Tiny Five-Stroke Engine Promises Big Fuel Economy

[SlowHands]

the five-stroke engine might be a great stopgap between current technology and the Next Big Thing

Keith Barry - WIRED - 08/21/09

this design is a 'thinking outside the box' idea --Ed.

The four-stroke engine has dominated internal combustion for more than a century, but a British engineering firm is ready to topple that technology with what it calls a 150-horsepower “five-stroke” engine said to offer the fuel economy of a diesel without the particulate emissions.

Ilmor Engineering, a firm that is co-owned by Roger Penske and supplies Honda engines to the Indy Racing League, spent almost 20 years developing the three-cylinder engine. Two cylinders operate on the conventional four-stroke cycle and empty their exhaust into a third low-pressure expansion cylinder, which allows the expansion and compression processes to operate independently. The prototype engine was first displayed at the 2009 Stuttgart Engine Expo, and its being readied for real-world, under-the-hood testing.

The Otto cycle four-stroke engine has pretty much been the standard for 132 years, but the five-stroke engine might be a great stopgap between current technology and the Next Big Thing.

According to Ilmor, the 0.7-liter engine is capable of 150 brake horsepower and weighs 20 percent less than engines with a similar output. Brake specific fuel consumption of the prototype is 226 g/kWh, which is a 10 percent improvement over current four-stroke technology. Even better, Ilmor says the technology is “100% conventional” and doesn’t require any new manufacturing techniques.

Ilmor says that the prototype five-stroke engine, based on a design by Gerhard Schmitz, has an overall expansion ratio “approaching that of a diesel engine – in the region of 14.5:1.” Along with its light weight and relatively high output, the extra work done in the low pressure (LP) cylinder provides for better fuel economy.... [Read More]

[jhu]

0.7 Liters and 150 HP? Wow! Although not unexpected from a firm that delivers race car engines to teams.

[JusBringIt]

Very impressive!...0.5L for extra economy anyone? . I used to think my 2.5L was small...Now I feel completely obliterated by the fact that and engine less than 1/3 the size of mine produces just 13 less hp.

[Chuck]

Food for thought:

• 2000 5-speed Honda Insight 995cc gas engine: 67hp (excluding 13hp electric motor)
• 5-speed Honda Insight with transplanted 1.2 liter TDI engine: 94hp
• 700cc 5-stroke engine: 150hp

Imagine the results!

[phoebeisis]

600 cc 4 cylinder motorcycle motors-dead stock, not racing motors-make about 108 HP at the rear wheel which is maybe 130 hp at the crank.
The power output of this motor isn't exceptional-same as a conventional motorcycle engine.

Of course those 600 cc motors spin to close to 15000 RPMS and probably make peak power at 12000rpms or so(just guessing since I don't follow then closely anymore).These motors get terrible FE of course-under 40 mpg in normal use with total weight of maybe 650 lbs with a 210 lb human rider.

I assume that the grams per KWHr produced -roughly 300 mls per KWHr is good. I think that is roughly 12.5 KWHR per gallon?? 1000mls x 1/300 x3.78=12.5 KWHrs per gallon??

Didn't steam engines reuse lower pressure steam?
Charlie

[JusBringIt]

Motorcycles do make that power at much higher rpms. The power to size ratio of motorcycles didn't really leave the impression this engine presumably would, as it wont spin nearly as fast.

[seftonm]

If 226 g/kWh is the best BSFC that engine has to offer, then it's still not quite in the diesel efficiency range. The old 1.9 TDI had a best of about 195 g/kWh.

[phoebeisis]

Anyone have a figure for an average sort of very good engine-maybe a Honda 4 cylinder, or the original Insight 3 cylinder??

Now these numbers 226 grams producing 1 KWHR- it is the best the motor does,right?
This must mean at full throttle, lowest pumping losses? Is it at the torque peak, or maybe at some lower RPM?

I'm guessing it is at some lower RPM than the torque peak, but maybe not. In the USA our engines are so big we rarely hit even the torque peak RPMS which is maybe 3500 for a V-8 and 4500 for a 6 cyl, and close to 5000 for many 4 cylinders.

In normal driving-level hy- with some city interstate onramps I'll hit maybe 2400 with the V-8 and roughly that-2800 maybe with the Prius.

Charlie

[chilimac02]

My 2.3L Honda Accord has 155hp... I can pull 41mpg (best tank). Imagine with that engine...

Since this is a Penske motor, will it go in the new Saturns?

[Elixer]

Anyone who studies much thermodynamics understands that as compression ratios increase so does efficiency. However traditionally it hasn't been worth manufacturers to increase the compression ratio much because to do so requires increasing the size of the cylinders. This greatly increases the weight of the engine without increasing it's power output. So there's a fine balance for FE. There are other problems to face too such as gasoline's tendency to ignite unwanted under high pressures (knock).

My guess is that they use the third cylinder to do an initial pressurization of the air or fuel-air mixture, before it's put into the next cylinders and goes through what normally occurs in a gasoline engine. Perhaps they also do something similar with the exhaust and give it an additional expansion cycle to eek out a bit more efficiency.

I just wonder about how well it would run in an older car as:

"This is because at the onset of knock a greater percentage of work can be extracted in the LP cylinder"

So they're running it at higher pressures closer to causing knock, so it would seem that it would be much easier for the "balance" of the engine to come out of whack.