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Knowing if deadtime is working correctly

EFI Tuning Fundamentals

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Was just curious, how would you go about knowing if the information you've entered for your inj dead time is working correctly? Would you just try to increase your decrease battery voltage and seeing if your afr's are meeting your targets?

You could do a whole analysis where you set up an adjustable power supply/voltage regulator to the vehicle or just the ECU, put it on a dyno, monitor wideband o2 and try different settings and different voltages. However that's a lot of work and you have to make a judgment call. If you have closed loop fuel trims it's usually going to correct for some of that.

If your ECU can do it, switching between batch (once per rev) and sequential (once per cycle) injection and checking there is no change in Lambda is a way to validate the deadtime for the current vehicle voltage. You can tune the deadtime value until switching causes no AFR change.

There's a couple of ways I use that give you a good idea if the dead time is in the ball park. If you tune the fuel delivery to achieve a fixed lambda (let's say lambda 1.00) and then add 11% fuel, this should result in the lambda moving to 0.9 (this calculation comes from the correction factor we teach in the course - Measured / Desired = Correction Factor or 1.00 / 0.9 = 1.11). If the lambda doesn't track your requested change then the dead time could be your culprit. Beyond this you can also disable the alternator to see how varying the battery voltage affects the AFR.

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