[bishopts]

Originally Posted by Mid_Life_Crisis

Update.....I went ahead and tried some 93 in my car.....waited until tank was nearly empty of the 87 and filled it up. About $10 extra on the fill. I drove it pretty mellow for about 50 miles to allow the ECU to calibrate to the higher octane and then started to get on it at different driving speeds from full stop to 30-80 mph runs, etc. I have to say, I'm now a believer. The motor clearly has more pulling power. Everywhere. I can feel it. I'm not saying I'm going to keep going with the 93 all the time, but it's good to know it opens up some more timing for extra fun.

Get it setup for e85 as well. If its tuned correctly you can switch between or mix them and open up a whole different driving experience.

[Mid_Life_Crisis]

From a search I just did on Google AI:


Is the GM LGX 3.6 V6 designed to advance timing and create more power if given higher octane fuel than the recommended 87 octane? In other words....is the ECU adaptive?


The short answer is: Yes, the LGX ECU is adaptive, but with a specific ceiling.
While the LGX 3.6L V6 is designed to run safely on 87 octane, its engine management system is sophisticated enough to hunt for more performance when conditions allow. Here is the breakdown of how that works and what you can actually expect.
The "High Octane" vs. "Low Octane" Maps

The ECU in the LGX uses two primary timing tables: a High Octane Map and a Low Octane Map.

• Knock Sensors: These are the "ears" of the engine. They listen for pre-detonation (knock).
  +1
  
• The Transition: When you run 87 octane, the ECU often detects trace amounts of knock under load and "steps down" toward the Low Octane Map to protect the engine. When you switch to 91 or 93, the knock sensors stay quiet, allowing the ECU to "advance" the timing back toward the High Octane Map.
• The Multiplier: The ECU uses a "Knock Learn Factor" to interpolate between these two maps. If the fuel is high quality, the ECU stays pinned to the more aggressive timing table.
  
  

Does it actually create more power?

There is a common misconception that high octane contains "more energy." It doesn’t; it simply resists detonation better.
In the LGX, using 93 octane won't turn it into a race engine, but it prevents the ECU from pulling power.

• In Hot Weather/Heavy Load: This is where you’ll feel it most. On 87 octane in 95°F heat, the ECU will aggressively retard timing to prevent knock, making the car feel sluggish. High octane prevents this "power pull."
• The "Ceiling" Effect: The ECU will not advance timing indefinitely. It will only advance up to the maximum values defined in the factory High Octane Map. Once it hits that limit, adding higher octane (like 100+ racing fuel) provides zero additional benefit without a custom aftermarket tune.

Summary of Benefits

Feature87 Octane Performance91/93 Octane PerformanceIgnition TimingMore conservative / RetardedOptimized / AdvancedHeat ManagementProne to power loss in summerMore consistent performanceFuel EconomyBaselineSlight improvement (1–2 MPG) possibleThrottle ResponseCan feel "mushy" under loadGenerally crisper
Export to Sheets



The Verdict

If you are daily driving in mild weather, 87 octane is perfectly fine. However, if you are looking for maximum "butt-dyno" responsiveness or are driving in high-heat environments, the LGX will utilize the extra octane to maintain its peak timing curves.

[arpad_m]

The AI gave you a correct summary, although one thing it didn't address is how long it takes for the ECM to switch back to the high octane table after not detecting any knock.

IIRC there is a minimal no-knock threshold for it to even start moving towards the high octane table, so it may take longer to get all the power back than one would expect after switching to 93 or better, it's definitely more than just a few minutes or a gallon or two used.

[bishopts]

ALL engine computers are adaptive. They have been since the 80s.
They will pull timing when knock is detected, add or remove fuel injected based on o2 sensor readings. Learn new throttle plate locations as carbon builds up on the throttle.
Sometimes they dont have limits to adjust and get kinda dumb. For example Ford fusion turbo engines will have slightly high readings in the low pressure fuel sensor, the pcm trying to adapt will completely turn off its own fuel and the car will die. It will restart and give you about 30 seconds before it does it again. You can unplug the sensor and drive it home.
Similar to if the adaptive fueling is flooding your engine then you can unplug the o2 sensors and it should let you drive it home.

