Fuse pull on tuned cars?

[davidscamaro]

Originally Posted by FasNuf

Ok, so what I know about knock and the low octane table. The low table is used when the engine detects knock, either from poor octane, high IAT's, too much advance or whatever. The ecm puts the engine into the low table for the amount of time defined in the ecm to lower timing and prevent further knock. This time can vary and is adjustable in the ecm. I have never heard of an engine staying in the low table and a fuse needing pulled. My opinion is based on the e67 genIV so maybe it's different elsewhere.

The E38 pcm found in the SS suffers from this hard lock to the low table. Even dynos have proven this to be true , wheel horse power increases after fuse pull with no drain or add of diffrent fuel additives

[FasNuf]

Originally Posted by davidscamaro

The E38 pcm found in the SS suffers from this hard lock to the low table. Even dynos have proven this to be true , wheel horse power increases after fuse pull with no drain or add of diffrent fuel additives

If it was mine, I would be looking for a source of knock to prevent the retard to the lower table. It shouldn't just be going there for no reason. Are we logging knock?

[FasNuf]

At least the tuner didn't copy the high table to the low table! Sorry, just looking on the bright side.

[Rons1le]

Ok, for the record it does depend on the tuner so ask. I asked mine he said octane tables in my car are turn off. Mine is only set to 93 and will not adjust.

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[mikeman]

Originally Posted by Rons1le

Ok, for the record it does depend on the tuner so ask. I asked mine he said octane tables in my car are turn off. Mine is only set to 93 and will not adjust.

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What happens when and if you get knock though? The engine goes boom? Bad idea to turn off the octane tables in the tune unless you always run race gas.

[FasNuf]

[Rons1le]

I'm running forced induction so it wouldn't matter it wouldn't be able to adjust in time anyways.. Mine has knocked before on the dyno and did not go kaboom..

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[Greenhornet2]

As long as the knock sensors aren't desensitized or turned off and the adjustability is left high you should be fine. Unless you run the wrong fuel. My car can pull timing and dump fuel when knock is sensed without having to drop to a low octane table. I honestly don't know if there's a low octane table in my tune anymore. I'll ask when i go to get dynotuned again.

[Rons1le]

I just asked for a more indepth answer and he said it does have about 4° of adjustability but if it does it will run like crap.

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[Bigdumogre]

Reading this thread made me pull the fuses again lol. Wonder if there is a way we can make a switch to do it

[Moto-Mojo]

I’ll say this bout all that. I’ve been hanging around here since 2012 and bought my SS in 2015. I’ve done the fuse pull several times (on 91 octane) and I can honesty say, it didn’t make one shit of difference. And I’m pretty ‘in tune’ with my 5 year old car. Sorry, call em the way I see em.

I just did this again last week. I suppose if I went from 85 to 93, I might feel a difference. I’m going to whatever the low table is set to, to the only thing I can get - 91.

[davidscamaro]

Originally Posted by Bigdumogre

Reading this thread made me pull the fuses again lol. Wonder if there is a way we can make a switch to do it

Were there is a will there is a way , look into line lock threads to find your answers. People have done this , not for pcm but for abs, to use factory launch control with line lock.

The same mods could be used for controlling the fused links for the pcm 5/20 fuses , only hot when ignition on

[Bigdumogre]

Originally Posted by davidscamaro

Were there is a will there is a way , look into line lock threads to find your answers. People have done this , not for pcm but for abs, to use factory launch control with line lock.

The same mods could be used for controlling the fused links for the pcm 5/20 fuses , only hot when ignition on

Thanks that’s a idea

[ZED SLED]

Originally Posted by FasNuf

Ok, so what I know about knock and the low octane table. The low table is used when the engine detects knock, either from poor octane, high IAT's, too much advance or whatever. The ecm puts the engine into the low table for the amount of time defined in the ecm to lower timing and prevent further knock. This time can vary and is adjustable in the ecm. I have never heard of an engine staying in the low table and a fuse needing pulled. I would question why it's staying in the low table, not pulling a fuse as a band-aid. Any knock is unwanted, even if it's your headers rattling on your frame.
My opinion is based on the e67 genIV so maybe it's different elsewhere.

IIRC, it was a software bug in the PCM first found in 2011 on a 2011 L99 that prevented the software from returning to the hi table after going back to 93. Since then the rage was to do the fuse pull. Everyone who did so got an instant 50hp from the ole butt dyno. Except for me. My 2010 LS3 behaved the same, because it never had under 93 in it or apparently no bad gas either. But this was a real thing and the only fix is the fuse pull, or battery disconnect for a period of time. The question I never saw answered is, was this ever fixed by GM? Seems like people up into 2015MY were swearing by the fuse pull.