- Calibrations
- Getting Started with DIY Custom Cals
The basics (and just the basics) for getting started doing your own custom cals.
So, you want to build your own cal for your car? Here's a breakdown of the basics of what is required and possible.
Overview of the ECU structure:
All of the Chrysler computers from the T1/T2/T3/T4 era store both the operating code and calibration data on the same memory chip. The factory used an EPROM (Erasable-Programmable-Read-Only-Memory). This chip is a 28-pin ceramic DIP with a quartz window. When the window is exposed to a specific wavelength of UV light for a short time, it will erase the contents of the chip. In all generations, the EPROM is soldered into place. In the case of the SMEC and SBEC, the entire computer is also encased in a potting compound to protect it from the elements.
The operating code (what I call the 'codebase') is in fact the code that reads and scales the various sensors, and calculates the operating parameters based on the calibration data. The calibration data is tables, and constants in various formats.
To do your own cal, 1st, you'll need a computer suitably modified for accepting a custom cal (chip).
Getting at the chip:
Required tools/materials:
Exacto knife or razor blade
Small nylon/plastic scraper (SMEC or SBEC only)
LM - In the case of the LM, the modifications are limited and relatively simple. The LM has no potting compound and the EPROM is exposed. But, you still must remove the EPROM and replace it with a socket. If you have an LM, you can skip below to 'Removing the chip:'.
For both the SMEC and SBEC, the potting compound will need to be cut away from the EPROM so that it can be de-soldered and removed. Be sure to remove the potting from both sides of the board. Use an exacto knife or razor blade to carefully cut an outline of the chip about 1/8" larger than the pin footprint. The potting compound is relatively soft and easy to remove. I use a small screwdriver and a nylon scraper to carefully remove the potting compound from the chip and board (both sides). Then, I cut the chip leads with the Dremel and pull it out.
Removing the chip:
Required tools/materials:
Soldering Iron (available from various places, including Radio Shack)
Solder sucker or solder wick (available from Radio Shack)
Dremel (optional) with cutoff wheel
Small pliers or hemostat (available from Radio Shack)
Now, you can remove the chip. The simplest method is to cut the EPROM leads with a Dremel cutoff wheel (being careful not to damage the computer board, which may render it useless), remove the chip from the board, and then de-solder the individual pins. You will need to use a solder sucker or solder wick to remove all of the solder from the thru holes. The 2nd option is to carefully de-solder the pins while still attached to the EPROM. Again, you will need to use a solder sucker or wick. The 2nd method is slightly more difficult and time-consuming simply because it is more difficult to remove the solder with the chip in the way. With either method, be careful not to overheat the ECU board. Otherwise you could risk damaging the solder pads and/or traces - meaning at best a difficult repair; at worst a useless LM.
Personally, after cutting the pins with the dremel and removing the chip, I clamp a hemostat to the pin, and hit it with the soldering iron. When the solder gets soft, I pull the pin out. After removing all of the pins, I go back and heat up the thru holes and suck the solder out from the opposite side with the solder sucker.
Once you have the chip removed, make sure to clean up any remaining potting compound and/or solder rosin/debris. I use a plastic brush attached to my dremel, on the low speed setting. It removes the potting compound very nicely and cleans everything up.
Adding the socket:
Required tools/materials:
Soldering iron
Solder
28-pin socket
First, lets start with socket choice. There socket needed is a 28-pin DIP. You can get a socket at Radio Shack, but these sockets are typically not suitable for high-vibration environments. The risk is that the chip will vibrate loose while going down the road causing the engine to misfire or stall possibly damaging the chip in the process. But, they have been used with success. A better choice would be a machine-pin socket. These are available from every electronics supply (Mouser.com and Digi-key.com likely being the least expensive). These have a more precise fit to the pins on the 28-pin chip and will not vibrate loose. On the other hand, the socket or pins can wear out if you plan to insert/remove the chip many times. If you think you will be swapping chips regularly, then Id suggest an Aries ZIF (Zero-Insertion-Force) socket. These are more expensive than the Radio Shack or machine-pin sockets, but they will allow you to install the chip as many times as you want without damaging the socket or chip, and they hold the chip very securely.
Ok, now that you have the socket, you simply need to install it and solder it onto the board. The thru holes in the board should be clean and clear and the socket should drop right in. If it doesnt - dont force it; go back over the holes with the soldering iron and sucker. There is usually a notch in the socket to denote which pin is #1. There should be a 1 printed onto the ECU circuit board. Align the socket to it to avoid future confusion.
