New global emissions regulations are resulting in increasing engine temperatures and pressures. Federal Mogul, a designer and producer of pistons, piston rings, cylinder liners, and related valvetrain components for engines in the high-performance, light-vehicle diesel, heavy-duty, and high-end gasoline engine segments, is responding to this challenge by developing enabling and direct friction reduction technologies. As Director, Engineering and Technology–Powertrain Energy, Federal Mogul, Keri Westbrooke is responsible for all North American applications engineering activities for automotive and heavy-duty pistons, piston rings, liners, and ignition design and has global responsibility for steel piston technology. SAE Magazines Assistant Editor Matthew Monaghan recently spoke with Westbrooke to learn more about these technologies:
What makes pistons/rings such a major contributor to mechanical losses?
Just the shear reciprocating mass and tight fit of the piston. The ring-to-bore friction is substantial; it’s obviously there for a reason—to provide sealing; and then the piston itself we’re fitting them tighter and tighter and you’ve got a fairly significant surface area in the piston on the simple piston skirts. Between the two of them, they are part of the problem in the robbing of the power of the engine. We feel somewhat responsible that we’re part of the problem; we’re trying to be part of the solution.
How have Federal Mogul’s products adapted to the emissions and fuel economy challenges?
In the past, leading up through 2010 the engine manufacturers had a fairly simple solution to emissions. That was essentially increasing cylinder pressure and raising temperatures within the cylinders; it’s all to do with their combustion recipes. The net effect on our components was higher temperatures and higher pressures. Then when the strive for fuel economy came along, we got into the downsizing, moving from 15 L to 13 L in the truck arena and down to 11 L in some of the fleet engines. That as well added to the temperatures and pressures in the cylinder, so we’ve been facing a tougher and tougher challenge as time has gone on, both mechanically and thermally.
How are products designed to handle the increased temperatures and cylinder pressures?
First of all for the mechanical loading, we’re looking for strength, structure, ruggedness, but when you get into the temperature loading you try to do one of two things. We want to cool the components down, particularly the piston, so that we’re not running into thermal damage of the material. All materials are made to have some sort of finite temperature resistance, but at the same time the engine manufacturers would like the components to run fairly hot so they can take advantage of the thermodynamics. We are challenged with cooling to the safety of components but still remaining at fairly elevated temperatures. That in the later generations of engines is causing us some interesting challenges.
Is weight reduction an area you’re trying to address in your designs?
Three years ago we probably would have told you that strength and cooling were paramount and we were taking little notice of mass. The answer now is not quite the opposite, but we are now expected to come up with solutions that are lighter and lighter mass. There are a couple of reasons for this, but the obvious one is if you can reduce the reciprocating mass, you are directly reducing friction in the engine because of the loads on the pins, rods, and bearings. The bulk of the friction in a piston typically comes from the skirt. In the Magnum [Monosteel piston], we are reducing the contact area. The other attribute of that Magnum piston is that you’re taking a big chunk of metal away and lightening the piston, you almost end up with the best of both worlds, lower friction forces plus lighter weight. We are on a quest for lighter mass even in the face of escalated temperatures and pressures.