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Old 02-08-2017, 12:18 PM   #82 (permalink)
t vago
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Originally Posted by skybolt View Post
So, ... if I understand correctly, injector size and pressure must be for fuel use by pure calculation rather than tuning by observation, trial and error. I've noticed that changing # of cylinders alters the uSec saved value, but this doesn't extend to injector size, injector delay and fuel pressure. If I modify injector size and fuel pressure, shouldn't it change the saved value in uSec? Perhaps it has and I haven't noticed. If I have injectors set to 1, and change uSec to value N, and leave injector size at 246, should I expect to have it change fuel pressure to reflect the change in uSec? If so, your calculations must get a bit ... involved. Perhaps changing injector size/pressure overwrites uSec but manually setting uSec in essence overrides size/pressure?
Meant to explain what is going on here, but my computer died while I was composing the explanation, and I forgot to get back until now.

Ys, injector size and fuel pressure are meant for calculation purposes. They're meant to get you to the ballpark. Fine-tuning still requires manually fiddling with the usec/gallon and injector delay values.

I tested the code with changing both the fuel pressure and the injector size, and the usec/gallon figure changed. The thing is, you're going to have to do a major change in fuel pressure to see any difference, because the code uses the square root of the fraction difference between the reference and system fuel pressures.

The calculation only goes one way for now. Directly changing the usec/gallon figure does not change either system fuel pressure or the injector size. Hm... It easily could, though, at least with regard to injector size.

I am working on adding matrix math into the code. Once that happens, I can implement a much better way to calculate the usec/gallon and injector delay values, that does not require knowledge of system fuel pressure nor injector sizes. It will not only get you into the ballpark, but it will place you at third base with the batter hitting a home run.
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