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8 - Plug Head advice
Moderators: KeithZ1R, chrisu, paul doran, Taffus
Flame speed does not change much in the gas/air mixture.... BUT the distance that the flame front needs to travel does change significantly- as a result of turbulence. So as revs increase the burn happens faster because of the extra swirl speed of the gasses in the combustion chamber.
Are you planning to re-programme the advance curve for the hybrid????
AL
1981 J1
Yes, I think I haven’t spent enough time on it.
My main focus was the low end, getting it to tick over nice and not to pink at 4000rpm. All this while trying to stop the exhaust from sooting its end.
One nice thing it can do…. You can set the cranking timing independently so it can be delayed till after TDC, this is much kinder on the starter motor and starter clutch as the motor never “kicks back†when cranking.
I’ve really only pulled a few degrees of advance out of it at top end. I don’t think anywhere near enough...but more testing will help identify that. Possibly I should take out 10-20% of advance all the way through the rev range- perhaps a little more at 4000 rpm.
Once I’m happy with that I’ll go back to the fuelling as well.
Back to the dyno soon then.
My main focus was the low end, getting it to tick over nice and not to pink at 4000rpm. All this while trying to stop the exhaust from sooting its end.
One nice thing it can do…. You can set the cranking timing independently so it can be delayed till after TDC, this is much kinder on the starter motor and starter clutch as the motor never “kicks back†when cranking.
I’ve really only pulled a few degrees of advance out of it at top end. I don’t think anywhere near enough...but more testing will help identify that. Possibly I should take out 10-20% of advance all the way through the rev range- perhaps a little more at 4000 rpm.
Once I’m happy with that I’ll go back to the fuelling as well.
Back to the dyno soon then.
z650/1400 bonneville hybrid.
The standard advance curve for the 'J' is 'all in' at 3,550 to 3,250 RPM depending on which line (dash) you use.
4,000 RPM is for checking with a strobe to ensure full advance has been cleared.
Modern fuels (optimised for modern lean burn engines) probably means 2 or so degrees retarded from standard ignition setting and the eight plug efficiency saving probably qualifies for another 2 or so degrees of retardation.
Have you got a gas curve from the dyno you can throw up?
AL
4,000 RPM is for checking with a strobe to ensure full advance has been cleared.
Modern fuels (optimised for modern lean burn engines) probably means 2 or so degrees retarded from standard ignition setting and the eight plug efficiency saving probably qualifies for another 2 or so degrees of retardation.
Have you got a gas curve from the dyno you can throw up?
AL
1981 J1
Zed1015 suggested a little more retard, (28 -34 deg advance).
I will get a better handle on this when I get back to the dyno and see whether power improves as I retard a little- its pretty easy to change both ig timing and fuelling at the press of a button- so consecutive pulls can be done in a moment.
This should establish a baseline from which I can work back.
I don't have a gas curve. Although I do use a lambda sensor in the exhaust I can draw upon, but I dont use it in closed loop mode.
Although even using the lambda data is more complicated than I was expecting. Stuff like enrichment when the throttle is opened confuses the transients- and of course when you short shift thru the gears this effect is probably greatest.
I was advised by the FI people that drivability is the greatest challenge setting up FI and using a lap-top on the passenger seat to tune in real time is the best way. On a bike this is difficult.
I'm hoping that I can use a windows 7 tablet attached to the tank to do the job.
My primary goal last year was to get the bike running and then fine tune the issues. Surprisingly the FI was not the greatest of issues- the main reason for this was simply that the bike ran fast ok.
It was the slow speed transients that were the biggest challenge as well as hot and cold starting. I spent a bit of time on these issues and got the bike running ok.
Having got the fuelling "good enough" my attention turned to other issues like the wheels and the oil leak- and of course using the bike.
We seem to have got to the bottom of the oil leak issues- a cracked cam cover and a crack between the oilway and the C/B for the outboard 6mm cylinder head bolts (I guess this was from beadblasting the head as these counterbores have not been re-machined).
I'll post more about the FI tuning on my project blog as I get into it in the spring.
At the moment I'm fitting out my shed workshop to get all my bike stuff out of the house.
It all seems to take time.
I will get a better handle on this when I get back to the dyno and see whether power improves as I retard a little- its pretty easy to change both ig timing and fuelling at the press of a button- so consecutive pulls can be done in a moment.
This should establish a baseline from which I can work back.
I don't have a gas curve. Although I do use a lambda sensor in the exhaust I can draw upon, but I dont use it in closed loop mode.
Although even using the lambda data is more complicated than I was expecting. Stuff like enrichment when the throttle is opened confuses the transients- and of course when you short shift thru the gears this effect is probably greatest.
I was advised by the FI people that drivability is the greatest challenge setting up FI and using a lap-top on the passenger seat to tune in real time is the best way. On a bike this is difficult.
I'm hoping that I can use a windows 7 tablet attached to the tank to do the job.
My primary goal last year was to get the bike running and then fine tune the issues. Surprisingly the FI was not the greatest of issues- the main reason for this was simply that the bike ran fast ok.
It was the slow speed transients that were the biggest challenge as well as hot and cold starting. I spent a bit of time on these issues and got the bike running ok.
Having got the fuelling "good enough" my attention turned to other issues like the wheels and the oil leak- and of course using the bike.
We seem to have got to the bottom of the oil leak issues- a cracked cam cover and a crack between the oilway and the C/B for the outboard 6mm cylinder head bolts (I guess this was from beadblasting the head as these counterbores have not been re-machined).
I'll post more about the FI tuning on my project blog as I get into it in the spring.
At the moment I'm fitting out my shed workshop to get all my bike stuff out of the house.
It all seems to take time.
z650/1400 bonneville hybrid.
Yes! and if you are after wringing the very very minutest gain out of the combustion process then tuning folklore states you should orientate your spark plugs with the gap facing towards the center of the combustion chamber so that the earth strap is not shrouding the spark or use a surface discharge type plug.
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