Distributorless ignition and Rover 14CUX EFi

General Chat About Electrics, And Ignition Systems.

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stevieturbo
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Re: Distributorless ignition and Rover 14CUX EFi

Post by stevieturbo »

The links I added I had googled and saved...oops, but seem very similar to some links already posted.

But suggesting the OEM injection ecu wants, or uses a high voltage spike from the primary....seems highly implausible, when there are docs stating it's a 12v signal it wants...in fact, 7v reduced via the resistor.
Very few electronics want to see high voltage spikes and will use circuitry to clip them for their own safety.


Some of the info was from these ( and seem same links as mentioned )

http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

http://www.g33.co.uk/pages/technical_fu ... ction.html

https://en.wikipedia.org/wiki/Lucas_14CUX


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Re: Distributorless ignition and Rover 14CUX EFi

Post by DaveEFI »

stevieturbo wrote:
Sun May 23, 2021 9:36 pm
The links I added I had googled and saved...oops, but seem very similar to some links already posted.

But suggesting the OEM injection ecu wants, or uses a high voltage spike from the primary....seems highly implausible, when there are docs stating it's a 12v signal it wants...in fact, 7v reduced via the resistor.
Very few electronics want to see high voltage spikes and will use circuitry to clip them for their own safety.


Some of the info was from these ( and seem same links as mentioned )

http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

http://www.g33.co.uk/pages/technical_fu ... ction.html

https://en.wikipedia.org/wiki/Lucas_14CUX
The snag with your theory is that on a standard setup that same pulse feeds the tach. So if it were 12v from the coil, then a 12v pulse would work the tach. And anyone who has ever fitted an aftermarket ECU knows it won't.

That switching off low volts to an inductor (coil) produces a higher voltage pulse is the very principle behind an ignition system.
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Re: Distributorless ignition and Rover 14CUX EFi

Post by GDCobra »

stevieturbo wrote:
Sun May 23, 2021 9:36 pm
The links I added I had googled and saved...oops, but seem very similar to some links already posted.

But suggesting the OEM injection ecu wants, or uses a high voltage spike from the primary....seems highly implausible, when there are docs stating it's a 12v signal it wants...in fact, 7v reduced via the resistor.
Very few electronics want to see high voltage spikes and will use circuitry to clip them for their own safety.
DaveEFI wrote:
Mon May 24, 2021 7:17 am

The snag with your theory is that on a standard setup that same pulse feeds the tach. So if it were 12v from the coil, then a 12v pulse would work the tach. And anyone who has ever fitted an aftermarket ECU knows it won't.

That switching off low volts to an inductor (coil) produces a higher voltage pulse is the very principle behind an ignition system.

You guys are probably way ahead of me on this, I'm not too experience with analogue electronics, I have a little expeience with digital stuff.
I've heard that tapping into the connection on the -ve side of the coil gives a "flyback signal" by this I'm asuming that when the ground is removed from the primary coil (how the coil is triggered) the breakdown of magnetic flux in the coil induces voltage in the coil which is then picked up on the -ve terminal.
More or less what Dave has indicated in his last sentence of his post if I understand correctly.
My understanding is that is what is depicted in the diagram I pointed out on the G33 site titled "Primary Ignition Waveform" however I'm making way more assumptions than I generally like to at this point!

I guess if you forget about "flyback" and magnetic fields breaking down then the -ve terminal would be at 0v when connected to ground and 12v via the coil when the ground is disconnected to trigger ignition so maybe I'm not clear on this "flyback" behaviour


In lieu of this knowledge and in an attempt to remove as many assumptions as possible the reason I initially wanted to get this signal from the (4) coils is that it's the closest I can get like-for-like with the original single coil setup.
I know it probably doesn't seem like it but i was actually trying to simplify the scenario.

My later attempts at using the NODIZ's TACHO output (both directly and using it to fire a small coil) were due to the NODIZ getting upset with the diodes being present. I'm resonably confident this could work in terms of signal style (may need a little more work) but unfortunately is not going to be useable due to frequency issues.
I do have some ideas for circuits to double the frequency but I'll be getting into greater complexity which is my golden rule on how not to solve a problem, I also have no way of testing any circuit I make so unless it was to work straight out of the box I'd have no way to know if that were the problem or not.

