cparke

Now that I totally understand how the fuel pressure regulator works, there is another part of the fuel injection system I need understand---the fuel injection time.

The inputs read by the ECU to control the air-fuel mixture (MAF, ECT, IAT, RPM, Throttle position, etc.) are used to decide the injection time and thus how much fuel to inject into the bank (thanks to the FPR, the flow rate through the fuel injector is always the same regardless of changes in fuel pressure or intake manifold vacuum pressure).

However, on a V6 with two banks, it seems the ECU only has one fuel injection time even though it has separate fuel trim values? Or, is the single fuel injection time value reported in the ECU measuring blocks the fuel injection time for one of the banks? Or, does it cover both banks depending on which bank's injection is active at the instant it is sampled?

Seems contradictory to me that the ECU can maintain separate air-fuel ratios in the two banks while applying a single injection time to both banks for a rpm cycle.

S4 Terrorist

AF ratio, fuel trim, IDC and timing is always changing to try to maintain AF ratio. That is also the reason to have open loop mode for monitoring 02 sensor voltage.

4Rings::G2 boosted::

which is calculated from the sensor values. This value is then modified based on the long and short term trims for each bank, which results in two independent injection times for each bank.

If the ecu is in an open loop, that's it, if the ecu is in closed loop then there's a follow on step during which the ecu reads the O2 sensors and re-adjusts the trims based on whether the O2 readings are leaner or richer then stoic ratio (14.7:1)

cparke

Thank you (once again). Excellent description, and what I suspected.