Can electronic ignitions do this?

o0norton0o said:
Jim,... 2 questions.

1) Why don't magnetos have a spark timing advance? (and don't only say because they don't need one) Explain why

2) Why is spark timing so critical in other forms of ignition but not magnetos? Considering that the spark timing takes into account the speed at which a chosen fuel burns and the speed of the piston, Why can a magneto ignore these things?
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Older Lucas magnetos (like the one on 16H, 88SS or on the Venom) has manual retard/advance and a lever on the handlebar. Retarded only for starting or when engine labouring at large throttle opening (uphill). Other times fully advanced. Bikes like 650SS, Atlas or Vincent has autoadvance fitted to the magneto drive sprocket. The Manx don't need any advance adjustment as it don't have a kick start. When you push start it, if it fires back, you don't break your leg. My Manx starts happily with anything between 38 BTDC and 12 ATDC. As low end torque is nonexistent, no benefit in retarding. You never ride it on low revs.
Spark timing is only critical if you want max performance throughout the rev range, fuel economy, low emissions and engine heating. For its time magnetos did the job good enough and was more reliable than points ignition where any electrical system fault left you stranded.
Edit: Most EI systems I've seen available for our bikes has full advance at revs over 3000 to 4000 Rpm. So not much better than mechanical autoadvance units.
 
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Mike40M said:
Older Lucas magnetos (like the one on 16H, 88SS or on the Venom) has manual retard/advance and a lever on the handlebar. Retarded only for starting or when engine labouring at large throttle opening (uphill). Other times fully advanced. Bikes like 650SS, Atlas or Vincent has autoadvance fitted to the magneto drive sprocket. The Manx don't need any advance adjustment as it don't have a kick start. When you push start it, if it fires back, you don't break your leg. My Manx starts happily with anything between 38 BTDC and 12 ATDC. As low end torque is nonexistent, no benefit in retarding. You never ride it on low revs.
Spark timing is only critical if you want max performance throughout the rev range, fuel economy, low emissions and engine heating. For its time magnetos did the job good enough and was more reliable than points ignition where any electrical system fault left you stranded.
Edit: Most EI systems I've seen available for our bikes has full advance at revs over 3000 to 4000 Rpm. So not much better than mechanical autoadvance units.
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Yes, most EIs are fully advanced in the range you say.

Which is important, because the speed at which they advance ie the advance curve, varies MASSIVELY!

With such huge variation under 3k ish, between the available systems, ALL of which seem to work just fine, how can the actual timing figure at these revs be so critical ?

I’ve ridden a few bikes with either manual advance or fixed ign and they have always performed brilliantly at all revs.

Back in the day, when folk dragged sidecars around and testers were obsessed with minimum snatch free speed in top gear, and they were using extremely low octane ‘pool’ petrol, I can imagine this topic was more prevalent.

However (my opinion only) these days, with the way we use our bikes, I am extremely sceptical about the need for complicated advance curves beyond the need for safe and reliable starting.
 
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I have always wondered why they didn't call it "automatic retard" instead of automatic advance since the only purpose of the mechanism was for ease of starting (retard). Once the engine is running, "full ignition advance" works at pretty much all RPM. As an example, Honda street motorcycles of the same era as the Commando had 10,000+ RPM redlines and had the same advance "curve" as the 7000RPM Norton - all advance in by 2500-3000 RPM. In fact, it is the same for pretty much any four cycle vehicle engine. The AMOUNT of advance (in degrees) may vary considerably depending on the engine design (typically combustion chamber) but the RPM at which full advance occurs is pretty much the same.
 
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MexicoMike said:
I have always wondered why they didn't call it "automatic retard" instead of automatic advance since the only purpose of the mechanism was for ease of starting (retard). Once the engine is running, "full ignition advance" works at pretty much all RPM. As an example, Honda street motorcycles of the same era as the Commando had 10,000+ RPM redlines and had the same advance "curve" as the 7000RPM - all advance in by 2500-3000 RPM. In fact, it is the same for pretty much any four cycle vehicle engine. The AMOUNT of advance (in degrees) may vary considerably depending on the engine design (typically combustion chamber) but the RPM at which full advance occurs is pretty much the same.
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The point at which they achieve full advance is similar but the curve getting there varies a lot with the available Commando systems, as has been shown graphically on here by folk.
 
