idle spark

[YetiLove]

hi! I need a little help with my timing tables. im using tuner pro and my idle spark is set at 20 in all the cells that the car idles in. tuner pro is showing 8-12 degrees and im getting 8-12 degrees at the crank. if I use a number lower then 20 the timing will drop by a degree or two but stays around 8. I would like to adjust my timing some to see if I can get more vacuum at idle but the computer seems determined to stay around 8. burning a chip and checking is starting to get old... any suggestions on what I could change other then the idle and off idle spark tables? any thing above 1,000 rpm gives me spark within a degree or two of what it should be.

bjyl
7427 pcm
4l60E
TPI
E fan code
sb 350

[dave w]

I think I would check the setting for altitude spark bias. Maybe try ZERO?

dave w

[delcowizzid]

bias settings should never be changed they are just there so the ecu can do negative number calcs only.there are a lot of spark tables and scalers that may take spark away like coolant temp corrections air temp corrections altitude correction idle overspeed correction even one for low octane corrections.the fact that logged advance matches whats showing at the crank means some table is offsetting your spark just have to crossreference data against the bin and find which one is doing it

[dave w]

the fact that logged advance matches whats showing at the crank means some table is offsetting your spark just have to crossreference data against the bin and find which one is doing it

I agree with this comment. I think the "one" doing it is altitude spark bias.

dave w

[YetiLove]

altitude spark bias set to zero solved the problem. any reason why this does this? every thing I read says not to mess with the bias

[steveo]

well yeah, you probably have to take every value in the table affected by that bias and minus the bias to get the real value. you have overridden this and removed the ability to set negative values, so now the table values are real.

that is unless the person creating the xdf placed the bias in the calculation for the table, which it sounds like didnt happen.

since its up to the xdf creator to do so, you need to edit the table parameters and check 'conversion'. if there's both an X and a Y value in there, you can probably trust that the bias is applied to the table for you. if it's just X, you'll have to calculate manually or fix it.

every thing I read says not to mess with the bias

if you're happy with the results, there's no reason you can't mess with the bias.

[dave w]

altitude spark bias set to zero solved the problem.

I'm glad I could help.

dave w