Thanks for the links Stevie, I'll check them out although they are locations I'm familiar with but could have missed some detail.

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Re: Distributorless ignition and Rover 14CUX EFi

Post by stevieturbo »

DaveEFI wrote:
Mon May 24, 2021 7:17 am

The snag with your theory is that on a standard setup that same pulse feeds the tach. So if it were 12v from the coil, then a 12v pulse would work the tach. And anyone who has ever fitted an aftermarket ECU knows it won't.

That switching off low volts to an inductor (coil) produces a higher voltage pulse is the very principle behind an ignition system.
I've never had any issue with any tach and ecu I've used over the last 20 years.
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Re: Distributorless ignition and Rover 14CUX EFi

Post by stevieturbo »

If you apply a signal to the efi ecu....do you have an easy way of knowing it it is happy with what you are sending it ?

ie. if you just fed it a simple switched 12v, could you see a response from it to know if it's good or bad ?
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Re: Distributorless ignition and Rover 14CUX EFi

Post by DaveEFI »

GDCobra wrote:
Mon May 24, 2021 4:55 pm
stevieturbo wrote:
Sun May 23, 2021 9:36 pm
The links I added I had googled and saved...oops, but seem very similar to some links already posted.

But suggesting the OEM injection ecu wants, or uses a high voltage spike from the primary....seems highly implausible, when there are docs stating it's a 12v signal it wants...in fact, 7v reduced via the resistor.
Very few electronics want to see high voltage spikes and will use circuitry to clip them for their own safety.
DaveEFI wrote:
Mon May 24, 2021 7:17 am

The snag with your theory is that on a standard setup that same pulse feeds the tach. So if it were 12v from the coil, then a 12v pulse would work the tach. And anyone who has ever fitted an aftermarket ECU knows it won't.

That switching off low volts to an inductor (coil) produces a higher voltage pulse is the very principle behind an ignition system.

You guys are probably way ahead of me on this, I'm not too experience with analogue electronics, I have a little expeience with digital stuff.
I've heard that tapping into the connection on the -ve side of the coil gives a "flyback signal" by this I'm asuming that when the ground is removed from the primary coil (how the coil is triggered) the breakdown of magnetic flux in the coil induces voltage in the coil which is then picked up on the -ve terminal.
More or less what Dave has indicated in his last sentence of his post if I understand correctly.
My understanding is that is what is depicted in the diagram I pointed out on the G33 site titled "Primary Ignition Waveform" however I'm making way more assumptions than I generally like to at this point!

I guess if you forget about "flyback" and magnetic fields breaking down then the -ve terminal would be at 0v when connected to ground and 12v via the coil when the ground is disconnected to trigger ignition so maybe I'm not clear on this "flyback" behaviour


In lieu of this knowledge and in an attempt to remove as many assumptions as possible the reason I initially wanted to get this signal from the (4) coils is that it's the closest I can get like-for-like with the original single coil setup.
I know it probably doesn't seem like it but i was actually trying to simplify the scenario.

My later attempts at using the NODIZ's TACHO output (both directly and using it to fire a small coil) were due to the NODIZ getting upset with the diodes being present. I'm resonably confident this could work in terms of signal style (may need a little more work) but unfortunately is not going to be useable due to frequency issues.
I do have some ideas for circuits to double the frequency but I'll be getting into greater complexity which is my golden rule on how not to solve a problem, I also have no way of testing any circuit I make so unless it was to work straight out of the box I'd have no way to know if that were the problem or not.

Thanks for the links Stevie, I'll check them out although they are locations I'm familiar with but could have missed some detail.
According to what I've read online of the Nodiz installation instructions, its tach output gives the correct frequency to drive a tach, but at 12v. If yours is producing half speed I'd ask the supplier why. It simply makes no sense to me. And if course in your case both the tach and ECU tach come from the same point, the coil, so must be identical in frequency. So with the correct tach frequency from the Nodiz, the only reason it won't trigger the Lacus ECU must be a question of level.
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Re: Distributorless ignition and Rover 14CUX EFi

Post by DaveEFI »

stevieturbo wrote:
Mon May 24, 2021 5:25 pm
DaveEFI wrote:
Mon May 24, 2021 7:17 am

The snag with your theory is that on a standard setup that same pulse feeds the tach. So if it were 12v from the coil, then a 12v pulse would work the tach. And anyone who has ever fitted an aftermarket ECU knows it won't.

