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Nobody cares about, "testing BTU", nobody said anything about, "heat value", I didn't say anything about, "stored energy". People only care about how their car is going to run when they fill up their tank, and not listen to all the BS.
Nobody cares about, "testing BTU", nobody said anything about, "heat value", I didn't say anything about, "stored energy". People only care about how their car is going to run when they fill up their tank, and not listen to all the BS.
You repeatedly brought up some octane making more power than another. If you want to determine which fuel makes more power, then you need BTU not octane.
Making more power from different fuels. That's an entirely different discussion than using the correct octane for the application.
My god there is some crazy BS in this thread. There is no way that running 100 octane fuel in a engine designed for 93 is going to make more power. The only way it would make more power in that situation is to increase timing or boost. And a stock engine, SC or is going to be less efficient with increased octane over what it was desigmed for. These engines do not ADD timing, they will pull timing if detonation occurs but but will not increase timing beyond the max timing reference in the tune wether it is stock or custom tune.
And before all the internet gurus start taking shots, I do know a little something about engines and octane. I run a 632 big block in my dragster with 16.8 to 1 compression that makes 1225 hp with a single carb and 116 octane leaded race fuel. If I could run 112 safely I would do that and guys that run the same combo at elevation do run 112.
My god there is some crazy BS in this thread. There is no way that running 100 octane fuel in a engine designed for 93 is going to make more power. The only way it would make more power in that situation is to increase timing or boost. And a stock engine, SC or is going to be less efficient with increased octane over what it was desigmed for. These engines do not ADD timing, they will pull timing if detonation occurs but but will not increase timing beyond the max timing reference in the tune wether it is stock or custom tune.
And before all the internet gurus start taking shots, I do know a little something about engines and octane. I run a 632 big block in my dragster with 16.8 to 1 compression that makes 1225 hp with a single carb and 116 octane leaded race fuel. If I could run 112 safely I would do that and guys that run the same combo at elevation do run 112.
I haven't seen anyone say running higher octane would make more power. A few suggested it would make less power, which I and @fnbrowning have disputed.
Higher octane only indicates more knock protection. It isn't an indicator of power potential.
And a stock engine, SC or is going to be less efficient with increased octane over what it was desigmed for. These engines do not ADD timing, they will pull timing if detonation occurs but but will not increase timing beyond the max timing reference in the tune wether it is stock or custom tune.
This is the part I have yet to see testing on. What I see you say is that because my car was designed for 87 and the fuel and timing maps are set for 87, running 95 will decrease efficiency and thus output.
GenV engines will also pull power in order to stay below the torque value in the driver demand table. So the ECU has the ability to manipulate throttle plate position, fuel and timing if it's exceeding the torque delivered at a given gear + RPM+ driver pedal position. This is why a lot of folks would talk about the ECU "detuning" modifications.
Fake driver demand target: If say 1,000 rpm has a 100ft lb limit at 80% pedal. And this engine would make 120ftb at 80% pedal position, then the ECU will compensate in order to deliver less torque.
GenV engines will also pull power in order to stay below the torque value in the driver demand table. So the ECU has the ability to manipulate throttle plate position, fuel and timing if it's exceeding the torque delivered at a given gear + RPM+ driver pedal position. This is why a lot of folks would talk about the ECU "detuning" modifications.
Fake driver demand target: If say 1,000 rpm has a 100ft lb limit at 80% pedal. And this engine would make 120ftb at 80% pedal position, then the ECU will compensate in order to deliver less torque.
This is the part I have yet to see testing on. What I see you say is that because my car was designed for 87 and the fuel and timing maps are set for 87, running 95 will decrease efficiency and thus output.
I don't truly know with these engines if using say 100 octane unleaded race fuel vs 93 will decrease power but I would not think it will be as efficient. I will ask my engine builder about this. He is one of the best sportsman builders in the country and also has worked on NASCAR and Pro Stock engines. I'm sure there has been some real world Dyno time testing fuels.
This is VP 100 octane unleaded fuel, why in the world would you want to pay $25 a gallon for fuel that isn't going to have any benefit at all...
In your scenario 87 required and running 95? Why would you use it even if the performance is the same, it for sure won't be better. Your power to weight ratio may change since your wallet will be lighter.
I don't truly know with these engines if using say 100 octane unleaded race fuel vs 93 will decrease power but I would not think it will be as efficient. I will ask my engine builder about this. He is one of the best sportsman builders in the country and also has worked on NASCAR and Pro Stock engines. I'm sure there has been some real world Dyno time testing fuels.
This is VP 100 octane unleaded fuel, why in the world would you want to pay $25 a gallon for fuel that isn't going to have any benefit at all...
