Programmable ignition timing

acotrel said:

comnoz said:

...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...

Click to expand...

Thanks, Jim. The mid-range response is what I am on about.

I've always suspected that running full advance right across the rev range might not be providing the best.

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 ?

Click to expand...

Since the cam (or ports/pipe of the two-stroke) don't work at the lower rpms, you can/should run a bit more advance to make up the difference. The problem you run into at higher rpms, where everything begins to play well together, is that the BMEPs start getting up into the detonation range, so, as you point out, you hope to avoid detonation by doing so.

What would really help all of this is to have some manifold pressure sensor to help bring up the timing during partial throttle settings. We run a terrible compromise by not having a vacuum advance, since the combustion process goes lean and slows down in the rarified atmosphere of high manifold vacuum. We try to fix this by artificially richening the part-throttle positions. Adding additional advance corrects for this quite nicely, increasing the engine's economy and warding-off washing the bores with fuel.

btw, I got a kick out of your statement about having to sit and wait for the Indian's "throttle response". 'Reminds me of the four-cylinder car I currently drive during inclement weather.

Nathan

My mistake in slightly derailing this thread. Not the first time I have seen it happen here, and for various reasons.
But in this case, the 'curve' topic is very relevant to racers, much less so to plodders like me.
I was just defending the reliability of the PowerArc.
I have no clue how suitable it is to programming for optimum power production.
Moving on....

SteveA said:

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.

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...

The Czech unit is http://www.ignitech.cz/en/
or from NZ distributor who runs one in a road Ducati and seems to know lots about them.
http://www.fastbikegear.co.nz/index.php ... 8e54ce7900

I run one in my BMW race bike.
Instead of running off the chain driven cam it now runs off the end of the crankshaft with a single pickup.
My favourite feature is the soft rev limiter that you can program.
You can also set up the timing curves.
Seems to handle total loss with a lithium battery too.
If you can load a pic on to the net you can set one of these up.
Saying that I have a Boyer still in my Combat and a still in the packet Pazon that I was going to swap it out for.
For my BMW R90s I just leave the points as they work ok.

.

I just use a simple Boyer running a double ended Honda coil. If I think to join the leads at the cutout switch it works well, and with the low comp. and methanol fuel everything is hunky-dory. However I always look for more. I once had a discussion with a friend who owns Motech - makes engine management systems. He mentioned the desirability of having a rheostat fitted to the throttle to give its position to the control box. He also mentioned that when he was in the UK he fitted a system to a 4 cyl. Honda with injectors simply placed in the carb bell mouths and picked up a second per lap on a race circuit. If you watch that Youtube video of Hailwood on the Ducati at Mallory in about 1978, Barry Ditchburn was on the Motec Honda, I think that was the bike.

https://www.youtube.com/watch?v=0LnNP7mw7XY

How do you delete your post, if it appears twice by accident ?

Ah man cheesy and tomspro thanks for trying to spend more of my money on stuff I can't resist. Peel has adjustable threshold pressure and vacuum on/off either way switches to trigger ignition curves and other stuff. Plus a steam punk adjustable boost pop off valve. Dang hot rods seem over flowing with extra wires and tubes and hoses. In Peel's case its easy to take belt on/off Drouin so might only need two curves even if not the Nth degree maxed out. Some swear by Powerarc while others swear at it, just like the world opinion of our basic Commandos eh. There was report of an unstable fit of Powerarc on cam end so an adaptor cone was made which I snagged while hot. Now comnoz reports the powerarc can't retard off peak in smooth enough steps, hm, don't know if that's an issue on Peel but will pow pow with Powerarc to see if he's aware or even cares or has alternative. Main thing I focused on in Peel's ignition calculations was enough octane for full adv. spark for maxim torque pressure w/o detonation up to 17:1 effective CR. We have the graphs that show all the ignition curves of off the shelf units compared so can't go too wrong starting within them. How do ya even know what's best if not equipped like comnoz or Big D etc? My DIY hay seed method is headphones on knock sensor in middle of head and bar mount G meter performance gizmo on top of normal engine monitoring plus peeking at plugs and inside now and then. Best ignition advance per plug heat range should leave the thermal stain on hook electrode just before the bend to the end. Btw Jim sweat tiddy crank pick up to mimic, but you knew that.

