Afm not working correctly?

[Bill 1960]

This is another reason why your AFM doesn't turn on as frequently as it should, you are running low octane fuel that produces less power.

My experience, on 5.3 and 6.0 stock engines that I tuned and logged with HPT was that with stock programming, the timing did not change between using 87 or 93. Neither did the ET which I measured with instrumentation.

With high octane I WAS able to advance the timing more, which did give more power / lower ET in a tuned scenario.

My conclusion was the factory maps were optimized for 87 and there was no HP gain from increased octane in stock condition.

The science, to the best of my understanding, is that octane above what is sufficient to avoid detonation, yields no benefit. So if an engine is seeing knock retard on 87, there’s certainly a case to be made that higher octane will benefit. I would certainly be interested in seeing some comparisons of logs of timing and KR values on a stock engine and tune with different fuels.

PS- and I apologize for not realizing this is the hybrid section, although we’re apparently not discussing a hybrid. Maybe someone can get this moved?

 

[Amaster]

Eh screw it I probably already pissed off an elite member as is. But thanks guys I now know never to own a hybrid of one of these cheers!

 

[Rocket Man]

So what motor do you have, @Amaster? And don’t worry, nobody gets pissed off here. That’s other forums. This place is great. We don’t judge, we just help.

 

[swathdiver]

My experience, on 5.3 and 6.0 stock engines that I tuned and logged with HPT was that with stock programming, the timing did not change between using 87 or 93. Neither did the ET which I measured with instrumentation.

With high octane I WAS able to advance the timing more, which did give more power / lower ET in a tuned scenario.

My conclusion was the factory maps were optimized for 87 and there was no HP gain from increased octane in stock condition.

The science, to the best of my understanding, is that octane above what is sufficient to avoid detonation, yields no benefit. So if an engine is seeing knock retard on 87, there’s certainly a case to be made that higher octane will benefit. I would certainly be interested in seeing some comparisons of logs of timing and KR values on a stock engine and tune with different fuels.

PS- and I apologize for not realizing this is the hybrid section, although we’re apparently not discussing a hybrid. Maybe someone can get this moved?

Blackbear tuned my 5.3 for 93 years ago so I can't run a test with 87. I remember always running 93 or higher in my Buicks in the 1980s and 1990s. Sometimes, I'd buy 104 unleaded and boy did it make it feel like I was driving another car. The tune back then wasn't changed at all. While I did make 1/4 mile test runs back then between fuels, I cannot remember and think the timeslips are in my garage or my brother's.

As always I caveat my experience that this does not apply to the 5.3 DI motors.

 

[Amaster]

@Rocket Man I

Blackbear tuned my 5.3 for 93 years ago so I can't run a test with 87. I remember always running 93 or higher in my Buicks in the 1980s and 1990s. Sometimes, I'd buy 104 unleaded and boy did it make it feel like I was driving another car. The tune back then wasn't changed at all. While I did make 1/4 mile test runs back then between fuels, I cannot remember and think the timeslips are in my garage or my brother's.

As always I caveat my experience that this does not apply to the 5.3 DI motors.

I would love 104 ummm that's the good stuff put not for my yukon lol. b.t.w @Rocket Man I have 5.3 or 327 vortex flex fuel direct injection I think! Main reason I posted here is cause I thought since it was a flex fuel and the AFM I had a hybrid. I never knew there was a full on hybrid these years.

 

[swathdiver]

@Rocket Man I

I would love 104 ummm that's the good stuff put not for my yukon lol. b.t.w @Rocket Man I have 5.3 or 327 vortex flex fuel direct injection I think! Main reason I posted here is cause I thought since it was a flex fuel and the AFM I had a hybrid. I never knew there was a full on hybrid these years.

With FlexFuel, you can run any combination of ethanol and gasoline up to E85 which is 83% alcohol. Technically, you could also burn E85R, which Sunoco sells in 5 gallon cans or 55 gallon drums which is a full 85% alcohol. My truck gets its best gas mileage with an alcohol content of between 16% and 22% or so. Mixing fuels keeps the octane rating up and costs down!

If you do have ethanol close by, don't just try a tank and go back to gasoline. Run 4 or 5 tanks so it will get up to full strength and your computer system will adjust for it. You'll find that it makes more power, idles and runs smoother, operates a little cooler and is more fun to drive, even the transmission likes the stuff.

It even cleans the injectors and intake and combustion chambers and pistons.

Yes, the mileage will not be the same, we don't measure its performance in mpgs, but rather in cost per mile to operate. Sometimes it pays to run it, sometimes it doesn't, depends on the market prices.

Here are my truck's stats after four years of running:

 

[Rocket Man]

@Rocket Man I

I would love 104 ummm that's the good stuff put not for my yukon lol. b.t.w @Rocket Man I have 5.3 or 327 vortex flex fuel direct injection I think! Main reason I posted here is cause I thought since it was a flex fuel and the AFM I had a hybrid. I never knew there was a full on hybrid these years.

I assumed you had the hybrid or the 6.2 which call for 93. At least i think the hybrid calls for it, @BG1988 would know for sure. But you should try a few tanks of the E85 like @swathdiver mentioned.

 

[Amaster]

I assumed you had the hybrid or the 6.2 which call for 93. At least i think the hybrid calls for it, @BG1988 would know for sure. But you should try a few tanks of the E85 like @swathdiver mentioned.

Would if could lol. Unfortunately no station sell it around me. Closest one is the next town over I think thanks anyhow. Also thanks for the info @swathdiver

 

[swathdiver]

Would if could lol. Unfortunately no station sell it around me. Closest one is the next town over I think thanks anyhow. Also thanks for the info @swathdiver

Check the Gas Buddy app for stations selling it every so often, they come and go. In the last four years, we've gone from 7 to 12 or more stations in the two county area.

 

[BG1988]

My experience, on 5.3 and 6.0 stock engines that I tuned and logged with HPT was that with stock programming, the timing did not change between using 87 or 93. Neither did the ET which I measured with instrumentation.

With high octane I WAS able to advance the timing more, which did give more power / lower ET in a tuned scenario.

My conclusion was the factory maps were optimized for 87 and there was no HP gain from increased octane in stock condition.

The science, to the best of my understanding, is that octane above what is sufficient to avoid detonation, yields no benefit. So if an engine is seeing knock retard on 87, there’s certainly a case to be made that higher octane will benefit. I would certainly be interested in seeing some comparisons of logs of timing and KR values on a stock engine and tune with different fuels.

PS- and I apologize for not realizing this is the hybrid section, although we’re apparently not discussing a hybrid. Maybe someone can get this moved?

you don't have a VVT equipped engine...

mine advances upwards of 38-42 degrees with 91oct....

i'm sure it would be higher with 93 or 100oct (not worth spending 12$ a gallon).. In 2007-08, the actuator has 62-degree rotation. GM part number 12585994.