I have an idea related to the E-Timer that even we purist would probably not object to. What about a device that can be attached to the Model T, temporarily for training purposes, that will tell you if you have your spark advance in the ideal position, and if not, which way to move it to get it there? It would be a great training aid for new drivers, and those that don't understand what the spark advance does and why you adjust it, or even seasoned drivers that want to hone their skills. Maybe an LED read out, green for the right position, yellow band on either side of green for close but a little too much or too little, and red outside of that for not even close.
I have no idea what it would cost to develop that, but maybe some of the work is already done? Maybe there would be no market? Just thinking out loud.
Hal, unless you are running on battery the spark timing is set by the magneto. The plug can not fire until sufficient voltage is developed in the coil secondary. That event is determined by the position of the magneto, the timer only completes the circuit that connects the coil to ground. The timer position can possibly keep the plug from firing but it doesn't determine when the plug fires except in a very gross sense. At least that is my understanding of how the magneto ignition system works. As an aside, that is one benefit of running on a battery or distributor, that is, the timer or distributor does determine when the coil fires. I'm sure I will be corrected if I'm in error.
The pulses from the magneto are separated by 22.5 crankshaft degrees. The timer has enough adjustment if there is no slop in the linkage to alter the timing by close to 90 crankshaft degrees. So, while operating the ignition on the magneto, there are four timing choices to choose from.
You are correct about ignition operation on DC or dizzy ignition - infinitely variable ignition timing.
There are people who don't know which of the 4 positions to pick, but if you are running on BAT, there would definitely be an optimum position, and if 12v, the performance would be fairly good.
I did not and can't object to the e-timer but i fail to see the need or the 400.00 expence? I have a strong working mag and i can easly crank start on mag. After about 3 years i have yet to do anything to my Anderson timer so? After cranking i set the advance to 25 to 12 so i fail to see any gain? If i was to use batt ignition maby but with a good mag why? PS,Ive only owned T's since maby 92 93 so i must need more experance?? Baffled Bud.
Peak torque on the T engine is at 900 rpm. With standard gearing (3.64:1) this is at about 22 mph in high gear. Peak torque is the result of the maximum charge being retained in the cylinders before the compression stroke and therefore the maximum pressure on the power (expansion) stroke.
Stress on the crankshaft is partially dependent on how hard the connecting rods push on it and when they push on it.
Having too far advanced ignition timing increases the stress on the crankshaft because peak pressure comes too soon in the power stroke and the peak is greater than it would be if the ignition timing was correct for those engine operating conditions.
Incorrect ignition timing can add unneeded stress to the crankshaft, hastening its failure.
Choices of ignition timing in 22.5 degree steps are likely inadequate at low engine speeds (near peak torque) and high manifold pressure (lots of throttle).
Operating the stock ignition on battery power or having an E-Timer, dizzy, True-Fire or any other ignition capable of infinitely variable ignition timing is probably better for the crankshaft.
The big IF is whether or not the operator knows where the optimum ignition timing is.
Optimum is in a different place on a Z-head engine at sea-level versus a stock one at 5,000 feet elevation.