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Injector compensations tables

EFI Tuning Fundamentals

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Hi All,

I'm learning along with a friend on a Mazda MX5 NC using OEM ECU.

MX5 NC are using a returnless fuel system.

He has changed injectors for bigger injectors, trying to do things right we want to set the right values for deadtime relative to voltage and differential fuel pressure in an existing 3D table.

Is the injector manufacturer supposed to give us this information ? As the most we can find is the deadtime relative to battery voltage.

Also we have a 2D table to calibrate for flow rate compensation relative to manifold pressure which we're told to calibrate using the same method as for MAF calibration.

That implies to have a calibrated MAF before hand.

And I feel this gives a lot of room for errors as you could compensate AFR target discrepencies by either adjusting this table or MAF scaling sensor table.

Both having different impact on potential other tables.

That's where I get confused, might be looking for too much perfection ?

Thanks for your help in advance.

Attached Files

In the perfect world you'd be wanting to purchase injectors that come with plug & play data in the correct format for your ECU. This becomes more important with factory ECUs if you want everything to work as expected. The first part (which it seems like you've got your head around) is that you can get yourself into a b it of a mess if you're trying to rescale the calibration for a new intake/MAF AND injectors at the same time. I always try to do dial in one first and then the other unless you have a LOT of experience with the particular model of car and a collection of data you can rely on.

The 2D table for injector scaling vs MAP 'should' need little work as it should follow a similar trend irrespective of the injector size. The 3D dead time however is a little trickier. What I'd suggest is you use the dead time data that is supplied and scale the rest of the table to suit. This should get you in the ball park and you can then fine tune to suit using the techniques outlined in the course.

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