OK, now you have a socketed computer. What to do with it? Well, its kind of useless without a chip in it.
Burning the chip:
Required tools/materials:
Chip burner
Chip
.bin file to burn to the chip
First, you will need a burner. There are many types/brand available, but your best bet is to buy a Willem style burner from eBay. The cost is ~$40 (or less), and it will burn/erase every type of chip that could be used in our ECUs (and then some). Also, the Willem software is free and open-source.
Also, before I go into burning the chip, I want to talk about the various chips that can be used. The original chip used was a 28-pin DIP, 16k or 32k EPROM (Erasable-Programmable-Read-Only-Memory). An EPROM is a ceramic chip with a quartz window. The window is used to erase the chip by exposure to UV light. A specific type (wavelength) of UV light is required. Commercial UV erasers are about $100 minimum. They are fully enclosed and usually incorporate a timer to keep from over-exposing the chips. But, you can use a handheld "germicidal" UV light. They cost about $20. But, there is no protection for the user, and no timer. Also, they are much lower power. So the danger of skin exposure is less, but they also take longer to erase the chip (~10min). A regular fluorescent bulb or even a "plant" light won't do the job. Exposure to sunlight, in theory, can erase the EPROM. But, the required exposure time is ~10 hours not very practical. The price of flash memory chips is decreasing rapidly. As such, they are a very viable alternative to the original EPROM chips originally used by Chrysler. Also, they do not require the use of a UV eraser. But, they will require a burner capable of erasing them.
Chip choices:
LM:
27C128 16k 28-pin Ceramic DIP
27C256 32k 28-pin Ceramic DIP
29C256 32k EEPROM (Electrically-Erasable-PROM) 28-pin Plastic DIP; These are out-of-production in the 28-pin DIP and as such are expensive when you can find them.
27SF512 64k Flash Memory 28-pin Plastic DIP; These are actually cheaper than the 27C256 at this point in time.
SMEC:
27C128 16k 28-pin Ceramic DIP; only for the 16k bins (T2/S60 based)
27C256 32k 28-pin Ceramic DIP
29C256 32k EEPROM (Electrically-Erasable-PROM) 28-pin Plastic DIP; this chip is out-of-production in the 28-pin DIP and as such are expensive when you can find them.
27SF512 64k Flash Memory 28-pin Plastic DIP; this chip is actually cheaper than the 27C256 at this point in time.
SBEC:
87C257 32k 28-pin Ceramic DIP; this is currently the only chip available for use in the SBEC. This chip is the same as the 27C256, except that it has a built-in address latch. There are no EEPROM or Flash memory chips with similar configuration available.
I wont get into the support of the burner. The Willem has a good form with a ton of information. And, there are TM guys that can guide you if you get stuck.
Offsets: Heres where things can get confusing. Ill try to explain as simply as possible, without confusing you with too much HEX or hacker jargon. Interrupt vectors are special subroutines called when certain outside events happen (for example, the HEP input is triggered). The microprocessor expects the end of the memory space to contain the locations of these special routines. If these are NOT at the correct address, the code will likely not run at all. The address of these routines is always located at the end of the .bin file. So, the offset is required when the .bin file is smaller than the chip size. For example, if the .bin is 16k (LM or T2/S60 SMEC), and youre burning it to a 32k chip, you need to offset the .bin by 16k to put it at the end. If you are burning a 16k .bin to a 64k chip (27SF512), you need to offset the .bin by 48k. Heres a breakdown:
.bin size Chip size offset (hex)
16k 16k 0 (0x0000)
16k 32k 16k (0x4000)
16k 64k 48k (0xC000)
32k 32k 0 (0x0000)
32k 64k 32k (0x8000)
This is the offset you put into the programmer when you load it. Heres where it can get more confusing this is different from the D-Cal offset due to the location of the chip in the microprocessors memory space. Dont get the 2 offsets confused.
Once you get the offset configured correctly, simply load up the chip and burn it according to your burners instructions.
Now, just load the chip into your newly socketed ECU, plug it back into the car, and give it a try. Id suggest starting with the stock .bin for your car first, before trying to tune. This will help rule out any problems with the chip or ECU modification.
