We’re all familiar with the venerable Otto cycle—intake, compression, expansion, exhaust. But that’s just not enough for veteran race engine builder and performance aftermarket mogul Bruce Cower. He added another two. The Crower Six Stroke promised to boost power and efficiency while eliminating the cooling system altogether years ago. So what happened to the concept engine?
The Crower Six-stroke may be old news to a lot of you, but apparently I’ve been lost in an engineering Bermuda Triangle and have only now learned of its existence. First, a little about Bruce. Crower is a truly epic figure in hot rodding. They guy built and sold parts for ’32 roadsters in high school. Today Crower Cams sells ultra-high-performance cams and a ton of other go-fast accessories.
Crower is a mechanical genius. And like any mechanical genius, he can’t stop rethinking engineering conventions. Like cooling. Seriously, radiators and cooling systems are huge, heavy and inefficient. If only there were a way to eliminate them altogether while retaining all the benefits of a water-cooled engine. Crower thought of a way: The six-stroke engine.
On a very basic level, Crower’s system works like this: Squirt water directly into the combustion chamber.
Water injection happens after the exhaust stroke. Water hits the hot piston, instantly turns to steam and expands, providing an additional power stroke while cooling the engine. It’s brilliant. And it works.
Crower built a functional single-cylinder prototype. The thing runs without any cooling system. And it runs cool. This is what Crower told Autoweek way back in 2006:
“It’ll run for an hour and you can literally put your hand on it. It’s warm, yeah, but it’s not scorching hot. Any conventional engine running without a water jacket or fins, you couldn’t do that.”
The secret, of course, is in the cams. Crower developed double-lobe exhaust cams that keep the exhaust valve closed after the first power stroke. This recompresses the combustion gasses and increases the force of the steam stroke.
There are many benefits to the Crower six stroke. The steam stroke provides extra power. You can replace heavy cooling systems with a small water tank. The engine runs so cool that Crower estimates you’d be able to bump compression all the way up to 13:1 on low-octane pump gas.
Again, from Autoweek:
“I’ve done this many times on regular engines: 15-to-1 on gasoline for the first five seconds works pretty good until you get some chamber heat and then suddenly it gets into pinging. But with the chamber being chilled, I bet 12-, 13-to-1 will be no problem on cheap fuel. So what we can maybe do is have fuels that aren’t quite as good…It’ll save a nickel a gallon not having to keep three grades going.”
Overall efficiency, says Crower, could also be boosted into the stratosphere:
“Can you imagine how much fuel goes into radiator losses every day in America? A good spark-ignition engine is about 24 percent efficient; ie., about 24 cents of your gasoline dollar ends up in power. The rest goes out in heat loss through the exhaust or radiator, and in driving the water pump and the fan and other friction losses. A good diesel is about 30 percent efficient, a good turbo diesel about 33 percent. But you still have radiators and heavy components, and fan losses are extremely high on a big diesel truck.”
Crower thinks the six-stroke could reach 40 percent, easy.
So that was all in 2006. What happened to the Crower Six-Stroke? Unfortunately, Crower fell ill and was unable to continue research. According to representatives from Crower Cams, the project is currently on hold.
Hopefully Crower or the engineers at Crower Cams can revive the project. It showed a lot of promise and we’re in dire need of cheaper, high-efficiency engines.