Ignition advance curves

I noticed this comment by Kenny Cummings:
'Kenny, I've used Ignitech box on Yamaha single roadracer, but not on Norton. It's a great product. You can tailor the advance curve to anything you want with a laptop computer.

Ken '

I think it would be great to have the ability to programme the advance curve, however I have no idea about how to assess the requirements of the motor in that regard. I use a Boyer ignition system with a double ended Honda coil, which is supposed to give fixed timings. It works well, but I've always wondered how the timing curve is adjusted to give best performance in programmable systems. Is it done on the basis of dyno output, or on the way the bike performs on various circuits ? I'd like to know the best way to maintain maximum torque throughout the whole rev range for a given motor configuration ? Could someone please point me towards good text on this subject ?

http://www.ignitech.cz/english/aindex.htm

Aco, these blokes may be of interest.. http://www.powerdynamo.biz/eng/info/curves.htm

Optimalizing ignition curves just short of much detonation in worse conditons requires a shop dyno or timed runs to speed and some detonation detection method. Best power is when spark causes most pressure just after TDC but not enough just before TDC to blow up. Generally advancing gives more power but in some engines near redline power improves by retarding some or piston just out races the flame pressure. There a graphic out I think by DynoDave that has most the Cdo ignition systems curves all plotted at once to see the general ball park to aim for then fine tune from there.

A dyno would be the best way to find max torque vs. ignition timing.

I've tuned car ignition curves on the road with an electronic distributor, but this is with a detonation-prone engine that I know makes more torque with more advance and better fuel, so when I'm on pump gas, I advance midrange timing until it detonates.

I planned to run my 850 with Tri-Spark on the dyno set for 26, 28, 30 and 32 degrees, but have not had time. And that just shifts the whole curve. Custom plotting is a whole new game available with some units. Ideally you'd want to plot with a throttle position or vacuum sensor, too...

acotrel said:

I noticed this comment by Kenny Cummings:
'Kenny, I've used Ignitech box on Yamaha single roadracer, but not on Norton. It's a great product. You can tailor the advance curve to anything you want with a laptop computer.

Ken '

I think it would be great to have the ability to programme the advance curve, however I have no idea about how to assess the requirements of the motor in that regard. I use a Boyer ignition system with a double ended Honda coil, which is supposed to give fixed timings. It works well, but I've always wondered how the timing curve is adjusted to give best performance in programmable systems. Is it done on the basis of dyno output, or on the way the bike performs on various circuits ? I'd like to know the best way to maintain maximum torque throughout the whole rev range for a given motor configuration ? Could someone please point me towards good text on this subject ?

http://www.ignitech.cz/english/aindex.htm

Click to expand...

Looks like we're getting too many Kennys on the list, and people are confusing them. The quote above was from me, Ken Canaga, not Kenny Cummings. To make it more confusing, I was responding to Kenny Martin. Still, no insult in being mistaken for Kenny Cummings.

A bit more about the benefits of a programmable advance curve. In general, as you increase the compression ratio on a given engine, the amount of advance required for max power at high rpm decreases. So if you raise the compression ratio significantly, the stock ignition settings are no longer optimal. If you're using a normal ignition with fixed advance curve, retarding it to achieve max power also retards the timing at low speeds, and that's not always good for easy starting and good low speed performance. Probably of more interest on a race bike than a street bike, but still something to consider. In the application I used the Ignitech for, a 640 cc Yamaha SRX-6 roadracer, the stock timing was not adjustable except by fitting an offset key to the rotor, or modifying the trigger coil mounting, neither of which are easily done in the dyno room or at the track. The Ignitech allowed me to easily change the advance curve with a laptop computer, without touching anything on the engine.

As Whitworth Ranch pointed out, the best way to get maximum benefit from the programmable feature is on a dyno, but I think you could also find some improvement by making changes and then road testing. For a Norton, I'd start out by just copying the advance curve from something like the Tri-spark, and then playing with it some, particularly the mid-range part. More time consuming, but a good excuse for some fun experimenting.

Ken

I use methanol in my 850 motor. From my early days of racing, and a lot of other involvement with fourstrokes, it is normal to advance the ingition timing by about 4 degrees, if you are simply changing a stock motor from petrol to alcohol. So currently I run about 34 degrees advance, which seems to work very well with the standard comp. ratio. I have the carburation very lean everywhere, except on the main jet. However I've never had any knowledge as to what the optimum changes in timing are across the rev range. I know that with the two strokes, the timimgs are usually retarded for high revs on racing machines, but they are a totally different kettle of fish. On our Kawasaki H2 motors, the heads are reshaped, but we don't increase comp. ratios - seems to be a recipe for disaster, and we use the standard timings for petrol, when running alcohol. Both our H1 and H2 are diabolical - my brother usually wins every speedway sidecar race he enters with them, and you just don't need the H2 750, the H1 500 is enough for any situation.
Thanks for your comments guys