Coming soon
Making/modifying your own binary (.bin) file
Setting up your LM/SMEC/SBEC to be 'flashable'
Datalogging the LM/SMEC/SBEC
So, you want to build your own cal for your car? Here's a breakdown of the basics of what is required and possible.
Overview of the ECU structure:
All of the Chrysler computers from the T1/T2/T3/T4 era store both the operating code and calibration data on the same memory chip. The factory used an EPROM (Erasable-Programmable-Read-Only-Memory). This chip is a 28-pin ceramic DIP with a quartz window. When the window is exposed to a specific wavelength of UV light for a short time, it will erase the contents of the chip. In all generations, the EPROM is soldered into place. In the case of the SMEC and SBEC, the entire computer is also encased in a potting compound to protect it from the elements.
The operating code (what I call the 'codebase') is in fact the code that reads and scales the various sensors, and calculates the operating parameters based on the calibration data. The calibration data is tables, and constants in various formats.
To do your own cal, 1st, you'll need a computer suitably modified for accepting a custom cal (chip).
Getting at the chip:
Required tools/materials:
Exacto knife or razor blade
Small nylon/plastic scraper (SMEC or SBEC only)
LM - In the case of the LM, the modifications are limited and relatively simple. The LM has no potting compound and the EPROM is exposed. But, you still must remove the EPROM and replace it with a socket. If you have an LM, you can skip below to 'Removing the chip:'.
For both the SMEC and SBEC, the potting compound will need to be cut away from the EPROM so that it can be de-soldered and removed. Be sure to remove the potting from both sides of the board. Use an exacto knife or razor blade to carefully cut an outline of the chip about 1/8" larger than the pin footprint. The potting compound is relatively soft and easy to remove. I use a small screwdriver and a nylon scraper to carefully remove the potting compound from the chip and board (both sides). Then, I cut the chip leads with the Dremel and pull it out.
Removing the chip:
Required tools/materials:
Soldering Iron (available from various places, including Radio Shack)
Solder sucker or solder wick (available from Radio Shack)
Dremel (optional) with cutoff wheel
Small pliers or hemostat (available from Radio Shack)
Now, you can remove the chip. The simplest method is to cut the EPROM leads with a Dremel cutoff wheel (being careful not to damage the computer board, which may render it useless), remove the chip from the board, and then de-solder the individual pins. You will need to use a solder sucker or solder wick to remove all of the solder from the thru holes. The 2nd option is to carefully de-solder the pins while still attached to the EPROM. Again, you will need to use a solder sucker or wick. The 2nd method is slightly more difficult and time-consuming simply because it is more difficult to remove the solder with the chip in the way. With either method, be careful not to overheat the ECU board. Otherwise you could risk damaging the solder pads and/or traces - meaning at best a difficult repair; at worst a useless LM.
Personally, after cutting the pins with the dremel and removing the chip, I clamp a hemostat to the pin, and hit it with the soldering iron. When the solder gets soft, I pull the pin out. After removing all of the pins, I go back and heat up the thru holes and suck the solder out from the opposite side with the solder sucker.
Once you have the chip removed, make sure to clean up any remaining potting compound and/or solder rosin/debris. I use a plastic brush attached to my dremel, on the low speed setting. It removes the potting compound very nicely and cleans everything up.
Adding the socket:
Required tools/materials:
Soldering iron
Solder
28-pin socket
First, lets start with socket choice. There socket needed is a 28-pin DIP. You can get a socket at Radio Shack, but these sockets are typically not suitable for high-vibration environments. The risk is that the chip will vibrate loose while going down the road causing the engine to misfire or stall possibly damaging the chip in the process. But, they have been used with success. A better choice would be a machine-pin socket. These are available from every electronics supply (Mouser.com and Digi-key.com likely being the least expensive). These have a more precise fit to the pins on the 28-pin chip and will not vibrate loose. On the other hand, the socket or pins can wear out if you plan to insert/remove the chip many times. If you think you will be swapping chips regularly, then Id suggest an Aries ZIF (Zero-Insertion-Force) socket. These are more expensive than the Radio Shack or machine-pin sockets, but they will allow you to install the chip as many times as you want without damaging the socket or chip, and they hold the chip very securely.
Ok, now that you have the socket, you simply need to install it and solder it onto the board. The thru holes in the board should be clean and clear and the socket should drop right in. If it doesnt - dont force it; go back over the holes with the soldering iron and sucker. There is usually a notch in the socket to denote which pin is #1. There should be a 1 printed onto the ECU circuit board. Align the socket to it to avoid future confusion.
