I'll have to take a look into that. Do you happen to know the specs on it? Stall speed, diameter, years used?

BTW, I also blew $20 on TunerCats database of prom ID codes. You feed it the four character broadcast code and it spits out the model year, engine rpo, emmissions rpo'*, platform usage, and whether or not it was superceeded by another prom. All the data is probably from GM'* tech bulletins, but it'* handy to have when scouring the DIY sites looking for other bins to compare against.

Another reason to stick with the old style ECM. They are not sophisticated in comparison to more modern OBD-II PCM'*, but their simplicity when it comes to making changes has it'* advantages. With only 32K available for both code and data, how sophisticated can it be

Which reminds me, I have to go scour the local U-pull-it yards this weekend to get some more cannon-fodder for the eprom burner. I'm going to carve up one calprom and make a zif socketed one.

My 89 fleetwood has the 440t4 with a 4.5L v-8. I'm not sure about the torque convertor deal, but it has one helluva cooler on it. And mine has 240k on i'm sure everything original. So that trans has seen some abuse, and none of this car looks touched. It might have a different gear ratio, because I believe it goes like this, 1-2 39, 2-3 65, 3-4 ??. Speedo stops at 85, but flashes faster the faster you go. I think I hit 100, but that pos doesn't feel the least bit safe. Considering the RPM-band, I have no idea what gear ratio might be in this thing. But it'* worth a shot. I bet that 440 could hold up if you took care of it... 80k is a bit much, but if you can't break it, what'* the point in having it?

from what i have found the Caddy'* with the 4.9L that had a 2.73, 2.97, or a 3.33 all had a 1825 stall

and Curt does have the 1420 stall with a 2.84 Diff and a 35/35 chain :P

Thanks all

I'll file that knowledge about a higher stall speed TC for later use. The extra 400rpm in stall speed would come in handy on drag strip launches

The first of the special tuning bits showed up in the mail yesterday (An adapter from Craig Moates for reading the EPROM while it is still soldered into the calprom) It'* not absolutely needed, but it makes the job of reading stock proms a little easier. I still want to sacrifice one calprom by adding a zif socket to it...so I can quickly erase, burn, and swap new 27C256 eproms into the car.

I'm digging around the house this morning looking for enough parts to get my old passive backplane PC system running again. It'* the only PC I have left with an ISA slot, which is what my eprom reader/burner needs to operate. (I splurged a little this week and bought a new USB eprom burner/reader...but it is in transit somewhere between Germany and here)

Ok, for the easily amused, here'* the stock ASSK Calibrator prom in binary along with a text file dump of all the tables and constants.

http://clmartin.no-ip.org/90_Bonneville/ASSK_Stock.txt

http://clmartin.no-ip.org/90_Bonneville/ASSK_Stock.bin

If you want to burn your own, you'll need a 27C256 eprom or an erased calibrator.


As a comparison, here'* the calibrator GMTuners ginned up based on the ASSK prom with the addition of a blower on the stock LN3:

http://clmartin.no-ip.org/90_Bonnevi..._Blower_v1.txt

http://clmartin.no-ip.org/90_Bonnevi..._Blower_v1.bin

You can see a lot of differences right off the bat. A lot of the switch table stuff was by my specific request. Most of the error codes have been turned off. In the constants table the RPM fuel cutoffs have been raised and the VSS cutoff moved up to the top peg to disable the cutoff.

The rest of the tables are based on his judgement about the combination of an LN3 and a 94 M62 blower tacked on top. This set of values will be the basis from which I'll be working. Because the swap changed directions, I don't expect his changes to the calibration to be right, but they are as good a place as any to start from.

I kinda got things bass-akwards..I guess I should show you all how to get at the ECM and what'* "In The Black Box" (actually, ours are bare aluminum )

First off, to get to the ECM, you will need a 7mm socket, a 10mm socket, and a 1/4" socket. You'll also need an 8mm wrench or socket to disconnect the battery.

Open up the passenger side door and here'* what you see...



The ECM is behind the glovebox on the far right corner of the dash. You get at it by removing the two wing-nuts on the black trim panel (down near the carpet) and the two trim screws just behind the glovebox.

With that, the plastic trim panel will drop down. Disconnect the courtesy light and you can get the trim panel all the way down to the floor. The ECM is held in by one 10mm nut and a little plastic flap on the lower left corner. Disconnect the three electrical connectors, remove the nut, and the ECM can slide up, out, and all the way out from under the dash.