MexicoMike said:
I have always wondered why they didn't call it "automatic retard" instead of automatic advance since the only purpose of the mechanism was for ease of starting (retard). Once the engine is running, "full ignition advance" works at pretty much all RPM. As an example, Honda street motorcycles of the same era as the Commando had 10,000+ RPM redlines and had the same advance "curve" as the 7000RPM Norton - all advance in by 2500-3000 RPM. In fact, it is the same for pretty much any four cycle vehicle engine. The AMOUNT of advance (in degrees) may vary considerably depending on the engine design (typically combustion chamber) but the RPM at which full advance occurs is pretty much the same.
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Well, on any LIGHTLY LOADED vehicle engine.
The vacuum advance used on cars & trucks reduced timing advance when larger throttle openings signalled heavy load.
 
"The point at which they achieve full advance is similar but the curve getting there varies a lot with the available Commando systems, as has been shown graphically on here by folk."

Yes, it does vary with many aftermarket electronic ignitions...but it didn't with engine designers even though mechanical advance units can be adjusted to various curves. I suspect that the aftermarket advance curves that don't go full until (say) 5000 RPM are trying to simulate a bit of what vacuum advance does (did) on conventional ignitions - provide better efficiency under light load but that comes at the expense of less initial power if you go to WOT at, say 3000 RPM. Of course, if you are already at 5000 RPM when you go to WOT, there's no difference.

FWIW, I've been working a lot lately with a 1976 Honda CB400F and all of the five E-ignitions I have found available for it retain the OEM mechanical advance unit - all in at 2500 RPM; they do not use "electronic" advance. I suspect, though I don't know this to be true, that the limited amount of power available until around 6000RPM, makes any power reduction that would result by retarding the ignition up to 5k unacceptable..
 
The situation in a combustion chamber when an engine is running is a balance between compression ratio, ignition advance and jetting. Higher octane rated fuel can allow higher compression without knocking. Normal carburetors cannot usually be adjusted finely enough for best performance when using petrol, so they are usually a bit rich. Raising the compression ratio or advancing the ignition, usually has the same effect as leaning off the jetting - which is the aspect most guys adjust. If we are looking for maximum torque, the crank angle as which combustion begins can be important. It depends on what revs the engine is doing, and needs to start earlier as the revs rise. A computerised engine management system with injection, has been proven to be better, than a carburetor and fixed timing. However it depends on the flexibility of the fuel - methanol hides-up the tuning errors - it is much more forgiving, but even with that, the closer you are to the optimum jetting, the better.
 
If you have a look at the race with Mike Hailwood on the Ducati at Mallory - you will see Barry Ditchburn on the start line with the Motec Honda. Is was fitted with Richard Bendell's Motec engine management system. They fitted the injector nozzles into the bell mouths of the carburetors, and turned-off the usual fuel supply. They immediately cut a full second off their lap times. (A throttle position sensor is needed.)

 
I was looking for an explanation of why every other vehicle uses variable timing in their ignition and a magneto doesn't need one....

When my dad was a kid, the first car he learned to drive had an advance lever on the steering wheel, so once you accelerated you also advanced the lever to change the spark timing. Eventually that mechanism was automated in modern distributors. So, I get the sense that variable spark timing is an important "thing". So why does it matter less in a magneto, when it seems essential in everything else??
 
My 1950’s BTH magneto has a manual advance/ retard and I also have a drive sprocket with built in automatic, centrifugal advance/retard for use with a fixed timing magneto.
These were fairly standard with magnetos.
 
jseng1 said:
...many street riders seem to get along with fully advanced Commando style magnetos but I've gone to the trouble of providing a retard lever to enable easy non-kick back starting. Morris came out with this and I adapted their lever to the Joe Hunt because Morris doesn't provide a mag for the Commando. See the Commando retard lever below as it applies to the Mag that mounts on the points cover.
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Would you care to show the internal mods that accompany that lever?
Thanx...
 
acotrel said:
If you have a look at the race with Mike Hailwood on the Ducati at Mallory - you will see Barry Ditchburn on the start line with the Motec Honda. Is was fitted with Richard Bendell's Motec engine management system. They fitted the injector nozzles into the bell mouths of the carburetors, and turned-off the usual fuel supply. They immediately cut a full second off their lap times. (A throttle position sensor is needed.)

