Cylinder select error

[JeepsAndGuns]

Those are hex vaules and the way the XDF is commented is wrong. You just found a major flaw in the $8D XDF. Since most of the work has been done for V8 I suppose is why no one ever noticed.

The comments "Use 0 for 8 Cylinders Use 128 for 4 Cylinders Use 192 for 6 Cylinders " are wrong. I went into the XDF paremeter and tried all the options and could not find one that would show proper hex for any of the entries, entered like that?

If you open Edit XDF Paremeter and change Significant to 0. Then use comment:
Use 0 for 8 Cylinders.
Use 16 for 4 Cylinders.
Use 8 for 6 Cylinders.
Use 24 for TBI.
It all comes out properly in hex.

I commented my XDF to say:
"Use 0 for 8 Cylinders.
Use 16 for 4 Cylinders.
Use 8 for 6 Cylinders.
Use 24 for TBI.

Hex values are
00=8cyl
18=tbi
10=4cyl
08=6cyl
"

Wow really? I thought robert said that there have been people using 8D on 6cyl's, so have they never caught this? Or have they and just not shared it? If they havent caught it, how does their engines run with the wrong value.

And also, If thats to get the correct number of cylinders, then how come tbi is also in there? If you change that to tbi, then how does the ecm/bin know what engine its running, doesnt it need to know if its running a V8, I4, V6, etc..?

Wait, are we talking about 0x09 or 0x293?

Edit: So if I changed my test harness bin to 192 for 6cyl, and thats when my cylinder select error started, then what did I change it to? If what you listed above is indeed for the 0x09 value, then I will change it to the proper value and retest and see what happens.

[RobertISaar]

guys, you're overthinking it....

there are multiple places in the BIN that define cylinder count.... some are for certain operations.

the one with the 0/128/192 is for engine speed and airflow calculations, the number itself is actually a 0-1 multiplier, 128 is half of 256, therefore, it's used for 4 cylinders. 192 is 6/8 of 256, therefore it's used for 8 cylinders.

the original calculations were done assuming a V8 engine(or at least that's the max GM wanted to be able to control) with 4 pulses per revolution on the reference circuit from the ICM, that's why the multiplier is needed. if you wanted to run a single cylinder, you could change it to 32, 64 for 2 cylinder, 96 for a 3 cylinder, etc....

the other one, the bit encoded value, that's for DTC and limp-home operation, and i think nothing else.



so, the XDF really needs to have both locations and both with tips if running anything other than a MPFI/TPI V8.

[dave w]

Just read that whole thread. My head is spinning just a bit. But by the end, it looks like yall found the same value that I did at 0x293. So using the 7427 tbi memcal, and changing that value to 18, you still got the cylinder select error? I have my test harness all laid out and ready to test, also have a few 7427 V8 tbi memcals. I have a couple of tbi injectors, but I do not have any of the resistors yall mention using to put between the injectors and the ecm. If you do not have a test harness set up at the moment, can give me instructions on what to do/change, I would be willing to help out out with testing. What did you end up using? If I am reading post number 120 correctly, you used $A1? it also looked like you were changing the cylinder number to 18, the 8D xdf I have says use 0 for 8cyl, 128 for 4cyl, and 192 for 6cyl. I'm thinking changing that value (0x09) to something other than those 3 values may not work right. Did you have sucess running a tbi engine with the 7727?
I would like to try some testing myself, if you can tell me what to do about resistors and the injectors, so I don't fry something.
I agree with yall that being able to run tbi with the 7727 would be handy for conversions.

I don't have a '7727 / '7730 harness for testing. I'll take you up on your offer to do some testing, it's greatly appreciated!

I ran out of time to do any further testing for a TBI '7727.

I used a memory adapter board with the '427 PCM TBI Memcal using a 27SF512 chip with the $8D .bin file. Resistors are not needed for testing when using Noid Lights or 4 TPI injectors on each bank. It should be Ok to not have injectors plugged in. The first test I'd like to have help with would be to set the $8D definition .bin file for cylinder hex value to the $18 Mark posted and see if the cylinder select error occurs? With my test, I got a cylinder select error with 0x293 set to hex $18.

Thanks,
dave w

[JeepsAndGuns]

guys, you're overthinking it....

there are multiple places in the BIN that define cylinder count.... some are for certain operations.

the one with the 0/128/192 is for engine speed and airflow calculations, the number itself is actually a 0-1 multiplier, 128 is half of 256, therefore, it's used for 4 cylinders. 192 is 6/8 of 256, therefore it's used for 8 cylinders.

the original calculations were done assuming a V8 engine(or at least that's the max GM wanted to be able to control) with 4 pulses per revolution on the reference circuit from the ICM, that's why the multiplier is needed. if you wanted to run a single cylinder, you could change it to 32, 64 for 2 cylinder, 96 for a 3 cylinder, etc....

the other one, the bit encoded value, that's for DTC and limp-home operation, and i think nothing else.



so, the XDF really needs to have both locations and both with tips if running anything other than a MPFI/TPI V8.

Ok, now I am really confused?
So are you saying the way in the xdf is correct, or the way mark posted is correct?
So is 192 correct to run 6cyl MPFI?

[RobertISaar]

in one location, yes. in another, no.

at 8293, you need 08.
at 8009, you need 192.

that should work with a 6 cylinder MPFI engine.

[JeepsAndGuns]

in one location, yes. in another, no.

at 8293, you need 08.
at 8009, you need 192.

that should work with a 6 cylinder MPFI engine.

Ok, thats what I have the test bench bin set to, and so far its working with no cylinder select error.