After-market conversions

After-market conversion kits, for converting standard engines to operate on E85, are generally not legal in U.S. states subject to emissions controls unless you get your converted vehicle independently EPA certified. This is despite the fact that the exhaust emissions from any such converted cars are improved by utilizing higher percentages of ethanol in the gasoline blend. Unfortunately, EPA certification costs in excess of $23,000 and you additionally have to prove that your vehicle will maintain low emissions for at least 50,000 miles after the conversion. Most individuals won't give up their vehicles for the requisite 50,000 mile test period. Likewise, conversion kit manufacturers generally don't certify their kits due to the onerous and expensive burden of these laws. The kits would have to be tested with every model vehicle for which they are to be sold. If a kit is already certified as described, the EPA Federal Test Procedure for an individual's conversion costs $750.00. One can request a reduction of payment of down to 1% of the car's added retail value due to the conversion. A minimum fee may apply if the value added is not seen to be very high.

Similarly, U.S. Federal law prohibits the manufacture of many such conversion kits for sale in the U.S. unless they are EPA certified. The origin of this ban dates to when conversion kits for using compressed natural gas were originally sold. The ban was enacted to prevent the sale of such conversion kits due to safety concerns. This ban on the manufacture of kits is at odds with the fact that these kits, once existing, are legal in all states but CA, and most states offer some sort of tax break for converting your vehicle (See tax breaks.)

One Brazilian after-market kit is available legally in US States that do not have restrictive emission controls. The kit will permit the conversion of 4, 6, or 8 cylinder engines to operate from fuels ranging from pure gasoline to a mix of gasoline and ethanol to pure ethanol, including E85. It operates by modifying the fuel-injection pulses sent to the fuel injectors when in 'A', or alcohol mode instead of 'G', or gasoline mode. (In 'G' mode, no modification to the fuel-injection pulses is performed.) This conversion kit modification serves to extend the control range over which the ECU can adjust the air-fuel ratio to achieve an oxygen sensor reading measured before the catalytic converter that falls within nominal stoichiometric ideal combustion limits. The general belief is that this conversion kit operates in its 'A' mode simply through lengthening the individual pulse-widths of fuel-injection pulses, thereby increasing fuel flow per injection pulse by roughly 30%, whereas in 'G' mode, it acts simply as a straight pass through for fuel-injection pulses. Due to the nature of this kit, it is fully reversible (see below for other approaches).

Other than the one Brazilian after-market kit, no other pre-manufactured E85 conversion kits are known to exist. Nonetheless, it is still possible to modify existing non-FFV engines to operate on pure E85 without the use of this particular after-market kit.

The primary method used to convert non-fuel-injected cars is two-fold. First, any non-compatible rubber parts and gaskets and terne gas tanks and terne fuel lines are replaced. Then, it remains necessary to increase the fuel rate of flow by roughly 25% - 30%. This can be accomplished in one of any of several different ways, depending on the specific details of the fueling system. In the early 80's auto makers were required to make vehicles ethanol compatible, so most newer vehicles will handle E85 with no problem. If a car is converted though, the ethanol will clean out the gunk left over from the gasoline and plug the fuel filter. Replace your fuel filter after about 600 miles!

For non-fuel-injected engines, this may be accomplished through increasing the diameter of the carburetor running jets to a size that is slightly larger in diameter. The theoretical change is not to increase the hole diameter by 25% to 30%, but rather to increase the area and hence the fuel flow rate by 25%-30%. Hence, the diameter of the jets must be increased by \sqrt{1.25} to \sqrt{1.30} times their original diameters, while keeping the general shapes at the opening of the jets as close to nearly the same as possible. (The idling jet must also be increased in diameter in addition to the running jet, primarily to accomplish successful starting in colder weather.) An excellent starting point, if one doesn't want to experiment with multiple test trials over the 25% to 30% range, is simply to increase the fuel flow by 27%, which just requires increasing the diameter of the jets by a factor of \sqrt{1.27} times the original diameter.

For older vehicles, an even simpler non-conversion 'conversion' is possible once any non-compatible rubber gas hoses and cork gaskets and such are all replaced with ethanol-resistant materials. For older vehicles with a manual choke, it is possible simply to leave the choke slightly engaged even when the motor is warmed up, and the conversion is complete.

For converting later-model fuel-injected cars and trucks, fuel injection-pressure boosters can be installed, to increase fuel-injector fuel rate flow. It may be difficult to get your mixture right, plus there is a safety risk of more leaks in your fuel system. Likewise, if you do choose this method, you may loose some of your compatibility with running on pure gasoline, from moving the air fuel mix farther from optimum for what is needed for running on pure gasoline.

The disadvantage of most of the above conversions is the conversion is permanent, without changing out or removing added parts.

If any of these conversion techniques are used, especially in older vehicles in which there may be rust or other residue present in the fuel tank, it may be necessary additionally to replace the fuel filter within 400 to 600 miles, as ethanol has a tendency to release any trapped rust or gasoline fuel gum or residue, which can cause the fuel filter to become blocked. Once replaced, life expectancy of the new fuel filter should be normal, barring an exceptionally dirty gas tank or fuel system.

Interestingly enough, running E85 in a vehicle can actually improve fuel efficiency if the fuel delivery system was especially gummed up. This improvement remains if the vehicle is returned to operation on gasoline only.