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Discussion Starter · #1 ·
http://www.damninteresting.com/the-six-stroke-engine/


Under the hood of almost all modern automobiles there sits a four-stroke internal combustion engine (ICE). Though the efficiency of the design has been improved upon significantly in the intervening years, the basic concept is the same today as that used by the first practical four-stroke engine built in the 1870s. During every cycle in a typical car engine, each piston moves up and down twice in the chamber, resulting in four total strokes… one of which is the power stroke that provides the torque to move the vehicle. But the automotive industry may soon be revolutionized by a new six-stroke design which adds a second power stroke, resulting in a much more efficient and less polluting alternative.

In a traditional ICE cycle, 1) the fuel/air valves open as the piston moves down, which draws air and fuel into the chamber; 2) the valves close as the piston moves back up, putting the air/fuel mixture under pressure; 3) the mixture is then ignited, causing a small explosion which forces the piston back down, which turns the crank and provides the torque; and finally 4) the exhaust valves open as the piston moves back up once again, pushing the byproducts of the fuel explosion out of the chamber. This leaves the piston back in its starting position, ready for another cycle. This process is repeated thousands of times per minute.

The clever new six-stroke design was developed by 75-year-old mechanic and tinkerer Bruce Crower, a veteran of the racing industry and a the owner of a company which produces high-performance cams and other engine parts. He had long been trying to devise a way to harness the waste heat energy of combustion engines, and one day in 2004 he awoke with an idea which he immediately set to work designing and machining. He modified a single-cylinder engine on his workbench to use the new design, and after fabricating the parts and assembling the powerplant, he poured in some gas and yanked the starter rope. His prototype worked.
His addition to the ICE design is simple in principle, yet a stroke of genius. After the exhaust cycles out of the chamber, rather than squirting more fuel and air into the chamber, his design injects ordinary water. Inside the extremely hot chamber, the water immediately turns to steam– expanding to 1600 times its volume– which forces the piston down for a second power stroke. Another exhaust cycle pushes the steam out of the chamber, and then the six-stroke cycle begins again.
Besides providing power, this water injection cycle cools the engine from within, making an engine’s heavy radiator, coolant, and fans obsolete. Despite its lack of a conventional liquid cooling system, his bench engine is only warm to the touch while it is


Crower invites us to imagine a car or truck (he speaks of a Bonneville streamliner, too) free of a radiator and its associated air ducting, fan, plumbing, coolant weight, etc.

“Especially an 18-wheeler, they’ve got that massive radiator that weighs 800, 1000 pounds. Not necessary,” he asserts. “In those big trucks, they look at payload as their bread and butter. If you get 1000 lb. or more off the truck…”
Offsetting that, of course, would be the need to carry large quantities of water, and water is heavier than gasoline or diesel oil. Preliminary estimates suggest a Crower cycle engine will use roughly as many gallons of water as fuel.
And Crower feels the water should be distilled, to prevent deposits inside the system, so a supply infrastructure will have to be created. (He uses rainwater in his testing.) Keeping the water from freezing will be another challenge.
Bruce Crower holds a patent on the new design– which he is still developing and tweaking– but he estimates that eventually his six-stroke engine could improve a typical engine’s fuel consumption by as much as forty percent.
 

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Oh, what a wonderful idea, carrying another huge tank full of fuel, that isn't anywhere near as explosive as petrol...
I just don't think the extra weight from this would ever be made up for by the steam pressure.
Our enormous 45-inch diameter steam engines, on 60psi of steam pressure, only make 132 horsepower, so how a water injection system could provide anywhere near as much as a normal second power stroke I have no idea.
 

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Discussion Starter · #3 ·
I don't think you do it for the power, I think it is purely an economical thing.
If the engine is turning ANY heat energy in to usable power, then it is more efficient.

As a stationary engine on a workbench, that is pure efficiency gain.
However, we will have to see if it produced more power than is required to move the weight of the fuel tank, however I am sure it will be.

Besides, the weight of a full tank of water, can't weight MUCH more than the entire cooling system of an engine surely?
 

