Jan
28
An Ethanol Engine For Maximum Output
January 28, 2010 | 8 Comments
Not since the Ford Model T has a U.S. engine manufacturer produced a market oriented ethanol fuel engine. Or more accurately, one optimized for ethanol. The engineering firm Ricardo and supporter Growth Energy who promotes ethanol have built and lab tested an ethanol engine that uses ethanol for maximum output. That means compression, lots of it, and the corresponding fuel economy and power.
Ethanol’s fuel density is lower than gasoline, when mixed to the E85 standard as much as 30% of the fuel mileage economy can get away. But ethanol is much higher octane and a higher heat vaporization which when exploited flips the disadvantage to an advantage. What’s that mean?
Ricardo’s lab results point to an engine half the displacement. Or as Ricardo chose, downsize most of that and still leave a up to a 30% fuel economy advantage. The swap is a GM based 6-liter gasoline V-8 of one test mule with the heavily boosted 3.2-liter EBDI engine – resulting in up to a 16.8% fuel economy improvement and a 6.6-liter turbo diesel V-8 for a second on road demonstration vehicle. The test mules are GM Sierra 3500 HD pickups. Ford’s Super Duty might get a real answer someday.
In the heavy duty pickup market engine torque is a key performance metric. Ricardo expects their engine to offer more than 1.5x the torque of the gasoline engine and match the torque of the 6.6L turbo diesel engine while weighing 400 to 500 pounds less than the diesel. That’s a lot to grasp when adding in the near 17% fuel economy gain.
Ricardos Ethanol Engine. Click image for the largest view.
Ricardo’s technology is called Ethanol Boosted Direct Injection (EBDI). The EBDI engine can accommodate ethanol blends ranging from 0 to 85% ethanol (E0 to E85). Ricardo is still collecting lab data, but with an E40 (40% ethanol / 60% gasoline) Ricardo can achieve a mpg that approaches the pure gasoline fuel using a fuel with less energy per gallon and a considerable price advantage. The E40 blend uses approximately 10% less BTUs per mile (6,590 vs 7,260) than gasoline. So, using E40 would be about equal in a gasoline comparison. Ricardo believes the future may hold a significant advantage in pricing where ethanol is much cheaper. That is dubious, corn follows oil in near lockstep. BTUs are BTUs. But availability – ethanol could have a huge advantage in tight circumstances. A must be fueled and go situation might demand the EBDI technology for some operators.
How does Ricardo get that compression advantage? Luke Cruff, Ricardo’s Chief Engineer in the Gasoline Product Group said, “Compression ratio is a function of two things: geometric compression ratio and boosting pressure. The turbochargers and other variable devices can adjust the boosting pressure, which allows you to have different effective compression ratios. Diesel engines today run about 17:1 compression ratio which is trending down because the emission regulations while this engine’s compression ratio is closer to 11 to 1.” Note, he’s not saying what the peak compression is.
Rod Beazly said, “We took the stock V-6 and redesigned every component. We are getting diesel-like performance out of an engine that was originally designed to be lightly turbocharged. With our heavy boost we have increased the cylinder pressures to diesel-like levels. We had to work on the bottom end and on the crank and in order to get enough of the ethanol into the engine we had to use two fuel pumps. We have an integrated manifold with charge air coolers and EGR coolers help cool down the combustion system. We have two parallel/sequential turbochargers and although our block and heads look unchanged from the outside, inside they are highly modified with structural changes to support the higher cylinder pressures. We also have a high-voltage ignition system to ignite the large amounts of ethanol.”
As you’re suspecting now, EBDI isn’t a cheap option. In volume production, the engine is expected to retail for $4,000 to $4,500 more than the base gasoline engine or approximately half the premium associated with a diesel engine. The diesel premium is expected to grow to $9,500 by 2013 in order to comply with more stringent air pollution standards. The flip side is fuel economy savings would offset the EBDI’s price premium versus today’s gasoline or deisel engine over the life of the vehicle—allowing the owner to get the increased torque performance “for free”.
A look over the chart shows how the fuel mix can be managed to exploit the EBDI advantage. At low load high efficiency, gasoline at 60% and ethanol at 40% just uses the 11:1 built in compression advantage for a $0.29 per mile saving. While in a high torque situation at 15% gasoline and 85% ethanol the advantage is power output with 284 extra pound feet of torque and still saving $0.04 per mile.
Ricardo's Fuel Comparison Chart. Click image for the largest view.
Fuel mix? There’s a problem. Ethanol pumps are all E85 now, so far no pumps are out there for choosing your own mix. But even at an E85 mix alone, the advantage is there. There’re a whole lot of delivery companies with vehicles in this engine range with their own tanks and storage that can switch. And it would pay over time.
It looks like the major technology is in the turbochargers. Getting to mechanical 11:1 compression isn’t so hard and the know-how to hold together 17:1 and higher is common. Ricardo seems to have Honeywell building what one must hope is a fast acting variable turbo that will stay together under hard use for 150K miles or better.
Ethanol also offers better emissions. The other companies, Ford and Dodge can’t let this challenge go unanswered. The future looks good for ethanol, naysayers being caught in the ignorance loop – “GM has just recently introduced a 1.4 L turbocharged engine for the Chevy Cruze. We believe that using EBDI technology, you could have a 1.4 L engine power a mid-size car. That would give you approximately the same engine displacement to vehicle weight ratio as the 3.2 L engine in the heavy-duty truck,” says Ricardo. High performance isn’t going away anytime soon.
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why are we still hell bent on corn when there are far more energy dense sources per weight like algae? the reproductive cycle of algae is exponentialy greater than that of corn and it would not effect a vital food stock. if a crop of corn were lost to blight, parisites or what have you what do you think that would do to both corn and fuel prices? algae can be completly contained so as not to be effected by any of those factors.