Q&A: Fritz Indra, Increase Displacement to Save Fuel?

Gary Witzenburg
0507 Q And A 200

While hybrids and fuel cells vie to replace gasoline ICEs as the propulsion system of the future, those who toil every day to improve the gas engine's efficiency contend there's a lot more life in that faithful horse. Former GM Powertrain Advanced Engineering Executive Director Fritz Indra, who just retired April 1, 2005, says increasing an engine's displacement actually can boost its efficiency without increasing its cost, complexity, mass or external size:

"Fuel economy is not driven by the engine but by the vehicle, primarily its mass, plus aerodynamics. Vehicles are becoming bigger and heavier... more content, more air bags, improved structure...and to accelerate more mass, you need more energy."

"The customer likes his torque and doesn't want to give up performance, so increasing displacement is the best and cheapest way to do it. When you do that, you get higher torque, and then technologies such as DOD [Displacement on Demand, GM's cylinder deactivation], make more sense because you can expand the range where the engine is running on DOD. If you have too small an engine in a heavy vehicle, DOD makes no sense because you're always running at a relatively high load, and the engine will not shift to DOD."

"Looking back over the years, it's unbelievable what we have done with increasing displacement. Some years ago, the distance between the bores was 12 mm. Now it's down to ten, nine, eight, and in some cases only 5 mm. Our Ecotec engine started as a 2.0L, is now 2.2 and may end up at 2.4L. Our small-block V8 started as a 4.8L, then 5.3, 5.7, 6.0 and now 7.0L."

"We want to get the absolute maximum displacement out of every engine. When you squeeze out the displacement, it's always the same size and bore spacing, and you're not raising the mass. Together with the right engine technologies, you can more than compensate for the higher displacement because you can run it in part load in a much wider speed range."

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