How to find your injector dead time
06-08-2011, 11:51 AM
#31
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Yellow RX-8 injectors @ 13.2 volts. I ramped the dead time down from 2 ms to ~1.2 ms before the engine died. There are two distinct slopes:
I had been running with a dead time of 1.0 ms but was leaning out as the intake temperature went up. I retuned for 1.45 ms based on the 2 vs 4 squirts method. Too early to say how that works. I'm not clear on how to square that with a 0.8 ms intercept here.
I had been running with a dead time of 1.0 ms but was leaning out as the intake temperature went up. I retuned for 1.45 ms based on the 2 vs 4 squirts method. Too early to say how that works. I'm not clear on how to square that with a 0.8 ms intercept here.
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06-09-2011, 06:29 AM
#35
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Yellow RX-8 injectors @ 13.2 volts. I ramped the dead time down from 2 ms to ~1.2 ms before the engine died. There are two distinct slopes:
I had been running with a dead time of 1.0 ms but was leaning out as the intake temperature went up. I retuned for 1.45 ms based on the 2 vs 4 squirts method. Too early to say how that works. I'm not clear on how to square that with a 0.8 ms intercept here.
I had been running with a dead time of 1.0 ms but was leaning out as the intake temperature went up. I retuned for 1.45 ms based on the 2 vs 4 squirts method. Too early to say how that works. I'm not clear on how to square that with a 0.8 ms intercept here.
I have RX8 injectors too, 1.45ms seems rather high for a relatively modern injector deadtime though?
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06-09-2011, 08:54 AM
#36
Supposedly the y-intercept is the deadtime, but I see a huge difference between the published deadtime and the experimental values achieved by users. I'm using the published data and it works fine. I had to retune fuel though.
deadtime for RC750 high impedance
10V 1.36ms
11V 1.12ms
12v .92ms
13v .76ms
14v .63ms
15v .50ms
Nice and linear from 13v-15v. My question is how can a big *** injector have a shorter deadtime than a smaller injector? Seems like smaller would be faster.
deadtimes: http://injector-rehab.com/shop/lag.html
deadtime for RC750 high impedance
10V 1.36ms
11V 1.12ms
12v .92ms
13v .76ms
14v .63ms
15v .50ms
Nice and linear from 13v-15v. My question is how can a big *** injector have a shorter deadtime than a smaller injector? Seems like smaller would be faster.
deadtimes: http://injector-rehab.com/shop/lag.html
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06-09-2011, 09:16 AM
#37
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I'm not sure how to interpret it. Nor am I confident that 1.45 ms is the right dead time -- it does seem too long. The two measurement methods disagree considerably here. (1.45 is from the 2 vs 4 squirts method.) Barring any brilliant insights the flow may actually have to be measured when driven with the MS. But I am planning on going full sequential this summer, which will change the drive electronics, so I don't want to go to the effort of measuring flow until I have the final setup.
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06-09-2011, 09:32 AM
#38
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here's the thing, all the deadtime code does is add that value to the end of your calculated pulsewitdh. if the code calculated 1.7ms and you have a deadtime of .8ms, it will fuel 2.5ms total.
Just pick a number and go with it. Tune the voltage correction curve to mirror that of the published rates and be done with it.
Just pick a number and go with it. Tune the voltage correction curve to mirror that of the published rates and be done with it.
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06-09-2011, 09:36 AM
#39
Yeah, but you only have a finite amount of time to get the next pulse into the cylinder on time. If you list a deadtime that is too long, then it may not start squirting until past the point you desire. The shorter the deadtime the better until you exceed the mechanical limit.
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