Cheers Dave.
First of all, thanks for the feedback, I know I may seem dumb at times as some (most!) of this is outside my area of expertise but it is helping.
DaveEFI wrote: ↑Tue May 25, 2021 12:28 pm
I'm assuming the Nodiz will come back fully checked -
and that the tach output now delivers one pulse per ignition event at the stated 12v level, as it says it does in the instructions. So I'd be inclined to try that direct to your Lucas ECU, bypassing the 6K8 resistor. Do make sure both the Lucas and Nodiz are grounded at the same point, though.
I'm hoping this too Dave but from conversations with them I don't think that will be the case - I've been wrong before though!
I will check this by plugging my Transistor/Relay-coil setup in and reading the tachometer, if that doesn't report the correct value then no point in trying with the EFi, even if it was happy with the signal it would be outputting the wrong amount of fuel (half what it should).
I'd much prefer to use this as I have some experience with digital circuits with (what I believe are) more controlled signals rather than this flyback pulse which is really just electro-magnetic noise in my view. Although to be fair it does do a good job in it's native environment!
DaveEFI wrote: ↑Tue May 25, 2021 12:28 pm
Incidently, with the relay coil pulse amp, some experiments here using a spare SD1 5 pin relay, gave better results on the 'scope replacing the transistor MegaSquirt specified with a Darlington type. I used a TIP 122 as I have them in stock. It has more gain than a single transistor and made sure the switching side was fully on.
I'm already on the same wavelength (no pun intended) as you there Dave, I took your advice from the earlier post and used the TIP122 transistor.
I also found much the same circuit here:
http://www.brumster.com/index.php/hacks ... -level-ecu
Where he's using a regular transistor, I have some of these too so if I go down the TACHO signal route I may also try his circuit. Only advantage being that the smaller transistor can be fitted into a relay casing as he shows so a neater install.
I'll be proving out with the TIP122 first though, which is what I have already put together, as I suspect this has the better chance of success.
DaveEFI wrote: ↑Tue May 25, 2021 12:28 pm
I simply didn't even consider the diode thingie because of the rats nest the wiring makes.
I've actually got quite a neat setup with the diodes, they all live within a convoluted tube covered loom so not even obvious where they are. This was originally the same loom as used to feed the coils.
This may be part of my problem, the closeness of the diodes and being confined in the loom could be causing some interference issues or possibly even heat.
In readiness for the return of the NODIZ I've altered this by separating the diodes and the feeds to them (slightly) further and only having a thin covering on the setup (for now at least), this is also separate from the wiring to the NODIZ as much as possible to reduce possibility of any "cross-talk" between them.
I can also "take this to the next level" with a spare set of coils I have, on this the diodes are kept much further apart and also further from the NODIZ loom, this is as good as I can practically make this. Apart from adding some shielding which could also be a possibility.
DaveEFI wrote: ↑Tue May 25, 2021 12:28 pm
FWIW on my own car, a Rover SD1, the rev counter is an open frame type, so easy to get at the electronics. So gutted a spare unit of the electronics, leaving just the meter movement, and fitted a modern chip designed to drive a rev counter from a low voltage signal. This would be more tricky to do on the more usual steel cased sealed units, though.
All the instruments on my car are separate 'pods', like old style Lotus Elan or simlar. They were new just over 20 years ago when I build the car but the doesn't mean "modern", based on the fact the tacho is fed from this flyback I guess not.
Going from memory the casing is plastic, rather than metal as it would be on a proper old unit, and I may be able to gain access and modify the internals if it comes to that. However that is the least of my worries, the tachometer is "sortable" one way or another, worst case would be to replace with a new unit (only problem there would be getting something to match my other instruments).
The main issue is being albe to get a signal that will run the EFi and NOT mess up the function of the NODIZ.
DaveEFI wrote: ↑Tue May 25, 2021 12:37 pm
BTW, I'd guess the Zener in the diode circuit is there to clamp the maximum voltage to the lowest which will work reliably. As it's bad practice to have high voltage pulses flying around the car, if not needed.
So could you clarify does a Zener pass voltages above their threshold value or limit the voltages passed through to that value.
For instance if I have a 12V Zener with (say) 7V on the input will I see that on the output or would I only see output voltages greater than 12v (when the input rises to this level)?
I need to go and dig out my electronics coursework, it may be 20+ years old but I don't think the concept of Zener diodes changed in that time!