higher octane
03-01-2012, 01:53 PM
#21
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Join Date: Feb 2012
Posts: 41
When you have less air intake restriction the motor will run leaner until the 02 sensors read a change and the ECU adds fuel or retards ignition timing(usually adding more fuel to maintain around a 14.7 air-fuel ratio,depending also on throttle position and manifold absolute pressure and other variables such as air temp and coolant temp),87 octane is Ok if the computer does one of those two things. Leaner mixtures run hotter and(more gasoline will cool the charge)requiring a less volatile burning gasoline with a (higher octane) to reduce chance of detonation a.k.a. "knock". PreIgnition is different than Detonation, the charge ignites due to hot spots on pistons,plugs, protruding combustion chamber edges.etc, which will stay hot enough all the time, igniting when the fuel is shot into the cylinder prior to desired ignition. If the 414 HP Mustang ECU could advance ignition timing based on higher octane sensing ECU adjustments (really done by a knock sensor), then it would probably make a lot more power, depending on some dynamics based on that particular engines knock threshold, mean best torque, piston dome shape, combustion chamber design,stroke length and other factors which determine whether or not more advance would benefit torque and H.P., but some ignition advance over stock almost always gives more power and sometimes lots more.
ever since i put headers intake and exhaust of my car my car feels weird on 87...im not sure maybe it is in my head but on 87 my car tends to feel sluggish when im pushing pass 60 and in 93 its drives smoother..i know its just breathing mods but im spending about 2.70 extra which isnt that serious so i rather spend the 2.70 and feel better
Last edited by rr1982; 03-01-2012 at 02:06 PM.
03-07-2012, 09:33 AM
#22
You're not getting what the octane number means.
A higher octane fuel can resist pre-ignition due to higher compression better than low octane fuels. If your engine is lower in compression (like ours) and does not require a higher octane fuel, then there will be no difference in running high or low octane.
The other qualities of the fuel are going to be the same (comparing 2 ratings for the same fuel maker) including the additives and the energy content.
If you run a lower octane level in a car designed to run a higher one, and the system is able to change the timing enough to prevent knock, then you will have lower power output, but possibly nothing else. Worst case is that you start having knock (pre-ignition) and lower power output. But if a system is designed to run on 87, then you wont gain anything by running 91.
A higher octane fuel can resist pre-ignition due to higher compression better than low octane fuels. If your engine is lower in compression (like ours) and does not require a higher octane fuel, then there will be no difference in running high or low octane.
The other qualities of the fuel are going to be the same (comparing 2 ratings for the same fuel maker) including the additives and the energy content.
If you run a lower octane level in a car designed to run a higher one, and the system is able to change the timing enough to prevent knock, then you will have lower power output, but possibly nothing else. Worst case is that you start having knock (pre-ignition) and lower power output. But if a system is designed to run on 87, then you wont gain anything by running 91.
03-07-2012, 05:26 PM
#23
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Join Date: Jun 2011
Location: Seattle, WA
Posts: 312
Without a simple and apt analogy, it just won't sink in for some people. You can explain the chemistry and engineering involved till your head explodes and they'll still not comprehend. So I'll give it a go.
Higher octane than your engine is designed for is like buying XXL-sized condoms when you're packing standard fare. You can keep your foot on the gas all you want . . . 100% of the time, but it ain't gonna grow any bigger.
Higher octane than your engine is designed for is like buying XXL-sized condoms when you're packing standard fare. You can keep your foot on the gas all you want . . . 100% of the time, but it ain't gonna grow any bigger.
03-07-2012, 08:03 PM
#24
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Join Date: Jul 2011
Location: Toronto, Canada
Posts: 258
Without a simple and apt analogy, it just won't sink in for some people. You can explain the chemistry and engineering involved till your head explodes and they'll still not comprehend. So I'll give it a go.
Higher octane than your engine is designed for is like buying XXL-sized condoms when you're packing standard fare. You can keep your foot on the gas all you want . . . 100% of the time, but it ain't gonna grow any bigger.
Higher octane than your engine is designed for is like buying XXL-sized condoms when you're packing standard fare. You can keep your foot on the gas all you want . . . 100% of the time, but it ain't gonna grow any bigger.
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