Mod memcal jumper DRP 2 to DRP 4 on 16197427 ECU

**rsicard** · 02-01-2015

Gentlemen:

Performed jumper mod per HP tuners article jumpering Pin 56 for going from DRP 2 to DRP 4. After mod was done, plugged in 16197427 ECU into 1994 Big Block Suburban and it ran rough as though in limp home mode? Removed jumper from Pin 56, plugged ECU back in, started Suburban and it ran smooth. Pin 56 is the sixth terminal over from the left per the picture from HP tuners article. Wondering what went wrong. Maybe someone here can shed some light on the situation.

**1project2many** · 02-01-2015

I had to look at your other posts to figure out what you're doing. Have you made the software changes to select the correct fueling mode? Hardware change alone is not sufficient.

If you've been tuning the PFI intake in TBI mode then you might not be delivering enough fuel if you cut the injection pulses in half.

**rsicard** · 02-01-2015

Originally Posted by 1project2many

I had to look at your other posts to figure out what you're doing. Have you made the software changes to select the correct fueling mode? Hardware change alone is not sufficient.

If you've been tuning the PFI intake in TBI mode then you might not be delivering enough fuel if you cut the injection pulses in half.

Thanks VERY much for the reply. Have started with BJKW binary and have smoothed binary same per directions on this site. Also jumpered current sense resistors and inserted jumper per instructions in HP tuners picture on this site. With the jumper installed, the engine ran rough. Did not monitor the exhaust with a Wide Band EGO. Should have and then I would know that it was trying to run on too lean a mixture. This is an Edelbrock TBI to MPFI conversion. Edelbrock (502 cu in 29 Lb/Hr kit) did not specify to modify the ECU hardware. They only supplied a supplied chip to be installed. The 454 was bored out .030" and stroked to 4.25" for 489 cu in. This was done some 8 years previous and at the time bought Craig Moates APU1 stuff to tune it not knowing what the hell I was doing. Today it has become much clearer through folks like yourself what SHOULD be done to tune older GM EFI. Would VERY MUCH appreciate your thoughts on this matter.

**rsicard** · 02-01-2015

Originally Posted by 1project2many

I had to look at your other posts to figure out what you're doing. Have you made the software changes to select the correct fueling mode? Hardware change alone is not sufficient.

If you've been tuning the PFI intake in TBI mode then you might not be delivering enough fuel if you cut the injection pulses in half.

What you have said is what I have surmised. Did not adequately answer your post. No, software changes not made to correct fueling mode. Only found a binary that yielded something closer to a smoother and cleaner/leaner running engine. Understand that doubling the time between injector pulses will yield a leaner mixture. Now, if successfully getting it to run on the 4 DRP versus the 2nd DRP, by what approximate percentage should the on-idle and off-idle tables be enrichened to start with? Just a good guess will do. Then can go back, install the memcal jumper, correct the BJKW binary on and off-idle tables by some percentage and then start retuning from that point.

**1project2many** · 02-01-2015

Now, if successfully getting it to run on the 4 DRP versus the 2nd DRP, by what approximate percentage should the on-idle and off-idle tables be enrichened to start with?

That's a great question. If the code is operating in PFI mode (this is selectable in software) it will adjust synchronous pulsewidth to deliver the correct amount of fuel for synchronous delivery based on the number of injection events. But whether or not you need to make additional changes depends on how you've adjusted / affected asynchronous fueling. Fuel delivered asynchronously is independent of DRP's. It is event triggered and is based on table values and clock "ticks." With asynchronous fuel delivery in mind the answer, of course, is "Enough."

BTW, in synchronous TBI mode the injectors do not fire every second DRP. There are two injector drivers, each one alternates firing on every second pulse, which causes one injection event with each DRP. If Edelbrock has utilized both injector drivers then (presumably) half of the injectors are firing with each DRP.

This page describes fueling modes and selection on the hardware / memcal side and presents the only source of reference information we have for fueling modes. The information appears to have been scanned from GM documentation and does have some errors but this is what we've been working with.
https://web.archive.org/web/20030204...ECM/inj_op.htm

**rsicard** · 02-03-2015

Originally Posted by 1project2many

That's a great question. If the code is operating in PFI mode (this is selectable in software) it will adjust synchronous pulsewidth to deliver the correct amount of fuel for synchronous delivery based on the number of injection events. But whether or not you need to make additional changes depends on how you've adjusted / affected asynchronous fueling. Fuel delivered asynchronously is independent of DRP's. It is event triggered and is based on table values and clock "ticks." With asynchronous fuel delivery in mind the answer, of course, is "Enough."

BTW, in synchronous TBI mode the injectors do not fire every second DRP. There are two injector drivers, each one alternates firing on every second pulse, which causes one injection event with each DRP. If Edelbrock has utilized both injector drivers then (presumably) half of the injectors are firing with each DRP.

