Tuning '94 chev Suburban Big Block

[rsicard]

Rolly... You're over thinking this!




A scalar, by any other name, still does the same job.

Understand. The description in the LH column is different than what is presented in TunerPro for the four letter code in the 16197427 ECU. It is really difficult to get the confidence that performing the change in the binary will yield the appropriate binary for the MPFI (batch fire mode) in the 489 Big Block. There must be significant variable(s) for selecting going from TBI to MPFI. Have not yet seen these significant variables. There is one variable that describes CID for one cylinder. When multiplying by 8 cylinders, the total displacement does not work out. Hard to build confidence.

[dave w]

I think the Edelbrock binary (.bin) file is not for the 16197427 computer, it's only 32K in size? The 16197427 .bin file is 64K in size. Can you post the definition file (.xdf) you are using with the Edelbrock .bin file?

The MPFI conversion is not easy for a beginner. Generally, the MPFI conversion is not the first ever experience someone starts off with. Generally, a beginner will start off with a completely stock or nearly stock engine with a completely stock binary (.bin) to learn TunerPro and learn the parameters of the .bin file. The learning curve you have set out for yourself, by choosing to do a MPFI conversion as your first .bin has put you on an extremely steep or nearly vertical uphill learning curve.

Myself and other members here at gearhead-efi.com can provide compen$ated help if you would like to go that route? Maybe it would be a good plan for you to get the help of a "hired gun" to get you up to speed and help you build confidence?

dave w

[1project2many]

Understand. The description in the LH column is different than what is presented in TunerPro for the four letter code in the 16197427 ECU. It is really difficult to get the confidence that performing the change in the binary will yield the appropriate binary for the MPFI (batch fire mode) in the 489 Big Block.

I get that. GM never released the 7427 with PFI. Even the Edelbrock calibrations I've seen are not configured exactly the same as GM typically did with PFI swaps. What we talk about here is a combination of information from several sources that attempts to make the swap in the way we think GM would do it. This is not a road frequently travelled and over the years the path has varied as well as the results. Unlike Avionics, there is no program here to ensure you are not taking a risk before you are allowed out into the world. It's ok, though. If something goes wrong with the car you can pull it over and figure out what happened. ;)

There must be significant variable(s) for selecting going from TBI to MPFI. Have not yet seen these significant variables.

I'm not sure what you're looking for. There is no single value that makes the switch work. A successful conversion involves changing multiple values that work together to provide correct fuel in all driving conditions. The information Dave provided gives you the best starting point you will get.

There is one variable that describes CID for one cylinder. When multiplying by 8 cylinders, the total displacement does not work out.

Huh??? Stock BBC cal value is 56.66. 56.66 * 8 is 453.28. Actual displacement is 453.96. How much closer does the value need to be? Maybe you are expecting a level of precision from the tune and the ecm that really aren't there??

As far as changes related to injector strategy you will find that individual cell-by-cell tuning may be required after switching to "PFI Mode." Although the ecm calculates the correct amount of fuel to deliver based on calculated airflow and the number of injection pulses per revolution, it is not able to account for changes that occur because the manifold is not fuel soaked, because fuel is delivered at the valve, because response time during acceleration and deceleration change with the location of the injectors. When moving from four or two pulses to one, you might find that incorrect voltage compensation values meant to adjust desired "on" time affect driveablility in a dramatic way. This is another value the ecm cannot fix on its own. Additionally, you may need to do a "sanity check" on the values Dave W has posted to ensure they will work for your engine configuration. Watching the scan tool, looking at IPW and other related values is critical to help diagnose what happened.

FWIW, one of the best and most talented "ecm hacker" type guys I knew was in Avionics. Although he spent many, many hours teaching himself code he also had an advantage over all of us trying to decipher GM code back then. Because he had access to Motorola documentation, he found that many of the tech sheets for Motorola chips and circuits designed for automotive use came with example computer code. Quite often that code and the circuit matched GM equipment very closely. Where many of us had to work with dealership repair technician service literature and do our best to RE the circuits and the code, this individual had access to insider notes from the guys who designed and often built the parts GM was using. Maybe none of that information is available today but if I had access to that library I'd be searching for anything related to GM ecm's.

[rsicard]

I think the Edelbrock binary (.bin) file is not for the 16197427 computer, it's only 32K in size? The 16197427 .bin file is 64K in size. Can you post the definition file (.xdf) you are using with the Edelbrock .bin file?

The MPFI conversion is not easy for a beginner. Generally, the MPFI conversion is not the first ever experience someone starts off with. Generally, a beginner will start off with a completely stock or nearly stock engine with a completely stock binary (.bin) to learn TunerPro and learn the parameters of the .bin file. The learning curve you have set out for yourself, by choosing to do a MPFI conversion as your first .bin has put you on an extremely steep or nearly vertical uphill learning curve.

