Timing, Which to Believe?
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Pro
Joined: Jan 2005
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From: San Jose Ca
Timing, Which to Believe?
I'm getting close to dyno tuning my new 383 (read: year old, 7k miles) for the first time and there is a question concerning the discrepancy between what is in the timing tables of LT1 edit and what is reported by Datamaster. I remember that this subject had come up in the past, but at the time I wasn't paying much attention (that'll teach me!). Currently, my timing in the 90, 95, and 100kpa levels are 35 degrees to 36 degrees. This is actually quite close to my stock file. When scanning via datamaster starting around 5k, the timing is reported as ~39 and continues to increase to 41 degrees at 7k. So not only is there an initial discrepancy (offset?) of ~3-4 degrees, but it's not linear! So my question is, which value do I believe and use while trying to find the optimum timing for WOT power? This has really been confusing me for awhile now. If I remember correctly, the general consensus was that there was an additional factor or table that isn't accessible with LT1 edit causing the difference. So is my engine currently running 36 degrees above 4k as reported in LT1 edit, or is it really climbing to 41 degrees by 7k?
Thanks in advance!
Thanks in advance!
Drifting
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From: GA
The timing tables are only part of the total timing, there are other factors as well, ie: Power Enrichment Mode Spark Advance, Maximum Knock Retard in Power Enrich Mode, Maximum Knock Retard Degrees When Not In PE, Highway Mode Spark Advance vs. Load, Startup Spark Advance vs. Coolant Temperature, Maximum Spark Advance, Coolant Temp Spark Correction Disable Temp, And spark retard from knock counts.
Thread Starter
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Joined: Jan 2005
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From: San Jose Ca
Well as far as any retard factor, it's not an issue as I programed out the knock sensors due to the solid roller cam (don't worry, I've watched the knock counter enough that there is no legit knock anyway). So is Datamaster reporting the truth then? 41 degrees at 6.5k-7k seems a bit higher than optimal.
Drifting
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From: GA
I'm guessing that 41 degrees is the "max spark advance" programmed into the .bin...So with all conditions being met, 41 is probably right. Your table probably maxes out at the 39* you mention, then it adds in PE spark advance, etc.
I would agree with what Alvin said...ignore the actual values, and focus on how much power you are making/where, vs any knock counts.
If the engine likes it..hey, it can't be wrong, right?
I would agree with what Alvin said...ignore the actual values, and focus on how much power you are making/where, vs any knock counts.
If the engine likes it..hey, it can't be wrong, right?
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From: San Jose Ca
Originally Posted by Morley
...If the engine likes it..hey, it can't be wrong, right?
Drifting
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From: GA
Originally Posted by MaxLean
True, true. Where is this PE spark advance you are refering too? I have yet to see it in either tunercat or lt1 edit.
I have only glanced through the LT1 bins, spend 99% of my time on the $6E and $8D ECU's
Melting Slicks
Joined: Dec 2000
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From: Fremont Oh
My experience with Autotap making my runs is that the ECM /PCM seems to ad up to about 3 degrees to what I programmed in with LT1 edit.
No fun running 10 pounds of boost over 100kpa and the PCM wanting to give me 30 dergees of timing... I agree there are many factors that tend to add more timing.
Mo
No fun running 10 pounds of boost over 100kpa and the PCM wanting to give me 30 dergees of timing... I agree there are many factors that tend to add more timing.
Mo
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Thread Starter
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Joined: Jan 2005
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From: San Jose Ca
Originally Posted by Morley
Ok, you piqued my curiosity and I went looking...what kpa are you pushing at 5-7k? Depending on that you could be running as much as 50* advance (If I'm reading the tables right)
Drifting
Joined: May 2003
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From: Charlotte NC
St. Jude Donor '05
theres a max timing value set in constants. It shouldn't ever go over that amount.
Take it and run it on the dyno with say 35 in the higher RPM spark tables. Listen to it on the dyno, you can hear when a car is lazy because of not enough timing. THe guys that run the dyno can probally help you with this feel also.
Take it and run it on the dyno with say 35 in the higher RPM spark tables. Listen to it on the dyno, you can hear when a car is lazy because of not enough timing. THe guys that run the dyno can probally help you with this feel also.
Drifting
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From: GA
Originally Posted by MaxLean
The kpa is 95-100. Timing acording to lt1 edit and tunercat, if I add all timing tables I can find, should be 36, but datamaster reports 41. Coolant temp vs adv vs rpm is 0 at opperating temp, btw.
Last edited by Morley; May 28, 2005 at 01:07 PM.
Drifting
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From: GA
Originally Posted by Alvin
Its in there, look harder. just under cylindar volume
Drifting
Joined: May 2003
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From: Charlotte NC
St. Jude Donor '05
Originally Posted by Morley
Nope. under cylinder volume are 6 constants for EGR followed by air injector, then a TPS constant followed by all of the TCC constants.
Than you dont' have the latest revision. I can take a snapshot of it if you'd like.
edit:
Right of TC's website
http://www.tunercat.com/pdfs/ecm_$da2.pdf
Its right under cylindar volume
Drifting
Joined: Mar 2005
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From: GA
Originally Posted by Alvin
Than you dont' have the latest revision. I can take a snapshot of it if you'd like.
edit:
Right of TC's website
http://www.tunercat.com/pdfs/ecm_$da2.pdf
Its right under cylindar volume
edit:
Right of TC's website
http://www.tunercat.com/pdfs/ecm_$da2.pdf
Its right under cylindar volume
Drifting
Joined: May 2003
Posts: 1,730
Likes: 1
From: Charlotte NC
St. Jude Donor '05
Originally Posted by Morley
Yep, my definitions are out of date I guess, don't have that constant in DA2 or DA3
If you email John at Tc@tunercat.com he will give you the updates.