OK, now you have a socketed computer. What to do with it? Well, its kind of useless without a chip in it.
Burning the chip:
Required tools/materials:
Chip burner
Chip
.bin file to burn to the chip
First, you will need a burner. There are many types/brand available, but your best bet is to buy a Willem style burner from eBay. The cost is ~$40 (or less), and it will burn/erase every type of chip that could be used in our ECUs (and then some). Also, the Willem software is free and open-source.
Also, before I go into burning the chip, I want to talk about the various chips that can be used. The original chip used was a 28-pin DIP, 16k or 32k EPROM (Erasable-Programmable-Read-Only-Memory). An EPROM is a ceramic chip with a quartz window. The window is used to erase the chip by exposure to UV light. A specific type (wavelength) of UV light is required. Commercial UV erasers are about $100 minimum. They are fully enclosed and usually incorporate a timer to keep from over-exposing the chips. But, you can use a handheld "germicidal" UV light. They cost about $20. But, there is no protection for the user, and no timer. Also, they are much lower power. So the danger of skin exposure is less, but they also take longer to erase the chip (~10min). A regular fluorescent bulb or even a "plant" light won't do the job. Exposure to sunlight, in theory, can erase the EPROM. But, the required exposure time is ~10 hours not very practical. The price of flash memory chips is decreasing rapidly. As such, they are a very viable alternative to the original EPROM chips originally used by Chrysler. Also, they do not require the use of a UV eraser. But, they will require a burner capable of erasing them.
Chip choices:
LM:
27C128 16k 28-pin Ceramic DIP
27C256 32k 28-pin Ceramic DIP
29C256 32k EEPROM (Electrically-Erasable-PROM) 28-pin Plastic DIP; These are out-of-production in the 28-pin DIP and as such are expensive when you can find them.
27SF512 64k Flash Memory 28-pin Plastic DIP; These are actually cheaper than the 27C256 at this point in time.
SMEC:
27C128 16k 28-pin Ceramic DIP; only for the 16k bins (T2/S60 based)
27C256 32k 28-pin Ceramic DIP
29C256 32k EEPROM (Electrically-Erasable-PROM) 28-pin Plastic DIP; this chip is out-of-production in the 28-pin DIP and as such are expensive when you can find them.
27SF512 64k Flash Memory 28-pin Plastic DIP; this chip is actually cheaper than the 27C256 at this point in time.
SBEC:
87C257 32k 28-pin Ceramic DIP; this is currently the only chip available for use in the SBEC. This chip is the same as the 27C256, except that it has a built-in address latch. There are no EEPROM or Flash memory chips with similar configuration available.
I wont get into the support of the burner. The Willem has a good form with a ton of information. And, there are TM guys that can guide you if you get stuck.
Offsets: Heres where things can get confusing. Ill try to explain as simply as possible, without confusing you with too much HEX or hacker jargon. Interrupt vectors are special subroutines called when certain outside events happen (for example, the HEP input is triggered). The microprocessor expects the end of the memory space to contain the locations of these special routines. If these are NOT at the correct address, the code will likely not run at all. The address of these routines is always located at the end of the .bin file. So, the offset is required when the .bin file is smaller than the chip size. For example, if the .bin is 16k (LM or T2/S60 SMEC), and youre burning it to a 32k chip, you need to offset the .bin by 16k to put it at the end. If you are burning a 16k .bin to a 64k chip (27SF512), you need to offset the .bin by 48k. Heres a breakdown:
.bin size Chip size offset (hex)
16k 16k 0 (0x0000)
16k 32k 16k (0x4000)
16k 64k 48k (0xC000)
32k 32k 0 (0x0000)
32k 64k 32k (0x8000)
This is the offset you put into the programmer when you load it. Heres where it can get more confusing this is different from the D-Cal offset due to the location of the chip in the microprocessors memory space. Dont get the 2 offsets confused.
Once you get the offset configured correctly, simply load up the chip and burn it according to your burners instructions.
Now, just load the chip into your newly socketed ECU, plug it back into the car, and give it a try. Id suggest starting with the stock .bin for your car first, before trying to tune. This will help rule out any problems with the chip or ECU modification.
Coming soon
Making/modifying your own binary (.bin) file
Setting up your LM/SMEC/SBEC to be 'flashable'
Datalogging the LM/SMEC/SBEC
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