The MSD 4217 also has an auxiliary 0 to 5 volt input that can be connected to a baro sensor, a map sensor or a throttle position sensor. The voltage input will cause the timing to ramp from one pre-programmed curve to another. Jim

worntorn said:

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

Click to expand...

No intent to offend Glen, I guess I have just seen too many 'ignition' threads........

I agree that a road bike, with a compression ration suitable for pump fule!, is unlikely to benefit from programmable ignition. Racers always seek and edge, with as few as possible explosions.

My own current approach is to throw on a Boyer with Steve Maney's crank pick up.....get it all bedded in and the consider an affordable programmable system, in both cases with full knowledge that in the '70s my best choice was the fixed ignition that I used with no real issues. However, that was an 850 with huge mid range, and the current build is a 750 shorts stroke that might need a little help there.....Jim's comments are really interesting for that. And the adjustable limiter has to be a good thing compared to no limiter.

I was definitely in the market for programmable ignition for my non Norton project bike which has full race cams, 10.5 to one compression and Australian V8 super car style heads, etc etc. With all of the engine mods it is impossible to know what advance curve will suit the engine without experimentation.

Inquiring about programmable ignitions, I found that one of our club members known as "Mr. Gadget" ,due to his tendency toward fitting new and complicated things, had fitted programmable Dynatec ignition to his more or less stock engine. He had three unit failures in about five years and ten thousand miles of use, so that particular programmable ignition seemed like a complication that brought more trouble than it was worth.
No doubt there are others that will stand the test of time, but it sometimes takes quite awhile for these electronic weaknesses to show up on our vibrating old beasts.( see various Trispark threads).

So I consulted with a couple of well known engine builders, got their best guess as to what the ideal curve might look like for my engine, then had Pazon make a fixed system to that curve, but using two drivers instead of one for doubled spark energy.
I hope the curve works because a new program with some other curve is another five hundred dollar bill!

Glen

Black box boyah users might get Jim Schimdt's Race Book as he explains how to change the curve/slope of these for racer acceleration out of turns. Good success on your expensive stab in the dark Wortorn.

Has anybody got some info on the shape of the curves used in the various MotoGP bikes ? Also have any MX bikes got programmable ignition systems ? I'm interested in what Jim Schmidt has to say and how the data was obtained.

Aw man now ya jumped tracks into whole 'nother world of ignition curves - plus feedback sensors at MotorGP level, traction and launch and wheelie control per section of tract according to angle and G force + temperature and moon phase to compensate for the extreme harmonic spiking and dampening of ports power band every few 100 rpm range. Filter though these leads and let us know what might apply to our ancient clunckers.
https://www.google.com/#q=ignition+curv ... otorcycles

acotrel said:

Has anybody got some info on the shape of the curves used in the various MotoGP bikes ? Also have any MX bikes got programmable ignition systems ? I'm interested in what Jim Schmidt has to say and how the data was obtained.

Click to expand...

Moto gp bikes will not have curves, they will have at least 3D maps as a base but will be much more complicated than that. Some MX bikes had switchable ignition curves back in early 2000s Im not sure what they looked like but Im pretty sure they will have almost no relevance to a Norton, being way over square with 4 valve pent roof chambers, high compression ratios and what would have historically been considered very radical cam profiles.

Cheesy said:

acotrel said:

being way over square with 4 valve pent roof chambers, high compression ratios

Click to expand...

Click to expand...

I think those are the key points in general especially the combustion chamber, which has little in common with the two valve hemispherical chamber near all Brit twins had, including Ducati's of the same period.
Perhaps the cost outweighs the overall gain having a classic ignition that has a map for each gear via a gear position sensor, crank shaft position sensors and throttle position sensor as a lot of modern road bikes have including those with carburetors.
A good deal of those with fuel injection have multiple fuel and ignition map modes, a Commando with FI and a Motec might be a little over the top.

