Apr
7
A Boxer Engine Turned Inside Itself
April 7, 2011 | 4 Comments
Pinnacle Engines unveiled plans last week to commercialize a breakthrough ultra-efficient engine due for production by 2013. The claims for the new engine design are enabled significant reductions in fuel consumption and greenhouse gas emissions without increasing vehicle cost. Pinnacle also announced it has raised $13.5 million in venture funding from NEA, Bessemer Venture Partners and Infield Capital. The idea has legs now.
What is a Boxer engine? Its an engine with the cylinders directly opposite, no ‘V’, no line in a row. You’ve seen them in VW Bugs and Subarus plus some very sophisticated BMW motorcycles, and its very popular in small aircraft. What Pinnacle has done is engineer the cylinders in the center with the crankshafts out at the ends (Pinnacle Engines Technology link). Seems logical, but two crankshafts?
Pinnacle Engine At Ignition. Click the link in the text for the Pinnacle Technology page. Image credit Pinnacle Engines.
Pinnacle Engines uses proven ideas about engine efficiency and combined them with breakthrough engineering to create something entirely new. The company developed and patented an ultra-efficient engine design based on a four-stroke, spark-ignited (SI), opposed-piston sleeve-valve architecture using conventional engine manufacturing techniques.
The design is enhanced through the use of the ‘Cleeves Cycle’, which Pinnacle Engines has been developing and refining since its inception. “Cleeves Cycle” is named after James Montague (Monty) Cleeves, who is founder of Pinnacle. The Cleeves Cycle can switch back and forth from the Otto cycle (constant volume combustion) to the Diesel cycle (constant pressure combustion) depending on operating conditions. It seems that is accomplished by the sleeve valving that allows air fuel charge in and exhaust out. There doesn’t seem to be a method to simply move the crankshafts closer or further apart or change the length of the connecting rods. More thoughts below.
The press release and technology pages suggest additional efficiency improvements can be realized by incorporating variable valve timing, using a low-cost variable compression ratio mechanism, direct injection, and turbocharging.
Pinnacle says cuts fuel consumption by 30-50 percent compared to a conventional gasoline engine. This has to been seen going to market, as a midstream 40% gain is a major improvement and a claim begging for proof in the field.
Pinnacle’s ultra-efficient engine license is reported to first power scooters and rickshaws in Asia where the cost of fuel is much more sensitive than in the developed west.
The Cleeves Cycle idea has a certain very practical attribute. Variable compression opens the door to be compatible with most fuels including gasoline, diesel, natural gas, propane and their biofuel replacements such as ethanol, methanol, butanol and most any other liquid that can be ignited under compression. Even more impressive is the adaptability to mixed fuels. Fill up with ethanol, drive a few hundred miles to methanol territory and on another day find oneself filling up with gasoline or even diesel.
Most press and blogs overlook this, but this is a major market adaptability feature that abolishes competition if fuel markets get really tight.
That likely has a marked effect on the opening market. While rickshaws and scooters aren’t going to light up any westerners, having a transporter that can fill up with whatever is cheapest at the moment will light up the far east common traveler. It’s only a matter of time until the circumstances become important in the west as diversified fuel source “trickles up” in the economy. You might want one of these sooner than you think.
With a fresh $13.5 million in hand and former Cummins executive Ron Hoge named Chairman and CEO, the prospects look good.
But the “how” in the variation between constant volume combustion and constant pressure combustion hasn’t been answered to real satisfaction. Perhaps your humble writers suspicion that the timing of the two crankshafts is the key. Ones notes the graphics aren’t showing the connection between the crankshafts. Speculation in the comments is welcome.
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This seems like the latest in a long line of ‘game changing’ super efficient engine designs we read about but never come to the market.
Hopefully, with solid backing, this one really will make it to the showrooms.
One way to deal with the crankshaft timing dilemna is to have each crank connect to a torque converter which independently powers a central fluid pump. The fluid medium induces rotation in the transmission which connects to the differential (or chain drive, whatever)in the traditional manner. Differences in crank cyclic timing due to mechanical input variations between banks of cylinders (or even individual cylinders connected to a given crank) would be evened out by the central pump.
This actually isnt a new design, the commer TS3 was a diesel boxer engine with a similar design, but it had a single crankshaft rather than two, and the pistons connected to it with rocker arms
this is a small version of the F&M marine diesel used in ww2 subs with modern injection