question cpi/pfi mode

[myburb]

I have 7427 running $OE bin that started off as a 7.4 truck bin. Under flags there is a setting called "cpi/pfi mode. On a normal tbi bin that is unchecked. Under comments it states that it changes the injector firing from twice per revolution to once. When I set the box and gave it a try with still tbi it ran and drove fine. Can anyone tell me what exactly the setting and unsetting of the box is supposed to do?

[Hog]

Since you are running TBI you wont notice a difference as your injectors provide fuel to all cylinders. If you had an actual Port Fuel Injected intake manifold, you would notice the difference as you toggled that box.

That was a horrible explanation, I hope someone betters it.

peace
Hog

[myburb]

I drove all day yesterday with box ticked/set. Drove very well, started cold. Differences were it ran slightly leaner ( I only run open loop ) and it took slightly more tps to to travel the same road. The afr on the wb seemed slightly smoother as it transitioned cell to cell. By slightly I mean very very little. So It seems the most important part would be the change to the memcal to invoke the different trigger sched. So I still don't know what checkng the box does but my test is over.

[dave w]

I have been thinking, unless a CPI memcal is being used changing the CPI/PFI mode parameter will not change anything. I have been thinking the TBI current sense resistors would keep the PCM in TBI mode. ... Maybe the CPI memcal is configured to trigger the injector (CPI I think had only one injector) every 4th distributor reference pulse? ... Maybe try using a CPI memcal with the CPI/MPFI parameter set? dave w