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There's two things to think of Cam:
Weight depends on how you were to work it.
If you were to replace the cooling system with exactly that weight of tank, I'd imagine you'd be topping up fairly often, maybe even once per day?
The other thought to bear in mind is time. Every 2 times you were injecting water, you could have had one more petrol power stroke in there, and believe me you'll get far, far more power out of that than steam pressure.
For something that just has to chug happily away all day (ie. Small boat outboard, generator, etc) I think this would be a wonderful design.
I doubt it will ever make it into the automotive sector though, simply because you would not gain enough power to make efficiency worth it. Yes, you're burning less petrol, but you are generating less energy per time than a standard engine.

I don't feel this is a particularly clear way to put things, but I can't think of a better way to phrase it :/
 

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Why wait another two cycles for the power, the clever money at the minute is on clean burning two strokes, which are using compression techniques from both ends so the piston moves and the combustion chamber moves as well. Maybe a few years off release, but there are boffins working on this, and it's exciting.
 

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Now that sounds more like it ;)
If it's still in development, are we allowed to request a wider powerband? :p
 

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Discussion Starter · #7 ·
I think you may be missing the point. He isn't trying to male it powerful! He is simply trying to make it more efficient....and it does, by turning the wasted heat energy in to useful energy.

Maybe it will only be used for generators and such.... who knows.
 

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Idk Fish, efficiency is a measure of useful energy created per consumption... Fact is steam power just doesn't create as much as petrol power. So while it consumes less "fuel" and creates cleaner emissions, that's only because it's doing something altogether less useful instead of a power stroke :p
I'm really struggling to get what I'm trying to say into proper words, can you tell? :p
But it's the Ecotech argument all over again. My dad's 2l turbo gets about 70mpg because it doesn't have to work very hard, purely because of the amount of power it creates. Meanwhile my friend's 1l Fiat has to rev its bollocks off to go anywhere and so isn't any better.

As I see it, and this is purely in my own eyes, the trick is getting more power cleanly, rather than trying to add in another stroke that will harness altogether less energy. Still, figures and statistics are needed to see if his design will produce enough energy from this extra water stroke to offset the fact you're losing power while it occurs.
McLaren have this concept right, their new MP4's biggest selling point for me is the fact that it generates the most horsepower per gram of CO2 of any engine currently around. That's efficiency!

I think that made sense?
 

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Discussion Starter · #9 ·
Yeah, I can see your point...
Although we shall have to see :p

I mean, if it is generating NO heat, or at least very little heat, that extra energy MUST be going somewhere...
As opposed to a 4 stroke or 2 stroke that IS wasted energy.

I guess it is debateable.
How do we know that the steam stroke isn't powerful? Are we just going on an assumption?
I mean... Steam CAN be pretty powerful, considering it instantly vaporises in the cylinder and expands by however many 100 or 1000's of times its original volume...
 

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Because I work on Steam Engines as a volunteer job, and our most powerful one uses absolutely ridiculous pressures (Minimum lifting pressure 120psi) to only generate 900 horsepower, and the cylinders are 24 inches across and 40" stroke.
That's 1190 Litres each, so our 2400 (2 cylinder, rounded up) litre engine generates the same power on huge steam pressure as a 10L petrol engine... and less than something like the Veyron which runs 8 litres, albeit with a few turbos ;)

--have just realised how this comes across.
I am not saying my word is gospel, or that there's no better way to use steam that would give more power. But with this kind of difference between them, I doubt it will ever be in the same league...
 

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Discussion Starter · #11 ·
Now, my understanding is that a steam engine heats the steam in a pressure container, then that pressure is released in to the cylinder moving the piston.

That is surely different to injecting water which then vaporises directly within the cylinder?
 

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Pressure is still a measure of how much volume you are moving though Cam, if it was more powerful to inject water into a heated cylinder, would they not do that with a steam engine?
Putting cold water into a hot cylinder is just not going to give the straight up energy release of heating water until it becomes steam, then continuing to heat it to a silly pressure.
But yes, I agree that this is great for something like a generator, but I don't think you'd ever compensate for the weight and power loss of this method in something automotive.


