Jeep SBEC PCM tuning (91-95)

Hello everybody,

I spent several hours reading this thread and I began to get excited and reached a point of ecstasy with @a_kelley and @sev80 work, as well as with the follow-up and promotion of the project by @GarageBuild , but as I approached the final page I began to Filled with mixed feelings about the unfinished project, I was ready to take out my money and pay for this great modification. And now I am intrigued to know the status of the project.

Any news or progress with the project?

thanks for the time you spend helping
 
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I continued some more with the supercharger, got an m62 instead of the m45, with a 60mm pulley. It's doing 0.5 bar boost but I ran out of injector room. Also between 2000 and 2750rpm it runs real lean as it it is still in closed loop but can't manage to compensate as it's at 0.4 bar boost.
 

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RCD said:
Hello everybody,

I spent several hours reading this thread and I began to get excited and reached a point of ecstasy with @a_kelley and @sev80 work, as well as with the follow-up and promotion of the project by @GarageBuild , but as I approached the final page I began to Filled with mixed feelings about the unfinished project, I was ready to take out my money and pay for this great modification. And now I am intrigued to know the status of the project.

Any news or progress with the project?

thanks for the time you spend helping
Click to expand...
Sorry friend. I went ahead and edited my first message on page 1 to update what happened on this project so the next person doesnt eventure down here and find nothing.

Basically this is what happened:

Akelly and I got pretty far into this project and then eventually Akelly moved on so we never finished it. We got as far as building a DOS based toolset to flash the ST based late 94-95 SBECIIs and Akelly wrote some rudimentary tools to read and modify fueling/spark tables for SBECs but it was very alpha stage and after that the project kind of stopped. I ended up paying Chris Jensen to write me a tune, so my efforts on this project waned as I dont have enough deep knowledge in assembly language to continue Akelley's work and I already had a professionally written tune for my rig.

I have some of the code and work we did still but Akelley has moved on and sold all his jeep stuff. There's some good contributions towards the last 2-3 pages of this thread with schematics and other stuff, but any work or mention of work you find in these pages were never completed.

If YOU have the technical prowess and want to pick up where we left off from, I'm happy to work together.
 
RDC_ZJ said:
Thanks. It's not perfect, probably never will be, but given the original will likely never see the light of day this might be useful to someone at some point. It's about as accurate as I can get it without spending loads more time on it and poking around inside of a working one. I actually rebuild the PCB from the schematic, in the same software that I use to make the schematic, to make sure the traces match the original board and that things are connected correctly.

View attachment 404862 View attachment 404863

If anyone notices anything wrong or has any info on anything in there, like U9 in the power supply, let me know. I spent too much time as it is looking thru as many old Motorola datasheets for SMPS chips that I could find and nothing came close.
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nice project! I have been contemplating building a plug and play replacement ECU based on the speeduino project, somebody already figured out the crank and distributor sensors and all the circuits have been designed just need to add an 8 volt regulator and layout the board. Tuning a speeduino is just connect it to a laptop and go for a drive.
 
AdamRosas said:
nice project! I have been contemplating building a plug and play replacement ECU based on the speeduino project, somebody already figured out the crank and distributor sensors and all the circuits have been designed just need to add an 8 volt regulator and layout the board. Tuning a speeduino is just connect it to a laptop and go for a drive.
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this would be super sweet. got any links to where the crank and distributor sensors have been figured out? i'd love to read on it
 
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Here is some more info. 00013 is to deteremine which gearbox type and there is thepcm software numbers (some have two different ones)
 
Winnox said:
View attachment 445240 Here is some more info. 00013 is to deteremine which gearbox type and there is thepcm software numbers (some have two different ones)
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Winnoc,

Awesome work. Can you share your latest maps youve built? It's interesting looking through this
 
AdamRosas said:
I built a programming interface out of a relay board and a boost converter and have started working on
erasing and writing the EPROM without de-soldering the chip. I can get the chip ID and erase the ST chips
but was having problems erasing the Toshiba chips. I have a DOS era EPROM programmer that can
program the Toshiba chips, so I got a logic analyzer and wired it up, but I still had issues with the
code. Sometime after I made the post I figured out the problem, I just needed to add a little delay to the
code to allow the 20 volts to be applied to pin 45 before interacting with the EPROM, I deleted the post
because it became irrelevant. I'm pretty confident I can program the ST EPROM's and likely the Toshiba
chips as well. We'll see, how using relays to switch between data and programming voltage, will work out.

