Shocking Study: cars get BETTER fuel economy with E30 than p

Shocking Study: cars get BETTER fuel economy with E30 than pure gasoline

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http://www.ethanol.org/pdf/contentmg...inal_12507.pdf


Quote:
While only three non-flex-fuel vehicles were tested in this study,
there is a strong indication that non-flex-fuel vehicles operated on optimal ethanol blend levels, which are higher than the standard E10 blend, can obtain better fuel mileage than on gasoline. The Ford Fusion and Toyota Camry obtained a HWFET mileage on E30 of 1% greater than on Tier 2 gasoline; the flex-fuel Chevrolet Impala showed a HWFET mileage of 15% on E20 better than Tier 2 gasoline, as shown in Figure ES-1.

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When a vehicle had successfully “learned” an ethanol blend level, it was then subjected to a HWFET on the SuperFlow AC motor-driven chassis dynamometer to obtain highway fuel economy and emission data. The highway fuel economy data were used to determine if there was an optimum ethanol blend level at which the vehicle attained a better-than-calculated fuel economy. The optimum ethanol blend level was determined by plotting the HWFET fuel economy against the calculated economy. If several ethanol blend-level HWFET fuel economies were higher than the calculated fuel economy, the one with the greatest difference was selected as the optimum ethanol blend level for that vehicle.

In the HWFET testing, ethanol blend levels of E20 in the flex-fuel Chevrolet Impala, E30 in the non-flex-fuel Ford Fusion and Toyota Camry, and E40 in the non-flex-fuel Chevrolet Impala resulted in miles-per-gallon fuel economy greater than predicted based on per-gallon fuel Btu content and in some cases, better than gasoline. An FTP-75 was run (in triplicate) on all the test vehicles at these ethanol blend levels.

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Virtually all vehicles manufactured since the early 1980s utilize a computer to monitor and adjust specific engine parameters that affect fuel economy and tailpipe emissions. These systems attempt to adjust the amount of fuel delivered and ignition timing to the optimal level for performance, drivability, and emissions.

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During closed-loop operation of the ECU, the interaction of the oxygen sensor and fuel injectors is adjusted to the oxygen content of various ethanol blends to obtain the stoichiometric AFR. However, during open-loop conditions, the ECU varies the amount of time the fuel injector is turned on based on the target fuel map held in the ECU program. This program has been developed for gasoline and E10. Those values will not deliver the proper amount of fuel with higher ethanol blends. This is where the short-term and long-term fuel trim values come into play.

If more correction than normal is needed, as determined by the ECU target fuel map, the ECU uses the short-term fuel trim strategy option to compensate. The ECU short-term fuel trim programming allows the ECU to adapt and adjust the injection duration quickly, delivering the correct amount of fuel. When higher ethanol blends are used, the initial output of the ECU results in a lean mixture. When a specific injector on-time is commanded, the oxygen sensor signals a change in operation, by changing either to a rich or lean AFR. However, if the response is not what the ECU anticipates, the injection timing is adjusted until the expected response is observed. This phenomena is referred to as “learning.” Short-term fuel trim is a very fast-responding adjustment, while long-term fuel trim adjusts via the “target fuel map” stored in the ECU.

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The Toyota Camry gave an engine fault code on E70 but ran well on E65. The Camry operated very close to the calculated fuel economy throughout the range of the tested fuels. HWFET fuel economy values for the eight tested blends were below calculated for all blends except E30. There is a definite peak at E30, which indicates an optimum blend level for this vehicle, shown in Figure 10.

The Chevrolet Impala (non-flex fuel) gave an engine fault code on E70, but ran well on E55. The Impala operated very close to the calculated fuel economy throughout the range of the tested fuels. HWFET fuel economy values for the eight tested blends were very close to calculated values for all blends except E40. There is a definite peak at E40, which indicates an optimum blend level for this vehicle, shown in Figure 11.

The flex-fuel Chevrolet Impala ran well on all ethanol blend levels. HWFET fuel economy values for the nine tested blends were above calculated values for all blends tested. There is a definite peak at E20, which indicates an optimum blend level for this vehicle, shown in Figure 12.

The Ford Fusion gave an engine fault code on E50, but ran well on E45. HWFET fuel economy values for the six tested blends were below calculated values for all blends except E30. There is a definite peak at E30, which indicates an optimum blend level for this vehicle, shown in Figure 13.

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It is notable that the Ford Fusion and Toyota Camry obtained a HWTET mileage on E30 of 1% greater than on Tier 2 gasoline, and the flex-fuel Chevrolet Impala showed a HWFET mileage of 15% on E20 better than Tier 2 gasoline, as shown in Figure 14.