Test Fuel For Alcohol - MTD P90 series Shop Manual

P90 Series Vertical Shaft Engines

Test fuel for alcohol

Fuels currently on the market contain a wide array of additives. Some of these additives oxygenate the fuel. Oxy-
genated fuel reduces emissions, and is required in some parts of the United States. Fuel make-up varies seasonally
and geographically. Ethanol is the primary additive used to oxygenate fuel.
Ethanol in fuel creates a lot of problems for gasoline engines. The biggest problem is that alcohol attracts and
holds water. This corrodes the metal components of the fuel system, especially the carburetor. Alcohol also does not
produce as much heat as gasoline when burnt and it burns at a different stoichiometric ratio. This results in less
power for the engine.
A 10% ethanol (E10) mix is acceptable for MTD engines. Anything higher than that will result in performance
issues.
NOTE: E15 and E85 fuels are not to be used in any
MTD engines.
There are several alcohol test kit available commer-
cially. See Figure 4.1.
Generally these kits involve mixing a measured
amount of water and gas together and seeing were the
boundary layer is. See Figure 4.2.
The test kit should come with a chart to compare the
boundary layer height to alcohol percentage.
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Figure 4.1
Figure 4.2