Fuel injector dead time interpolation.

Hi all,

I have just installed some bigger injectors in to my turbo mx5 powered kit car and after some advice.

I am running a Mega squirt MS2 and the dead time data does not allow me to input a table rather a fixed dead time at 13.2 volts and a Battery voltage correction (milliseconds per volt). (i have attached a screen grab from the software.)

The injectors are 648cc Injectors and I have the following deadtimes @ 3 Bar fuel pressure.

8V - 2800us

10V - 1620 us

12V - 1160us

14V - 860us

15V - 760us

With some rough guestimate interpolation I came to a 965us dead time at 13.2 volts am I close enough here or is there a better way to interpolate the data?

Also what would the battery voltage correction be (my guestimate once again is 144us but feel i may be well off here)

I know the mega squirt ms2 is quite outdated, basic and not terribly well regarded in the tuning community but need to make it work for now.

Thanks in advance

Craig

I think that the linear interpolated value for 13.2v would be 980 uS. The dead time changes relative to voltage are not linear:

8-10v is 590uS/v

10=12v is 250 uS/v

12-14 is 150 uS/v

14-15 is 100 uS/v

I would probably use 200 uS/v as the battery correction since most corrections are for slightly lower voltages. The consequence of not being able to describe the injector correctly just means when you request a 10% fuel trim (in a table like coolant temp compensation), you will not get exactly 10% unless the battery voltage is 13.2v. The errors will be pretty small however for anything but idle and cranking. And you will just end up compensating with the values you enter in the idle and cranking fuel tables. I suggest just giving the 980 / 200 a try, and get on with the tuning process.