Hailing from Peterborough in Cambridgeshire, England, but working today at Fiat Chrysler’s mega-complex in Auburn Hills, Michigan, Chris Cowland jokingly refers to himself as a British import. He might be an import, but the fuels engineer still has what sounds like the most American job going as FCA’s director of advanced and SRT powertrain. In addition to his other duties as the man who helped bring the Dodge Hellcat’s 707-horsepower 6.4-liter supercharged V-8 beast of an engine to life, he’s a fuels engineer, an expert on the composition and operational properties of gasoline. He’s become a strong advocate for upgrading the quality of gasoline so that internal combustion engines can run cleaner
in coming years, as the law demands.
Automobile Magazine: Tell us a bit about how gasoline has evolved in the U.S. and what you’re looking to do.
CC: If we go back in history, gasoline really hasn’t changed a huge amount in the U.S. over the last 30 or 40 years. There were a couple of big changes. One came about for emissions, when we went from leaded fuel to unleaded fuel, which was to make feasible catalytic converters. That was in the ’70s, during the fuel crisis. Then, a few years ago, we had a reduction in sulfur content in gasoline, which again was to help after-treatment-type devices, catalysts. But the biggest thing we’re really looking forward to now is a potential octane rating change.
AM: You want higher-octane gas?
CC: It’s really about efficiency. Clearly, [regulation means] we’ve got lots of CO2 improvements that we’re looking for, and one of the big limiting factors on how efficient we can make a gasoline engine is the compression ratio that we can run in that engine. The compression ratio is typically limited to keep the engine from knocking. But it’s limited by the octane level of the fuel.
AM: Any given fuel will have a maximum compression ratio it can withstand without knocking. At that point, if you want to prevent knock, you need higher octane, correct?
CC: Correct. If you put too high a compression ratio into an engine, we have to retard the spark timing so it doesn’t knock. That loses efficiency, so what we really want to do is drive the compression ratio up but keep the optimum spark timing. We need octane.
AM: Please explain knock.
CC: Effectively, it’s a phenomenon that occurs when we get some very high-pressure oscillations within a cylinder. Instead of having a flame-front spread out in a gasoline engine in a smooth, controlled manner, a number of other ignition points occur within the chamber. For example, if the exhaust valves are hot … a lot of extra combustion events occur. In a turbocharged and downsized engine, it’s actually very, very dangerous to the engine. High pressures can start to damage pistons and cylinder heads. We have to avoid that situation. So what we’re really looking to do is to be able to design an engine around higher-quality fuel. We’ll get as much efficiency as we can because there’s an easy relationship between increased compression ratio and increased thermodynamic efficiency.
AM: What would that look like, compression-ratio-wise?
CC: If we look at the modern trend of downsized, boosted engines, typically they’re running in the 10-10.5 to 1 static compression ratio. … The ideal geometric compression ratio would be between 14 and 15.
AM: What’s that going to take, in terms of octane ratings?
CC: We have two different rating systems for octane—one in North America, one for the rest of the world. We use the anti-knock index (AKI) here in the U.S., which is actually the research octane number (RON) plus the motor octane number (MON) over two. If you go outside NAFTA, everybody uses RON. The typical premium fuel in the U.S. would be about a 94, 95 RON fuel, which is a 91 AKI fuel. There’s usually about four or five points difference between AKI and RON. That is, 93 AKI would be about 98 RON. That’s the number we believe we need to get to: 98 RON versus today’s pump standard fuel in the U.S., which is about 91 RON (or 87 AKI).
AM: So essentially make premium regular. Sounds simple, but is it? What is it going to take to get us to 98 RON? More ethanol?
CC: There are a number of ways that this increase in RON value could occur. One is we stick with today’s E10 (ethanol ratio), and that effectively means that more of the fuel that’s in the refinery would get used for something [other than gasoline]. You can add ethanol, and there are many people in the industry that believe we should use E15 or E20 or E30 in order to get there. There are some differences in the industry as to whether we should use ethanol or shouldn’t. Clearly the ethanol industry would like to promote higher levels in gasoline. Some of the oil companies don’t favor ethanol. At FCA, we’re a little agnostic. We want the octane value. We need to know what the maximum ethanol value would be relative to that octane level, but we don’t want to be prescriptive with the oil companies. We believe going forward that it will have to be the automotive industry, the oil industry, and the regulators working together if we’re ever to see a change in octane. It can’t be one of those elements pushing by themselves.