The X-axis for the injector latency tables is labelled incorrectly in AccessTuner Race. I had always assumed that this tables was looked up based on measured barometric pressure in kPa, but it is a bit more complicated. In retrospect, that also makes no sense.

A value is pulled from this table based on load and rpm:



Then that value is subtracted from current measured barometric pressure.

This difference is then used as the X-axis for lookups to the latency tables.

The intent is, I think, to come up with an estimated manifold vacuum, and thus correct its influence on injector behavior due to the returnless design.

 

Interesting find.

However the values might be derived, the availbale latency table does effectively control the actual injector latency.

 

so for a boosted engine the far right column will be for all settings in boost ?

 

someone unplug the baro and see?

 

No.
You will be referencing ambient (unless you decide to plug the BARO into the IM, which is a project unto itself).

 

Apparently, a greater pressure differential between the fuel rail and the manifold actually requires more dead time. Getting latency right under vacuum conditions is probably the most important function of these tables.

When load exceeds 1.25 it will lookup up a number from the bottom row of the table above, roughly 100-110, and subtract that from the baro reading.

101kPa is sea-level pressure, so the difference would the 0 to -15 columns.

So, these tables don't account for boost as they are, but the additional pulse width that might be added is probably pretty tiny.

Speaking of strange-but-true baro compensations, there is also a correction to the front o2 sensor for altitude.

 

Well, yeah. It is a WB feedback. There would have to be BARO compensation since there is a density component to that sensor.

 

Is there a way to translate this to simple dead times graphed by time (ms) and voltage? I'm validating values for my stock reds and haven't been able to find an easy answer after a handful of searches.

In meantime (while waiting for the flame and/or answer) I'll just keep searching... This has got to be documented somewhere.

 

Interested thread, This is really helpful and I stimulate you for more info. This is the way to expose your info. Now I can get all the info just from one boost. :D