Originally Posted by OhioRiverCigarette
Is that a 2% difference in heat? If so what is the difference you see in horsepower, mileage, etc?
What is the difference in EGT?
it may not be 2% on the nose it may be more or less depending on your mods. in the truck in my sig at hiway cruise I see about 500* egt running bio and on the dyno I went from 462Hp on petro to 447hp on bio without the spray.I'm not 100% sure about the numbers but I think petro diesel has like 28,000 BTU per litre and bio has like 17 or 18,000 btu per litre the actual cetane # for bio is quite a bit higher than petro which in a way makes up for the BTU loss. as far as milage is concerned, who cares I make bio for like .80 a gallon but for those who do care my milage dropped from about 19 mpg to 16 mpg in a 2006 6.0, in the sig truck I havn't checked it
All these #s are within a few percentage of each other. Based on just plain energy value, diesel fuel is ~130,000 BTU/gal and 40 cetane compression ignition point is ~225F , bio is ~125,000 BTU/gal anywhere from 49-62cetane based on feedstock and a varying compression flash point of 270-410F
So energy wise thats 3.8% less energy. which proven on the dyno comes out to 3.2% power loss. On the road fuel economy wise 19 to 16mpg, is a 15% loss. But the extra 11.2% loss comes from the high cetane being that it takes more heat to light, therefore delaying the power. An economy tune with advanced timing would reduce this loss, but unless you get the exact same oil and have it tested, you should error to safe side and leave timing alone.
On the dyno, you are essentially seeing a direct relation of energy, running hot and in the power on the dyno, the cetane isnt a factor. But at normal highway speeds, and lower internal temps, you see a greater loss. But in my book if its $.80 vs $3.90 you could have a 79.41717% reduction in fuel economy, and you are still saving $ vs pulling up to the pump
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