That switching off low volts to an inductor (coil) produces a higher voltage pulse is the very principle behind an ignition system.
I've never had any issue with any tach and ecu I've used over the last 20 years.

Can I ask which vehicle you've converted from dizzy/single coil to multiple coil where the OEM tach works from the after market ECU directly?

Perhaps the most common UK tach of that period is the Smths RV1. That is directly connected to the coil negative and requires a high voltage pulse to trigger it.

Here is a quote from the MegaJolt installation instructions:-

********************************************************************



Using the Tach Out on the MJLJ

Many tachometers can accept the signal emitted from the Tach Out on the MJLJ module. This Tach Out signal provides a 12V pulse for every ignition event. You may use this to provide the signal to compatible tachometers, or to provide a signal to a separate Engine Control Unit, data logger, or other device which requires this signal.
Tachometers that require a high-voltage kickback pulse

Some OEM-style tachometers detect the RPM signal by sensing the high voltage fly back pulse from the ignition coil. In distributor based setups, there is only one ignition coil from which to detect this pulse. With a wasted spark system, this 'signal' is spread across multiple coils. As a result, you will need a way to combine these pulses across multiple coil packs to drive your tachometer.

The following circuit allows the fly back pulse to be detected across individual coil packs while still isolating the coils from each other.

Tach circuit.jpg


************************************************************************

Since you apparently don't believe me. :D
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Re: Distributorless ignition and Rover 14CUX EFi

Post by GDCobra »

stevieturbo wrote:
Mon May 24, 2021 5:27 pm
If you apply a signal to the efi ecu....do you have an easy way of knowing it it is happy with what you are sending it ?

ie. if you just fed it a simple switched 12v, could you see a response from it to know if it's good or bad ?
When the EFi ECU gets an ignition signal it invokes a routine which performs more or less all of the work required to control the engine, I don't have any way of seeing what it's doing at this level BUT one of the things it does do is re-start the fuel pump (this runs for about 3 seconds at boot up to charge the sytem and then stops until it sees the engine turning). The fact that I don't see (hear) the fuel pump restart when I feed that TACHO pulse from the NODIZ to the 14CUX indicates to me that it is not happy with it. This could be because it does not 'like' the form of the pulse (voltage levels, duration or whatever) or it may be that the system has a calculation for minimum frequency so unless it calclates the engine is rotating at least (say) 100 RPM it doesn't complete its process. Without working through the routine I have no way of knowing if that is the case.

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Re: Distributorless ignition and Rover 14CUX EFi

Post by GDCobra »

DaveEFI wrote:
Mon May 24, 2021 6:20 pm
So with the correct tach frequency from the Nodiz, the only reason it won't trigger the Lacus ECU must be a question of level.
Problem with that statement is "What is the correct frequency to drive the tach?", This will depend on the specific tachometer in use, I don't think NODIZ (or any manufactuer) can safely assume that just because the vehicle uses an 8 cylinder engine that the tachometer will require 4 pulse per crank revolution, could just as easily be 2/rev or even 1.

I agree that this system should have configuration for setting the output frequency. and infact their beta version of the software did have a series of buttons for just this purpose, the problem is that this did not work (killed comm's between PC and NODIZ when pressed). I was hoping that setting the trigger wheel to "36-1 8 cylinder" would imply a 4 pulse/rev' output but it does not and from conversations with them it seems there is no way to this output.
DaveEFI wrote:
Mon May 24, 2021 6:20 pm
So with the correct tach frequency from the Nodiz, the only reason it won't trigger the Lacus ECU must be a question of level.
This is the problem. The output frequency from NODIZ is NOT correct and is not correctable (that's the way it seems at the moment at least), I know this is the case as the tachometer reads half correct value.

