help for determinition ignition curve SQ4 4f 600 iron head 1939

[mboelis]

Who can advise me about the best setup for an ingintion curve for my SQ4 4f 600 iron head 1939. I made a first setup as the picture below, but have not other parameters and info with the best advance with different rev. speeds.

idle 900 rpm / advance 0 degree
1500 / 8 degrees
2000 / 14 degrees
2500 / 20 degrees
3000 / 26 degrees
3500 / 32 degrees
4000 rpm / full advance 38 degrees
max rpm 5400 / full advance 38 degrees

full advance 8 mm BTDC = 28.25 degrees

I look forward to your comments



Regards Marco

[david.anderson]

Your advance curve is linear. While I have no experience with setting an advance curve, or with a 600 4F, it is normal for the initial rate of advance to be more rapid, with the rate of advance slowing after 2000rpm. Or at least for the initial advance setting to be considerably higher at 12 to 15 degrees advance at 1000rpm. At 2000 rpm an advance of 20 to 25 degrees would normally be expected with ignition advance from that point being more gradual. Possibly 28 to 30 at 3000 rpm with only a slight increase from there.
While not a 4 cylinder have a look at these advance curves for the Pazon ignition on a British twin. The advance curves shown are similar to the advance curve that was established for a couple of cars that I watched being adjusted and set on a dyno.
http://www.pazon.com/ignition-system/su ... 2volt.html
Your restoration is superb and we are waiting to see more.
David

[mboelis]

Thanks David,

The inginition is programmed. Based on experience from other 4F owners. I take this as default setting to start with.

[nevhunter]

I think that's about all they are. Just achieve an idling situation. Not very sophisticated is it? Could be improved on maybe. The 38 degrees seems about right IF it sticks there you will have a very fast idle. Nev

[markus.nikot]

My 4F6 32 ran good with fixed advance, even starting wasn't a problem. After fitting a mechanical regulation i use this only for setting the idle speed a little down if necessary. A quick increase should be OK.

Markus