One Ignition 12v supplying edis/coilpack/mjlj

MartinM · Post by **MartinM** » Thu Jan 17, 2008 7:09 pm

brentp wrote:Martin, what shorted out internally that blew a trace? Was it a 5V or 12V section of the board?

12v IIRC - on two V2 boards- my first ever one and one that I repaired for someone else. I expect the V3 board would do the same, but I'm not going to try it

alexander · Post by **alexander** » Sat Jan 19, 2008 12:10 pm

hi all,
just back on the original question of wiring the 3 power wires, i just want to add that i ran a single wire from the alternator +ve, through a singel 30A fuse, then through a relay. the relay is turned on by the old coil +ve wire.

my comment here is simply about using the relay, not on the merit or otherwise of multiple fuses.

regards
alexander.

MartinM · Post by **MartinM** » Sat Jan 19, 2008 12:16 pm

I would have just used the old coil wire - it's (probably) fused already, will (should) be thick enough, and has exactly the right characteristics you need (+12v on cranking and running)

Adding the relay seems, to me, to be a bit over-complicated and introduce an electromechanical device that's not really needed (needs mounting, needs connecting, more to go wrong etc etc)

....my $0.02, of course

alexander · Post by **alexander** » Sat Jan 19, 2008 12:34 pm

hopefully one relay wont bring the system down

, but there were complications. i have installed this in a lotus europa, which has the grand total of 2 fuses for all circuits in the car! gotta love that 60s lotus engineering. it also has a smiths RVI type tachometer, through which the coil current previously passed. i feel sure that tachometer wont work with all the current for the 3 devices passing through it. the smiths RVI tachometers are another story, of course, and i am just reading through the forums regarding that issue, having just finalised the installation today (in the sense that the car started) hence my random comments!

regards
alexander.

MartinM · Post by **MartinM** » Sat Jan 19, 2008 12:37 pm

Fair enough - you didn't mention any of that before

Very keen to see what VR sensor waveform you're getting...

alexander · Post by **alexander** » Sat Jan 19, 2008 12:50 pm

hi martin.. no problem re your comment! the sense of keeping it as simple as possible is undeniable.
i did have a look at the waveform on an oscilloscope today, noting however that today was the first time i have ever actually attempted to use one.

it was well defined, and all said, it is certainly allowing the motor to rev out very freely. the issues i am having with missing is under part throttle acceleration; floor it, and the problem goes away, so hopefully it is a mapping issue, but i am presently speaking from a position of little experience.

one thing i noticed however, is that the amplitude of the wave varied throughout the rotation of the trigger wheel. the wheel and teeth are so small, and the gap between teeth and sensor is only about 0.5mm, so i think the amplitude variation is being caused by the tiny amount of runout which resulted from the gearstock slice being drilled out.

anyhow, touch wood, it will all be sorted, leaving me with one very cool little device. just for good measure, i sawed the top part of the old distributor cap off, and glued a clear acrylic cover over the space, so i can impress my friends and acquaintances with my handiwork!!

regards
alexander.

alexander · Post by **alexander** » Sat Jan 19, 2008 12:59 pm

now i am getting myself confused with the different forums and have now foolishly posted the picture twice (didnt think it worked first time) and raised the matter of the trigger wheel in no less than 3 places

i do have more to say about it, and will continue in a thread in the Operation forum, called "mapping advance issues" right now.

cheers!

MartinM · Post by **MartinM** » Sat Jan 19, 2008 1:00 pm

Yes - the overall amplitude of the sine wave is highly dependent on sensor <-> wheel distance.

IIRC in my experiments a run out of about 1mm between sensor and (big steel) trigger wheel, with a nominal gap of about 3mm, changes the amplitude by around 50% between closest and farthest points.

Did you use a dividing head and a mill to make that, or did you jump through hoops to make it on a lathe? I've only got the latter (and no dividing head).

How is it registered on the spindle?

Got any pictures of the car?

Excellent work though so far!

Post by **brentp** » Sat Jan 19, 2008 6:12 pm

MartinM wrote:
Adding the relay seems, to me, to be a bit over-complicated and introduce an electromechanical device that's not really needed (needs mounting, needs connecting, more to go wrong etc etc)

....my $0.02, of course

Typically the benefit of the relay is to relieve the current requirements on the ignition key- you may not want to pass all of the high powered electronics through that switch. Overloading the ignition key switch over time would introduce it's own failure mode, which makes the relay scheme more reliable in the end. Having said that, it's not 100% clear if this is exactly Alexander's case- a wiring diagram would be clearest.

Edit: Understanding Alexander's description more- it would seem that you could re-use the same fused, switched circuit that the original coil was driven from, providing it's fused rating is adequate. If this is correct, the relay and extra wiring additions may indeed be redundant...

Patriq · Post by **Patriq** » Sat Jan 19, 2008 10:21 pm

brentp wrote:
MartinM wrote:
Adding the relay seems, to me, to be a bit over-complicated and introduce an electromechanical device that's not really needed (needs mounting, needs connecting, more to go wrong etc etc)

....my $0.02, of course
Typically the benefit of the relay is to relieve the current requirements on the ignition key- you may not want to pass all of the high powered electronics through that switch. Overloading the ignition key switch over time would introduce it's own failure mode, which makes the relay scheme more reliable in the end. Having said that, it's not 100% clear if this is exactly Alexander's case- a wiring diagram would be clearest.

Edit: Understanding Alexander's description more- it would seem that you could re-use the same fused, switched circuit that the original coil was driven from, providing it's fused rating is adequate. If this is correct, the relay and extra wiring additions may indeed be redundant...

I'm re-using the old +12V feed for the old coil. It now goes directly to coil, EDIS and MJLJ. In regards to what is mentioned previously in the thread - should I put an extra fuse with lower value where I feed the MJLJ to spare it if something shorts out ?

Post by **brentp** » Sun Jan 20, 2008 8:29 pm

Patriq,

I'm running a near identical installation as yours.

Ignition switch -> "ECU Relay", 20A fuse. This fuse drives all the "ECU" components (fuel, ignition, EDIS, coil pack).

Of course it would not hurt to individually fuse each component. You just need to find the right balance for protecting each circuit and sub-circuit. Studying what Automotive OEMs do would with wiring harnesses would be a good example, and that's what I emulated with my installation.

Inside the MJLJ, the circuity after the 5V regulator is supposed to be over-current protected. So you should be OK there.

There are a few components before the regulator (protection diodes, capacitor). Assuming the unit was assembled correctly, in a practical sense these components could be considered no less reliable than the actual +12V supply wire going to the unit. Just trying to layer in some perspective.

Regards,

Patriq · Post by **Patriq** » Mon Jan 21, 2008 8:07 am

Ok, thanks !

Then I'll leave it as it is.

By the way - I don't have a ECU. This is a 1970 car with double 45 Weber engine.