Programmable ignition timing

I was watching a TV programme on building a Chev V8 race motor yesterday. One thing they did was fit weaker springs to the bob weights in the ignition system to make it advance quicker.
I understand that Boyer supply a programmable ignition system and am wondering if anyone here has used one ? In setting my bike up, I always use fixed advance and jet up to it. I wouldn't have a clue about how to determine the optimum advance curve for various applications. The other thing which interests me is the variety of tapers available in Mikuni carb needles. I use methanol with the richest Mikuni petrol needle in Mk2 Amals. There is obviously advantage in trying various other needles. My feeling is that with a fixed compression ratio varying the timing has a similar effect to varying the jetting in a lot of circumstances. I use low compression with a lot of advance and very lean jetting, and I don't intend to increase the comp. ratio. I realize there are two things at play - the timing would be dependent on the revs, and the jetting dependent on throttle opening. In my mind I find it difficult to reconcile the two.
I found a bit on the web interesting reading, however the guys were talking about building their own system and didn't seem to have much of an idea about what is really needed.

I've not tried it on a Norton, but I have played with ign curves etc on Triumph twins and triples.

In my experience, these old engines are not so sensitive to such things. What does make a big difference is having a big, powerful spark. A degree or two, or three, either way doesn't register as a difference, its the same when changing advance curves.

Only my own experience of course. Others may have had different.

FWIW,
I do not advocate the PowerArc system, but the interface is available and the software is free to download.

I do not advocate the PowerArc system

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Pete, I am interesting in hearing any reasons why you feel that way?

The advance curves I've seen tend to peak out at 3000 RPM on parallel twin OHV engine configurations (British motorcycles). My experience is that the Norton's mechanical advance unit is good for 24 crankshaft degrees (12 degrees stamped on the back), so the real benefit is a starting advance of 8 degrees BTC, which makes the Norton much easier to start. You cold do as well with a toggle: set starting advance for what lights the fuse best, then toggle to optimum full advance when warm.

Given the timing chain and the fluctuations it must induce with any timing mechanism driven off the cam any timing target is an average at best. The best trigger for timing would be a crank position sensor system. Boyer has one and I believe Jim Comstock demonstrated one. But does the Norton really benefit from such sophistication?? In a pre emission controls environment I'd think not, but I am wide open to hear the counter point. A million years ago I had a 1937 Indian Chief, it had a spark advance on the right handlebar and the throttle on the left. I gave it full retard to start and full advance to run, the fact that the advance was on the handlebar lead me to believe that there was some benefit to controlling it while motoring, I was 16 at the time and had no clue, but the engine had a much lower redline than and English motorcycle. I varied the advance under many different conditions and could not discern any difference.

Far from a QED.

Bill.

1up3down said:

I do not advocate the PowerArc system

Click to expand...

Pete, I am interesting in hearing any reasons why you feel that way?

Click to expand...

It's just that it didn't work out for me. Maybe I had too much endplay or maybe it just didn't jive with my particular needs. I will say that I used no less than 6 programs in 3 separate units, with and without advance curves, single fire and duel fire confugurations. I am sure they have their place, just not on my bike.

The technical issue is really about having a dynamic advance, one that adjusts to engine loads and speeds. A programmable IE certainly can help a particular engine set up i.e. it compression ratio, cam, carburetion and exhaust but once running its fixed within its parameters. Norton motors do not lend themselves to modern sensors that are necessary for engine management system, and frankly without fuel injection, never a realistic possibility.

pete.v said:

1up3down said:

I do not advocate the PowerArc system

Click to expand...

Pete, I am interesting in hearing any reasons why you feel that way?

Click to expand...

It's just that it didn't work out for me. Maybe I had too much endplay or maybe it just didn't jive with my particular needs. I will say that I used no less than 6 programs in 3 separate units, with and without advance curves, single fire and duel fire confugurations. I am sure they have their place, just not on my bike.

Click to expand...

Interesting. My experience has been just the opposite.
I installed a PowerArc in mt 72 Combat soon after I acquired it in January of this year.
It has worked flawlessly. (Except for the time the bolt securing it to the cam got loose - now good to go with some blue Loctite)
I have not tried any but the factory set curve.

I had Todd at McBees in Detroit install the powerarc on my 75 e-start...couldn't be happier! Starts right up...runs great. I don't have the specifics on the timing settings but relieved to be riding again. Worthwhile investment.