Now, to get at the calibrator prom, the little aluminum flap/cover comes off. Remove the two 1/4" sheetmetal screws and off it comes. Open the locking levers on either end of the calprom and it will pop out.




Since this is a little exploratory surgery for your amusement, I'll take the rest of the srews out of the ECM housing and you can have a peek inside: Here'* the circuit board. Towards the top is an aluminum heat-sink with all the driver circuits for the sensors and motors from the motor. On the right are some more of them. In the middle is the processor, some programmable logic arrays with Delco tags, and the socket for the CalProm.




Here'* the backside of the board...nothing much to note here, all the components are on the front of the board, the back is just solder joints and circuit traces.




Now, the stuff we are going to change is all inside the calibrator prom, so lets go pop the cover on one and take a peek inside. Four little platic tabs keep the blue plastic cover on the calprom. Gently pry them up on one end and you can remove the cover.



Inside, you find one 27C256 EPROM which contains all the software and data for the ECM (not much, it'* only 32K Bytes in size)

Next to it is a circuit board that runs the Knock Sensor. While this seems like a goofy place to put it, I guess it made sense to GM. Up until the mid 1980'*, the knock module used to be a seperate module on the firewall of the engine compartment. Then GM moved it to inside the CalProm. Probably to keep people from tampering with it.

Last two components, hiding underneath the knock module circuit board, are a pair of resistor packs that serve as the pull-up resistors for various sensor circuits.

Ok, time to read the EPROM...



Here I have the prom connected to an eprom burner/reader. I'm using Craig Moates'* adapter header to plug it into a standard 28pin DIP socket. Later on, I'll be butchering one of the proms to replace the EPROM with a 28pin ZIF socket to make swapping EPROMS a little easier.

Had a light day at work, ended up back at the house around 2:00pm. I figured I might as well do some more work on the project.

One thing I have to do is modify the calibrator prom so it is easier to change EPROMS. The ZIF socket is in the mail someplace on it'* way here, but I can still take a few of the sacrificial calproms and get them ready to use.

First, GM uses two different styles of proms. Both have the same pinout of the industry standard 27C256 EPROM. The first style is a programmable logic array chip. The second is a 27C256 EPROM. You may find either under the cover of a calprom. The difference is that the 27C256 EPROM can be erased by exposing it to UV light and is reusable. The logic array can only be burned once, so it is a disposable item. You can spot the difference by peeling off the little silver "DECO" tag with the broadcast code on it. If there'* a clear, round, window underneath then it is an EPROM and can be reused.

Second challenge is getting the sucker off the CalProm without destroying either it, or the CalProm'* contacts. To do this, use your fingers to push the knock circuit board out of the way (there'* a little bit of overlap of the board over the EPROM, so it needs to be moved a little to let the EPROM come up.) Next, take a small, flat bladed, screwdriver and gently pry up on both ends of the eprom. That will lift the eprom out of the plastic Calprom and bend the leads up a little. It should look like this:



With the EPROM raised up, take the tip of a hot pencil style soldering iron and touch it to each pin of the EPROM, right where the contact from the CalProm is soldered to it. wait a split-second and use the tip of the iron to push the contact back into the socket. Keep doing this on all 28 pins of the EPROM. Try to pry the EPROM up a little more, most of the pins will be free of the contacts, the few that are still tack soldered to the contacts just need the tip of the iron a second time to release them. When you are done, you should have a CalProm that looks like this:




Ok, now we need to really tin the contacts with solder so the ZIF socket has pads to mount to. Normally you would just insert the ZIF socket into the contacts and solder them in from the back, but the way the CalProm'* plastic carier is made, that isn't possible. So the next best thing is to turn the contacts into pads, bend the socket'* leads out at a 90 degree angle away from the socket, then solder the socket in place from the top. (I'll have photos of this process as soon as the socket gets here! )

Here'* the calprom with it'* contacts filled with solder, ready to have a socket solder into it.

Yeah, they didn't use the logic arrays very often. Pull a dozen CalProms and you might hit one with a logic array instead of the EPROM. I'm surprised they didn't use them more often, since they are cheaper.

Doesn't matter from our perspective though, if your calprom has the array, pitch it in the trash and replace it with an EPROM and keep on truckin with the project.

Little ticked this morning. The zif sockets I ordered got mis-routed by UPS and are back in Mesa, AZ to start their journey all over again. (Which means the clowns in brown might actually get them to my doorstep next Tuesday instead of yesterday.)

Time to make a run to Orlando and visit Skycrafters.