16168625 BHAN modifications for TBI to TPI conversion questions>>

[bybyc5]

In most non SFI OEM MPFI applications from GM, the ECM only had one injector driver. The only exception I can think of is the Turbo Sunbird, Turbo Grand Am, Sy/Ty and a Quad 4 application (Beretta?), that used the '7749, that has two injector drivers, but in saturated mode (Sy/Ty for sure), only one driver was used. in Peak and Hold mode (Sunbird and Grand Am), both injector drivers were used.

So inside the PCM there is only one driver for my 16168625 PCM. Then the control circuit for this driver must split inside and come out via two pins labeled "TBI A driver" coming out on pin A-16, and "TBI-B driver coming out on pin A-9. Or am I still lost?

Must be for some kind of LHM, in the event of one injector failing?

Thank you, I'm learning here!

Keith

[Six_Shooter]

No, your PCM should have two injector drivers, what I was talking about was OEM MPFI applications, which your PCM was never used in.

[EagleMark]

The reason I suggested switching to $0D is because so far all these PCMs can... no if you only have one injector driver we may have found a difference?

Also your BHAS was superseded twice to BLCR so that may be a better start.

Six, he was just advised on another forum that there is no need for resistor change? The TBI to MPFI doc clearly states:

Injector Drivers

Next you will need to change two resisters in the PCM. This modification is necessary to disable the Peak and Hold function of the injector drivers. The resistors are called sense resistors and sense the current to the injectors. The resistors have to be changed in order to run 8 MPFI injectors, 6 is OK but 8 puts too much current load on the resistors.

Port injectors come in two types: Peak and Hold (low impedance) and Saturated (high impedance). This modification only works for Saturated (high impedance) injectors.


You will need to remove the stock resisters and install a solid wire jumper in there place. It would be best to check with a electronics store, as to the best type of wire to use in this application. Another option is to salvage a couple pieces from some other dead electronic device.

Here's a picture of what your looking for.

[EagleMark]

May as well bring this back up here too... memcal mod!

dimented24x7 states in a 2006 thread:

There are three firing modes in the PCM: TBI/batch/bank fire. The memcal mod is needed to tell the injector drivers when to fire. The injector drivers for MPFI are software driven using the timer output compare lines. There is a hardware timer/flag in the MCU with its rate set by the memcal configuration that is used to trigger one of the two injector drivers at the appropriate interval.

Somewhere 1project2many said this is redundent as the Bit checked CFI/MPFI mode did the same thing?

So someone that could read code better then I could see what changes are made when 0x400B is checked?
Here are notes from $0D XDF, now between 2006 and now there was TONS of work done to these PCM dissasembly and masks from some great people. Like Deminted24x7, HaulinAss, 93V8S10, Fast305/355 to give credit from just memory

Title: CPI/PFI Mode

Location: 400B-Bit 0

Usage: Air Fuel Mode Words

Tips: To change between TBI and CPI/PFI injector firing strategies. Checkmark if you will be using Central Port Injection or Port Fuel Injection. TBI fires the injectors twice per crankshaft revolution. CPI/PFI fires the injectors once per revolution. PCM modifications are also required.

I'd like to know why I can run and tunea $0D MPFI without the Memcal mod? Actually if I add it the vehicle runs like crap?

[JeepsAndGuns]

The 16168625 will run $0D just fine. I have personally done it.

I also have a 16197427 based MPFI system. I simply followed all the instructions in the MPFI zip file linked above. I have the jumper wire installed in my memcal, because thats what the zip file said to do. I have not had a chance to try it without the jumper wire, as I have been tied up with work, and installing some headers and trying to get to the exhaust shop to put my exhaust back on. So I have been driving it very little lately. But seeing the posts lately about some saying yes you need it, and some saying you dont, has made me very curious.

[EagleMark]

The only thing that makes sense at this point is the jumper was needed before the bit for CFI/MPFI was found? Still does not explain why mine runs great without the jumper and horrible with...

[JeepsAndGuns]

And mine seems to run great with it, but I have never tried it without it. So it makes me really curious.