Advance shown by MJ is roughly half actual advance!!

General Topics for configuring, operating and tuning the Megajolt. Also see the <a href="http://www.autosportlabs.net/MJLJ_V4_Operation_Guide">Operation Guide</a>

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Richard_M
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Advance shown by MJ is roughly half actual advance!!

Post by Richard_M »

I am installing a MJLJ V3 on my Triumph Spitfire 1296.

I've got past the connection issues and VR positioning woes etc etc, and the car now idles nicely on EDIS alone at 10 degrees advance.
Once MJ is connected, at idle the MJ software says 10 degrees and the pulley/timing gun (basic Gunson unit) agree.
As revs increase however, the advance as shown at the crank goes out of sync with the advance MJ displays.

For instance, with the car at 2500rpm, I have set the map set so that the ignition should be 25 degrees advanced, yet at the crank pulley my dumb simple Gunson timing light is showing advance of approx 48 degrees!!
The backfiring, spluttering and glowing exhaust also indicates more advance the MJ has planned.

It's almost like there's a multiplier being applied to the map - of approx x2 - but I can't find any mention in the V3 software of such a thing.

All help appreciated - thanks.

Richard

brentp
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Post by brentp »

That is very strange. Can you measure the pulse width of the PIP signal at a known RPM to see if the megajolt is sending the correct ignition advance command to the EDIS module?

The width of the pulse in microseconds determines the ignition advance based on Ford documentation. You'd need an oscilloscope for to make this measurement.
Brent Picasso
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brentp
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Post by brentp »

Following up; did you ever figure this out?
Brent Picasso
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