determining optimal timing

[Little G]

Is there some sort of calculator to determine the correct spark advance? I just don't know where to start with this.

[9secfirebird]

start with the stock setting in the computer.

[Little G]

Okay, I'm looking for a calculator of some sort that would take various parameters and spit out an optimal timing. I am well aware of my stock tables, however they are more geared toward emissions than power, in addition to the fact that I use 93 octane gas and the setup is now slightly different than stock. Is there such a thing or is adding spark and subtracting where it knocks the only way to tune?

[Ian]

I would think that every engine would be slightly different, even if it was the same type of engine. If thats the case, then it looks like trial and error is the best method, or get a rough idea from someone else and tune from there.

[Fasterthanyou]

We'll talk more in person on Thursday at Matt's. I'll have my catalog ready for you to get your exhaust parts ordered.
The gist of timing is mostly head design and cam. Other things have very little effect on the main SA table. For emissions purposes the timing is tailored to the desired AFR.
General rules: Lean mixtures require more timing than stoich. Really dense cold air also requires more timing. On a cold engine start the pcm is trying to lite the cats as fast as possible and to do this they usually have a tad slightly retarded timing from optimal and run EXTRA rich. If you lean out the cold start AFRs a tad you'll want to add a degree or 2.
Generally speaking knock counts are bad but don't get caught up in the "oh look, knock counts, gotta take out timing at that spot in the main SA table." The pcms run tests on the system ALL the time, especially OBDII. One of those tests is to make certain the knock sensors are working properly. How do they know they're working? easy, they advance the timing until some knock counts are seen! So if you're only getting a couple knock counts and it isn't happening EVERY time you're in that "cell" then don't worry about it. Might even try adding a couple degrees in that cell to see if it increases the counts or not. That's how I determine if it's ecm or actual.
The other way to tune is make a change, do an acceleration run on a patch of road that is flat, measure the time it takes to go from one speed to another, since you've got stick you can assume no clutch slip and use RPM instead of vehicle speed. This is the best determination. BTW, that'll be $3405.64 or a 6-pack of Yuengling :P lol

[Little G]

Well then... I'll bring a 6pk of Porter with my usual 12pk of Amstel on Thursday. :mrgreen:

[NJSPEEDER]

Well then... I'll bring a 6pk of Porter with my usual 12pk of Amstel on Thursday. :mrgreen:

you'll be in florida on thursday dumb ass :roll:

later
tim

[Little G]

oh yeah...rain check, Prevost.

[Tru2Chevy]

oh yeah...rain check, Prevost.

You want to leave a credit card so we can order the flanges and what not that you will need for your headers? :wink:

- Justin

[foff667]

We'll talk more in person on Thursday at Matt's. I'll have my catalog ready for you to get your exhaust parts ordered.
The gist of timing is mostly head design and cam. Other things have very little effect on the main SA table. For emissions purposes the timing is tailored to the desired AFR.
General rules: Lean mixtures require more timing than stoich. Really dense cold air also requires more timing. On a cold engine start the pcm is trying to lite the cats as fast as possible and to do this they usually have a tad slightly retarded timing from optimal and run EXTRA rich. If you lean out the cold start AFRs a tad you'll want to add a degree or 2.
Generally speaking knock counts are bad but don't get caught up in the "oh look, knock counts, gotta take out timing at that spot in the main SA table." The pcms run tests on the system ALL the time, especially OBDII. One of those tests is to make certain the knock sensors are working properly. How do they know they're working? easy, they advance the timing until some knock counts are seen! So if you're only getting a couple knock counts and it isn't happening EVERY time you're in that "cell" then don't worry about it. Might even try adding a couple degrees in that cell to see if it increases the counts or not. That's how I determine if it's ecm or actual.
The other way to tune is make a change, do an acceleration run on a patch of road that is flat, measure the time it takes to go from one speed to another, since you've got stick you can assume no clutch slip and use RPM instead of vehicle speed. This is the best determination. BTW, that'll be $3405.64 or a 6-pack of Yuengling :P lol

deja vu :lol: