Came across this on the
Recent debates and publicity concerns surrounding the introduction and use of "Green Fuels" has raised the question of the effects of these alcohol based fuels on the materials used in our components.
The use of ethyl alcohol mixed with petrol up to concentration of 10% (E10) has been common practise in the USA since the fuel crisis of the 1970's. This blend is now regularly available in Australia and in limited supply throughout Europe. Higher levels of mixes of 22% to 85% (E22 to E85) are used in Brazil and the latest trend has been for vehicle manufacturers to develop Flexible Fuel Vehicles (FFV's).
These FFV's and South American vehicles have all been specifically designed to accommodate the use of these high concentrations of ethanol.
Advantages and Disadvantages
The addition of ethanol to petrol has an effect on both the performance of an engine and also its interaction with the different materials it comes into contact with.
• Change in Octane Number
The addition of ethanol, up to a certain level, improves the octane number giving better anti-knock properties that can be helpful to older and higher performance engines that were designed for high octane fuels.
• Change in Volatility
A fuel's ability to vaporise has an effect on performance and on emissions. The addition of ethanol has the effect of lowering the temperature at which the fuel vaporises thereby improving combustion and cold starting but can increase the possibility of a vapour lock.
• Increase in Oxygen Content
In addition to hydrogen and carbon ethanol also contains oxygen. The replacement of hydrocarbons with oxygen has the effect of weakening the air-to-fuel ratio. This lowers emissions, lowers mpg and raises NOx in vehicles without a three way catalyst.
• Effect of Water Solubility
The addition of ethanol causes fuel to become hygroscopic (absorbs water). This has several different effects. It becomes acidic and conductive causing both a chemical reaction with certain materials and galvanic reaction causing corrosion. As water is heavier than petrol then a layering effect can occur with stored fuel having a higher water content settling to the bottom where fuel pick-ups are located.
• Lubricating Effect
When mixing with 2 stroke fuels it has been noted this can cause phase separation in breaking down the oil and petrol content causing a loss of lubrication. Under other conditions it can act as a solvent washing oils from metal surfaces thereby increasing engine wear.
Ethanol readily permeates through elastomers and plastics resulting in a deterioration of these materials.
Component Design Compatibility
For fuel blends containing less than 5% ethanol the concentration is low enough not to cause any significant effect. For 5% to 10% blend then some changes are recommended, (albeit that the USA has been subjected to this concentration for sometime without any known problems). For above 10% the effects of ethanol are known to cause problems and the necessary modification that would be required would extend beyond those of just our product content in a vehicle.
E0 to E10 blended fuels have been in use in the USA since the late 1970's and have had no significant effect on the performance or durability of our product. Using blends above E10 are not recommended as effects of these have yet to be fully investigated.
The company is already effecting changes of materials in sensitive components. Needles will be produced in nickel silver whilst orifices will be made from manganese bronze. Diaphragms and O rings to be upgraded to Viton or other suitable material. Rubber petrol pipe to be internally lined or upgraded. This ongoing process should be completed by 2012.