[Mid_Life_Crisis]

This is all pretty much over my head but interesting. I'm not going to get a tune for this car....just enjoy it as it is....a seriously fun back road daily driver. Just nice to know I can get a bit more pep with the higher octane.

[Matt1LE]

Originally Posted by bishopts

Get it setup for e85 as well. If its tuned correctly you can switch between or mix them and open up a whole different driving experience.

But how difficult is it? I know all you need to do on a SS "LT1" is activate 1 pin on the engine wire harness for the cpu to recognize E85. (besides o-ring and injector change)


I thought about it, but I heard you need to do a lot of work.

[bishopts]

Originally Posted by Matt1LE

But how difficult is it? I know all you need to do on a SS "LT1" is activate 1 pin on the engine wire harness for the cpu to recognize E85. (besides o-ring and injector change)


I thought about it, but I heard you need to do a lot of work.

On the SS your. Adding a flex fuel sensor that detects how much alcohol is in the fuel. The wire to the pcm is the signal wire for that sensor. Then you go into the pcm with hp tuners and click the checkbox that determines if the pcm should be looking for alcohol content.

I would guess the 3.6 would be pretty close to the same thing but I've never really looked into it. I will dig through the wiring diagrams later and get back to you on it.

[Goingnowherefast]

Originally Posted by bishopts

On the SS your. Adding a flex fuel sensor that detects how much alcohol is in the fuel. The wire to the pcm is the signal wire for that sensor. Then you go into the pcm with hp tuners and click the checkbox that determines if the pcm should be looking for alcohol content.

I would guess the 3.6 would be pretty close to the same thing but I've never really looked into it. I will dig through the wiring diagrams later and get back to you on it.

The LGX ecu does not have a pin that we can use for flex fuel. I.E. E85 tunes can be done via HPT but keep in mind this will be either a full 93 tune or a full E85 tune - no blending in-between those ethanol levels.

[arpad_m]

Originally Posted by bishopts

On the SS your. Adding a flex fuel sensor that detects how much alcohol is in the fuel. The wire to the pcm is the signal wire for that sensor. Then you go into the pcm with hp tuners and click the checkbox that determines if the pcm should be looking for alcohol content.

Just a small correction, the stoich table needs to be populated as well, because the stock SS tune has 14.1 or so (corresponding to ~10% alcohol) in every cell, regardless of alcohol content.

(I can't triple check the exact value right now, because the only windows computer in the house is in use, but it's 14.1 or something very close to it. The point is there is no progression in the table, it's a flat line by default.)

[arpad_m]

Originally Posted by Goingnowherefast

The LGX ecu does not have a pin that we can use for flex fuel. I.E. E85 tunes can be done via HPT but keep in mind this will be either a full 93 tune or a full E85 tune - no blending in-between those ethanol levels.

This sucks, GM apparently didn't want to help LGX owners.

An E85-only tune essentially means one has to buy and blend fuel at home, because pumps provide varying E levels, theoretically anything between E50 and E85 can be labeled as "E85", and I've noticed that E content varies slightly even for the same station and the same pump unit. Now this might just be a TN thing, but given how permissive the regulation is, I don't think gas stations bother to blend to the exact same E content with every single shipment.

[bishopts]

Originally Posted by arpad_m

Just a small correction, the stoich table needs to be populated as well, because the stock SS tune has 14.1 or so (corresponding to ~10% alcohol) in every cell, regardless of alcohol content.

(I can't triple check the exact value right now, because the only windows computer in the house is in use, but it's 14.1 or something very close to it. The point is there is no progression in the table, it's a flat line by default.)

Correct. It does need to be tuned for it.
I was just saying what's required to "turn it on"

[bishopts]

I cant really find much info on the ecm crossing over to other platforms. Usually you can look at similar platforms and find pins they use that might be dormant with your current setup. But things like the cts, ct5, xt6 all use a different ecm than the camaro does. I even looked into impala. Lacrosse, malibu. Colorado. The pinouts are way different vs the camaro.

[lowke]

It seems like avoid knock is priority for the ECU. So premium will give more power and a healthier engine. Money well spent imo.