gets down to 1/4 tank

 

Nothing is my answer. The Pcm does not switch to Low Octane mode becasue your at a 1/4tank of gas, or so I do not believe it does.

 

If you get knock retard with less than a quarter tank the PCM will put you in the low octane table. Put 5 gallons back in and it will reset back to the high octane table. I beleive thats right , somebody correct me if I'm wrong.

 

Mine does nothing since my low octain table is the same as the high octain.

 

We have pretty much eliminated the "quantity of fuel affecting advance" myth. I don't know the exact permission here on posting specific URL's of other boards (some LS1 sites are really strange on that area), but as an assistant to the development of EFILive V6, there are some interesting threads on this topic in the user forums at www.efilive.com.

Thanks!

MRK

 

From EFILive.com (see High and LOW Octane thread-I bumped it):

"There appears to be alot of myths and confusion about the High and Low Octane tables in the LS1 PCM.

Well, hold onto your hats, we here at EFILive have been torturing our poor LS1's with junk fuel getting to the bottom of what really happens...

The PCM will ALWAYS try to run with the High Octane Table values, however if there is a MAF or Knock DTC set, it defaults to the Low Octane Table only.
But with a vehicle that has neither of those faults set it actually does a 'blend' of the two tables, it does not totally switch between one or the other.
In an upcoming release of EFILive there will be a new PID that will show you what percentage of the High Octane table values are being used (I'll refer to it as the Octane Multiplier).
Say for example the High Octane table has a value of 20 degrees, the same load point on the Low octane table has 10 degrees, and your octane multiplier is set at 50%, the final timing value would be 15degrees, if the octane multiplier is set to 75% it would result in 17.5 degrees, etc.

So what changes the Octane Multiplier value?, I have personally logged this on my car so I have seen it first hand. Basically any sustained amount of knock above about 2 or 3 degrees causes the Octane Multiplier to head towards 0%. It is a constantly changing value, it does NOT get reset to 100% when you fill up with fuel, the only thing that will bring it back to 100% and keep it there is minimal knock activity.
This has been tested on my own 2000 Commodore and emarkay's Camaro.

The PID will be supported for most LS1 powered cars/trucks.
On that note, if anybody has a BIN file or LS1 Edit file from a 2003 & 2004 Truck and 2004 C5, please PM me. "


FWIW- joel