Advance retard? 17, 19, 21?

[dickie]

I had my tuned gt186 on Darrel Taylor's dyno last weekend; very interesting chap, a nice guy but Mick Abbey definitely makes a better cup of tea. But I digress.
My scooter was in real pickle (or rather I was) and i'd been messing with everything and anything to get it running right. It turned out to be a loose baffle.

The ignition was initially fixed at 23 degrees due to having removed a kytronic. So we retarded it to 20 and ran it up on the dyno; no discernible difference. Next I knocked it down to 18; still the same. At 16 degrees it was clipping the power a little so we left it at 18.

Unfortunately I was rushing to get back so we didn't manage to get more data with the kytronic' s various curves but to me, the lack of difference between firing angles was an eye-opener.

Affects different states of tune differently?

Discuss.

[Adam_Winstone]

Might not have shown a huge difference between the static timings on the dyno but it would likely make the difference between getting to your destination or sitting broken down on the side of the road!

PS - The above relates to the more advanced static firing points tested, rather than the pros and cons of advance retard. Edit: PS added as re-reading suggested clarification was needed.

[Warkton Tornado No.1]

I don’t know if there is a definition for tuning, but imagine most people see it as getting all factors to work in harmony for the best delivery of power over a usable range.

Personally having run race engines, I’m in the camp that believes in retarding ignitions where ‘maximum benefits’ are sought. I first felt the advantage when I bought a ‘discarded’ internal rotor Motoplat ignition from Ray Kemp many years ago that retarded something like sixteen degrees over a range from 2500 to 10000, having advanced fully between 0 & 2500. The drive out of, say, Cadwell Park Club circuit hairpin was a revelation, but the top end dropped off because those were pre-dyno days relying on home tuning.

However, a top tuner Ralph Saxelby still runs fixed internal rotor Motoplat ignitions on his & Ryan’s Group Six motors & they were by no means shabby the last time I witnessed their performance in 2015. IMHO, Ryan's was the quickest motor @ Cadwell Full circuit on that occasion, despite the winning Italian 'invasion!'

It would be naive to think that Ralph's motors may not run even better, though, with a retarding set-up.

Kart non-gearbox engines used to perform over a phenomenal rev range, yet, years ago, the retard was only something like two degrees on the TKM motors.

My conclusion is that ignitions should be ‘mappable’ best set up on a dyno because ‘one size fits all’ is not the best solution.

[dickie]

Might not have shown a huge difference between the static timings on the dyno but it would likely make the difference between getting to your destination or sitting broken down on the side of the road!

PS - The above relates to the more advanced static firing points tested, rather than the pros and cons of advance retard. Edit: PS added as re-reading suggested clarification was needed.

Agree (obviously) which was why we left it at 18.

I also agree that my rambling introduction didn't help; yes, I'm only taking about static timings here.

My intention was to show that we found no difference in the shape or size of the power curve between about 3000 and 8500 rpm with timing anywhere from 23 down to 18 degrees. In other words, reliability without performance loss.

[Warkton Tornado No.1]

I meant to say that the selection of fuel comes into the equation.

Tesco Optima was the best commercially available according to another tuning Guru.

What do you use, out of interest?

I think that the 'least' practicable retard from OEM settings (as DT set yours) is the best compromise for fixed ignitions & I currently aim for 19° BTDC, rather than the popular 17° that I hear about.

[dickie]

To be honest I'm a bit half- arsed when it comes to fuelling up. I use regular unleaded from the garage I'm at. Having said that I don't tend to wander far from home so consequently I tend to use shell regular unleaded.

[Warkton Tornado No.1]

To be honest I'm a bit half- arsed when it comes to fuelling up. I use regular unleaded from the garage I'm at. Having said that I don't tend to wander far from home so consequently I tend to use shell regular unleaded.

I'm not sure it's a good idea to use the lower grade fuels on an old engine or one that is tuned. Most of us tend to use a combination of both, so it could be a worst case scenario!

It's not a myth about fuel quality, either. Shell sell good fuels (Nitro) & I use no other in my old Turbo Diesel with well over 200 000 on the clock @ the recommendation of the Independent Service Agents. The engine runs noticeably better on it.