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Just for a change I think you'll find that you're wrong. It was a Mocheck Honda, nothing to do with Motec
 
grandpaul said:
Would you care to show the internal mods that accompany that lever?
Thanx...
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Here's a Harley mag (note the wierd cam lobes). The retard with lever just an eccentric tube that fits over the points arm pivot. Turning the alum arm moves the points arm so its retarded approx 20 deg for starting.

What you want is full advance just off idle RPM. Once the bike is started you may as well have full advance - that's the best option for either a mag or EI. Few EIs can achieve that.
From what I 've heard there are programing limitations with the EIs
Can electronic ignitions do this?
 
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If I were to install one of these JH magnetos behind the barrels, I'd use the AAU on the magneto drive sprocket since I have the drive gears and chains for a pre-Commando. Only thing holding me back is I'm not sure the timed breather is enough for my engine and I can't put a sump breather on because my exhaust is in the way. Not like the old days where one could find an exhaust builder that would do the work without a year long wait. Plus, I don't know the secret handshake to get one of the few doing exhaust work to respond. Never tried a phone.... but I digress a lot.

Obviously, the easiest install of a JH magneto is on the end of the cam, but I would never put one there myself. Every time I've low sided on the street looking for a limit it has been on the timing side. I'd be tempting fate.

TriSpark has a programmable Firebox Pro that can be programmed to modify the ignition curve including a feature for start retard. Cost is about the same as the JH magneto. It can be pre-configured from TriSpark for single fire or wasted spark. I'm do not know what its limits are. It requires some space for the control box, but at least the smarts are not behind a hotter than hell points cover.
 
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Of course the standard AAU can be modified to provide faster movement to max advance if you want it in earlier than around 3k by substituting weaker springs or using the old shade tree method - remove one of the two advance weight springs. ;)
 
Seeley920 said:
Just for a change I think you'll find that you're wrong. It was a Mocheck Honda, nothing to do with Motec
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I am only going by a conversation I had with Richard Bendell. It was a Barry Ditchburn Honda the system was fitted to in the 1970s, however I cannot be certain on which circuit it was tried. Richard mentioned he only sold complete engine management systems - not parts of one. He recently sold Motec to Robert Bosch. But I have seen his system on a superbike with sensors all over it. I wonder how they handle the data ?
 
With my bike, the only part of the rev range which matters to me, is the bit between 5,500 RPM and 7000 RPM. If I race, the revs stay within those limits. A better shaped ignition curve in that area might contribute something, but I would not expect much. I suggest the main thing which holds Commandos back is carburation when using petrol as fuel. The boost which comes from using methanol is mainly about less error in jetting. With my bike, when using methanol, the difference between fast and slow is one quarter of a thou in internal ID of the needle jet, and I use the leanest needles.
Methanol needle jets are about 1.6 times the I.D. of petrol needle jets, so flow about twice the amount of methanol which has 0.8 times the calorific value of petrol. Because correct jetting is achievable with methanol, the bike is much faster than it would ever be when using petrol.
The taper on the needles is important. It the mixture richens too quickly as the throttle opens, poor throttle is the result. My 850 has as good throttle response as any other bike I have ridden.
The number of variables involved are not confusing when you know what happens.
 
The only carburetors I know of, which can give finer needle jet adjustment than normal, were the Lectron carbs of the 1970s which were used on some two stroke race bikes - very expensive.
With my bike on methanol, going from a 0.117 needle jet to a 0.1165 needle jet made a very big difference to the way it accelerated. 0.116 is too lean.
I make the jets and use number drills.
For petrol, a gas bottle with flow meter might be useful, and ream the jets with jewelers' reamers.
 