This page describes fueling modes and selection on the hardware / memcal side and presents the only source of reference information we have for fueling modes. The information appears to have been scanned from GM documentation and does have some errors but this is what we've been working with.
https://web.archive.org/web/20030204...ECM/inj_op.htm

Thanks very much for the info. How does the ECU determine asynchronous versus synchronous? Is the mode set via a hardware jumper, or is it set in the ECU binary file via Moates APU1 Autoprom and TunerPro RT software? I will go back and further review TunerPro RT software. You are a great resource on this subject.

**1project2many** · 02-03-2015

Ugh...
Software can select
Hardware can select

Software when program working
Hardware in backup mode

Asynchronous is primarily for transitions such as AE, stall saver. It's a means to deliver event based fuel when needed.
Synch for all else.
Some calibrations (4.3 V6 tbi) set for asynch all the time. They don't run well.

**1BadAction** · 02-03-2015

Originally Posted by 1project2many

This page describes fueling modes and selection on the hardware / memcal side and presents the only source of reference information we have for fueling modes. The information appears to have been scanned from GM documentation and does have some errors but this is what we've been working with.
https://web.archive.org/web/20030204...ECM/inj_op.htm

^ Someone needs to save that HTML file to the server here. I'll probably post it on my boat forum under the tow pig section also... That type of info is GOLD.

**rsicard** · 02-13-2015

Originally Posted by 1project2many

Ugh...
Software can select
Hardware can select

Software when program working
Hardware in backup mode

Asynchronous is primarily for transitions such as AE, stall saver. It's a means to deliver event based fuel when needed.
Synch for all else.
Some calibrations (4.3 V6 tbi) set for asynch all the time. They don't run well.

In addition to adding the jumper to the Memcal and jumpering the current sense resistors, what needs to be changed in the TunerPro RT file for the ECU? Change from TBI to PFI etc.? Please advise. Thanks.

**1project2many** · 02-13-2015

I can only provide the information found in the HPTuners MPFI conversion thread:

First you have to modify the Memcal. Install the jumper as shown in the picture.
If you can't solder, find somebody who can.

You've already done this, I believe, based on the info I've posted previously.

Second you need to modify a few of the AE sync to async and BPW values and set the fuel mode to
PFI.

Switches:
1 CPI or PFI 1=PFI

Constants:
Sync to Async BPW<= 1.296998 Msec
Async to Sync ( Or PFI Double Fire) 1.495362 Msec
AE Min Aysnc or TBI Min Aysnc PW 1.90735 Msec
AE Max Aysnc or TBI Max Aysnc PW 6.10352 Msec
Low BPW Offset vs BPW Table Bias .0305176 Usec
Min Period Double Fire 0 Usec
Deg Delay From DRP to Inj Fire 0 Degrees
Sync Min BPW 1.296998 Msec
Sync Default BPW 1.693727 Msec
Cylinder Volume 1.0266 L/Cyl
Injector Flow For TBI 6.335433 Gms/Sec *OR* Injector Flow for PFI 12.67087 Grams
Async to Sync if Map > (TBI Only) 104.4 kPa
Async to Sync if RPM > (TBI Only) 6375 RPM
Sync to Aysnc if MAP > 104.1 Kpa
Sync to Async if RPM > 6350 RPM

And for completeness, a link to get the paper with the jumper mod and a pfi definition file:
http://www.gearhead-efi.com/Fuel-Inj...ull=1#post2855

**rsicard** · 02-13-2015

Originally Posted by 1project2many

I can only provide the information found in the HPTuners MPFI conversion thread:

You've already done this, I believe, based on the info I've posted previously.

And for completeness, a link to get the paper with the jumper mod and a pfi definition file:
http://www.gearhead-efi.com/Fuel-Inj...ull=1#post2855

1Project2many:

Again, thanks for your input. Have not made the changes to the ECU binary file that you posted. Will do so and get back with any concerns. That is quite a number of (software) changes to make to the ECU binary file. As for the link at the bottom of the post, I need to go look for the PFI definition file. Will look yet don't quite understand the "PFI definition file". Please clarify. Thanks.

**Nasty-Z** · 02-13-2015

Originally Posted by rsicard

1Project2many:

Again, thanks for your input. Have not made the changes to the ECU binary file that you posted. Will do so and get back with any concerns. That is quite a number of (software) changes to make to the ECU binary file. As for the link at the bottom of the post, I need to go look for the PFI definition file. Will look yet don't quite understand the "PFI definition file". Please clarify. Thanks.

The working 7.4 calibration that Ken posted on the HP tuners link has all of the modifications done already , it will be a good start for a MPFI setup like what you are doing . I know this as I worked with Ken when we did my 454 and then my 502 in my '94 Dually with the Edelbrock MPFI setup .

TOM

**rsicard** · 02-17-2015

Originally Posted by Nasty-Z

The working 7.4 calibration that Ken posted on the HP tuners link has all of the modifications done already , it will be a good start for a MPFI setup like what you are doing . I know this as I worked with Ken when we did my 454 and then my 502 in my '94 Dually with the Edelbrock MPFI setup .

TOM

TOM: Must have missed something from what you said about Ken posted a 7.4 calibration. Please steer me towards that calibration that already has the modifications. Thanks a bunch.