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Old 08-25-2009, 08:38 AM   #15
gtbaldini
 
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If you have a custom tune and are happy I wouldn't try this. It may reset the computer and your out a custom tune.
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Old 08-25-2009, 09:25 AM   #16
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Originally Posted by EAkrish View Post
I am wondering if it will work with a tune also pq. I guess I can try it and let everyone know.....
It'd seem to me that the tune might already compansate for this I'm sure it wouldn't hurt to try though.

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Originally Posted by EAkrish View Post
Mine was running real good b4 the tune and amazing after the tune. I also did my tb porting b4 I got the tune. Just amazing! I might not even mess with it. I don't want to lose the tune, if that's even possible?
I can't speak for the new PCMs, but the ones that were used with the LS1 cars wouldn't simply default to the OEM tune, because it's my understanding one is actually writing over the OEM tune and the PCM doesn't know the otherwise. I'd disconnect my battery for nights at a time and plug it back in and it was still fine. I'd remove PCM fuses and it was still fine. (FWIW - I could tell the custom tune was in there because I had my idle RPM raised from like 550 to 750, because of my converter, and it remained the same before and after.) That's just what happened to me though, and that wasn't with the current model PCMs...

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Originally Posted by gtbaldini View Post
If you have a custom tune and are happy I wouldn't try this. It may reset the computer and your out a custom tune.
See above...
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Old 08-25-2009, 09:33 AM   #17
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All the buzz about this so I figured why not try it. I pulled mine last night. No change in my car at all this morning. None. Zero. Zip. Nada. My L99 launched like a rocket from day one so I didn't expect anything.
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Old 08-25-2009, 09:36 AM   #18
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Originally Posted by monza66mo View Post
All the buzz about this so I figured why not try it. I pulled mine last night. No change in my car at all. None. Zero. Zip. Nada. But my L99 launched like a rocket from day one so I didn't expect anything.
Too bad, but if there weren't complaints before, there's no loss.

Thanks for sharing
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Old 08-25-2009, 09:42 AM   #19
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I tuned in HPTuners on my LS1 and if it is the same for an L99/LS3, this is what happens when you pull the fuses:

There are two tables values used for spark timing - high octane table and low octane table. If you use 93 octane from day one, your computer is using spark timing from the high octane table. If you got a tank of 87 from the dealer, the engine experienced premature detonation and the knock sensors went crazy, and told the computer to use the low octane timing table. What is supposed to happen is after a while of not seeing detonation from the knock sensors, the computer (ECU)tries the high octane spark timing table again. (This doesn't appear to be happening - THIS IS THE PROBLEM!!!!).

The values in the high octane and low octane tables are NON-VOLATILE MEMORY (meaning they are there even if you lose power -like when you do the fuse pull). These tables are usually adjusted when you get a custom tune, and burned into the non-volatile memory. So therefore if you get a custom tune YOU WILL NOT LOSE THESE "TUNED" VALUES with the fuse pull.

What WILL happen with the fuse pull is your volatile memory will be reset. This includes long term + short term fuel trims, knock retard, etc... but what is important in this case is the little parameter that determines which spark table to use will reset...meaning if you were running from the low octane tables before (safe + slow mode), after the fuse pull it will force the computer to try the high octane table again (super giggle fun happy rockin' mode).

However it is important to note that you shouldn't need to try the fuse pull if you've only used high octane gas since getting a custom tune, because burning the tune to the ECU resets all volatile memory. This is why it will go through the idle re-learn process and may run a little weird for the first 20 minutes or so after burning a tune or pulling the fuses.

Pulling the fuses is no different from recovering from a dead battery. The only reason I could see that it would be a problem to pull the fuses is if GM wanted to run diagnostics on the cars with the problem and needed to see the volatile values.
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Old 08-25-2009, 09:50 AM   #20
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Quote:
Originally Posted by wh0rsep0wer View Post
I tuned in HPTuners on my LS1 and if it is the same for an LS3, this is what happens when you pull the fuses:

There are two tables values used for spark timing - high octane table and low octane table. If you use 93 octane from day one, your computer is using spark timing from the high octane table. If you got a tank of 87 from the dealer, the engine experienced premature detonation and the knock sensors went crazy, and told the computer to use the low octane timing table. What is supposed to happen is after a while of not seeing detonation from the knock sensors, the computer (ECU)tries the high octane spark timing table again. (This doesn't appear to be happening - THIS IS THE PROBLEM!!!!).

The values in the high octane and low octane tables are NON-VOLATILE MEMORY (meaning they are there even if you lose power -like when you do the fuse pull). These tables are usually adjusted when you get a custom tune, and burned into the non-volatile memory. So therefore if you get a custom tune YOU WILL NOT LOSE THESE "TUNED" VALUES with the fuse pull.

What WILL happen with the fuse pull is your volatile memory will be reset. This includes long term + short term fuel trims, knock retard, etc... but what is important in this case is the little parameter that determines which spark table to use will reset...meaning if you were running from the low octane tables before (safe + slow mode), after the fuse pull it will force the computer to try the high octane table again (super giggle fun happy rockin' mode).

