Iím interested in trying to determine the baseline performance of my magneto using the ď1156 Bulb TestĒ.
I performed this test last night, as described in this procedure: http://www.mtfca.com/discus/messages/708324/MAGNETO_TEST-760271.pdf
At engine idle, I had a healthy 8-9 volts and the bulb was bright.
At moderate throttle, I had around 15 volts and the bulb was very bright.
The problems and questions come at determining the output at high engine speed. I could goose the throttle to obtain high RPMs, but I was uncomfortable holding it there to get an accurate measurement. The sound and vibration of the engine under high RPM when the car is stationary is like a singer sowing machine ready to come apart! Iím using a Simpson 260 and the sweep of my needle seems to lag behind the RPMs and move slow. So by the time I goosed the throttle and then backed off, the needle was already falling. I managed to get it up to around 17-19 volts and the bulb was very very bright, but it was momentary.
1. Does the bulb need to be connected directly to the magneto post to get an accurate measurement? Does the ground connection need to be close to the post as well? I connected the bulb to the red lead at the firewall terminal block and the other to the ground screw on the horn. I connected the meter at the same points.
2. Should I try with a more responsive (faster) meter or are they all the same? This is just my lack of experience with analog meters.
3. Is the high (engine) speed measurement taken while goosing the throttle or opening the throttle and holding it there? Seems very hard on the engine, but again maybe Iím showing my in experience.
Any thoughts on the measurements I posted above? My car idles great and runs great on magneto. The primary reason Iím going down this path is because my car does not start on mag. Iím trying to rule out the magneto (which was rebuilt, magnets charged), before moving to the coils which are a complete unknown.
Perhaps your chasing the wrong thing?
Give me a call and I can help. I can talk faster on the phone than type on this damn computer.
I have noticed most of those bulbs blow at 18 volts.
That is usually good enough to run on Mag.
Keep a supply of bulbs on hand if you plan to do that test on a good Mag.
Or you could test the output of the magneto this way: