Newbie Q's, max RPM possible & application assitance

EW57 · Post by **EW57** » Sat May 24, 2008 5:29 am

Greetings, I'd like to find a programmable ignition to work with a 90 degree v-twin engine. Attached is the timing diagram, with the MJLJ work with this setup? Also, what is the maximum RPM's attainable with the MJLJ? Thanks!

MartinM · Post by **MartinM** » Sat May 24, 2008 9:50 am

Well, ignoring the injector requirements, which the MJLJ will obviously not do....

...and answering the easy question, the MJLJ/EDIS/standard coil combination won't do more than about 9500rpm in its four cylinder version, by design (I've got the details somewhere of why it tops out at that rpm, but not sure where....)

So is your engine fixed timing or variable - diagram makes it look like fixed?

Could you use a MJLJ/EDIS combination? Not sure - it makes my head hurt looking at the diagram

When the front cylinder is at TDC and the firing position (720 degrees), the rear cylinder is halfway through its inlet cycle i.e half way down the cylinder.

That's certainly not a standard 4-cyl engine configuration (eg see http://www.grc.nasa.gov/WWW/K-12/airplane/powert.html), but it might be what happens on certain cylinders in an 8-cyl engine....and whether that means there's some chance of adapting something from an 8-cyl MJLJ installation is the bit that makes my head hurts (..and SWMBO is telling me to go out and do stuff NOW!

)

EW57 · Post by **EW57** » Sat May 24, 2008 12:58 pm

Thanks for your reply, I should have mentioned that the stock ECU doesnt function correctly when the injection system is replaced with carbs, which is why I'm looking for a replacement (ignition only) programmable unit.

Theres a four tooth trigger (three short, one long) on the flywheel & a sensor to read the pulses, then the signal went to the ECU and the variable timing was taken care of there, so as far as the OEM sensor is concerned, its fixed timing. I've gotten the advance charts from the stock ECU (RPM/TPS).

Thanks again!

Oliver Sedlacek · Post by **Oliver Sedlacek** » Tue May 27, 2008 6:42 am

No, it wont work as standard. The EDIS is only intended for use with equally spaced firing intervals. You would also have to add a 36-1 crank sensor wheel.

EW57 · Post by **EW57** » Tue May 27, 2008 1:27 pm

the 36-1 wheel could be made to work I think. Oliver, Forgive me for being dense, but is there enough programmable advance/retard to pull it off, or are there other non-standard mods that could be done, or would it be in my best interest to look for other alternatives? (which I havent been able to find easily)

Thanks again!

Oliver Sedlacek · Post by **Oliver Sedlacek** » Tue May 27, 2008 2:28 pm

Unless Brent thinks otherwise, I would look elsewhere. The EDIS just isn't designed for this application, and fiddling with advance/retard doesn't help.