In your scenario 87 required and running 95? Why would you use it even if the performance is the same, it for sure won't be better. Your power to weight ratio may change since your wallet will be lighter.
This is my previous engine 632 9 degree heads, 1320 hp@7300 and 1000 ft lbs of tq with a single carb. Sunoco 116 fuel
Not even sure why running 95 in a motor designed for 87 will hurt more than the wallet. I think it simply won't be any better but not worse. That's what I am curious about. Some have even said it will hurt economy and startup time.
Meanwhile....
The OP has (intelligently....) bowed out of the conversation.
The C6 gen was tuned for best performance on 93. Dunno about the C7, but one might assume that is also.
Below that octane, they'll pull timing, and that WILL cost performance. They will run on 87... But why would anyone do that?!
At 93, the timing will revert to the base map, and deliver performance as programmed.
Above that, there will only be benefit if some detonation is present and timing is still being pulled. Maybe GM cut the tuning right to the edge.
I've seen no hard evidence that octane increased above optimum costs performance, just rumors of 'spongy acceleration', with the explanation of 'slower energy release'.
Tough for me to imagine that running a couple of points over optimum would be measurable.
In CA, at the pump, we could only buy 91. Here in Oregon 92 is the norm. OP didn't say what his local premium was. If it's low, blending in some 100UL is of performance benefit.
Up to him to weigh the cost/benefit ratio...
The C6 gen was tuned for best performance on 93. Dunno about the C7, but one might assume that is also.
Below that octane, they'll pull timing, and that WILL cost performance. They will run on 87... But why would anyone do that?!
I've seen no hard evidence that octane increased above optimum costs performance, just rumors of 'spongy acceleration', with the explanation of 'slower energy release'.
Tough for me to imagine that running a couple of points over optimum would be measurable.
In CA, at the pump, we could only buy 91. Here in Oregon 92 is the norm. OP didn't say what his local premium was. If it's low, blending in some 100UL is of performance benefit.
Up to him to weigh the cost/benefit ratio...
I would assume GM will not be dumb enough to waste time on programming it for octane most of us will not have easy access to.
I am low on gas and that's all I can get?
I've also heard of gains from a part that the dyno or track doesn't agree with. IMO, SOTP dynos are generally worthless at best and misleading at worst.
I honestly doubt it can be measured or if it could, probably not significantly different.
93 is the available premium in alot of areas.
Since the KR strategy is so good, they're going for the best possible perf, and letting the ECU correct for any shortcomings.
I don't know how close to the edge factory maps are to detonation on 93, whether there is more performance to be gained with octane above that or not.
If I had a dyno and all the time in the world, I'd pass the info along...
Back in the E36 M3 days, the performance chips were mapped for 92, but they would run fine on CA 91.
Until they went to the track.
I cautioned my customers to add in some 100UL to bring the octane up a smidge if they were going.
I could tell who didn't listen by the blown headgasket!
Cars today are much more sophisticated. They do say in the manuals that it's ok to run a bit lower octane, and the higher octane. This is because the electronics have become much better at handling knock, and not do any damage, and not relying on the driver to keep his foot out of it. It's an advertising, sales thing. The car then seems cheaper to drive.
The BTU/lb of energy of 91-93 premium is the same as regular 87. (within the margin of error) The heavy aromatic content is slightly different (same concentration) to get the higher octane value. Distillation, flame speed, burn rate, vaporization, etc... all practically the same.
Cars today are much more sophisticated. They do say in the manuals that it's ok to run a bit lower octane, and the higher octane. This is because the electronics have become much better at handling knock, and not do any damage, and not relying on the driver to keep his foot out of it. It's an advertising, sales thing. The car then seems cheaper to drive.
But by retarding the timing because you used lower octane gas, you can avoid knock BUT lose power. So yes, it seems cheaper to fill up but you spend more than you would have with the right octane. My E85 capable truck does that. E85 is cheaper and the sticker shock at the pump is less but you don't go as far either.
I also tried the E85. It does work but like you said, the milage is really BAD. Not worth it. I'm not as sure about using 87 vs 91, yes it will make a bit less power, but not sure the milage would be all that bad.
I also tried the E85. It does work but like you said, the milage is really BAD. Not worth it.
I'm not as sure about using 87 vs 91, yes it will make a bit less power, but not sure the milage would be all that bad.
Both mileage and power. Towing up a hill was drastic enough to be noticed and since I wasn't prepared for it to suck that much or even at all, I suspect it is real.
Not sure since the only way to do that would be to measure it under heavy load to see the KS remove timing.
