Quote:
Originally Posted by dcb
not until someone with a tbi tries it at least.
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I tried the comparitor circuit. I built it on a perf board and put the IC in the middle.
Here is the picture.
I used one 4 pin plug and one 4 pin jack to allow it to be easily removed or added in.
I found that the circuit squared off the whole wave form from the injector.
Here is a scope trace
Chevy 454, TBI, @ 2000 RPM. Top trace injector pulse, bottom, comparitor signal.
The result was I was showing 50 MPG! That's on a large motor home.
I think it was counting the narrow pulses as the injector signals, not the wide pulse.
Maybe some bias circuit would get the actual pulse width modulation we want.
I tried a variable resistor in the cold side of the reference voltage to adjust the switching point, but that didn't do the job.
I also tried a transistor inverter circuit between the injector pulse and the comparitor input but that didn't work either. I haven't had time to check out why yet. I wanted to see if the flipped signal would be accepted by the MPGuino.
I am going to try the filter circuit next. I'll build it on the perf board.
Lee