Combat performance issue - RITA

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" Modern MoSFETs will have lower power consumption than the original transistors. "

Better U F O tecnology these days , harder to get though .



Er . . . :(
 

motorson

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I guess to be fair Lucas didn’t let anyone know the advance curve of the original RITA. We got that information from Dave Comeau aka DynoDave on his Atlantagreen website. Modern MoSFETs will have lower power consumption than the original transistors.
This is correct as far as it goes. DynoDave's curves of different ignitions show that the Lucas Rita comes closest to the original points curve and most electronic ignitions lagged behind that curve. So, what I wanted to know is if this new company engineered the same curve that the Rita had or if they missed it like most of the electronic ignitions do. Of course, DynoDave had to get each ignition in hand to be able to do his testing. I wanted to skip the step of buying one to test before deciding to put it on my bike. As far as heat and power consumption go I believe Rex's probably does that in two ways. One, by using more efficient components and the other by charging the coils for less time before releasing the spark. My impression is that no coil needs to be charged for very long before being ready to deliver maximum spark - demonstrated by the fact that an old V8 used only one coil to fire all 8 plugs which meant that it had to charge up 4 times per revolution of the engine.
 

ILLF8ED

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It doesn’t confirm your question, but Rex’s statement is with their replacement board “The ignition timing is exactly the same using the original sensor.” I have been running their board in my combat for over a year and have not had any pinging. All other ignitions I have used this was a problem.
 

baz

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It doesn’t confirm your question, but Rex’s statement is with their replacement board “The ignition timing is exactly the same using the original sensor.” I have been running their board in my combat for over a year and have not had any pinging. All other ignitions I have used this was a problem.
Great info
Thank you
 
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I like Rita Ignitions, I have one on my Norton. I tried one on my Vincent using a tiny Nology coil 3 ohms resistance. The coil melted after running for only about half an hour. Later I used that ignition with twin Lucas 6 Volt coils and it worked fine. The Lucas coils do get warm, but they are capable of dissipating the heat. I think the reason the Rita uses so much power is that the dwell is really long.
 

baz

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It doesn’t confirm your question, but Rex’s statement is with their replacement board “The ignition timing is exactly the same using the original sensor.” I have been running their board in my combat for over a year and have not had any pinging. All other ignitions I have used this was a problem.
I have ordered a Rex's replacement board
I will make a housing for it and find a space for it
I'll keep the Rita on the bike ready to plug back in if necessary
I'm hoping this will help with the marginal charging at low rpm my Alton alternator gives me
 

cliffa

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I have ordered a Rex's replacement board
I will make a housing for it and find a space for it
I'll keep the Rita on the bike ready to plug back in if necessary
I'm hoping this will help with the marginal charging at low rpm my Alton alternator gives me
It will be interesting to hear your feedback on how it compares baz. I wonder about the Alton output too ( with Boyer power box) so I’ve just ordered a Sparkbright Eclipse as they give an accurate indication of what’s going on.
 
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baz

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It will be interesting to hear your feedback on how it compares baz. I wonder about the Alton output too ( with Boyer power box) so I’ve just ordered a Sparkbright Eclipse as they give an accurate indication of what’s going on.
Ok I fitted the Rex's Rita today but before fitting I checked the voltage at the battery with ignition off and still fitted with original Rita
It was 11.96v at the battery ignition off
And 11.60v with ignition on
So I fitted the Rex's unit
Ignition off was 11.95v
Ignition on was 11.61
Engine running at 2000rpm with Rita 12.51v
Engine running at 2000rpm with Rex's 12.53
So I can tell barely any difference on current draw between Rita and Rex's on my bike
 

baz

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I'm surprised there wasn't a large difference with the current draw from the old unit to the new unit
When I asked Rex's speedshop they couldn't tell me what the current draw was
Only that it was less
Maybe I'm missing something ?
 

cliffa

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I'm surprised there wasn't a large difference with the current draw from the old unit to the new unit
When I asked Rex's speedshop they couldn't tell me what the current draw was
Only that it was less
Maybe I'm missing something ?
I think to get an accurate picture you need an ammeter in line to compare the current draw on each. Most multimeters now have a 10A option, so it should be possible to rig up something temporarily. ( not on the starter cable though ;))
 

baz

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I think to get an accurate picture you need an ammeter in line to compare the current draw on each. Most multimeters now have a 10A option, so it should be possible to rig up something temporarily. ( not on the starter cable though ;))
Well maybe
But what I was hoping for was a bit more charge at under 2000 rpm
The bike is fitted with a voltmeter and it's a bit alarming when I'm stuck in traffic with the lights on and it's dropping under 12v
I have extra led running lights so I'm probably asking too much of the system
I did once try running the Rita on a slave battery and the charge at idle was perfect
And with the Rita being known to be power hungry I'd thought a modern replacement would be less
But that's not the case
 

cliffa

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Well maybe
But what I was hoping for was a bit more charge at under 2000 rpm
The bike is fitted with a voltmeter and it's a bit alarming when I'm stuck in traffic with the lights on and it's dropping under 12v
I have extra led running lights so I'm probably asking too much of the system
I did once try running the Rita on a slave battery and the charge at idle was perfect
And with the Rita being known to be power hungry I'd thought a modern replacement would be less
But that's not the case
I understand. Out of interest which reg / rec are you using ?
 
