A new found Electronic ignition system!

[Puffs]

Right, wikipedia. I'll let Rossi know & I'm sure he'll do better next year.

Does wikipedia also say how much you gain?

But seriously: so no testing done at all?

[Guesi]

Hello
I plan to become a millionaire when I sold the 100 sets I have here....

Testing on the road has been done.

[Puffs]

Yes, dynotesting can be a bit expensive (in the order of one of your units), but seeing how fast it goes on the road isn't. Or timing how fast it accelerates.

Listen, I'm all on board with the idea (of finding an optimal time, rather than ° or mm), but wikipedia isn't proper development guidance. The 1ms they quote there (and not 1.3ms you aim for), was that for a 4T, or a 2T? Huge difference, 4T much higher P's. Stroke volume? Combustion chamber shape? + some more...

Good luck!

[arny]

Puffs, I see what you mean about Powerdynamo, it doesn't advance the timing. However it DOES what needs to be done: if you adjust timing in the midrange, it retards the timing at low and high RPM. The old 2T rule is that more advance favors mid-RPM, and less advance favors low and high RPM, so with fixed timing you have to compromise. Powerdynamo's characteristic means you can maximise mid-RPM advance, and it'll retard it in the low and high ranges, just as the engine wants... well at least enough that it won't knock at high RPM nor kick back at the low ones.

About Guesi's citation from German Wikipedia, I've found that article (I can read some German) and the 1 ms is quoted from this book: Richard van Basshuysen, Fred Schäfer (Hrsg.): Handbuch Verbrennungsmotor. Grundlagen, Komponenten, Systeme, Perspektiven. 2. verbesserte Auflage. Vieweg, Braunschweig u. a. 2002, ISBN 3-528-13933-1, S. 301ff. So I guess there is some substance to that... I wonder if the same rule applies equally to both 2T and 4T engines... Someone should look that book up

[Puffs]

The retarding PD/Vape do at low RPM is good. It will reduce the likelihood of the engine kicking back, and should increase the low-end power. Because of the low piston velocity in that RPM range, if the ignition occurs at 22°bTDC it will still be several ms before the piston reaches TDC. Retarding it by, say, 10° improves things quite a bit - less kick-back & more power (=running more effectively).

The high-end retarding in these PD/Vape systems is far less than at the low end. Consider that these engines rarely do more than 6-7kRPM, it's about 1° at best, and I'd say that's inconsequential. That retarding too is probably not by design either, but also to do with the frequency response of coils, or something along those lines.

There is a case to be made for advancing the ignition timing at the high RPM end, rather than retard it as happens to some extent with PD/Vape. This is because at that end, the high piston speed leaves too little time for the flame front to develop, so that the maximum pressure comes after the piston has been at TDC. If you ignite to late, you're missing part of the power the engine can develop: the engine runs less efficiently. In 4T engines this case is clear, and they all have advance mechanisms (historically mechanical, using centrifugal force, but nowadays electronic). For 2T engines, maybe that's too simple a view, because there are several other processes going on (like that at high RPM the mixture composition changes, the degree of scavenging/filling changes, + more). I think that historically, the majority of 2T engines did not have an advance mechanism, but I think that some had. The optimal ignition timing one could learn from dyno testing, or measuring the performance on the road. And it is likely to be different for different engines, depending on their state of tuning, etc, so the testing & measuring has to be done with a specific engine (here the ETZ250). Yet I suspect that the 'Handbuch Verbrennungsmotor' from 2002 deals exclusively with 4T engines.

If you want to look for applicable experience, maybe learn from experience in racing that has been done with 2T's for many years. I can share info from the manual for my YZ250LC. It's a 250cc 2T MX/race bike, tuned for a broad & strong power band. It has a reed valve on the intake & a variable exhaust timing; max power is not specified, but I've seen numbers ranging from 48 to 55HP (and even 62HP...). For the ignition timing they specify 1.2mm = 13.5° bTDC, which is a lot later than is customary for the ETZ (say 2.8mm or 22° bTDC). Presumably that will ease starting, but note they also specify "Advancer type: electrical". So it is being advanced, but I don't know by how much... Anyway, maybe that's not so applicable either. True, it's a 2T, but beyond that it's quite different from an ETZ.

IMO Testing & measuring on an ETZ250 would still be best.

[Puffs]

After a bit more thinking about this, I realised there is a problem with keeping the ignition at a set time before TDC, independent of the RPM. If you do that, the faster the engine turns, the more the piston will be below TDC at the moment of ignition. And if the mixture hasn't been compressed enough, it won't ignite. And if perchance it does ignite, the engine won't run effective.