Fast Eddie said:

I've not tried it on a Norton, but I have played with ign curves etc on Triumph twins and triples.

In my experience, these old engines are not so sensitive to such things. What does make a big difference is having a big, powerful spark. A degree or two, or three, either way doesn't register as a difference, its the same when changing advance curves.

Only my own experience of course. Others may have had different.

Click to expand...

+1

The best ignition I have encountered for ease of starting , smooth idle and good power is the late model Norton Commando twin point twin coil setup, tho mounted on a Vincent. It makes great fat blue sparks at the slowest kick over speeds. It has me thinking about converting the Commando back to points, tho the Boyer works just fine.
Also with the old Boyer though, it is said to be a very basic almost on and off advance curve. Doesn't seem to matter much.

Glen

Seems to me that Alan was musing the benefits of three options....and by the way guys, discussing the merits of one ignition versus another is off topic in this case:

Option 1, totally fixed ignition timing
Option 2, variable ignition timing, following a curve fixed into the ignition 'system' be it electronic or mechanical
Option 3, variable ignition timing that follws a programmable curve, meaning you can dial a curve into your needs, say on the dyno alongside variations in jetting etc.

Option 1 works, fairly well if starting the motor with a kick start or electric start isn't your biggest concern, it was adopted by racers successfully for decades, including the works Norton team that adopted the Luca Rita and then shorted the advance curve out....I know, I had one, recently found the diagram I drew of the circuitry, incluidng the advance curve shorting link. All you have to do is decide what max advance you want to run, likely to be between 28 and 31. Jet as you see fit.

Option 2 works too, but seems to generate huge debate over curves and almost no two electronic ignition suppliers come up with the same curve, so whatever you use, and however much you like it, it could probably be improved. Some suppliers must agree, because they offer either a choice of a number of fixed curves (selectable, not programmable - by you), or......

Option 3, the possibility to develop your own curve (truly programmable - by you - as long as you can use a computer). Option 3 is going to work if you have a significant resource in baseline curves (you are going to start by copying someone elses) and dyno time to experiment with curves with fixed jetting and then jetting changes and the more optimisation of the curve. Surely you will spring a few improvements. Your decision if you think this is cost effective and within your skill set. You mught even adopt this solution if you like teh curve of one ignition, but not the form of ignition, e.g. you like Power Arc curves say, but agree with others that the timing chest is a hostile place for an ignition, or want to use an inductive/hall effect crank mounted trigger in place of cam mounted optical trigger.

If you want to do it there is an economical system available from the Czech Republic called Ignitech. I havent used it but a number of UK and European racers of various capacity machines have, 2 stroke and 4 stroke. It is around €250, plus your effort in fabricating a pick up mount.

Far from getting to 3000 and running flat high compression motors may need to adopt some retard after 'full advance' to alleviate problems of detonation at higher RPM (when everything is fit to melt in there you turn the heat down a bit).

Now, my betting is that this thread runs and runs as a debate on which ignition people like...or dies now :shock:

Dead on subject is if able to monitor engine performance then as combustion conditions change with rpm and load d/t harmonics of intake and exht and cam profile programable allows fine tuning to squeeze a bit more out of engines. At some point [though don't know if applies to our low rpm blacksmither's] spark should be retarded off max adv d/t more lead time needed with faster closing of TDC volume and mixture density spikes that slow down and narrow spark kernal.
A change of octane can be compensated for better if programmable rather than just shift whole curve up or down.

I can think of Peel need of 4 curves with sensors and manual switches to select.
1. heavy loaded lugging up steeps on loose traction on 87 octane w/o boost - retared and rev limiter set low so any spin is limited to recoverable event.
2. Legal-ish curise loads on low octane for hi mileage and tire saving - close to what every ignition system curves end up.
3. Off road antics roostering about constantly with throttle snap rear steering w/o boost but water spray for 116 octane anti-detonation hi torque low-ish-mid range rpm - set adv to rise fast then mostly level off.
4. X-mass tree yellow lights lit > blip rpm up - > green lights > dump clutch with throttle snap to WOT and held WOT as kill tapped for instants of shifts front touch/bounced back to carried level far as we can making well over 10 PSI boost into 17+:1 CR's with ant-detonation fluids sprayed in as ignition switches to last funny shaped curve and backs off maxim torque spark before CR spikes to 20's.

