Distributorless ignition using GEMS coils and Hotwire system

[DaveEFI]

I'd expect any ignition only ECU to have a built in MAP sensor, so all you'd need is a vacuum feed to it.
As regards the tach adaptor, the diode method requires a connection to each coil. The pulse amplifier method - uses the coil from a standard car relay, and a transistor, only needs 12v, the logic feed in and out to tach, so can be mounted anywhere convenient, perhaps beside the tach if there is room. I think you can buy them ready made. I found it worked better than the diode method on my SD1 tach.

[garrycol]

I made the above tach module from resistors and diodes bought from a local electronics shop (together is about 1" square) - was only a few pounds - it is wired to the coil outputs of the edis module but equally could be connected to the coil inputs.

[GDCobra]

I'd expect any ignition only ECU to have a built in MAP sensor, so all you'd need is a vacuum feed to it.

That is one of the advantages of the MJ, unfortunately the NODIZ does not have that, it uses extrenal MAP.
As I don't really like the disadvantages of MJ which you have described (particularly lack of dwell control) I'm either looking at NODIZ or an alternative which I'm unaware of at the moment. Still looking though.

As regards the tach adaptor, the diode method requires a connection to each coil. The pulse amplifier method - uses the coil from a standard car relay, and a transistor, only needs 12v, the logic feed in and out to tach, so can be mounted anywhere convenient, perhaps beside the tach if there is room. I think you can buy them ready made. I found it worked better than the diode method on my SD1 tach.

I'm liking the sound of that, another thing I need to do some more looking into. I take it when the the coil is turned off the breakdown of the magnetic field causes a high(ish) voltage?

[SuperV8]

I'd expect any ignition only ECU to have a built in MAP sensor, so all you'd need is a vacuum feed to it.

That is one of the advantages of the MJ, unfortunately the NODIZ does not have that, it uses extrenal MAP.
As I don't really like the disadvantages of MJ which you have described (particularly lack of dwell control) I'm either looking at NODIZ or an alternative which I'm unaware of at the moment. Still looking though.

As regards the tach adaptor, the diode method requires a connection to each coil. The pulse amplifier method - uses the coil from a standard car relay, and a transistor, only needs 12v, the logic feed in and out to tach, so can be mounted anywhere convenient, perhaps beside the tach if there is room. I think you can buy them ready made. I found it worked better than the diode method on my SD1 tach.

I'm liking the sound of that, another thing I need to do some more looking into. I take it when the the coil is turned off the breakdown of the magnetic field causes a high(ish) voltage?

Looking at the NODIZ manual in the "triggering Setup/Crank/Cam Sensors" section it shows it needs a crank signal - so would not work from your (locked) dizy - So you'll also need to factor in a crank toothed wheel/sensor setup.

[GDCobra]

Looking at the NODIZ manual in the "triggering Setup/Crank/Cam Sensors" section it shows it needs a crank signal - so would not work from your (locked) dizy - So you'll also need to factor in a crank toothed wheel/sensor setup.

I don't have a locked dizzy, and the intention is to eventually get rid of the dizzy altogether (replace with cut of "dumpy dizzy" to drive the oil pump).
What I have is a 36-1 wheel monted to the front pully with a 2 wire VR sensor located adjacent. My understanding is that this (as well as other wheel types) is what is required by NODIZ.
I assembeled this during my exploits with MS.
As I'm looking at wasted spark no other sensor (such as cam to give engine phase) should be required.

[SuperV8]

Looking at the NODIZ manual in the "triggering Setup/Crank/Cam Sensors" section it shows it needs a crank signal - so would not work from your (locked) dizy - So you'll also need to factor in a crank toothed wheel/sensor setup.

I don't have a locked dizzy, and the intention is to eventually get rid of the dizzy altogether (replace with cut of "dumpy dizzy" to drive the oil pump).
What I have is a 36-1 wheel monted to the front pully with a 2 wire VR sensor located adjacent. My understanding is that this (as well as other wheel types) is what is required by NODIZ.
I assembeled this during my exploits with MS.
As I'm looking at wasted spark no other sensor (such as cam to give engine phase) should be required.

Ah, ok, yes this is what I was referring to. All good then.
Yes wasted spark doesn't need CAM sensor.

[DaveEFI]

This the schematic of the pulse amplifier. The original circuit used a plain NPN transistor - something like a 2N2222 - but I found a Darlington pair worked better with my tach. That may of course just be a funny with it. It didn't read on start up - then kicked in when you revved it, and then stayed working. With the TIP, you can see it kicking when cranking. If space is an issue, you can remove the coil from the relay. If not, you may want to either remove the armature from the relay or glue it up to prevent it buzzing.

