Warm spark bias??

[90C350]

Hey just a quick question? On the 7747 ecm does the warm spark bias get subtracted from the main sa table?? I mean If the warm spark bias is set to 9.84. Is that amount subtracted from the main spark advance tables?? It seems like i am loosing some spark advance when warm and therefor loosing some power. Does this make sense?? Thanks for any help.

[90C350]

Ok since no one now,s. I will answer my own thread. The warm spark bias is subtracted from your main spark advance and therefor reduces you total amount of spark. I now have mine set to 0 and can tune in a little more timing. And now whats in the main spark table is what is actually at my crank. Hope this helps someone else to??.

[doublelow49]

Hey just a quick question? On the 7747 ecm does the warm spark bias get subtracted from the main sa table?? I mean If the warm spark bias is set to 9.84. Is that amount subtracted from the main spark advance tables?? It seems like i am loosing some spark advance when warm and therefor loosing some power. Does this make sense?? Thanks for any help.

Your terminololy is a little confusing. Think you're talking about the Main Spark Bias which is normally set at 9.84 deg for the 7747 ecm. The ecm uses this constant to retard timing and could produce a negative timing value when necessary and it is subtracted from the main spark table to produce a value for timing at the crank. You wouldn't want to "0" this value.

There is also an Initial Spark Advance value, usually "0". This is the timing advance set at the distributor and should be what you see as a timing base with the est wire disconnected. Say, if you want to run 6* initial advance at the crank, then you should use this value as the ecm constant, otherwise you would be adding 6* across the timing table. This value is also subtracted from the main spark table.

There are also a couple of other timing tables, PE Spark Advance and %EGR Advance.

If you're using TunerPro to tune, the value you see in the Main Spark Table will be the net timing, main spark minus main spark bias minus initial spark advance values.

Buddy

[90C350]

That does make sense to me but, I have been talking to a few very experianced tuner's on third gen and they say just to Zero out the warm spark bias that way nothing is subtracted from my main spark table to make things easier to tune. I have an initial static timing of 2*btdc and have Zero'd out my warm spark bias, which is what it is called in my xdf file. I have had good success with do this mod and have been able to tune in my timing much better now. THanks for the help and I will check into your suggestions. THanks again!!

[doublelow49]

That does make sense to me but, I have been talking to a few very experianced tuner's on third gen and they say just to Zero out the warm spark bias that way nothing is subtracted from my main spark table to make things easier to tune. I have an initial static timing of 2*btdc and have Zero'd out my warm spark bias, which is what it is called in my xdf file. I have had good success with do this mod and have been able to tune in my timing much better now. THanks for the help and I will check into your suggestions. THanks again!!

90C350,

Ok, no problem dude. Think we're talking about the same thing, just different terminology. If you're running "0" Main (Warm)Spark Bias and rawhiding this engine, hope you have your spark table in good order.

Buddy