Ricardo has launched a full road test program to demonstrate its new spark-ignition flex-fuel engine technology designed to provide diesel-like torque but with reduced emissions, vastly lower engine mass, greater package efficiency, and significantly reduced cost.
The two-year test program will use two 2009 Chevrolet Silverado 3500 models, each powered by Ricardo’s Ethanol Boosted Direct Injection (EBDI) engine set up to run on a range of ethanol blends. The program replaces the heavy-duty pickups’ standard Duramax 6.6-L diesel V8 with the 3.2-L EBDI V6.
The program is being conducted out of Ricardo’s engineering center near Detroit. It follows extensive EBDI testbed work conducted by Ricardo over the past year in which the downsized and boosted combustion systems, optimized for ethanol fuel, delivered up to 30% fuel economy improvements.
The next step is proving vehicle performance, towing, and payload hauling on par with those of the much larger diesel (as well as those of GM's 6.0-L gasoline V8), said Kent Niederhofer, President of Ricardo Inc.
“We think the EBDI technology is scalable and suitable for use in passenger cars as well as commercial vehicles,” Niederhofer told AEI at a media event to kick off the program. “This program takes the first step of proving in the ‘real world’ what our dynamometer testing indicates is a viable power alternative with numerous benefits.”
Added Rod Beazley, Director of Ricardo’s Spark-Ignited Engines group, “We see packaging and application advantages with the EBDI, for vehicles that simply cannot fit a diesel and its aftertreatment,” he explained. “People are looking at downsized engines, but not as aggressive as this. We think an even smaller 1.4-L version would be an ideal solution for midsized cars.”
The Ricardo EBDI prototypes are based on GM’s “high feature” V6 architecture. They’re modified significantly to improve power and durability. Development was funded by Ricardo out of its R&D program.
According to Beazley, Ricardo’s testbed engines have produced more than 450 peak hp (336 kW) and 664 lb•ft (900 N•m) peak torque at 35-bar brake mean-effective pressure (BMEP), when running on E85. The testbed engine runs 140-bar (2030 psi) peak cylinder pressures.
Performance on straight gasoline is equally impressive, yielding more than 400 hp (298 hp) and 572 lb•ft (775 N•m) peak torque at 30-bar BMEP.
“We actually hit 825 N•m (1118 lb•ft) at 1600 rpm during testing of the gasoline version,” Beazley revealed. “We’re trading off boost and compression ratio, so we’re going to raise the comp ratio and reduce the boost in order to get more fuel economy on E85.”
The EBDI V6 in fully dressed form weighs 450-500 lb (204-227-kg) less than a fully dressed 6.6-L Duramax V8, without counting the diesel’s extensive SCR-based aftertreatment suite introduced for 2011 models. Ricardo engineers note the holistic benefits to vehicle curb weight and driving dynamics offered by the much lighter ethanol V6.
The engine is optimized through its electronic controls to run on any blend of ethanol and gasoline, or gasoline only, up to E85. Niederhofer said this calibration provides customers with a cost-effective choice of fuel, given the price differential at the pump between ethanol and gasoline. The engines as of mid-February were undergoing final calibration.
According to Beazley, the EBDI program was funded internally by Ricardo. He said the budget-efficiency helped engineers focus on value. The cylinder block, for example is cast by U.K. specialists Grainger and Worrall in standard 356-series aluminum; it employs steel liners.
A compacted-graphite iron (CGI) block would’ve been “nice to have,” Beazley said. However, the improvements made instead (upgraded head bolts, a main bearing ladder replacing separate caps, stronger crankshaft, and Federal-Mogul pistons, con rods, and bearings) were more than sufficient to handle the boosted engine’s “diesel-like” higher cylinder pressures and internal stresses, Beazley said.
The ethanol fuel required the addition of an additional fuel pump (the engine has two) to supply the Bosch direct-injection system. Delphi and Federal-Mogul provided valvetrain control and high-energy ignition systems. The purpose-designed intake manifold with integrated charge-air coolers was supplied by Behr, and the twin parallel-sequential turbochargers are from Honeywell.
The EBDI engine’s base compression ratio is 11:1. The testbed engine has been running EGR rates averaging 20%.
Ricardo engineers said the EBDI V6 would cost about $4500 more than a typical 6.0-L gasoline V8 as installed in a heavy-duty pickup (technically a medium-duty vehicle). But it would also undercut the approximately $8000 price of the current diesel option by an estimated $3500, based on current production volumes in the heavy-duty segment.
“Through the EBDI technology we’ve closed the gap in the energy content of a gallon of ethanol vs. gasoline, the 33% delta,” Beazley noted. “We recover the initial investment in the diesel engine and its aftertreatment. The thermal efficiency of ethanol is as high, or higher, than diesel. And the cost of ethanol at the pump is lower than gasoline.”
He said the EBDI vehicle test program will evaluate performance using various ethanol fuel blends. “We think there’s a blend compromise somewhere between E35 and E50 that gives good performance with good fuel economy, and will prove the cost-competitiveness of this technology.”