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Minimum pule width

John Appel

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I am using a G4 storm on my twin cylinder motorcycle engine. We have a throttle body on each cylinder and so we are using throttle position and revs for the axes on for fuel and ignition tables. Currently we are using a cam sensor and so we have one fuel pulse per engine cycle. On our fuel table we have a master value of 20 msec and at idle the no. in the fuel table is 14 so that the pulse width at idle is 20msec x 14% which is 2.8 msec. I want to try running the engine without the cam sensor and so I will have 2 fuel pulses per engine cycle ie. one pulse every engine turn. I then plan to halve the master value to 10msec to compensate. This means the pulse width will be down to 1.4 msec at idle.I may have to adjust the no. in the table to something a little greater than 14 to allow for the greater injector offset at short pulse widths. Do you think that the system will give good repeatability at 1.4 msec PW. What would you consider to be the minimum PW that would still give reliable operation. Regards, John

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You didnt mention if your 2.8mS is effective or actual PW.  I assume effective.  If so I would expect halving that will be fine. 

Note you dont need to change the master fuel number - the ecu takes care of that in its background calculation.  So, you can in theory switch between 1 engine cycle and 1/2 engine cycle injection rate without changing any other fuel settings.

Most modern injectors will start to get "non-linear" below about 1.5mS, but they are still usually quite repeatable until a good bit lower than that.   There are exceptions around though - for instance the old "Indy blues" were terrible at anything less than about 2ms, I suggest just try it and see.

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