Autosport Labs

does anyone know if the MSD Soft Touch Rev Control could possibly work as a rev limiter via the mjlj's rev limiter connector?

I don't know but I found http://www.msdignition.com/pdf/8728_frm%2023783%20.pdf and had a quick look...

If you've got one I would try it (at your risk, not mine), if you haven't I'd use something else (*)...

Trying it is subject to:
- It seems to use the points/pickup as a source of rpm, using either the white or violet wires
....you can't use the output of the VR sensor as an equivalent source of rpm, but the PIP line might work...
....and I think it has the same frequency as a set of points or a pickup ie once every ignition event so the rpm interpreted by the unit should be the same as the real rpm

- It looks like it grounds the coil when the set rpm is reached and most of the diagrams are for single coil setups. On EDIS you have 2 3 or 4 coils for EDIS-4, -6 and -8, so for a complete rev cut you'ld have to ground all the coils. This might be beyond what the unit is designed to do and might make it emit some smoke (a Bad Thing). Or you could just ground one of the coils for a partial rev cut.

(*) like connecting the rev limit output of the MJLJ to a relay/transistor/MOSFET that earths one or more coils

dr.occa wrote:does anyone know if the MSD Soft Touch Rev Control could possibly work as a rev limiter via the mjlj's rev limiter connector?

And responding to what you actually asked (!)...

...no - the MJLJ rev limiter is a on/off signal that is ready to use to drive a simple external unit when the rpm limit is reached, while the MSD unit is a bolt on unit that does all the sums inside itself using the points/pickup as a source of rpm

The MSD unit is designed to work with one coil- which, if adapted to an EDIS system (especially an EDIS-4) could drop enough power to prevent the engine from revving higher. Overall I would say the MSD unit is most useful as a design validation that the various REV_LIMIT approaches for the MJLJ will work reliably.

If it's simply sensing the (-) on the coil pack for the RPM signal it should work, in principal. The EDIS module / MJLJ will not detect rev limit is occurring. Agree, if you have one of these MSD boxes lying around you could investigate further. If you were to buy one, you might think about trying out some of the designs that use the REV_LIMIT output.

Speaking of which- my next immediate project is to get back on track with the rev-limit control and make that available for testing. The 3.2.1 firmware update caused a big detour in my schedule!

thanks for the insight thus far everyone. i'm hesitating putting the mjlj in at the moment. i take part in a lot of gymkhana courses and drift events. i peg the rev limiter a bit at times. it would make it a bit difficult for me to focus on the high speed drifts AND keeping the revs below PNR.