more of trial and error I think.
Cheers.
Jos
PS: My car has really transformed, it pulls & pushes simultaneously, doesn't backfire anymore, runs like hell...
If all else fails, consult the manual.
My blog: http://jacob-jos.blogspot.com/
My blog: http://jacob-jos.blogspot.com/
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Spockie-Tech
- Posts: 152
- Joined: Wed Jan 02, 2008 12:52 pm
- Location: Melbourne, Australia
The perfect Spark Gap is determined by how reliably your system can fire that gap under pressure.
Theoretically, a bigger gap means a larger initial fireball, less time for flame front growth to reach peak pressure, and therefore, *less* advance required, since faster flame growth means you dont need to light it so far in advance for the pressure to peak just past top-dead-center.
This is a good thing, since any pressure build up (caused by lots of advance) on the wrong (compression) side of top-dead-center is fighting the compression and costing some efficiency. So if you can increase the gap, and decrease the required advance for peak torque, then you should see efficiency improvements.
But, the wider the gap, the higher the voltage required to jump the gap, and the more likely the spark is to try and head off in another direction, rather than across the gap. EDIS systems should be able to help prevent this (and hance tolerate wider gaps), since there are less links in the high-tension side for the spark to wander off on.
Keep in mind though, that it is harder to push a spark through compressed air than ambient pressure air, and if youre engine is supercharged, its even harder again due to the higher pressures, I have seen EDIS rigs on bench test push a spark all the way from the center electrode to the ring of the plug.. but Id bet they couldnt do that in working pressure conditions.
If youre still dialling your engine in and getting it to run properly, stick with the standard gap for now though.
Once youve got it tuned up nicely, *then* you can start trying increasing the gaps and pulling some timing back out and see if you can make the same or better peak torque with less advance and a wider gap. Keep in mind that the spark plugs are also going to get harder to fire as they age and foul and a wider gap will cause them to misfire at an earlier wear stage than a narrow gap would.
Theoretically, a bigger gap means a larger initial fireball, less time for flame front growth to reach peak pressure, and therefore, *less* advance required, since faster flame growth means you dont need to light it so far in advance for the pressure to peak just past top-dead-center.
This is a good thing, since any pressure build up (caused by lots of advance) on the wrong (compression) side of top-dead-center is fighting the compression and costing some efficiency. So if you can increase the gap, and decrease the required advance for peak torque, then you should see efficiency improvements.
But, the wider the gap, the higher the voltage required to jump the gap, and the more likely the spark is to try and head off in another direction, rather than across the gap. EDIS systems should be able to help prevent this (and hance tolerate wider gaps), since there are less links in the high-tension side for the spark to wander off on.
Keep in mind though, that it is harder to push a spark through compressed air than ambient pressure air, and if youre engine is supercharged, its even harder again due to the higher pressures, I have seen EDIS rigs on bench test push a spark all the way from the center electrode to the ring of the plug.. but Id bet they couldnt do that in working pressure conditions.
If youre still dialling your engine in and getting it to run properly, stick with the standard gap for now though.
Once youve got it tuned up nicely, *then* you can start trying increasing the gaps and pulling some timing back out and see if you can make the same or better peak torque with less advance and a wider gap. Keep in mind that the spark plugs are also going to get harder to fire as they age and foul and a wider gap will cause them to misfire at an earlier wear stage than a narrow gap would.
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beachbuggy61
- Posts: 17
- Joined: Fri Feb 18, 2011 1:00 am
- Location: Central Coast, NSW, Australia
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Spockie-Tech
- Posts: 152
- Joined: Wed Jan 02, 2008 12:52 pm
- Location: Melbourne, Australia
I would start with whatever plug-gap most people use on your type of engine configuration with a standard ignition.. turbo, carb, VW etc. rather than what the EDIS might be able to handle to start with.
That way the advance curve and bahaviour will be similair to what other similair configuration engines use.
Once you get it all dialled in and solve your current power-drop issue, then you can try widening up the gaps to take advantage of the EDIS configuration. Keep it simple while you are looking for bugs, rather than introducing additional variations at this point.
That way the advance curve and bahaviour will be similair to what other similair configuration engines use.
Once you get it all dialled in and solve your current power-drop issue, then you can try widening up the gaps to take advantage of the EDIS configuration. Keep it simple while you are looking for bugs, rather than introducing additional variations at this point.