Never count out the leaders in real world technology. For readers familiar with auto racing the name Ilmor Engineering will sound a claxon. Ilmor is a creature of some sort of partnership with legend Roger Penske as a co-owner and surely a managing role of some kind. Honda, of motorcycle and auto fame is the major racing engine customer for the whole of the U.S. Indy car program running on ethanol and some of the worldwide Formula One teams. It comes as no surprise this company is on the bloodiest edge of technological development in internal combustion engine design.
Ilmor is going to develop a “5-stroke”, yes – that’s 5-stroke, engine up to auto scale. Ilmor has already shown Europe the lab model at the Stuttgart Engine Expo. The next engine, more of a test engine will be installed in an automobile. Now, its not said if the test auto will be road type or racing type, but real world testing will build out some more foundation under the lab model’s results.
The patented 5-stroke concept, which was invented by Gerhard Schmitz, utilizes two fired cylinders operating on a conventional 4-stroke cycle, which alternately exhaust into a central expansion cylinder, where the hot exhaust gases act on a third cylinder. The third cylinder is an additional low-pressure expansion cylinder decoupled from the expansion and compression processes of the 4-stoke pair, and enables the optimum expansion ratio to be selected independently of the compression ratio.
From that one has learned the expansion ratio, the value between the intake air into the 4-stoke cylinder and its exhaust gases are of considerable interest. The engine runs an overall expansion ratio in the region of 14.5:1, which approaches the ratio of a diesel engine. The advantage to following the expansion ratio in the design is the compression ratio can be reduced to delay knock (pre ignition, where the conditions inside the combustion chamber ignite the air fuel mixture) onset without a reduction in performance. These insights in the use of the thermodynamics has the running of the lab engine producing impressive fuel consumption readings over a very wide operating range.
The building of the new engine is a cast cylinder head, a machined solid cylinder block and separate electrically powered oil and water pumps. Two overhead camshafts operate the conventional coil spring valve gear with the camshaft for the 4-stoke cylinders running at one half crankshaft speed and the fifth stoke cylinder’s camshaft running at crankshaft speed. The engine is also turbocharged to increase the engine rating. The entire construction uses current manufacturing technology as well.
The payoff is in the early results. From 700cc peak power is 130 bulk horsepower @ 7000 rpm with torque up to 166 newton meters @ 5000 rpm using a paltry 226 grams of fuel per kilowatt hour.
Ilmor says the prototype is up and ready for road testing and could be used as a conventional engine or as part of a hybrid drive train. The company says it is “keen” a British term expressing a strong motivation, to find a partner to help develop the engine and it is talking to automakers and top suppliers about the technology.
It all sounds very good. Racing has for decades led the way in improvements in automobile technology and a new engine seems to be a logical step. Over time it may be possible for internal combustion engine builders to stay in the market of converting fuels to work. That race is really about thermodynamic efficiency, and Ilmor seems to get it.
Out there in the wilderness are other designs that offer mechanical scavenging of heat and thermal expansion to get more work per fuel molecule. One example is Kazimierz Holubowicz, a physicist skilled in quantum electrodynamics that has designed an engine that recycles the hot gasses multiple times. It’s a design known to run as well.
But this time it’s Ilmor Engineering, Roger Penske, Honda and others. While the basic invention comes from a lone inventor, it takes this level of skills, management and connections to get further along. From the press releases over the past few months on automobile model announcements calling out electric drive, a hybrid generator’s engine is of supreme interest.
As we saw last week from Professor Burke at UC Davis, the hybrid power needed will be low horsepower and very high efficiency. For the littlest engines its going to get very interesting to see what engines mate to what generators or alternators for hybrid drive trains. Ilmor might be just in time or simply to late.