SteveA said:

Seems to me that Alan was musing the benefits of three options....and by the way guys, discussing the merits of one ignition versus another is off topic in this case

Now, my betting is that this thread runs and runs as a debate on which ignition people like...or dies now :shock:

Click to expand...

My point was that my experience has been the same as Eddie's, old engines do not benefit from programmable ignition but do like a really hot spark. How is that so wildly off topic as to require your Moderation?

Glen

Low compression Norton motors are not real sensitive to timing.

High compression or highly tuned engines are very sensitive to spark timing. I have seen quite a few race engines with damage from a few extra degrees of advance.

If you look at the curve on the MSD ignition in my dyno video you will see the advance curve peaks at 3500 rpm and then slopes down to 28 degrees as the rpm gets over 5000. That curve really helps the midrange response.

That can not be done with the power arc, It only retards in large steps instead of a slope. Jim

comnoz said:

Low compression Norton motors are not real sensitive to timing.

High compression or highly tuned engines are very sensitive to spark timing. I have seen quite a few race engines with damage from a few extra degrees of advance.

If you look at the curve on the MSD ignition in my dyno video you will see the advance curve peaks at 3500 rpm and then slopes down to 28 degrees as the rpm gets over 5000. That curve really helps the midrange response.

That can not be done with the power arc, It only retards in large steps instead of a slope. Jim

Click to expand...

Thanks, Jim. The mid-range response is what I am on about. Sometimes in racing you can be balked in corners, and that response becomes important. I also had the experience of the Indian with the advance/retard twist grip and I found that as you wound the advance on the performance reached an optimum, too far and the motor sounded as if in distress. With an Indian there is no such thing as throttle response - you just sit and wait. I've found with my bike that the mid range torque is excellent, I just thought there might be a way of getting more with better application. Where did the MSD ignition come from ? I've always suspected that running full advance right across the rev range might not be providing the best. Also the variety of Mikuni carb needles which have been used in various early Japanese also makes me wonder. Years ago a friend of mine helped Kevin Magee through his crash and burn stage on a 851 Pantah which was fitted with 4 valve heads - he always used the lap top on the ignition system. He was an aircraft technical officer with one of our major airlines, so what he was doing might have been a bit of overkill. I'll have to phone him and pick his brains.

About the timing retarding after 3500 RPM. I believe the systems on the 70s Yamaha two strokes did that near the top of their rev range, I always thought it was to stop detonation. I would have thought retarding the ignition in the midrange would make the motor pull harder - apparently not so ? With my bike I use 32 degrees advance fixed timing - methanol solves a lot of tuning problems.
What advance does the MSD ignition give at 3500 rpm on your motor ? Using methanol I believe I can add 4 degrees to it.

Is this the unit you are using ? :
http://www.msdignition.com/instructions ... s/4223.pdf

hobot said:

Dead on subject is if able to monitor engine performance then as combustion conditions change with rpm and load d/t harmonics of intake and exht and cam profile programable allows fine tuning to squeeze a bit more out of engines. At some point [though don't know if applies to our low rpm blacksmither's] spark should be retarded off max adv d/t more lead time needed with faster closing of TDC volume and mixture density spikes that slow down and narrow spark kernal.
A change of octane can be compensated for better if programmable rather than just shift whole curve up or down.

I can think of Peel need of 4 curves with sensors and manual switches to select.
1. heavy loaded lugging up steeps on loose traction on 87 octane w/o boost - retared and rev limiter set low so any spin is limited to recoverable event.
2. Legal-ish curise loads on low octane for hi mileage and tire saving - close to what every ignition system curves end up.
3. Off road antics roostering about constantly with throttle snap rear steering w/o boost but water spray for 116 octane anti-detonation hi torque low-ish-mid range rpm - set adv to rise fast then mostly level off.
4. X-mass tree yellow lights lit > blip rpm up - > green lights > dump clutch with throttle snap to WOT and held WOT as kill tapped for instants of shifts front touch/bounced back to carried level far as we can making well over 10 PSI boost into 17+:1 CR's with ant-detonation fluids sprayed in as ignition switches to last funny shaped curve and backs off maxim torque spark before CR spikes to 20's.

Click to expand...

You need Jims EFI system, well not necessarily all of it. Just the crank sensor ECU, ignition bits and a carb. The ignition timing is a 2D map based on engine speed and manifold pressure (load) and also engine/air temp if desired. The system has the ability to switch maps with an external switch, 1 and 2 would be one map and then you are just one map short for 3 and 4 (Jims system probably doesnt have the map switching implemented but the hardware/software is capable of it)

discussing our Norton's ignition advance options is about as "on topic" as possible, this is great!

