Steve from SoCal Posted March 18 Report Share Posted March 18 Octane numbers relate to knock or pre-ignition, that has no bearing on power. Knock or pre-ignition has several factors, compression is one, chamber shape and mixture are others. Modern engines with knock sensors can adjust for different grades of fuel. With lower octane fuel developing lower power in these engines due to ignition timming/mixture changes to allow for the lower grade fuel. The flame rate or how fast the fuel burns is really the detail behind octane numbers At high altitude the air is less dense therefore naturally asperated engines don't produce the same pressue they would at sea level. Lower compression allows for faster combustion hence lower octane fuel. In aviation the development of piston aero engines can be traced to octane. The Big American Radial engines, RR and, Allison V12's of WWII were designed to use 115/145 octane fuel. These engines are suppercharged, they still run on 100LL agas but at much lower power than they are rated at. The Germans did not have high octane fuel and their engines were either larger displacement or lower powered than the allied forces because of this. Quote 2005 Peterbilt 387-112 Baby Cat 9 speed U-shift 1996/2016 remod Teton Royal Atlanta 1996 Kentucky 48 single drop stacker garage project Pulls like a train, sounds like a plane....faster than a Cheetah sniffin cocaine. Link to comment Share on other sites More sharing options...
noteven Posted March 18 Report Share Posted March 18 Myth: a diesel engine has to roll coal black clouds of smoke to produce sufficient power to move a pickup twuck Quote "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
jenandjon Posted March 21 Report Share Posted March 21 On 3/18/2024 at 1:54 PM, noteven said: Myth: a diesel engine has to roll coal black clouds of smoke to produce sufficient power to move a pickup twuck False. I actually don't see that much anymore. Quote Farmer, Trucker, Equipment operator, Mechanic Quando omni flunkus moritati-When all else fails, play dead I'm a man, but I can change, if I have to, I guess. Link to comment Share on other sites More sharing options...
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