While tidying up, I found the flow matching datasheet for my TVR injectors, along with my calculations for some of the open/close parameters in VEMS. I'm not sure how good the calculations are, but here they are more for discussion than anything else.
Test results (All tests done at 14vdc)
Static flow: 586cc/min.
Dynamic flow: 0.0136 grams per 2.5ms pulse @ 100 Hz. (ie a duty cycle of 1/4)
My calculations:
Using a fuel of density 0.6855 grams/cc this gives a static flow 6.696 grams/sec.
The dynamic flow is 5.44 grams/sec dynamic
It seems sensible to me to conclude that the dynamic case includes errors from opening and closing effects, whereas the static case does not. Therefore, the opening and closing effects account for an error of:
0.003137625 grams/pulse (Calculated as static flow for 2.5ms - dynamic flow for 2.5ms pulse)
This doesn't look like a lot, but it's approximately an 18% error for a 2.5ms pulse.
Now the big question to answer is: How do we account for this "missing" fuel in the pulsewidth calculation?
In the static case (ie if the injector is fully open), an will flow 0.00314 grams in 0.47 ms. So if the error is purely due to injector response time, then this is the answer.
However, if the ramp up of flow is assumed linear, the closing time is 0, and there is zero response time, then we need to extend the pulsewidth by 0.23 ms.
We can make the first 2 assumptions above since the dynamic flow data includes both opening and closing effects so we can pretend, at least mathematically, that all the error is at one end of the pulse. However, we can't assume zero opening time!
In reality then, the injector PW must errors to be taken out by VEMS @ 14v will be bounded by extensions of 0.23ms and 0.47ms.
Note that this does not take account of supply voltage variation. That's for part 2!
Please point out the flaws in my arguments now...
