lnferno
02-23-2003, 05:24 PM
Did you guys read this?
Car and Driver did an article showing that on the 6th gen Honda Accord V6s that you will actually lose 5 HP by using 91 octane -vs- 87.
I firmly believe that the reason for the lost power on the AV6 when running higher octane fuel is becuase of ignition timing issues. The AV6 is tuned and optimized for 87 octane fuel, and it does not adjust itself for other octane levels, so the amount of ignition advance is pretty much fixed on the AV6.
Higher octane fuels burn slower than lower octane ones (becuase the purpose of octane in fuel is to prevent combustion and not promote it), so to get maximum performance out of an engine running on a higher octane fuel than it was designed for you need to advance the timing so that the spark fires sooner. Doing this will allow the peak of the combustion cycle with the higher octane fuel to still occur at the piston's optimal point (90 degrees ATDC - After Top Dead Center).
Not advancing the timing when running a higher octane than an engine was designed for will cause the peak of the combustion cycle to occur after the optimal torque point (90 ATDC) and this is how you lose power. The peak combustion point might occur at something like 95 or 100 degrees ATDC which is not optimal.
Think of it like this.
You see a door that's open a crack, so instead of using the door knob and just pulling it open you push on the edge of the door towards the center of the door and let it open that way. As it opens you move your hand towards the outer edge of the door and push directly on the door instead of on its side.
When you're just starting to open that door, you have to put a lot more force on it to get it moving and rotating open than you do when your hand is on the side of the door on the outer edge and pushing directly on it. Pushing on the edge you don't have a lot of leverage.
So using 91 octane fuel on the AV6 forces the piston and connecting rod to sorta push on the edge of the crankshaft and not directly on its side. A similar amount of force is being applied between 87 and 91 octane, but becasue the timing is off with 91 octane, power as a whole is lost.
Don't put anything other than 87 octane fuel in your AV6!!!
Car and Driver did an article showing that on the 6th gen Honda Accord V6s that you will actually lose 5 HP by using 91 octane -vs- 87.
I firmly believe that the reason for the lost power on the AV6 when running higher octane fuel is becuase of ignition timing issues. The AV6 is tuned and optimized for 87 octane fuel, and it does not adjust itself for other octane levels, so the amount of ignition advance is pretty much fixed on the AV6.
Higher octane fuels burn slower than lower octane ones (becuase the purpose of octane in fuel is to prevent combustion and not promote it), so to get maximum performance out of an engine running on a higher octane fuel than it was designed for you need to advance the timing so that the spark fires sooner. Doing this will allow the peak of the combustion cycle with the higher octane fuel to still occur at the piston's optimal point (90 degrees ATDC - After Top Dead Center).
Not advancing the timing when running a higher octane than an engine was designed for will cause the peak of the combustion cycle to occur after the optimal torque point (90 ATDC) and this is how you lose power. The peak combustion point might occur at something like 95 or 100 degrees ATDC which is not optimal.
Think of it like this.
You see a door that's open a crack, so instead of using the door knob and just pulling it open you push on the edge of the door towards the center of the door and let it open that way. As it opens you move your hand towards the outer edge of the door and push directly on the door instead of on its side.
When you're just starting to open that door, you have to put a lot more force on it to get it moving and rotating open than you do when your hand is on the side of the door on the outer edge and pushing directly on it. Pushing on the edge you don't have a lot of leverage.
So using 91 octane fuel on the AV6 forces the piston and connecting rod to sorta push on the edge of the crankshaft and not directly on its side. A similar amount of force is being applied between 87 and 91 octane, but becasue the timing is off with 91 octane, power as a whole is lost.
Don't put anything other than 87 octane fuel in your AV6!!!