E85 releases less thermal energy then 91 oct pump gas, when compared at a 1:1 ratio and in a laboratory. Although, this is good to know, in reality "We really don't care". What we want to know is what to expect when a stoichiometric amount of ethanol (E100 or E85) is used in replacement of a stoichiometric amount of petrol containing proper octane ratings and/or even race fuels which use fossil fuel as the main ingredient to their product.
The most noticeable difference we've experienced between E85 and E100 is the capability of having a 9:1 air fuel ratio with E85 and not having the unused ethanol pass by the rings to thin out the engine's lubricating oil.
Heat is a main contributor to many causes of engine damage and engine failures. Although ethanol does lower engine operating temps, the engine temperatures can still reach levels high enough to start the softening of a given material, and when combined to the proper stoichiometric combustion of ethanol, a higher thermal energy will be released outward towards the engines next weakest point, causing damage over a given period of time. As in this image to the top/right showing us a cylinder damaged in an area that receives direct heat transfer from the combustion chamber directly above.
Lower engine operating temps that come with using E85 increases charged air density, which allows for more fuel to be burned in the combustion process. After all, fire can't exist without a very important catalysts that fuels it, and that catalysts is oxygen. The fuels maximum thermal energy is released at the pinnacle of its thermal expansion process, which is initially set off by a spark set through ignition timing. 15 degrees advanced means the fuels thermal expansion process is timed to start at 15 degrees before top dead center. The time it takes for a fuel to release it's max energy after igniting is called the burn rate. Ethanol burn rate is higher(burns faster) than 91oct. and increases it's burn rate faster then 91 octane as cylinder temperatures rise. In conventional race gas, burn rates decrease with octane. The higher the octane rating, the slower it's burn rate.
POWER AVERAGES FOR OEM IGNITIONS NOT DESIGNED TO BURN THE EXTRA AMOUNT OF FUEL; OEM "coil on plug" systems averaged capability of 100hp-115hp per cylinder on E85, compared to the same OEM "coil on plug" average output range of 130-145hp per cylinder with VP C16 race fuel. Ignition systems with OEM internal or external coils averaged maximum capability at 65hp-80hp per cylinder on 91 octane.
DETONATION: Why and how it happens.
Temperatures rise in a combustion area from the heat that is generated by the simple compression of the air /fuel mixture. Pre-mature detonation of a fuel, before the combustion process is complete, is due to the fuel having reached it's flash point from that heat. (This is why over heated engines are known to diesel for a bit after being shut off). Detonation can destroy pistons, piston rings, rod bearings, and crack piston wrist pins. The damage to engine components is caused from the fuels maximum thermal energy being released while the piston is moving upward into the compression stroke of the combustion process. It's like hitting the head of the piston with a sledge hammer while the piston is coming up.
Higher burn rate of ethanol means it's thermal expansion process needs to start later. Engines that are found to take higher ignition timing settings after the E85 fuel conversion were initially not using a fuel with a proper octane rating for it's given application. (octane level is what raises the temperature of what the fuel flashes at)
City driving conditions are difficult to mimic during a tune session due to the higher engine compartment temperatures which cause heat soak. Tuning the engine at a minimum of 190F is recommended.
Discovery of stoichiometric in E100 is 14.5 to 14.6 a/f compared to the 14.7 of petrol. Stoichiometric for a mixture of 85% ethanol and 15% petrol (E85) has a 14.6 to 14.7 a/f reading. Readable levels of oxygen after the combustion process had ended was near identical between ethanol and petrol.
Engine intake air temperature drops up to 120F on root style superchargers was noticed. Naturally Aspirated engines made more torque then horsepower compared to forced inducted configurations having a substantial outcome of both horsepower and torque.
Ethanol is superior to any fossil fuel at any octane rating and also burns cleaner, which is better for our environment. If you don't want to be part of the change from internal combustion engines, then, at least consider the fuel conversion.
Pro Street Import
Dec. 15, 2021
Special thanks to Brandon (Pigeon) Wellner.
Build-up at top caused by lack of lubrication due to water entering the cylinder.