Say the engine turns at 6000RPM, that's 100 revolutions per second, or 0.1 revolution per ms, hence 36°/ms. So if you ignite at 1.3ms bTDC, that equates to 46.8 °bTDC, or 12.4mm bTDC. By then, the exhaust port has already been closed for a while (that closes around 89°bTDC), but I fear the mixture still isn't compressed enough. By contrast, the standard ignition timing is around 22°bTDC = 2.8mm bTDC.

It is difficult to estimate the pressure inside the combustion chamber, particularly in a 2T, but I have tried to get an impression as follows:
1) Haynes quote, for the 243cc engines, a compression ratio of 10.5 to 1. Using that compression ratio, the volume of the compression chamber, with the piston @TDC = 23.14 cc.
2) If the plug sparks at the standard timing of some 2.8mm bTDC, there is still some 10.47cc to be compressed before the piston reaches TDC, giving a standard compression ratio at the time of ignition of 7.23:1.
3) If the plug sparks at 1.3ms bTDC, so 12.4mm bTDC @6kRPM, there is still some 46.37cc to be compressed before the piston reaches TDC, giving a compression ratio at the time of ignition of 3.5:1. I don't think that'll be very willing to ignite at less than half the normal pressure.

Now this is just an estimate, and what goes on exactly I cannot calculate, but taking into account when the exhaust closes will only make matters worse - I think 1.3ms is too early.

And the other thing is, if it would ignite, explosion pressure will build-up before the piston has reached TDC, so that the piston will have push into a much higher pressure. Consequently you would lose power (and increase wear). I think such an early timing will act as an effective rev limiter.

So before being convinced, I would like to see some test numbers. Dyno charts would be nice, but it could also be something like Top speed standard ignition = xxx, with 1.3ms ignition = yyy, or standing mile/kilometer timings.

[arny]

I don't think there is much difference in willingness of mixture to ignite between lower and higher pressure. Moreover, it seems the flame front always travels at a speed which completely burns the mixture in similar times, regardless of conditions. There are only two notable exceptions I'm aware of: 1) at low throttle the pressure is low and mixture burns slower; that's what vacuum advance is for (on 4-strokes anyway); 2) at high engine speeds turbulence speeds up the burning, that's why there is advance limit in 4T RPM advance mechanism, and high-RPM retardation in 2T ones.

[Puffs]

Yes, I see I only mentioned pressure & failed to mention temperature, but it's also that the mixture is being adiabatically compressed, i.e. heated up substantially due to the rapid compression. Anyway, we can think & debate all we want, but how efficient the combustion is in reality, that's something that can only be determined in tests. This is particularly relevant when proposing a system that's significantly different from convention (47°vs. 21°bTDC at the high end).

Once again, I'm not saying engine efficiency won't benefit from a timing like that, just that I'd like to see some objective test results.

[Guesi]

To make it clear: The main goal of our ignition is to end the fixing of the contact breaker timing setting. If you tried to fix the timing for example on an ES 250/2 with sidecar, you know what I mean...

Surely you can gain a little bit more power if you optimize the ignition timing on the electronic ignition, but this was not our first thought...

But feel free to program your own ignition with all the data you can get...

We have a different goal...

[Puffs]

Fair enough, I appreciate where you're coming from. And no, I have never worked on any bike with a sidecar, but I can imagine the sidecar gets in the way, if it's on the RH side.

This thread moved towards discussing benefits of various ignition systems, and we were interested to mention which ones control ignition advance. In that context you raised your system, which you claim to have quite an uncommon timing curve. Then it would be very interesting to share the consequences of that timing curve, particularly towards the high end (but also the low-mid), where you claim it deviates substantially from other systems.

I appreciate that you are not Honda or Yamaha, and do not have a similar development budget, and that performance gains expected from an alternative ignition timing are moderate. Yet there can be gains, in terms of starting, power delivery & fuel consumption, particularly compared to the conventional contact breaker ignition. I assume you intentionally designed your system to have that claimed timing curve, and that you verified the system to work as designed. So then it would be interesting to share more about the impact of your claimed timing curve to engine performance. We can all take for granted that the ignition lasts a long time, doesn't require adjustments & is easy to install, but surely some experience has been gained on the impact of that claimed timing curve on performance? Changing timing from the common 22° to 47°bTDC should have some noticeable effect. And once again: I see the curve, but are you sure that is what your system does?

[Guesi]

I sell MZ parts,but I am not the developer of this ignition. I buy it from some friends of mine, who developed it.So many of your questions are out of my knowledge.

I think it is a good alternative for contact breaker systems.

But as I said, it was never meant to squeeze out the last bit of power from the engine..

And optimizing the timing requires a lot of time (and money) because someone has to pay the testing.
This would rise the price, and this is not what I desire as MZ drivers are said to keep their money in their pocket

[Puffs]

OK, then I misinterpreted your "we decided to make our own" on your website.