From what Jim has said and my own experience, I suspect I can use much more ignition advance at midrange RPM as long as it retards sufficiently at higher RPM to stop detonation or burning something. As I've said I'm using methanol, and out of habit in low comp. motors I always advance the fixed ignition timing 4 degrees ahead of the specified petrol timing, and jet to that. I now suspect I can advance the static timing by more than that with advantage if I use a programmable system. I'm a bit puzzled about the differences between 650cc Triumphs and Commandos. A standard Bonneville on petrol runs 38 degrees advance, on methanol in the same motor, I'd run 42 degrees advance. The standard commando on petrol runs 28 degrees advance, and I run 32 with methanol. The Triumph has a shorter stroke and no squish bands in the head. However I would not have thought that would change the required ignition advance by 10 degrees. I do know that running methanol very lean with 32 degrees advance in my 850 is really beautiful, perhaps it can be even better ? There is one other factor however - on a race circuit we don't usually have the circumstance where the bike is running at full throttle and very high revs for long - I've never heard a four stroke detonate on methanol.

acotrel said:

From what Jim has said and my own experience, I suspect I can use much more ignition advance at midrange RPM as long as it retards sufficiently at higher RPM to stop detonation or burning something. As I've said I'm using methanol, and out of habit in low comp. motors I always advance the fixed ignition timing 4 degrees ahead of the specified petrol timing, and jet to that. I now suspect I can advance the static timing by more than that with advantage if I use a programmable system. I'm a bit puzzled about the differences between 650cc Triumphs and Commandos. A standard Bonneville on petrol runs 38 degrees advance, on methanol in the same motor, I'd run 42 degrees advance. The standard commando on petrol runs 28 degrees advance, and I run 32 with methanol. The Triumph has a shorter stroke and no squish bands in the head. However I would not have thought that would change the required ignition advance by 10 degrees. I do know that running methanol very lean with 32 degrees advance in my 850 is really beautiful, perhaps it can be even better ? There is one other factor however - on a race circuit we don't usually have the circumstance where the bike is running at full throttle and very high revs for long - I've never heard a four stroke detonate on methanol.

Click to expand...

Nortons run less advance than Triumphs largely because of the better combustion chamber. A Triumph has a highly domed head and domed pistons, creating a relatively poor flame path. This gets much worse when using high CR pistons.

I raced Triumphs with heavily modified heads with large squish bands, whereby I could achieve high CR whilst using standard pistons. In these engines I retarded the ignition a lot. In big engines where I used a 89mm stroke crank, I used 28 degree advance.

I'm pretty sure that Noursih engines also run between 28 - 32 ish degrees (from memory), again, this is due to a far superior combustion chamber compared to Triumph.

Thanks for that Eddie. I found this interesting, however I still don't really have a good idea what shape the curve should be, and whether this unit is flexible enough to achieve it :

http://www.burtonbikebits.net/boyer.htm

I think from what Jim has said, that with the methanol fuel, I could run about 36 degrees advance at about 4,000 RPM and retard to my original 32 degrees at 6,500 RPM. I don't know if that would be easy to programme into a Boyer. The balance between jetting and advance is a bit of a puzzle, especially if advantage is not there to be found. When jetting for methanol, you always have twice the leeway for error and still get the same result.
Any of you guys had experience programming a Boyer ?

Perhaps I misunderstand the Boyer sales pitch here, but to me there is a difference between 'programmed' and 'programmable'.....

So as far as I know Boyer 'programmed' the advance curve on this ignition. This approach allows Boyer to use the same box with a different programme for different applications, using whatever they curve they think best, but they don't give you the tools to do it yourself.....

Correct me if I am wrong guys.

This approach allows Boyer to use the same box with a different programme for different applications

Click to expand...

Do they even bother to vary the curve for different applications ?