Commando race ignitions

B+Bogus · Sep 19, 2023

SteveA said:
Name that currently competitive Commando! In fact, name that currently used race Commando!

Oh, go on then...
Richard Ford has been the Irish Road Racing Champion a number of times now, and at the moment he's racing 920 and 1007 Seeley Commandos with Bob Jackson Racing - he struggles to beat Andy Hornby's Trident (came second to him at Cookstown), and previously Guy Martin's Rocket 3, but he's generally up there. He recently won at Gedinne. He doesn't do the UK circuits except Tonfanau.
The Irish guys claim him as one of their own, but he's very English, and lives 100 yards from me!

B+Bogus · Sep 20, 2023

This is the Maney installation minus stator plate & cover.
Worth bearing in mind it runs a single pickup at twice the speed of the cam, so the advance curve will be compressed with a standard Boyer amplifier.
No reason why something like an Ignitech unit couldn't be used, so any curve you desire could be programmed in - something I'm considering.

Fast Eddie · Sep 20, 2023

B+Bogus said:
No reason why something like an Ignitech unit couldn't be used, so any curve you desire could be programmed in - something I'm considering.

I have not tested thoroughly enough on the dyno doing back to back compressions, but I am nevertheless of the opinion that these motors just don’t need an advance curve for track use. I reckon fixed ign is all they need.

Anyone have evidence or experience to the contrary ?

B+Bogus · Sep 20, 2023

Early Squarecase Ducati twins had a self generating EI which I believe was derived from an aero engine application.
The ignition 'curve' was essentially a step function which changed state from 3 degrees to 27 degrees BTDC at around 1500 rpm.
Great for a race engine, but makes the bike a bit of a pig around town

jseng1 · Sep 20, 2023

B+Bogus said:
Early Squarecase Ducati twins had a self generating EI which I believe was derived from an aero engine application.
The ignition 'curve' was essentially a step function which changed state from 3 degrees to 27 degrees BTDC at around 1500 rpm.
Great for a race engine, but makes the bike a bit of a pig around town

Actually that would work great on a Norton street bike if adjusted to 28 degrees. You want the early advance for more low end torque. The problem is that most EIs don't have the availablility of early full advance.

TBW · Sep 20, 2023

SteveA said:
Spike Livingstone at Ragged Edge Racing.

Essentially, it is a Seeley fairing but was in itself a copy of the Apollo fairing that Ken Inwood used to sell in both one and two piece versions. I had bought a one piece from Ken in 1977. I was able to buy one of the last 3 piece ones from him in 2009/2010. (BTW does anyone know if he is still with us?)

Spike already had a top half mould. The mould for the lower was made from my previous open bottomed Apollo/Seeley fairing and a few measurements, and is now a standard product for racers needing a catch tray. It has the bulges for the Rickman Frame because I insisted on them as authentic to the Apollo two piece and essential for Rickman lower engine mount lugs.

I don't think they were included in the one piece version, or if they were, they didn't last long!

Spike = top bloke, really knows his stuff and produces high qu products

acotrel · Sep 20, 2023

There is probably an advantage in having the ignition to advance as the revs rise, to compensate for the change in rock-over time. The combustion process is a fixed time event. It would cause maximum combustion presuure to stay at the same point in the rotation of the crank. The advance curve should probably be a function of the ratio of conrod length to the stroke. If we have the equation, it is easy to set up the advance curve in a programmable ignition system, When you use methanol as a fuel, the balance between ignition advance, fuel ixture and compression ratio is not so critical. But if I was going to race again, I might buy a programmable Boyer.

acotrel · Sep 20, 2023

jseng1 said:
Actually that would work great on a Norton street bike if adjusted to 28 degrees. You want the early advance for more low end torque. The problem is that most EIs don't have the availablility of early full advance.

My mate had a 750SS Ducati. He fitted an ignition system from a Honda V twin, which retarded at low revs and advanced as the revs rose. It made the bike much less harsh to ride. He had a bit of trouble getting the trigger to work. But he was a mechanic and had the instruments which allowed him to watch the system advance. I think the Honda was a VT750.
With a Commando, it is not easy to fit a crank operated trigger.
One thing of which I was never very aware - a four-stroke engine behaves silimarly to a two stroke in terms of the effect of the balance of the things which affect combustion. I never used to run my motors lean enough. That balance has a big effect on performance.