[GDCobra]

This the schematic of the pulse amplifier. The original circuit used a plain NPN transistor - something like a 2N2222 - but I found a Darlington pair worked better with my tach. That may of course just be a funny with it. It didn't read on start up - then kicked in when you revved it, and then stayed working. With the TIP, you can see it kicking when cranking. If space is an issue, you can remove the coil from the relay. If not, you may want to either remove the armature from the relay or glue it up to prevent it buzzing.

Thanks Dave.
I love diagrams, so much easier to understand than words.
I remember the expression "Darlington pair" but must admit don't recall the significance of it. Did study a bit of electonics many years ago but leant towards the digital side rather than analogue. From the diagram this looks like piggy backed transistors
Anyway, I think I can make sense of it, the transistor is acting in place of the current ignition control amplifier being tontrolled from the (logic level) TACH signal from the new ignition controller, the relay coil is replacing the ignition coil so effectively the same circuit as I currently have but slightly different components.

Couple of questions if you don't mind.
Would you expect to get any or significant EMI from the magnetic field collaps in the coil?
If so is it worth shielding this in some way?
I'm assmuing the mechanical components should be removed from the relay to stop audible noise (not that I'd probably notice in my car!)?

[DaveEFI]

In theory, the EMI would be no worse than from a coil, and most makes ran a wire from that to the tach. However, I fitted mine close to the tach to keep the output wire as short as practical. And wouldn't harm to build it in a metal box- lots of ally ones on Ebay. Usually called project boxes.

[GDCobra]

In theory, the EMI would be no worse than from a coil, and most makes ran a wire from that to the tach. However, I fitted mine close to the tach to keep the output wire as short as practical. And wouldn't harm to build it in a metal box- lots of ally ones on Ebay. Usually called project boxes.

Great stuff that Dave. I'm assuming the transistor is pennies rather than pounds (or tens of pounds), I have a number of relays around so no other cost.

[DaveEFI]

Like most electronic components, dirt cheap. Under 20p - but if buying only one you'll pay corkage.

[GDCobra]

Like most electronic components, dirt cheap. Under 20p - but if buying only one you'll pay corkage.

I'll start saving my pennies now, just with there wasn't always so much month left at the end of the money!

[stevieturbo]

What exactly is the issue with GEMS coils, that you seem to think will be a problem for an aftermarket system ?

And what is the issue with the tacho that needs all that messing about ? What exactly drives the current tacho ?

Another cheap ecu, although I don't think they do ignition only as such is Spitronics. But their systems are pretty cheap from South Africa and I think they can sell as complete kits.

But really, Nodiz is UK based....I'd expect support would be better because of that.

[DaveEFI]

What exactly is the issue with GEMS coils, that you seem to think will be a problem for an aftermarket system ?

And what is the issue with the tacho that needs all that messing about ? What exactly drives the current tacho ?

Another cheap ecu, although I don't think they do ignition only as such is Spitronics. But their systems are pretty cheap from South Africa and I think they can sell as complete kits.

But really, Nodiz is UK based....I'd expect support would be better because of that.

For any coil to give its best, it needs the correct dwell. The EDIS module has the correct dwell for EDIS coils - it may not have for the Gems ones. The MegaJolt (or rather the one I've played with) is only designed to work with an EDIS unit.

Older tachs are usually connected to the coil negative. The pulse produced there is relatively high voltage - up to about 50v. The tach outut from an ECU usually 5v. And when you go to four coils, you need a pulse from each of them.

The Nordiz does look promising - but why on earth omit a vacuum sensor, since pretty well every dizzy has one. To allow more advance to be used at low engine demand and improve economy.

If I were looking for the cheapest new solution, I'd check out Speeduino. You can buy the boards on Ebay for not a lot. It can cope with 4 ignition channels, and uses the same tuning software as MegaSquirt (Tuner Studio) which is pretty good.

[GDCobra]

What exactly is the issue with GEMS coils, that you seem to think will be a problem for an aftermarket system ?

There may be no problem at all but I like to consider what pitfalls I may encounter and pre-empt a solution to them.
I've asked a MJ vendor if it will work with GEMS coils and was told "Maybe but you are on your own if there are any issues".
DaveEFi has since indicated that some attributes (dwell in particular) are handled by the EDIS not the MJ hence if the value EDIS uses is not suitable for GEMS coils they will not work to their optimum, maybe not at all.

And what is the issue with the tacho that needs all that messing about ? What exactly drives the current tacho ?

Again, this may be a non-problem but want to know the options for working around.
Advice from Dave and Garry have provided 2 possible options for this.

Another cheap ecu, although I don't think they do ignition only as such is Spitronics. But their systems are pretty cheap from South Africa and I think they can sell as complete kits.

But really, Nodiz is UK based....I'd expect support would be better because of that.

Thanks for the advice on Spitronics, I tried to have a look at their offerings on their web site but it's not very cooperative.
Also I agree a UK based manufacturer should be better able to support, and so far communications have been good. I suspect this is the way I'm going to go.