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01-31-2005, 06:45 PM
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#1
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Lifetime Power Member
Join Date: Jul 2004
Location: London, UK
Posts: 862
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determining optimal timing
Is there some sort of calculator to determine the correct spark advance? I just don't know where to start with this.
__________________
2008 Mysterious Solstice GXP - teh hotness!
2002 Pewter V6 Camaro M5 ~ SOLD
mods: Gear, weight reduction, tuning
Fear the Gear. 13.585 @ 100.05 1.827
Beater: 93 Jeep Grand Cherokee
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01-31-2005, 08:33 PM
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#2
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Join Date: Oct 2004
Posts: 365
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start with the stock setting in the computer.
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AIM: blacktoprecs
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01-31-2005, 08:57 PM
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#3
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Lifetime Power Member
Join Date: Jul 2004
Location: London, UK
Posts: 862
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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?
__________________
2008 Mysterious Solstice GXP - teh hotness!
2002 Pewter V6 Camaro M5 ~ SOLD
mods: Gear, weight reduction, tuning
Fear the Gear. 13.585 @ 100.05 1.827
Beater: 93 Jeep Grand Cherokee
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01-31-2005, 09:53 PM
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#4
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Banned Camp Director Emeritus
Join Date: Aug 2004
Location: Somerset County
Posts: 8,395
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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.
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Quote:
Originally Posted by baddest434
and 1 more smart ass answer by you and i'm going to reach into this monitor and grab you by the throat
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01-31-2005, 10:16 PM
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#5
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Join Date: Aug 2004
Location: Montgomery NJ
Posts: 1,271
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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
__________________
, Jon
Owner of a Red Sled.
If it\'s EFI I can tune it. Specialize in 82-95 GM (yes Lt1\'s)
\"If you can leave black marks on a straight from the time you exit a corner till the time you brake for the next turn.......Then, you have enough horsepower\" - Mark Donohue
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01-31-2005, 10:26 PM
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#6
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Lifetime Power Member
Join Date: Jul 2004
Location: London, UK
Posts: 862
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Well then... I'll bring a 6pk of Porter with my usual 12pk of Amstel on Thursday.
__________________
2008 Mysterious Solstice GXP - teh hotness!
2002 Pewter V6 Camaro M5 ~ SOLD
mods: Gear, weight reduction, tuning
Fear the Gear. 13.585 @ 100.05 1.827
Beater: 93 Jeep Grand Cherokee
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01-31-2005, 10:42 PM
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#7
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NJFBOA Co-Founder
Join Date: Jul 2004
Location: All up in your kool aid!
Posts: 12,235
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Quote:
Originally Posted by Little G
Well then... I'll bring a 6pk of Porter with my usual 12pk of Amstel on Thursday.
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you'll be in florida on thursday dumb ass
later
tim
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01-31-2005, 11:24 PM
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#8
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Lifetime Power Member
Join Date: Jul 2004
Location: London, UK
Posts: 862
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oh yeah...rain check, Prevost.
__________________
2008 Mysterious Solstice GXP - teh hotness!
2002 Pewter V6 Camaro M5 ~ SOLD
mods: Gear, weight reduction, tuning
Fear the Gear. 13.585 @ 100.05 1.827
Beater: 93 Jeep Grand Cherokee
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02-01-2005, 08:19 AM
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#9
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Co-Founder / Site Admin
Join Date: Jul 2004
Location: Ewing, NJ
Posts: 22,473
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Quote:
Originally Posted by Little G
oh yeah...rain check, Prevost.
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You want to leave a credit card so we can order the flanges and what not that you will need for your headers?
- Justin
__________________
1999 Camry - Beigemobile DD
2002 Suburban - Wife's DD
2004 Grand Cherokee - Not running / Project / Selling?
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02-01-2005, 12:05 PM
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#10
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Keyboard Tough Guy
Join Date: Jul 2004
Location: Trenton, NJ
Posts: 6,341
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Quote:
Originally Posted by 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
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deja vu
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