Could someone tell me what this does and what the numbers in the table represent? degrees advance? or what? My table is full of 20's and larger numbers at all temperatures. I'm wondering if this means degrees added on top of the SA table? What have you all done as far as changing these numbers? Thank you

There is a spark coolant bias.
Then there is the coolant timing table.
LV8 is the load calculation the ecm does. It's based on grm/sec, and rpm to figure out how much load the engine is under.

So the bias is say 20d that is added to the spark timing calculation. Then there is the look up table that is referenced to coolant temp and load. The ecm then looks up the appropriate value in the table and then subtracts that from the timing calculation. Kind of a round about way of doing it...........

So if you have a bias of 20, and a table entry of 20 then there is no timing correction.

Generally there's not alot to be found there, other then if you have a cold run problem.

I'm confused because one of my tables (I guess the look up table) has RPM on one axis, but the Spark correction LV8 vs coolant temp doesn't have RPM. How could you even find the matching number on the other table to compare against or add the correction to?

The two tables are handled separately. The main SA table lookups are done using the RPM & LV8. Then the coolant compensation lookup is done using temperature and LV8. The two values are added together with the bias values then subtracted.

The coolant compensation table value doesn't depend upon the RPM. It is the same across the RPM range at that LV8 and temperature.

RBob.

Okay I'm starting to get it partially.
So two values ?? added together with the (what's the bias?) then subtracted from what?
I'm sorry I can't picture these things you're referencing yet.

I'm looking at my stock bin compared to the arap. My spark correction LV8 vs coolant table has all zeros in it. The arap table has (20's) and higher. I just can't picture what a 20 value would do to the values I have in the main spark advance table.

The purpose of a spark bias value is to be able to remove (retard) SA timing. The SA tables themselves are all unsigned numbers. Can't have a negative value in order to remove SA.

During the SA calculation the code uses a signed number for SA. Now there can be a negative SA value (retarded from TDC).

This works by having the code add up all of the SA values as looked up from each table. Then the bias value(s) are subtracted from that total SA value.

In the case of the coolant compensation table the bias term is 20 deg (stock ARAP). While working with this table any value that is set to 20 deg has no effect on the timing (20 - 20 = 0). If a value is set to 25 deg, then in effect 5 deg of SA is added to the total SA (25 - 20 = 5).

If a value (coolant comp table still) is set to 15 deg SA then in effect that will subtract 5 deg of SA from the total (15 - 20 = -5).

An example would be the main table at 24 deg SA, and the coolant compensation table at 15 deg SA with a 20 deg bias term (for coolant comp table).

Add together the two SA values: 24 + 15 = 39 deg.

Then sub off the bias term: 39 - 20 = 19 deg SA.

The end result is that the coolant compensation table subtracted 5 deg of SA from the total timing (main SA table only in this example).

If using TunerCAT they usually take into account the bias term for any table. In this case it becomes WYSIWYG. Can try to enter a negative value to test for this.

RBob.

oops correction I was wrong. I didn't have any bins open when it read zeros. I thought I did but it was very late last night when I was looking at this. Sorry for that stupid post.

RBob, thank you for going to the trouble to try to explain this to me. I've read it several times but I still don't think I understand what you're saying.

How do you know what the bias number is for a table?
My spark correction LV8 vs Coolant temp table has a lot of 20.04 values in the normal operating range of the engine. Should this tell me that my bias is 20 and that this table doesn't add or subtract anything from my total SA if a cell with a 20 is being used?

The bias term(s) are another calibration parameter within the bin/EPROM. In the case of ARAP & the coolant compensation table the bias term is at location $10A. The coolant compensation table starts at $10B. In this case they are next to each other (in the bin).

Off hand I would say that the 20.4's you are seeing are not making a change to the final SA term. But only if the bias term is also 20.4, which in stock ARAP it is.

Which editor are you using? Sometimes it is a good idea to double check things in the bin with a simple hex viewer. That way you can be sure of what your editor is really showing you.

RBob.

Great! that's what I thought. Great information.
I'm using TunerPro. How do I make it show me what value is in that bias location?
I'd just like to make sure it is the 20 in there.
In hex wouldn't the value there be $14 to be equal to 20-dec.?
Thanks again.

In order for TunerPro to show the bias term the location & description needs to be in the bin definition file (.ECU for TunerPro?, TunerCat uses a .TDF file).

You are correct about the $14 being equal to 20 decimal. However the bin will contain a different value. Most spark terms are in the form of (SA in degrees / (90 / 256)). Or SA / .352. So the 20 degrees of timing will be the number 57 decimal, or 39 hex.

This conversion is normally handled by the editor.

RBob.

I "replaced" the spark correc vs coolant Tº table by the following:

Since my thermostat is 190ºF (88º Celsius), I adjusted the fan ON & fan OFF as follows:

FAN ON: @ 91º C
FAN OFF: @ 89º C

With these values into the EPROM, my engine runs between 88º C & 91º C, thus temperature variation is only 3ºC. Since coolant temperature don't change (only 3º Celsius), spark advance don't needs corrections.

What do you thinks about this system?


Denis V.

TPIGIRL -

In tunerpro, open your ECU. In the ECU Menu go to "New ECU Item" (or press Ctrl + N).

Right click and be sure "show addresses in hex" is checked. if not, check it.

input the following:

start address = 10A.
columns = 1
rows = 1
element size = 1 (it is 1 byte, right guys? now two?)
bitmask = 0
factor = 1 (if not converting it to a "real world" value)
offset = 0
multiply, divide, etc = 0 (which is multiply)
map name = Coolant compensation bias (or whatever you wish to name it).

Keep in mind htere's a help file with TunerPro. I know its not the greatest or clearest, but its a start. =)

It is 57 on mine.

Super! Thanks a ton guys Mangus and Rbob!

:yourock:

yup. $39 (hex). if calculated (X * .351567) is 20.039 degrees.

TPIGirl - you can change the "factor" in the ECU Item to be 0.351567 to see the calculated value in the editor.