That said, I was thinking about this earlier.
In something like a big Jag or BMW, where most of the time they're barely even touching the levels of power they can produce, this might work to reduce consumption.
I was thinking earlier not on the angle of "Steam will generate more power than petrol" but started to consider engines that generate say, 300hp. They don't need that in the city, but they still will be using the same amount of petrol and heating up. Maybe in a system like that water injection could be used to scavenge a little bit more energy out of things.
You'd still want to turn it off completely when you put your foot down, but when the car is happily burbling along I think it might be quite a fine idea!
 

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Discussion Starter · #13 ·
I think you need to copmpletely ignore the idea of power! That isn't the aim of this...
Efficiency and power are two COMPLETELY different aspects.

And no, in a steam engine, they don't have that heat energy to spare.
The combustion engines first 4 strokes create the heat, wheras in a steam engine they need to burn fuel to heat the water.
 

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Ye-eees, but if it was better to produce steam by heating a cylinder, do you not think the cylinder, not a seperate boiler would be heated? :p
I just can't see an extra power stroke from a new fuel source being anywhere near what we need. Efficiency is a measure of how much energy you get from a power source, and steam just isn't as efficient as petrol power!
There's no free extra stroke here, it's using up time that would normally be used by a more effective combustion...
It's a very nice idea though, if there's a way to make it happen without adversely affecting the output from an engine I'm on that.
 

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Discussion Starter · #15 ·
So what if it takes more time?
Time in this context is a reference to speed and therefore power.

What it DOES do, is use up far MORE of the energy which is involved.
 

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The thing I'm trying to say is that in a small engined car, that's already horridly underpowered for its weight, this extra steam stroke would be lowering the average horsepower output of the vehicle, and as such would affect the performance it doesn't have even further. If you get something that's just about the right power this concept would be fantastic.

Also... I'd love to see how this feels... Having 2 different power strokes, I can't imagine if you'd be able to tell or what
 

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This sounds like more bending to emissions to save the planet. TBH the planets ruined any way, forget about the ozone layer, i mean politically and morally. we gonna kill ourselves either by nuclear war or man made super diseases or what not way before we die because of a polar ice cap melting mean for god sake weve got boats to live on if it does happen. I think its ridiculous as it is regarding 2 strokes being smoked out and engines being castrated to save a godamn polar bear! they massive and have huge claws and can kill anything they can look after them selves me having a stupid little pipe on my exhaust isn't going to help! 6 stroke bloody engine powered by water, seriously we arnt living in the 1800s!! Argg rant over.
 

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Discussion Starter · #18 ·
The definition of Efficient is:
Achieving maximum productivity with minimum wasted effort or expense

And by adding this extra power stroke, we are increasing productivity (even if only a little bit), by using [heat] energy that would otherwise be wasted.
THEREFORE, it is undeniably MORE efficient.

Even if you have to rag the tits off the engine more, it is still going to be more efficient as it is converting wasted energy to useful energy!
 

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Pressure is still a measure of how much volume you are moving though
No, totally different units, cannot be expressed as the same, and therefore can be mathematically proven to not be. Doesn't matter how big something is you can still get it high pressure, it just takes more energy to achieve this.

You can make things more efficient but so far no machine is 100% efficient, and probably never will be, otherwise you have achieved the holy grail of having perpetual motion. As for reusing heat, Sweden has some very interesting projects which involve reusing heat, they heat most of the municipal buildings with wasted heat from power stations, and have found ways to generate fuel from left over from paper production.

As for you Mayoh, you probably need to subscribe less to the clarkson school of environmental issues and start to look at the facts. Just a thought for you what is a polar bear doing any different to a soldier with a rifle?
 

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This sounds like more bending to emissions to save the planet. TBH the planets ruined any way, forget about the ozone layer, i mean politically and morally. we gonna kill ourselves either by nuclear war or man made super diseases or what not way before we die because of a polar ice cap melting mean for god sake weve got boats to live on if it does happen. I think its ridiculous as it is regarding 2 strokes being smoked out and engines being castrated to save a godamn polar bear! they massive and have huge claws and can kill anything they can look after them selves me having a stupid little pipe on my exhaust isn't going to help! 6 stroke bloody engine powered by water, seriously we arnt living in the 1800s!! Argg rant over.
this made me chuckle. i don't know if you're serious or not, but nice post.
 
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