Fuse Pull: Low Octane Fuel Fix For L99 and LS3. Reset Fuel Map for High Octane Fuel.

[ls2gto]

Originally Posted by Blueclyde

wh0rsep0wer:

I'm pretty amazed at the level of access you seem to have to automotive ECM calibration tables. I'm shocked the OEM's give out encryption keys to aftermarket software companies for this type of access. There must be some waivers signed for that. Do you actually have write access to those tables? If so it seems like an easy way to jack up an emissions calibration and subsequent catalyst life. I know most folks here have no concern about that but I could see a lot of so called "experts" out there with this type of tool really jacking things up.

So I can see from what you have shown, at least on the 2002 Z28, there are two cal tables. I guess my point revolves around the strategy code. I understand how you say it works in the presence of knock but why doesn't it revert after a key cycle? It would be really good to hear from somebody "in the know" from GM on this. No offense meant to you at all on this. You seem to know your stuff. Great info.

If you have about $500 sitting around and a lap top, you too can access your ECM and change things around to your heart's content (not a good idea actually unless you really know what you are doing). Just go to this site:

http://www.hptuners.com/


I have a 2009 Pontiac G8GT with the L76 6.0 V8 and the A6. I bought HPTuners for my 2005 GTO and had addtional licenses so when I traded the GTO in on the G8 last month, I was able to license the G8 and download the ECM data. I then made some minor changes like turning off the DOD (I did not care for the roughness, even though it was mild) and reflashed the ECM.

Anyway, just like the L99, the L76 also has high and low octane tables. This is what the HPTuners help section says about them:

Main Spark Tables
The VCM constantly looks up both High Octane and Low Octane spark tables and interpolates a value between the two tables based on the current Knock Learn factor. If the engine has been operating for a moderate time without any Knock Retard then Knock Learn is zero and the interpolation favors the High Octane table, if Knock has been detected then the interpolation will move towards the Low Octane table. During MAF failure the Knock Learn is set to maximum and the Low Octane table is used (HP Tuners speed density enhancements allow both spark tables to function).

By the way, the L76 is a premium fuel recommended engine and the quick reference guide says the engine will run on regular but run better on premium, obviously because of the different octane tables. On the other hand, the LS2 in my GTO was a premium fuel required engine and did not have different spark tables. I did not notice but did anyone confirm whether the LS3 has two octane tables?

[Camar0wn3d]

Originally Posted by ls2gto

If you have about $500 sitting around and a lap top, you too can access your ECM and change things around to your heart's content (not a good idea actually unless you really know what you are doing). Just go to this site:

http://www.hptuners.com/


I have a 2009 Pontiac G8GT with the L76 6.0 V8 and the A6. I bought HPTuners for my 2005 GTO and had addtional licenses so when I traded the GTO in on the G8 last month, I was able to license the G8 and download the ECM data. I then made some minor changes like turning off the DOD (I did not care for the roughness, even though it was mild) and reflashed the ECM.

Anyway, just like the L99, the L76 also has high and low octane tables. This is what the HPTuners help section says about them:

Main Spark Tables
The VCM constantly looks up both High Octane and Low Octane spark tables and interpolates a value between the two tables based on the current Knock Learn factor. If the engine has been operating for a moderate time without any Knock Retard then Knock Learn is zero and the interpolation favors the High Octane table, if Knock has been detected then the interpolation will move towards the Low Octane table. During MAF failure the Knock Learn is set to maximum and the Low Octane table is used (HP Tuners speed density enhancements allow both spark tables to function).

By the way, the L76 is a premium fuel recommended engine and the quick reference guide says the engine will run on regular but run better on premium, obviously because of the different octane tables. On the other hand, the LS2 in my GTO was a premium fuel required engine and did not have different spark tables. I did not notice but did anyone confirm whether the LS3 has two octane tables?

I just sent my interface module serial number to HPTuners in order to get the Beta software so I can access my LS3's ECU...as soon as I get that I will look to verify whether there are one or two octane tables.

[MARINE1991]

Why are the dealerships or GM not taking care of this problem....

[DDustiNN]

I keep seeing "ECM" vs. "ECU"... is there a difference? Or just different names for the same thing? And what do these acronyms even stand for? Thanks

[Camar0wn3d]

Engine Control Module (ECM) and Engine Control Unit (ECU)...I use them interchangeably (probably incorrectly) when I refer to the computer that controls the engine parameters.

HPTuners refers to a VCM (Vehicle Control Module) because it also talks to the Body Control Module (BCM), and PCM (Powertrain Control Module)

[DDustiNN]

Originally Posted by wh0rsep0wer

Engine Control Module (ECM) and Engine Control Unit (ECU)...I use them interchangeably (probably incorrectly) when I refer to the computer that controls the engine parameters.

HPTuners refers to a VCM (Vehicle Control Module) because it also talks to the Body Control Module (BCM), and PCM (Powertrain Control Module)

Thanks

[ttazzijr700]

i just took the fuses out after feeling for a while that there was a lack of power. I will put them back in the morning and see how it goes

[optical]

Awesome news for all the L99 guys!

[fosterr2]

Does anyone else remember reading in these forums about people gaining power and speed after there first service? wonder if dealers have been resseting peoples cars all along http://www.camaro5.com/forums/showth...ght=oil+change

[ls2gto]

Originally Posted by MARINE1991

Why are the dealerships or GM not taking care of this problem....

Maybe they have not figured out what is wrong yet. Like HPTuners says, the engines are supposed to adapt to knock conditions over time, but that does not appear to be happening with the problem cars. Thus, the fuse fix does not really solve the problem as someone already noted.

I do know that no one at the G8 board is complaining about the 361 hp L76, and with only 800 miles, my car definitely feels like it can do 0-60 in 5.3 as claimed by Pontiac. The L76 is similar to the L99 but does not have variable valve timing. It does, however, have the same 10.4:1 compression ratio.

I note from the spread sheets at the GM powertrain site that both the L99 and the LS3 are premium fuel recommended engines, so my guess is they both use high and low octane fuel tables (click on the "SS" for each engine at this site: http://media.gm.com/us/powertrain/en...a/10car_us.htm)


All that being said, it seems extreme that using 87 octane gas would increase the 0-60 time by a second or more, which is literally like taking on the order of 100 flywheel hp away. Most times I have seen actual comparisons between hp on high and low octane fuels, the differences have only been a few percent.

[tribone]

Ok guys. I just want to point out that I also received an increase in MPG while driving on the freeway for a little less than an hour.

I used to average 24.5 on the same freeways before the pull. After the pull i averaged 29.1 going 65mph.

My drive: from my house 91 West -> 605 North -> 105 West -> 710 North and off the freeway to my moms house.

Then back home: my mom's house 710 South -> 105 East -> 605 South -> 91 East and off the freeway to my house.

48.3 miles total.

[PQ]

I'm so confused.


Anyway, I was told that the fuel tables were automaticaly adjusting only one way. That it would adjust from high to low to protect the system but not from low to high. You can run high octane through the low tabled setting just fine but running low fuel through a high tabled system could damage your system.

Make sense?

[2011RS/SS]

Anybody that puts 87 octane in a V8 period should be bitchslapped. It redicious that the dealers have been putting cheap gas in these cars just to save a few bucks.

You should only have to let the fuses set out a hour at the most. The purpose is to wait till all the capacitors in the computer has discharged. When current is reapplied to it and the car is started up, it then begins to relearn its tables..

[salohi]