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I am building a 1960 650 Manxman project build it was an ex race bike so will be built as a Cafe Racer, it has a Lucas competition magneto with the auto advance set up but thinking of not using the auto advance and just direct drive it on the mag chain, but if the Lucas mag was or is no good I be buying a new Joe Hunt to replace it and there won't be no need at all to set it up with the auto advance as the newer JH products a bigger spark with more zap than the older magnetos, they are so good and a lot more compact to the old Lucas magnetos.
These new JHs are so good they don't need retarding for starting, I keep saying this all the time but as I said before everyone has retarding for starting set in their mines, set right they will start first kick every time without retarding the timing.
Back in I think 2011 when I did the rebuild of my motor and installed the new Joe hunt I made a video of the first start, the timing was static timed, and new PWK carbs from Jim installed with basic guess settings on the new carbs, first kick the Norton fired up, my mate was very impressed from a complete engine rebuild (replaced the crank cases) and my knack of one kick to bring it back to life, I was very impress with the Joe Hunt and haven't looked back, but of course I already knew how good they were from my old Triumph with the older Joe Hunt magneto, what else can I say and after 48+ years of owning my Norton it's the best ignition set up I have ever had and the JH works so well with the Amals.
As for hanging straight off the cam on the timing side I have no problems at all hanging in the breeze, if I did go down that side there be more damage to the Norton than the Joe Hunt, they are well built to with stand a bit of a slide down the road, the front cover might get damaged and are cheap to replace, I have 2 spare just incase but they just sitting in my spares collecting dust as well 2 spare tune up kits when I do need to put new point, the tune up kit comes with point, condenser and new plug leads.
As well the spark plugs gaps for the Joe Hunt are set at 18thu not the standard 25thu as normal setting and I also get longer life out of my spark plugs they run so much cleaner all because of that big spark that is produce from the JH.
What else can I say, I love my Joe Hunt magneto and how well it runs, my Norton loves it as well as it runs so good from slow to full on go and the faster it goes the bigger the bang, can't get any better than that in my opinion and was the best $720 I spent for my hotrod Norton.

Ashley
 
ashman said:
I am building a 1960 650 Manxman project build it was an ex race bike so will be built as a Cafe Racer, it has a Lucas competition magneto with the auto advance set up but thinking of not using the auto advance and just direct drive it on the mag chain, but if the Lucas mag was or is no good I be buying a new Joe Hunt to replace it and there won't be no need at all to set it up with the auto advance as the newer JH products a bigger spark with more zap than the older magnetos, they are so good and a lot more compact to the old Lucas magnetos.
These new JHs are so good they don't need retarding for starting, I keep saying this all the time but as I said before everyone has retarding for starting set in their mines, set right they will start first kick every time without retarding the timing.
Back in I think 2011 when I did the rebuild of my motor and installed the new Joe hunt I made a video of the first start, the timing was static timed, and new PWK carbs from Jim installed with basic guess settings on the new carbs, first kick the Norton fired up, my mate was very impressed from a complete engine rebuild (replaced the crank cases) and my knack of one kick to bring it back to life, I was very impress with the Joe Hunt and haven't looked back, but of course I already knew how good they were from my old Triumph with the older Joe Hunt magneto, what else can I say and after 48+ years of owning my Norton it's the best ignition set up I have ever had and the JH works so well with the Amals.
As for hanging straight off the cam on the timing side I have no problems at all hanging in the breeze, if I did go down that side there be more damage to the Norton than the Joe Hunt, they are well built to with stand a bit of a slide down the road, the front cover might get damaged and are cheap to replace, I have 2 spare just incase but they just sitting in my spares collecting dust as well 2 spare tune up kits when I do need to put new point, the tune up kit comes with point, condenser and new plug leads.
As well the spark plugs gaps for the Joe Hunt are set at 18thu not the standard 25thu as normal setting and I also get longer life out of my spark plugs they run so much cleaner all because of that big spark that is produce from the JH.
What else can I say, I love my Joe Hunt magneto and how well it runs, my Norton loves it as well as it runs so good from slow to full on go and the faster it goes the bigger the bang, can't get any better than that in my opinion and was the best $720 I spent for my hotrod Norton.

Ashley
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Ash - I'm not getting what you're putting down
Be clear - do you like your Joe Hunt maggy or not?
 
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