High Compression Ratios and Ethanol Blends Combine to Make a Super-efficient Car
May 10, 2013
Four years ago, American LeMans kicked off its first green racing season. The program, which requires teams to use alternative fuels such as ethanol blends (E10 or E85), clean diesel, or isobutanol is going strong today. Sponsored by U.S. Dept. of Energy, the Environmental Protection Agency (EPA) and SAE (Society of Automotive Engineers), it is an attempt to raise the visibility of environmental issues to an audience that might not otherwise be interested. They also wanted to show that green renewable fuels did not necessarily mean a sacrifice in performance or fun. Race winners are selected based on a score that combines how clean, fast, and efficient the car is, throughout the race.
Robert Kozak is an environmental biologist who spent much of his career working on vehicle emissions testing. As a bit of a self-proclaimed “racing nut,” he took interest in this phenomenon and spoke with a number of engineers working on the special cars that were being configured to compete in this race. Given ethanol’s lower energy content, he expected to hear stories of compromise and sacrifice. But he was surprised to learn of the fuel’s advantages, primarily its higher octane rating, which exceeds 100, and the superior low-end torque it produced in a properly configured engine.
This higher octane rating enables the use of higher combustion ratio engines, which, like diesels, are inherently more efficient. Cars today usually run combustion ratios between 8:1 and 10:1. Anything higher than that would lead to pre-ignition, or “knocking.” Some higher performance cars use higher compression ratios, but they require the use of premium fuel.
Surprised that this was not widely known, Kozak decided to dig deeper. He soon learned that engineers at Ford, Audi, and at R&D shops like Ricardo Engineering were well aware of this and are in fact, using it as part of their strategy to meet the 54 mpg EPA fuel economy standard for 2022. Other early proponents of these high octane engines include Steve Vander Griend, head of ICM Ethanol’s research and development group, as well as Charles Gray, Jr. director of the EPA’s Advanced Technology Division in Ann Arbor.
Today’s Ford Eco-boost engine is capable of running compression ratios as high as 14:1, if so configured. An engine of this type, which Kozak describes as “small lightweight turbo-charged, direct injected engine with computer-controlled valves,” running at this compression ratio (which could be accomplished with regular gasoline blended with 30 percent ethanol, or E30) could be as much as 40 percent more efficient than the more typical engines of today. But, adds Kozak, since these engines could be smaller and lighter, the car would get lighter, too, through a process that Amory Lovins calls “mass decompounding,” which translates into even greater vehicle efficiency.
Kozak became a believer. His company, Atlantic Biomass Conversions is focused on removing roadblocks to a bio-fuel powered future that can take advantage of this technology. One of these is coming up with enough ethanol to meet the demands of these higher blends. Since the Renewable Fuel Standard (RFS) requires that 21 billion gallons of ethanol must come from sources other than corn. That means a lot of cellulosic ethanol needs to be produced. They hope to address this with their “follow the crop” system.
So, the former emissions tester has now gone back to biology and when it comes to pollution, is now following Ben Franklin’s advice, trading in his pound of cure for an ounce of prevention. His company is developing portable biofuel processing modules that can go into the field and extract concentrated sugars from biomass, which can then be more easily shipped to ethanol refineries.
“We’re trying to overcome biomass recalcitrants, to break down various forms of plant biomass into their constituent sugars that can then be used for a variety of biofuels," Kozak told me in an interview. "Our goal is to come up with a system that can be portable or distributed, so that you can split up the consolidated bio-refineries into two steps: Put the conversion of the sugar (saccharification) in the field, so that you can ship what’s basically sugar water [instead of big heaps of biomass] hundreds of miles to the bio-refineries. We see that as the only way that the so-called cellulosic fuels, that I like to call total biomass, can work. This way you can make refineries that are crop-independent. Right now you can only economically ship the corn 30 to 50 miles. If you could ship longer distances, then that means, it doesn’t have to be just one crop, or one harvest time. The big roadblock is how to use multiple feedstocks for one refinery.”
But there are other roadblocks. One of them is regulation. The EPA’s new Tier 3 Vehicle Emission Standard has a “high octane, high ethanol” fuel component, which puts this scenario squarely on the table. But in the fine print, it leaves it up to the car manufacturers to ensure that the fuel is available, which is probably an unrealistic expectation. It also differs from the approach taken in prior regulations, such as the one the mandated that unleaded fuels be provided by the energy companies.
Car companies, Kozak said, are a bit reluctant to come out too strongly in favor of this technology just yet, perhaps for fear of starting trouble with the oil giants, choosing instead to keep their powder dry, waiting for the fog that currently blankets the road ahead to lift.
There is a marketing question, too. The idea that certain cars will require special fuel and will not run on regular gasoline is bound to raise questions about the availability of fuel, its cost, etc., much as it has with premium, diesel, and more recently, CNG.
Still, most car companies are taking a serious look at this, with the exception of Toyota, which is apparently sticking with its hybrid strategy. Kozak believes that advanced high compression engines can beat hybrids at their own game, given that they won’t require the additional weight and expense of the batteries. He offers the comparison of the Ford Fusion Hybrid which gets 47/47 for $27,200 vs. the 1.6L Eco-boost, which gets 25/37 for $25,290. Depending on one’s driving habits and requirements, some might consider that a toss-up. But, as Kozak, points out, if the high octane fuel were available, the Eco-boost engine, modified to a higher compression ratio (which would have to run exclusively on E30 or higher) would likely come out ahead. A 40 percent improvement would yield fuel economy of 35/52.
It’s certainly a compelling proposition, at least for the near to mid-term. I still wonder, though, if our goal is to eventually get away from fossil fuels altogether, E30 still requires 70 percent gasoline. If, on the other hand, we go to much higher blends, that leaves the question of where we can get all that ethanol from, without impacting the food supply.
Meanwhile, Kozak has gone from thinking about tailpipe emissions to thinking about how our fundamental understanding of plant cell wall structure, and in particular, the relationship between lignin and cellulose is not as complete as you might imagine. Most of the genetic revolution with genomes, etc. has been confined to the animal kingdom.
I think it’s a safe bet to say that that is about to change. Now all we need is an engine that can run on both and low octane fuel, and while we’re at it, that will work in conjunction with a hybrid powertrain, too.