Myself and other members here at gearhead-efi.com can provide compen$ated help if you would like to go that route? Maybe it would be a good plan for you to get the help of a "hired gun" to get you up to speed and help you build confidence?

dave w

Yes I have limited experience. Right now a converted 350 Vortec with 454 TBI, adapter, modified 4 barrel manifold on an engine stand with somewhat tuned 7427 ECU. Using early build APU1 and 27SF512 Flash Memory Chips and Moates G1 adapter. Second, tuned 1995 350 C1500 pickup. Smoothed the VE fuel map and it runs near stoic most of the time. Also at the earliest, modified a 454 big block to 489 cuin and installed Edelbrock Intake (batch fire MPFI) and fuel pump. Have had some exposure at tuning TBI/MPFI systems. Would like to learn more about tuning with TunerPro. In post number 65, you provided a sample from the Constants variables.

What is really of concern is, from what is seen in TunerPro with either the 1994-1995 0D or 0E broadcast codes, the sample injector FLOW RATES in the PDF file(s) are not included in the Scalers, Flags or Tables. In the scalars portion, under engine constants, there are listings for CPI, TBI and MPFI. Yet how is MPFI Selected?

I understand that I could pay you to come up with a binary file. How much would it cost? Yet I would like to learn how to do same. It is becoming obvious that TunerPro is a high level front end wherein changes to one variable will change an associated Byte or Word in the Binary file. To me, it is a matter of interpretation of the terms of reference being used when speaking of variables in TunerPro.

I just received a breakout board for the purpose of bench testing the ECU to see what happenes when changing certain variables in TunerPro. Already have the ECU connectors, with pig tails, for the 7427. Now it is a matter of connecting the pigtails to the breakout. Already have purchased MegaSquirt Stimulator Kit which should be here next week. Then assemble same. Then connect the breakout to the Stimulator and ECU. Am experienced in electronics (38+ years in Aviation Electronics) and this should not be that hard to do.

[dave w]

I think the attached .bin file will be EXTREMELY HELPFUL. The attached .bin has been tested, and is in use somewhere in North America.

The original .bin file I modified for MPFI is from a very well known aftermarket EFI company. The attached .bin file requires the Memcal Jumper Modification, and the solid wire modification to the sense resistors inside the PCM!!!

Standard Disclaimer; Use at your own risk.

dave w

[rsicard]

I think the attached .bin file will be EXTREMELY HELPFUL. The attached .bin has been tested, and is in use somewhere in North America.

The original .bin file I modified for MPFI is from a very well known aftermarket EFI company. The attached .bin file requires the Memcal Jumper Modification, and the solid wire modification to the sense resistors inside the PCM!!!

Standard Disclaimer; Use at your own risk.

dave w

Dave: Thanks very much for the reply. I will try that .bin file. Not sure what the attached .JPEG file is to represent. The attached image file is what was gleaned from the MPFI Modified $31 Aftermarket 454 Chip.BIN. Don't understand the vast differences between the two.

[sturgillbd]

Rolly,
The bin Dave posted is a $31 Mask. You need to load the $31 XDF. Different mask will show different values because the parameters are in different locations within the bin file.
Hope this helps,
Brian

[rsicard]

You guys are awesome. Thanks for the reply.

Rolly

[rsicard]

Rolly,
The bin Dave posted is a $31 Mask. You need to load the $31 XDF. Different mask will show different values because the parameters are in different locations within the bin file.
Hope this helps,
Brian

You guys as AWESOME. Thanks for the reply.

Rolly

[dave w]

I've attached the $31 .xdf and $31 .adx files you need for TunerPro RT.

dave w

[1project2many]

Rolly,
The bin Dave posted is a $31 Mask. You need to load the $31 XDF. Different mask will show different values because the parameters are in different locations within the bin file.

Yes! Maybe this helps explain some things.

Rolly, the different chip ID's you see, $31, $0E, and $0D, are identifiers for where the specific variables are arranged within the calibration. When you load an XDF, Tunerpro is instructed to treat each variable in each defined location a certain way. There will be a variable (or table) name and a conversion factor so the binary value represents a number we understand. If a .bin with the wrong mask ID is loaded then Tunerpro does not do any sanity checking. It will treat the variables as it has been instructed, giving each the predefined name and displaying the value according to the conversion formula. It could treat temperature as timing, throttle values as O2 parameters, or fuel injector size as rpm. For many this issue never comes up but unfortunately the 7427 and sister pcm's share three commonly used mask files.

[rsicard]

Again, you guys are AWESOME! Thank VERY much for the attached files. Exactly what was needed

Rolly

[rsicard]

I've attached the $31 .xdf and $31 .adx files you need for TunerPro RT.

dave w

Again, you guys are AWESOME. Thank ever so much for the attached files. Lesson learned.

Rolly

[rsicard]

I've attached the $31 .xdf and $31 .adx files you need for TunerPro RT.

dave w

Dave: Now I have confidence with the binary file and attached XDF and ADX files. Many thanks to you and the other fellows that chimed in. Attached is a graphic of the Injector Fuel Flow Scalars. The values look VERY reasonable. Thanks again.

Rolly

[rsicard]

I've attached the $31 .xdf and $31 .adx files you need for TunerPro RT.

dave w

Dave: Thanks again. The 1994 Suburban with big block 489 cuin Edelbrock MPFI conversion is running very well. It needs a little tweaking for some of the rich and lean conditions yet they are not that bad. Thanks to all of you fellows for all your help.

Rolly