27 replies to this topic

[mike.]

Reliability and tunability really.

There no moving parts to go wrong, its all electronic. The electrics are much more waterproof and you can place all the electrics out of the way of water spray from the grill.

Tuning wise you can set it up perfectly for your engine, so it has the perfect ignition advance etc at any given revs or load. Once its set it'll never move unlike a distributor.

If you do it right first time, MJ is a fit and forget setup.

[minihle]

Hi,

i have managed to do this:

 17423.jpg   86.57K   12 downloads
 17424.jpg   94.72K   12 downloads

I haven't test it yet, but i think it will work nicely... I have the pulley in 3D so if you need it, just pm me.

[Ethel]

The issue with rev counters is that MJ uses wasted spark, i.e. there are two coils that each fire a pair of cylinders together (one will ignite a charged cylinder, the other will be at the end of it's exhaust stroke, hence wasted). All that triggerwheels gizmo is, is a collection of diodes so you can link both coils without one interfering with the other




The trigger wheel is simple enough, it's teeth are equally spaced with one removed (located 90 degrees before the sensor at TDC) : 36 teeth + 36 gaps gives 64 sectors of 5 degrees.

[mike.]

So to get the rover rev counter working, you'd wire that trigger wheels wiring, into the + and - feeds for the coilpack, then the other end just extend it to the back of the rev counter?

[Ethel]

No, but nearly.

Both coils have a common +ve, the EDIS unit earths both of them, just like points in a dizzy. You'd connect to the outside 2 wires from the coil pack and feed the tacho via the zener diode.


There's barely a quid's worth of components used & one blob of solder.

[Teapot]

Bookmarking this thread and found I'd already saved this if it's any help.

[mike.]

I see. I'll have to get one of those, I was trying to find a new rev counter to fit into my current 3 clock set up but ideally wanted to keep the rover clock.

So, just to be sure - i'd just need to splice that trigger wheels thing into the outer 2 wires of the coil pack plug, and then route it to the rev counter?

[WiredbyWilson]

I used the output on the MJ ecu to run my standard rev counter and it's spot on!

Thos converter things are a bit of a gimmick i think......

[mike.]

I think I might give the MJ rev counter output a go first. It was only the fact that the guy I got my MJ off reckoned his blew a chip in the unit when he tried running his rover rev counter off the MJ - I don't know if this is a one off or if its even possible...

[Ethel]

From the ASL installation guide:

"Smiths RVI type tachometers

Note that there are two types of older Smiths tachometers: RVI - current sensing, and RVC - voltage sensing. These letters, and numbers indicating exactly which variant you have, are printed in small white lettering on the bottom of the face of the tachometer. RVI type tachometers work by routing the coil +ve supply wire through an inductive loop of wire inside the tachometer, and are not compatible with the MJLJ tach out signal or the tach out signal from the EDIS control module. If you have an RVI type tachometer, you can try routing the power wire for the EDIS coil pack only through the tachometer so the induction windings in the tach can pick up the spark firing events like the OEM system. This has been tested on a 4 cylinder British car with an OEM RVI tach and it gave excellent results. Other options are you replace the tach with a different type, have an add-on circuit board added inside (or build one yourself, see http://www.dinoplex....tachoconversion for a start), or replace all the inside working parts with those from a newer tachometer ie retain the original face, but change everything else. For that approach you need a donor which has the same angular swing per 1000rpm, as the Smiths gauge."

It's certainly worth trying connecting it to the MJ tach output. As a test (with dizzy ignition) you could whip your plugs out, disconnect the HT lead from the coil and see if the rev counter shows any life when you spin the starter. Assuming the engine turns over fast enough.


I'm not 100% sure where the tacho signal comes from, but the MJ has a socketed transistor array (uln2003) as a buffer for the external connections in case you make a booboo. It's readily available for only a few quid.

[rasputin22]

If the MJLJ tach out does not work, then try pin 11 of the EDIS CTO (Clean Tach Out)

[Kerrin]

Sorry to hijack but didn't want to make another thread about megajolt.

Basically, just a question to anyone running megajolt, are they easily compatable with any if not all of the digiatal guages available on www.Digital-Speedos.co.uk?

Many thanks,

Rich

Just set my KOSO gauge up with my MJ system, and the tach out (blue I think?) wire from the MJ just connects to the tach in on the gauge and works fine.

I set the tach input to high, and changed the cylinder setttings till it worked. Due to the lost spark system on the eids you need to used the 2 stroke setting with 4cyl to get the revs right.

[l_jonez]

i used pin 11 on the edis, you have to drill the little blanking piece out on the plug but other than that its easy and works fine