View attachment 364206
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Adam,


so im trying to understand how this works, do you have a wiring diagram for this interface you built? I see a few pics on Github but nothing more about how it's wired up or what parts are used? Will any usb relay work with the utility you worte? I assume the usb controllers have their own microcontrollers that needs to match the one you used.

Would appreciate your help! I want to flash a couple of my toshiba based sbec's!
 
So I've been trying to get a hold of PoulSirus from the Russian Jeep forums since 2022. He wrote the CDT and JMDRB tools that emulate a DRBII on a windows machine. Though I was unsuccessful in reaching him, I posted his CDT tool on Jeepforums and he must have found it years later and recently posted in the thread. I was thrilled to find it.

He posted a HUGE repository including the source code for CDT and JMDRB (I think theyre the same tool, one is russian, the other is english). The repository includes all of his research and files on the SBEC computers. There's tons of BIN files, datasheets, write ups, and the source code for his CDT and JMDRB tools.

It is very nice of him to share this with the Jeep forum. I am posting it here as well. It's like the oracle of SBEC stuff from all around the internet dating way back. He even has copies of CHEM and D-cal that the turbo mopar guys (and even before them) were using to tune their non jeep SBECs. He's gone as far as dumping the code for the ZJ's overhead console and going through it.


Here is a link to the download. I hope this helps everyone.

disk.yandex.ru

chrysler.zip

Посмотреть и скачать с Яндекс Диска
disk.yandex.ru disk.yandex.ru

If anyone wants to dig through this. I did invite Poul to post here as well and hope he can share more of his knowledge.

Maybe Adam can add all this stuff to his Github
 
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Adam, I got your flashing interface built with the relay board/boost buck. I got it to bootstrap the SBEC just fine and in boostrap mode, I can use the CDT tool (that I poosted in the zip file above) to communicate with the SBEC just fine while running SBEC_ON but when I got to use your utility, it seems like its not reading back the same bytes it's sending and erroring out.

Running any of your utilities will bootstrap, begin to upload the code but then error out.

I scoped the TX line and it looks fine, the levels look nice and square. I'm out of ideas on why your programs wont work.

I know you haven't been on here in a while but hoping you'll see this one day and help out. Wish I had your email address, no other way to get hold of you!

IMG_6797.jpg


IMG_6798.jpg


IMG_6796.jpg
 
The fact that you received something from the ECU is pretty encouraging.

I took the usb to serial adapter I am using apart, I has a second line driver chip, the data sheet claims that it boosts the line voltage to 10v and provides short circuit, over voltage protection and ESD protection.
Also switching the serial port with a relay is very noisy the capacitor is an attempt to filter the noise a bit and you may have to experiment with the value.

this is the usb to serial adapter I used

you can also find a board on aliexpress that appears to be very similar

20251123_155533.jpg
 
Winnox said:
View attachment 445240 Here is some more info. 00013 is to deteremine which gearbox type and there is thepcm software numbers (some have two different ones)
Click to expand...
the ECU is using CRC8 to checksum the EPROM, CRC 8 just adds all the bytes together to get an 8 bit sum then compares it to byte 5 through a subtraction operation and if the calculated sum and byte 5 are equal the checksum function returns if the checksum fails then the ECU stores error code 35, if you change anything in the EPROM the checksum should be recalculated so the checksum function succeeds and you don't always have and error code stored. I'm choosing to keep the software number the same and storing a correction byte at byte 12 (0x0C).
 
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