Hey guys I need some help identifying this memcal,(you guys that have seen multiple type ecms/applications). I got this thing from ebay as a corvette memcal, and in the picture, I could see the knock sensor circuitry, which means it had to be a 90-91 vintage(no knock circuit in memcal before 90). No sticker on prom, no biggie, didn't really care what was in the code anyway, I was gonna supply my own. So there is no marking code anywhere that means anything, because the number on the knock module doesn't really correlate to anything.....date code or something

heres the thing. It was supposed to be a corvette prom, but it has NO limp home mode resistors. I've seen '730 proms from a 4 cylinder that had no knock module, but never a memcal with a knock module but no limp mode resistors. Anyone have any ideas? I thought of maybe a 92(or 93?) vette that was LT1, but I've never seen one, so I dunno. Another long shot might be a prom from an LT5 vette? so scarce, I've never been inside one, let alone played with the ecm.....

The code inside has a funny mask ID, since its hard to tell if its a 27c128 or 27c256, I dumped the bin as both, and the mask ID(9th binary location) is $ED for the 128(more likely), but can't remember what is was for a 256 version. probably corrupted code anyway.

It's probably some some other application, but I wanna see if anyone has seen a memcal like this. One other thing, it doesn't look like someone took the parts out, I've been around electronics long enough to see that the solder joints for the knock circuit are machine made, and not resoldered.

thanks for any insight......one of those times where diy-efi.org searching might have gotten me some leads. Hope someone picks up that archive...

 

No-one has any ideas??????

 

I've never seen it before.

 

I didn't remember seeing your original post, hmm, the 15th was Friday. Missed it somehow.

If it is a 'vette memcal then the EPROM will be a 256kb. Check the maskid on that bin.

As for the netres, they should be small black plastic jobbies under the knock filter. At a minimum the ECM wouldn't see the correct cyl select if the netres aren't there (unless jumpered).

RBob.

 

OK, I'll re-check with the prom image for a 27c256 and see what the mask ID comes back as. Thanks for the info so far.

Yes, the netres resistors don't look like they were ever installed. This means either the car never ran right(if it was a corvette), is not from a corvette, or was in some kind of weird ecm that would have had a knock module, but no resistors.

Would you guys know if the LT5 ecm had limp home features? thats a long shot, but maybe.

I'l post a picture of it later tonight, just to show you what I'm looking at. Very weird. I'm still trying to get more information from this guy I bought it from. Really, for 20 bucks, its an interesting find though.

 

OK, I double checked the prom image, and the 9th byte comes back as AB, and tunercats checksum program also comes back with AB, and that the checksums don't match, probably corrupt. How can I post a copy of the bin? the attachment format is only a picture-type file extension. Here is a shot of the memcal, sorry for the poor quality, but you can see the resistors missing......

 

Sure enough they are not there. I am thinking that as you say the LT5 it may be. For posting the bin, change the filename extension from .bin to .jpg (or .gif) and try to post it (have no idea whether this will work or not).

RBob.

 

I'm trying a bitmap, as the board doesn't like the file as a jpeg. I can alway email if you are intested in seeing it. Thanks for all the help so far.

 

That actually worked (posting as a bmp). I found the maskid's of $AB and $ED as you did. Although is can't be a valid bin. It actually looks like it is partially erased: too many $FF's and other high values (lots of 1 bits).

RBob.

 

Cool! A new way to put bins on the board. Thats cool. I figured that the bin was currupt, since it did look like too many FF's like you said. Probably sat around without protection on the window for too long. The last thing I can try is to see what the knock circuit is tuned to (frequency), at least it may narrow down where it was from....I was also thinking that this thing might be some cadillac memcal, since they used only few engine types and all were similar bore size/cubic inches. Might have put limp-home on-board. I got no help from the guy who sold it......at least I have a spare carrier now, hahhah.

Bit off topic, but related, I found a cool new chip by Texas Instruments that could replace the knock circuit, TPIC8101, knock signal processor, couple that with a PIC and and crystal, you could put that on a board and get a configurable knock sensor processor for like 20 bucks. Programmable gain, center frequency, and integration time. very interesting.

thanks again.....

 

Hey guys,

this is old post back from the dead, but I wanted to give you guys a heads up to what I found here. The memcal is from an LT1, 92-93 vette, apparently, they had a knock circuit on the memcal, but no limp mode resistors.

with no markings, it was tough to find out any details, but I stumbled on a spreadsheet(awhile back) on the DIY-EFI ftp site, which has all the listings of P4 ecm knock module info, including a column which showed and ID resistor. This got me thinking, and taking it one step further, I checked out the knock circuit in better detail. it seems that the circuit has a pin which has this resistance tied to ground!! There are 8 pins on the part, and 4 are used to detect knock; power, ground, knock sensor in, and knock detect out. I noticed that two of the other pins are tied to something inside the circuit. I measured the one pin to ground, and wha-la, the resistance is the same as the board ID resistance. I checked this with all the memcals I have(like 15 or so, tons of flavors) every one of them checked out!

so it looks like there is a method of determining what a memcal is from by measuring a resistance. I have all the details in a word document, I can email to anyone who is interested......just give me a shout....