16168625 BHAN modifications for TBI to TPI conversion questions>>

[Six_Shooter]

From what I understand all TBI systems (in the same ECM) have the same hardware resistance, and cyl number is set in the bin only.

When going to MPFI, there are different resistances based on cyl count, that set the injector firing scheme.

TBI fires twice as often as MPFI and this hardware change makes that work with MPFI. Anytime I've tried to run a TBI ECM on MPFI without a change a such would not run correctly.

In reality the MPFI firing is 12345678. All injectors fire at the same time, at least when using ECMs original to MPFI. I haven't verified if this changes when using an MPFI converted PCM, such as the '7427 using $OD.

[bybyc5]

From what I understand all TBI systems (in the same ECM) have the same hardware resistance, and cyl number is set in the bin only.

I do have a 3rd 16168625 PCM that came without a memcal/chip. So plugging in my memcal should give me another usable PCM to "play" with?

When going to MPFI, there are different resistances based on cyl count, that set the injector firing scheme.

Not sure I follow this (I am new to this kind of tuning, making one PCM work for different system than originally designed).
Is this why the low impedance injector peak and hold resistors need to be bypassed for 8 high impedance saturated injectors?

TBI fires twice as often as MPFI and this hardware change makes that work with MPFI. Anytime I've tried to run a TBI ECM on MPFI without a change a such would not run correctly.

Does setting the Flag/Switch to "set" accomplish this? Or is the wire bypass needed still on the memcal?

In reality the MPFI firing is 12345678. All injectors fire at the same time, at least when using ECMs original to MPFI. I haven't verified if this changes when using an MPFI converted PCM, such as the '7427 using $OD.

So having Bank-1 and Bank-2 wiring really just splits the circuit load on the 2 injector drivers?

Thank you for your help!
I will get this figured out. I'm in for a penny in for a pound at this point!

Thank you,
Keith

[Six_Shooter]

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.

[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?