Yes Peel may have to follow comnoz path and may need two of em to boot if the powerarc can't accommodate. Won't be the first dead end money- time- effort- dream wasted on silly hobby horses. Peel's had decade long delays so got to cut her off at some point and see what happens on basic plan A before EFI which may not be needed to do what I want. I'm only into Peel power enough to demo the handling planting power on the curves so maybe someone else will take on her engine with more non vintage era features, various fuels and injectors and fancier head. May pester the Powerarc guy some more on Peel's special needs. I'd had deep discussions with the badest supercharged fuel injected top fueler drag bike builders to see how crude their injectors were and idled down with a piece of tape over a hole to jerk off when staging against torque converter+brake. I only got so much smarts to devote to this stuff anyway.

hobot said:

Yes Peel may have to follow comnoz path and may need two of em to boot if the powerarc can't accommodate. Won't be the first dead end money- time- effort- dream wasted on silly hobby horses. Peel's had decade long delays so got to cut her off at some point and see what happens on basic plan A before EFI which may not be needed to do what I want. I'm only into Peel power enough to demo the handling planting power on the curves so maybe someone else will take on her engine with more non vintage era features, various fuels and injectors and fancier head. May pester the Powerarc guy some more on Peel's special needs. I'd had deep discussions with the badest supercharged fuel injected top fueler drag bike builders to see how crude their injectors were and idled down with a piece of tape over a hole to jerk off when staging against torque converter+brake. I only got so much smarts to devote to this stuff anyway.

Click to expand...

The ECU really doesnt mind if it isnt driving injectors so you can still use a carb if you want and do away with the need for injectors and fuel pump etc. The other thing is that although it only has two switchable maps it is very easy to change a map. I am in the process of putting a similar system in my Rangerover and because the ECU is not very accessible I have used a bluethooth module and can tune it (alter settings such as rev limit, type of rev limit eg hard cut or timing retard as well as loading completely different maps) all from an android device, you know those things that used to be phones but are now too big and still too small to be used as a computer.

acotrel said:

comnoz said:

Low compression Norton motors are not real sensitive to timing.

High compression or highly tuned engines are very sensitive to spark timing. I have seen quite a few race engines with damage from a few extra degrees of advance.

If you look at the curve on the MSD ignition in my dyno video you will see the advance curve peaks at 3500 rpm and then slopes down to 28 degrees as the rpm gets over 5000. That curve really helps the midrange response.

That can not be done with the power arc, It only retards in large steps instead of a slope. Jim

Click to expand...

Thanks, Jim. The mid-range response is what I am on about. Sometimes in racing you can be balked in corners, and that response becomes important. I also had the experience of the Indian with the advance/retard twist grip and I found that as you wound the advance on the performance reached an optimum, too far and the motor sounded as if in distress. With an Indian there is no such thing as throttle response - you just sit and wait. I've found with my bike that the mid range torque is excellent, I just thought there might be a way of getting more with better application. Where did the MSD ignition come from ? I've always suspected that running full advance right across the rev range might not be providing the best. Also the variety of Mikuni carb needles which have been used in various early Japanese also makes me wonder. Years ago a friend of mine helped Kevin Magee through his crash and burn stage on a 851 Pantah which was fitted with 4 valve heads - he always used the lap top on the ignition system. He was an aircraft technical officer with one of our major airlines, so what he was doing might have been a bit of overkill. I'll have to phone him and pick his brains.

About the timing retarding after 3500 RPM. I believe the systems on the 70s Yamaha two strokes did that near the top of their rev range, I always thought it was to stop detonation. I would have thought retarding the ignition in the midrange would make the motor pull harder - apparently not so ? With my bike I use 32 degrees advance fixed timing - methanol solves a lot of tuning problems.
What advance does the MSD ignition give at 3500 rpm on your motor ? Using methanol I believe I can add 4 degrees to it.

Is this the unit you are using ? :
http://www.msdignition.com/instructions ... s/4223.pdf

Click to expand...

I use the 4217 ignition. I make pickup trigger units to fit the Norton.
With the engine I was testing I had peak timing at 31 degrees at 3500-4000 rpm. It depend on the compression and cam. Jim