By Jim Kerr
What comes first, the chicken or the egg? That is the dilemma faced by auto manufacturers as they introduce new fuel and powertrain technologies. Do they wait until the fuels are available before building powertrains that operate on it, or do they build the powertrains first and wait for the fuel?
E85, which is 85 per cent ethyl alcohol or ethanol, and 15 per cent gasoline, is one of those new fuels that creates this problem. While there are increasing numbers of filling stations in the central United States, right now there are only a couple of stations in Canada that sell E85 fuel. Both are located in Ottawa. However, E85 fuel could quickly be introduced across the country if the production capacity of ethanol was sufficient. It can be stored and pumped just as gasoline is now. The infrastructure is already here. All we need is the fuel. Or is that all?
Ethanol has less energy per kilogram than gasoline and produces more oxygen in the cylinders as it burns, which means vehicles would have to be recalibrated to operate on E85. Older vehicles would require bigger jets in the carburetor. Some older vehicles may also require different rubber fuel system components, but this would be minor. Fuel-injected vehicles would require different fuel delivery calibrations programmed into the computer. This would be relatively simple to do, but the problem is ensuring the vehicle always operates on the same fuel. Fill up with gasoline and you no longer have E85 in the tank. Now it is a mix of both fuels, and the vehicle requires different programming again.
2006 Chevrolet Impala LT. Click image to enlarge
So what we need is an engine that can run on any mixture of ethanol and gasoline. That is where the Chevrolet Impala Flex Fuel system comes into the game. In the past, GM had some small trucks and SUVs that could operate on different mixtures of ethanol-based fuels. These vehicles used a fuel sensor in the fuel line that signalled the computer how much ethanol was present in the fuel; the computer would add or subtract the amount of additional fuel required. Now, the Impala flex fuel system can perform this analysis without using any additional sensors.
GM has developed a Virtual Flex Fuel Sensor (V-FFS) software program that calculates the ethanol content in the fuel, instead of using a sensor to measure it. When the fuel level in the tank increases as the vehicle is refueled, the computer recalculates the percentage of ethanol in the fuel and automatically changes the air/fuel ratio. To do this, the computer temporarily stops the operation of other emission systems and monitors the oxygen sensors to determine ethanol content. The test is done several times until calculations remain stable. This can take several minutes when the engine is idling, but much less time at higher fuel flow rates.
There are no visible indications on the Impala that it is flex fuel-capable and there is no extra equipment. If your Impala has the 3.5-litre V6 engine and the eighth digit of the serial number is a “K”, then it is ready for E85. It even drives the same. When operating on E85, it does use a little more fuel, but green house gases are reduced dramatically. There is a slightly sweet smell to the exhaust and you have the satisfaction of knowing you are running on a renewable fuel resource.
Most of the Impalas sold in the United States will be flex fuel compatible. In Canada, about half of the vehicles will have this capability. GM is offering them at no additional cost compared to traditional gasoline-powered vehicles. They can be operated on gasoline now, but will be ready for E85 when it becomes available, as it surely will in the future. I don’t know if the Impala will be the chicken or the egg, but it does come before the fuel and it is ready for the future.