However it is important to note that you shouldn't need to try the fuse pull if you've only used high octane gas since getting a custom tune, because burning the tune to the ECU resets all volatile memory. This is why it will go through the idle re-learn process and may run a little weird for the first 20 minutes or so after burning a tune or pulling the fuses.

Pulling the fuses is no different from recovering from a dead battery. The only reason I could see that it would be a problem to pull the fuses is if GM wanted to run diagnostics on the cars with the problem and needed to see the volatile values.
Nice Read!!!!
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Old 08-25-2009, 10:04 AM   #21
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If you use 91 octane (it's the highest available in my area) will the computer use the high octane tables? Anybody?
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Old 08-25-2009, 10:14 AM   #22
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Quote:
Originally Posted by wh0rsep0wer View Post
I tuned in HPTuners on my LS1 and if it is the same for an L99/LS3, this is what happens when you pull the fuses:

There are two tables values used for spark timing - high octane table and low octane table. If you use 93 octane from day one, your computer is using spark timing from the high octane table. If you got a tank of 87 from the dealer, the engine experienced premature detonation and the knock sensors went crazy, and told the computer to use the low octane timing table. What is supposed to happen is after a while of not seeing detonation from the knock sensors, the computer (ECU)tries the high octane spark timing table again. (This doesn't appear to be happening - THIS IS THE PROBLEM!!!!).

The values in the high octane and low octane tables are NON-VOLATILE MEMORY (meaning they are there even if you lose power -like when you do the fuse pull). These tables are usually adjusted when you get a custom tune, and burned into the non-volatile memory. So therefore if you get a custom tune YOU WILL NOT LOSE THESE "TUNED" VALUES with the fuse pull.

What WILL happen with the fuse pull is your volatile memory will be reset. This includes long term + short term fuel trims, knock retard, etc... but what is important in this case is the little parameter that determines which spark table to use will reset...meaning if you were running from the low octane tables before (safe + slow mode), after the fuse pull it will force the computer to try the high octane table again (super giggle fun happy rockin' mode).

However it is important to note that you shouldn't need to try the fuse pull if you've only used high octane gas since getting a custom tune, because burning the tune to the ECU resets all volatile memory. This is why it will go through the idle re-learn process and may run a little weird for the first 20 minutes or so after burning a tune or pulling the fuses.

Pulling the fuses is no different from recovering from a dead battery. The only reason I could see that it would be a problem to pull the fuses is if GM wanted to run diagnostics on the cars with the problem and needed to see the volatile values.
Awesome read! Thanks. This clears things up very nicely!
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Old 08-25-2009, 10:21 AM   #23
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You only have 91 octane because you live in a higher elevation. the same is true for where i live. You don't need the higher octane at higher elevations. I am gonna go further on this speculation, as i believe what wh0rsep0wer said is correct and the cause for the cars to run better, but since no one has logged data from before and after the fuse pull....

Some are saying they have filled up with premium (91 or 93) gas since day one. Well if you got old gas that wasn't up to standards with the high compression of these engines it will easily cause the engine to knock thus kicking you into the low octane spark table, even though you have filled with premium since day one. Always fill up from a good fuel source that gets fresh fuel often, as it doesn't take long for gas to go bad.
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Old 08-25-2009, 11:51 AM   #24
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I'm at 900 miles now... should be ok for me to do it right? (auto 2SS) and start getting on her a LOT more?
From what we can tell, Yes.

Obviously this isn't a GM approved thing. But there shouldn't be any real risk.

FWIW.
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Old 08-25-2009, 01:15 PM   #25
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, but since no one has logged data from before and after the fuse pull....

.
I have dynoed mine before fuse pull 319rwhp 2 pulls back to back, and after fuse pull w/ in 5 minutes of the other 2 runs and picked up 8rwhp, 327rwhp.
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Old 08-25-2009, 01:26 PM   #26
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Originally Posted by SSOOCH View Post
If you use 91 octane (it's the highest available in my area) will the computer use the high octane tables? Anybody?
I'd also like to hear someone's take on this. 91 is the highest available (other than 100+ race fuel) here in California.
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Old 08-25-2009, 01:27 PM   #27
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I have dynoed mine before fuse pull 319rwhp 2 pulls back to back, and after fuse pull w/ in 5 minutes of the other 2 runs and picked up 8rwhp, 327rwhp.
yes, but why did you pick up 8rwhp? Was it because of colder intake temps, cooler engine, more spark advance from high octane table etc... There could be a million reasons for the increase in power, but if you log the run you will know exactly what is happening with the engine and why you made more power.

Also i could be the variance in the dyno. heck from airing up tires and positioning tires differently on the drum I have seen an 8 hp increase on the dyno.
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Old 08-25-2009, 05:57 PM   #28
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You guys are crazy. Your car quickly adjusts back to its original settings.

If you want your car to run faster, get some mods and get it tuned by a professional. That will give you real peformance gains that are permanent.
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