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techtalk:ref:engctl01e [2019/05/09 22:42] hippysmack created |
techtalk:ref:engctl01e [2023/08/07 19:43] (current) ixl2relax [REF: Engine Control - SUB 01E] |
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| - | ====== REF: Engine Control01 ====== | + | ====== REF: Engine Control - SUB-01E ====== |
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| ====== A Neat Timing Trick ====== | ====== A Neat Timing Trick ====== | ||
| + | The procedure is here at Wild West Cycle.com ((http://www.wildwestcycle.com/f_timingtrick.html)) \\ | ||
| + | <blockquote>It basically amounts to adding a TDC mark on the timing cup rather than on the flywheel. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?p=4018569&highlight=upgraded+crank+timing+mark#post4018569)) \\ | ||
| + | In theory that works fine. \\ | ||
| + | One thing to be aware of, though, is that dial-back timing lights and dual-fire ignitions on Harleys don't always get along. \\ | ||
| + | Dual fire was stock on bikes that have timing cups. \\ | ||
| + | The way a dial back light works is that it looks at the rpm of the engine based on the interval between firing pulses. \\ | ||
| + | Knowing the rpm, it can calculate how much time equals how many degrees of crank rotation, and delay it's strobe appropriately based on where you've got the dial set. \\ | ||
| + | You then use the TDC mark instead of the advance mark. \\ | ||
| + | In most four stroke motors, you get one firing pulse every 720 degrees of crank rotation. \\ | ||
| + | This is what the dial-back light is expecting to see, and it bases it's rpm calculation and strobe delay on it. \\ | ||
| + | Well, in a dual fire Harley motor, you get two sparks every 720 degrees of crank rotation, the real spark and the wasted spark. \\ | ||
| + | What's worse, they don't even come at even intervals: 405 degrees followed by 315 degrees followed by 405 degrees, ad infinitum. \\ | ||
| + | It confuses the hell out of a dial-back light, and really makes it's answer untrustworthy. \\ | ||
| + | If you're lucky, your light will filter the uneven interval and average the two. \\ | ||
| + | But you still have a 2X rpm assumption, which is going to mean you'd have to dial in twice as much timing as you actually want. \\ | ||
| + | I've seen people try to do it but using a dial back light on a dual fire HD is just a bad plan. \\ | ||
| + | It works fine if you've upgraded to single-fire, though. | ||
| + | </blockquote> | ||
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