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Well maybe
But what I was hoping for was a bit more charge at under 2000 rpm
The bike is fitted with a voltmeter and it's a bit alarming when I'm stuck in traffic with the lights on and it's dropping under 12v
I have extra led running lights so I'm probably asking too much of the system
I did once try running the Rita on a slave battery and the charge at idle was perfect
And with the Rita being known to be power hungry I'd thought a modern replacement would be less
But that's not the case
A bit off topic perhaps but you might try wiring the lighting circuit as per the MKIII where the lights have the option of running off the alternator only without running the battery down. I had your problem in heavy traffic with my BMW and with that there isn't a way to start it at all with a low battery. So, I ginned up a circuit with some diodes and a switch that would isolate the head light from the battery. You could wire in a Canadian MKIII assimilator that serves the same function. The lights don't care it it's ac or dc. An Enfield Bullet I work on has lights wired for AC only. They don't work unless the engine is running. I think it came from the factory that way.

For my Norton I eventually went to the three-phase alternator/rectifier combo but I don't remember if that was before or after the Rita died. I have had no trouble keeping the battery charged since, even running my electric vest.

As regards alternator/rectifiers: It is surprising how much parasitic current load the field on an excited-field alternator requires, on the order of 4-6 amps on the Bosch/BMW units IIRC. I eventually replaced the Bosch alternator on my BMW with a Saprisa unit made for Guzzis and Ducatis. The charge at low RPM far exceeds the Bosch, excited-field unit. It is a total-loss system like the Lucas so the zeners are wasting electricity anytime the system isn't using it.
 

SteveBorland

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Reference the attached document, the pick up is simply a coil. Meaning, it does not have any capability to advance the ignition. The advance circuit is part of the main module function.

Don't invent functionality.

Secondly, you will find reference to incorrect wiring affecting the advance. Fully retarded rather than advanced. Here are the words from the document:

'The Pickup is just a coil of wire and can be measured with a Mutimeter.
200-450 ohms - C and Low C types (270 ohms average)
1500-2000 ohms for the 2PU type.
600-700 ohms for the 5PU type ( Triumph factory fit)
If the pick-up leads are reversed by mistake, the ignition will still work and will not be damaged but the ignition point will be fully retarded (No advance) The engine will be appropriately poor in performance, maybe hard to start.'

Personally, when I saw mention of lack of rpms in a higher gear, my thought was of the ignition not advancing, not doing too much of it!

My RITA experience is limited to an ex Norton works unit. I knew it had an advance circuit for one simple reason, the unit exhibited no advance at all, because the works team in their wisdom had jumpered it out on the PCB. I discovered this when I drew the circuit out for my reference some time in '77 or '78. I am sure I still have that drawing somewhere.

Running fully advanced is fine for a race bike with no kick start, and bear in mind that a lot of racers in the '70s ran point ignition with the advance unit welded up and set fully advanced. Because the AAU had a habit of exploding, I know, had that happen, and it is why I got the RITA in the first place. I was able to fit the reluctor in the otherwise unusable camshaft.

However, given the options, and being very happy with the cheapest Pazon on my short stroke, and fully supporting FE's comments on cost, just bin it! What else should we do with old electronics :rolleyes:
The Rita advance is determined by the rotor shape (the bit that whizzes round past the pickup coil). From the description, I suspect that it's not the correct Norton rotor you have.
I have Rita systems on a bevel Ducati and a T150 triple. The Ducati system had problems this year for the first time in 20-odd years (due to a wire being cut by the rotor, but that's another tale), but otherwise has been stone reliable. I really like Ritas, but given the difficulty in finding a correct Norton rotor, I would also suggest looking at a Pazon system to replace it.Good quality and easy to install & setup. I'm very happy with the one on my 850.

If you do change to another ignition though, please don't chuck the Rita in the bin, there's people out there who would gladly take it off your hands!
 
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SteveA

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The Rita advance is determined by the rotor shape (the bit that whizzes round past the pickup coil). From the description, I suspect that it's not the correct Norton rotor you have.
I have Rita systems on a bevel Ducati and a T150 triple. The Ducati system had problems this year for the first time in 20-odd years (due to a wire being cut by the rotor, but that's another tale), but otherwise has been stone reliable. I really like Ritas, but given the difficulty in finding a correct Norton rotor, I would also suggest looking at a Paton system to replace it.Good quality and easy to install & setup. I'm very happy with the one on my 850.

If you do change to another ignition though, please don't chuck the Rita in the bin, there's people out there who would gladly take it off your hands!
The advance is performed by an electronic circuit in the amplifier box.

The rotor is a piece of metal, and whatever shape it is, its shape doesn't change at different rpm, so really it is physically impossible for the rotor to advance the spark.

But quite why you are responding to me, I don't know. I haven't owned a Luca Rita ignition since 1980! I currently have a Pazon installed, but have used a crank pickup with a Boyer supplied by Steve Maney.

Now back when I had a Rita I repaired it and kept it functioning for some time. And I drew out the circuit in detail to be able to do that, including the advance circuit.

Though as I said, the advance circuit was actually jumpered out on the board by the previous 'owner', the Thruxton Race shop!

And as the rotor whizzed around at various rpm, the timing remained where I set it, without advancing.
 

SteveBorland

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The advance is performed by an electronic circuit in the amplifier box.

The rotor is a piece of metal, and whatever shape it is, its shape doesn't change at different rpm, so really it is physically impossible for the rotor to advance the spark.

But quite why you are responding to me, I don't know. I haven't owned a Luca Rita ignition since 1980! I currently have a Pazon installed, but have used a crank pickup with a Boyer supplied by Steve Maney.

Now back when I had a Rita I repaired it and kept it functioning for some time. And I drew out the circuit in detail to be able to do that, including the advance circuit.

Though as I said, the advance circuit was actually jumpered out on the board by the previous 'owner', the Thruxton Race shop!

And as the rotor whizzed around at various rpm, the timing remained where I set it, without advancing.
Sorry about the wrong placement of my reply, it was intended as a comment on the Rita rather than as a direct response to you.

Regarding how the Rita does it's advance, I was basing my reply on this:
https://www.britbike.com/forums/ubbthreads.php/topics/32497/re-lucas-rita-notes where the claim is made.
I'm not a sparky, more a clanky, so I would be very interested in knowing if my quoted source is pie-in-the-sky (cannot possibly be so, I read this on the internet :) ). Interesting enough, the circuit diagram in this thread also mentions a mysterious jumper.
 

SteveA

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Sorry about the wrong placement of my reply, it was intended as a comment on the Rita rather than as a direct response to you.

Regarding how the Rita does it's advance, I was basing my reply on this:
https://www.britbike.com/forums/ubbthreads.php/topics/32497/re-lucas-rita-notes where the claim is made.
I'm not a sparky, more a clanky, so I would be very interested in knowing if my quoted source is pie-in-the-sky (cannot possibly be so, I read this on the internet :) ). Interesting enough, the circuit diagram in this thread also mentions a mysterious jumper.
It isn't pie in the sky, but like a lot of things it needs interpretation. First, inductive electronic ignition advance in a nutshell:

The ignition spark is triggered by pulses from the pick up, which are generated by the reluctor pole passing the pickup coil. Increasing the speed the reluctor passes the pickup coil will alter the induced electrical signal in the pickup coil, specifically the pulses get closer together in time! What the advance circuit on the board has to do is detect the signal and trigger the ignition to spark at the appropriate crank angle. (This is why it is always imperative to strobe the ignition timing to see what you actually get across the rpm range until the measured advance stops changing)

What your reference says is that the shape of the reluctor also 'shapes' the trigger signal, but more specifically it is saying that the induced voltage of that signal does not decay as quickly at higher rpm.....changing the point at which the spark is triggered. The signal is the input to the advance circuit on the board in the amplifier.

Reluctor shape may well influence signal shape, it would be difficult to be sure of the specific influence without testing various reluctor forms, which clearly Lucas did. I think there is a confusion also with the wording in this reference:


Which says at 4. 'The shape of the triggering poles on the reluctor are different for Fixed Ignition and Automatic Advance/Retard. It should therefore be noted that a four-stroke Reluctor will not run a two-stroke satisfactorily on Fixed Ignition'

This does not say that the reluctor shapes the advance curve, it says one type or reluctor is suited to a system with an advanced curve, and another type is suited to an ignition without and advance curve. Many 2 strokes do not use and advance curve. Note that often on a 2 stroke with electronic ignition the ignition actually retards at higher rpm to avoid detonation!

I would suggest that the RITA reluctor shape really gives a narrower profile running close to the pickup itself which will also influence the duration of the waveform, and if the physical curves weren't added the narrow reluctor ends would also have been a mechanically weak structure! We don't know what influenced Lucas to adopt that particular shape, so we can't discount mechanical strength or production/manufacturing needs as well as ignition advance.

However, the induced signal will change the trigger point whatever the shape of the reluctor, simply based on the speed it passes the pickup (refer again to bias voltage). And regardless of the influence the rotor shape may have, the advance is electronic and performed by the circuit in the amplifier box.

The actual RITA I owned had a basic square reluctor end so no fancy stuff there and was used with an earlier style of pickup, which required a modified timing cover to mount it. The ignition advance was jumpered out! So it was a fixed ignition type. However, as far as I can see, the advance circuit was present and basically the same as on advance models and later models!

My guess is that the square reluctor and the earlier pickup either gave a somewhat unreliable advance, or simply and more likely, continued to advance as rpm rose above 5000rpm, which is undesirable on any engine.

So the Norton race shop which was the former owner on my ignition either used a fixed ignition unit, or decided to jumper the advance out to run full advanced ignition on a race bike, that spent most of its life above 4000rpm.
 
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