Quote:
Originally Posted by Megadan
We aren't talking enough advance to really put any actual strain on the starter. If the idle/start ignition timing is 14*BTDC, with the peak advance being 26*BTDC(est)@4000rpm, and I manage to advance the pickup say 2 degrees, then we are talking 16*BTDC starting/idle with 28* at 4000rpm.
Considering most of the "performance" CDI units on the market have zero idle/start ignition retard built into them, they have the engines kicking over with 26 degrees of advance just to start, which is why they are such a pain in the rear end to cold start.
My modified head on the other hand... that will definitely make my starter cry a little bit. I calculated out my compression at 10.3:1 That might do a number on it lol.
The pickup advance modification is more of just an experiment to see if I can coax a little more pep in it's step in the middle of the power curve. Since I only plan to slot the bracket holes in the direction needed to advance it, I can always take it back to the factory position if needed. I do plan on eventually tossing on a programmable CDI though, as full control over the whole curve would be wonderful.
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On the engines I have had experience with, 28 degrees of advance is what you need at 2000-2500rpm, on its way up the rpm scale. 37-40 degrees maximum advance is where you want to end up. You either find the maximum advance on a dyno, or top speed runs in high gear. To amuse the younger set, I had an airplane with a Franklin 6 engine. It had Edison-Splitdorf magnetos that had an impulse coupling that delayed the magneto 35 degrees at start up until 7-800 rpm. Then the flyball governer kicked out the impulse coupling, and ignition timing went directly to 37 degrees advance. Understand that it delayed the entire magneto, not just the breaker points. Delaying ignition the easy way (points) causes hard starting because a magneto's EMF pulsates in varius areas around the core. The breaker points are timed to the period of maximum electronic pulse in order to get a very hot spark. That's probally more than you want to know about magnetos, even though the Hawk has one...ARH
