On the floor at the SAE World Congress at Cobo Hall this week sits a 2.0-liter Tigershark engine. Parts have been cut away and there are pretty colored lights inside, but the cool part – if you're interested in biofuels, anyway – is how the engine has been modified to turn the Dodge Dart into an E85-capable machine.
Despite being a Chrysler product, the engine was at the IAV Automotive Engineering booth, and IAV's business unit director for gasoline and alternative fuels, Chi Binh La, told AutoblogGreen that standard E85-capable engines use sensors to figure out how much ethanol is in the tank. The new Tigershark uses the engine management computer to determine the combustion characteristics "People throw in a sensor, sensors are expensive and if it fails, you're in trouble. What IAV has done here is we've taken a combined controls and calibration approach. It's amazing this wasn't thought of before," he said.
Basically, when you fill up at the gas station, the engine knows you've put fuel in. This triggers the first of two adaptive learning strategies – one coarse and one fine – that the engine goes through to figure out how much biofuel is in the fuel line. In the coarse check, it burns the new fuel for two seconds and looks at the O2 sensor (which modern gas engines have) and compares the air/fuel ratio from the new fuel to what it was before the fill-up to arrive at, roughly, the new blend. This is "good enough to meet emissions requirements and drivability," La said. Then, after the engine warms up to 80 degrees C, the fine adaptive learning happens. The computer again uses the O2 sensor to determine the balance, but it lasts longer and is more accurate the second time around. "It is using information from available sensors to calibration the flexfuel content," La said. Chrysler contracted IAV to work on the project, and IAV worked on the cold-start calibration, engine mapping and driveability and emissions work.
Chrysler hasn't officially said when the Dart will become flex-fuel capable (earlier reports suggested the middle of 2013), but Chrysler and IAV representatives on the show floor said the engine will be going into the 2014 Dart, which is due later this year.