Coolant based spark correction migration from $24A to $88

[f85gtron]

I've swapped to the 7730 ecm and am migrating as many configurations as possible. I'm having trouble with the coolant based spark correction vs map table. The $24A has values from map 40 to 0, but the $88 starts at 30 and goes up to 100. So, basically, i have numbers in 30 and 40 i can use, but the rest is ?
Also, the $24a values are negative offset while the numbers for a 3.1 Firebird are positive offset. (Mine's a 2.8 fiero mildly modded to breath better).
I'm not sure how to proceed.
Ron

[RobertISaar]

it's possible that the 24A values are being given in kPa-vacuum while 88 is in kPa-MAP.... 100kPa-MAP is 0kPa-vacuum, 90kPa-MAP is 10kPa-vacuum.

this is simplified a bit, but it may explain what you're seeing. it's also possible one or both of them have bad labeling. which 88 XDF are you using?

[f85gtron]

That would explain things a bit. I've checked it on a couple different xdf for $88 and the same labeling on both. My favorite is the one attached:

[RobertISaar]

that would be the one I made... I made that from my own disassembly of an $88 BIN, so I believe it to be correct. I have no idea if the 24A XDF is correct though.

[f85gtron]

$88 is called "Based Cool Advance Correction vs Load vs cool.temp" and runs 30-100, while the $24A "Cool Compensation Spark vs Vacuum" runs 40 to 0. Both tables in both xdf are in kpa in the x axis, deg in y axis

[RobertISaar]

sounds about right then. you'll at least have the 60-100kPa range covered from factory values in 88 then.

[f85gtron]

So, to clarify my understanding is that load and vacuum are opposite, whereas, load 100=vacuum 0. Is that a fair interpretation?

[RobertISaar]

yar.

100=0
90=10
80=20
70=30
60=40

[f85gtron]

10-4

[f85gtron]

It worked! Thanks!

[f85gtron]

Ok. One more question.
The coolant based spark bias in $24A is 20° and the bias in $88 was 35°. When i migrated the 20° over, my timing was SEVERELY advanced! My suspicion is that the scalers are flip flopped, upside down from each other, but wanted to confirm before screwing around with something i barely understand. My simple mind only feels comfortable with smaller numbers for advance.

[RobertISaar]

the bias may or may not be accounted for in the tables of one of the XDFs, but it is in the other?

[f85gtron]

It's accounted for in both. I migrated the 20° figure over to the $88 (from the 35° figure in the base tune) and got all kinds of knock. Aldl info showed advance into the 50's. Scared the crap out of me and i shut it down.

[RobertISaar]

do you happen to know if the bias was brought in before or after the table was imported?

the bias really doesn't need changed anyways unless you run out of room to go negative.

[f85gtron]

I think I'm starting to understand it more. So, effectively, I cut off the ability of the minus spark advance calculation by 15°, right?, so that's why 35° bias was better. So then if I add 5° more bias, say 40° , that should give it cushion?

I was just trying to directly migrate as much over as possible. I'm finding that's easier said than done!

[RobertISaar]

removing some bias isn't a big deal, it's when the bias is changed and the table values don't also change to reflect it.... then however much the bias was modified is immediately changed added/subbed to the overall advance.