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Re: Distributorless ignition and Rover 14CUX EFi

Post by GDCobra »

DaveEFI wrote:
Mon May 24, 2021 6:38 pm


Here is a quote from the MegaJolt installation instructions:-

********************************************************************
Using the Tach Out on the MJLJ

Some OEM-style tachometers detect the RPM signal by sensing the high voltage fly back pulse from the ignition coil. In distributor based setups, there is only one ignition coil from which to detect this pulse. With a wasted spark system, this 'signal' is spread across multiple coils. As a result, you will need a way to combine these pulses across multiple coil packs to drive your tachometer.

The following circuit allows the fly back pulse to be detected across individual coil packs while still isolating the coils from each other.

Tach circuit.jpg


************************************************************************

Fairly obviously this is the type I have. Any chance you could tell me what the suggested circuit was in "Tach circuit.jpg"?

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Re: Distributorless ignition and Rover 14CUX EFi

Post by DaveEFI »

GDCobra wrote:
Mon May 24, 2021 7:25 pm
DaveEFI wrote:
Mon May 24, 2021 6:38 pm


Here is a quote from the MegaJolt installation instructions:-

********************************************************************
Using the Tach Out on the MJLJ

Some OEM-style tachometers detect the RPM signal by sensing the high voltage fly back pulse from the ignition coil. In distributor based setups, there is only one ignition coil from which to detect this pulse. With a wasted spark system, this 'signal' is spread across multiple coils. As a result, you will need a way to combine these pulses across multiple coil packs to drive your tachometer.

The following circuit allows the fly back pulse to be detected across individual coil packs while still isolating the coils from each other.

Tach circuit.jpg


************************************************************************

Fairly obviously this is the type I have. Any chance you could tell me what the suggested circuit was in "Tach circuit.jpg"?
The diode circuit you already have.
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Re: Distributorless ignition and Rover 14CUX EFi

Post by GDCobra »

DaveEFI wrote:
Mon May 24, 2021 10:51 pm

The diode circuit you already have.
Ah, OK, was hoping that was the case. Thanks Dave, so at least I'm on the right track wtih the diodes but for some reason the have a negative effect on the ignition unit, I've not re-routed the diodes and output cable to keep them all further apart from each other and from the NODIZ wiring in the hope this will prevent any interference. I'm also using a new set of diodes "just in case".

Does that circuit have a Zener on the output?
This is one area I don't fully understand (and when I say "fully" I probably mean "hardly at all"), summing the 4 flyback pulses together via the regular diodes (in my simple mind) should give me the same signal I had from the single coil with the spike being whatever voltage the coil(s) dictate.
So why is a Zener needed/used for multiple coils but not for a single?

My (limited) understanding is that the Zener will allow voltages above their theshold (circa 15v in this case) through so this should "filter out" any of the lower voltage "noise" and only allow the peak/spike signal through (bearing in mind the Zener is place in series with the output) or have I got this the wrond way around? Does the Zener only allow voltage below the threshold through hence filtering out higher levels (i.e. the spike)?

Thinking while I'm typing, I think I may have just answered my own question!
Looking at the "Primary Ignition Waveform" diagram on this page "http://www.g33.co.uk/pages/technical_ig ... ystem.html" and thinking of superimposing that form 4 times with 90° phase shifts, it's possible that the sum of the waves will always have 'some' voltage and this needs to be filtered out.

Worth mentioning that in early tests the 14CUX worked as well without the Zener as it did with it, the tachometer did not. Perhaps the 14CUX has built in signal processign which performs a similar filtering operation which the simple tachometer does not possess.

Just waiting for NODIZ to return now to test all this. Fingers crossed the modified diode wiring does the trick.

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Re: Distributorless ignition and Rover 14CUX EFi

Post by DaveEFI »

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.

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 simply didn't even consider the diode thingie because of the rats nest the wiring makes.

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.
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Re: Distributorless ignition and Rover 14CUX EFi

Post by DaveEFI »

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.

Diodes are easy to check with a DVM which has a diode check function - most do. A working diode will show about 0.6 volt when correct connected, and a rubbish figure the other way round. 0.6v is the forward voltage drop of a working diode. A faulty one won't read this.
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Re: Distributorless ignition and Rover 14CUX EFi

Post by GDCobra »

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!

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