water injection = Higher Efficiency?

[IamIan]

Originally Posted by Apexaddicted

I think you may have misunderstood me. Everything in the cycle would be the same, save for the water injection, but the excess heat that is conventionally leeched to the coolant system would be limited. The goal of course would be to allow the injected water to absorb this heat and aid in expansion. The main argument that was brought up earlier in this thread was the lack of heat energy in the combustion chamber to fully vaporize all the injected water to steam.

Still curious if anyone has successfully done this yet before i waste more time on trying to improve the process. Anyone?

Sounds like you might be describing a 6 stroke engine.
Link

[oil pan 4]

Originally Posted by Apexaddicted

Still curious if anyone has successfully done this yet before i waste more time on trying to improve the process. Anyone?

Not on a gas engine.
Diesels and gas turbines respond well to water injection.

[Apexaddicted]

Originally Posted by IamIan

Sounds like you might be describing a 6 stroke engine.

No sorry, I'm not referring to the 6 stroke as described earlier in the thread. Water would be injected into the combustion chamber right before the compression stroke.

Another idea I have been considering is preheating the injected water. Obviously it would lower the ability to prevent detonation, but keeping the water close to the temperature of phase change would allot more of the energy to increasing cylinder pressure through water vaporization rather than just getting the water to that point. Does this make sense to anyone who is a little more calculator friendly?

[serialk11r]

Originally Posted by Apexaddicted

No sorry, I'm not referring to the 6 stroke as described earlier in the thread. Water would be injected into the combustion chamber right before the compression stroke.

Another idea I have been considering is preheating the injected water. Obviously it would lower the ability to prevent detonation, but keeping the water close to the temperature of phase change would allot more of the energy to increasing cylinder pressure through water vaporization rather than just getting the water to that point. Does this make sense to anyone who is a little more calculator friendly?

I think before compression stroke is not so useful for efficiency since that's just diluting the intake charge.

But yea if you heat the water to boiling point first (or actually, pressurize and heat to above the atmospheric boiling point, since it needs to be injected under pressure anyways) and then inject maybe in the middle of the expansion stroke you might be able to pick up some extra power and efficiency. The only issue with these quasi "6 stroke" things is that the actual heat capacity of the head and pistons and the amount of heat that gets transferred to them per combustion event isn't that high, as most of the heat leaves through the exhaust (some of which is picked up by the cooling system).

[wumpus]

Originally Posted by oil pan 4

Not on a gas engine.
Diesels and gas turbines respond well to water injection.

I would think that a wankel would be near perfect for design similar to the 6 stroke system
(it would switch between two gas power cycles/rotation and one gas and one water power cycle per rotation).

Pros:
wankel combustion chamber is a disaster. Plenty of heat to use.
wankel doesn't require extra cams. Might need direct injection (of both fuel and water)
No extra cams means you can switch back to standard operation (important since virtually all wankels left are either sports cars or sport coups). Might not be needed considering just how much heat is lost in a wankel.
RX-8s have such bad stock mileage that they are reasonably priced (if you can fix the gas thirst).
Cons:
You still have a compression cycle you don't want. Getting rid of it would likely require building the whole block from scratch.
A huge project if it requires direct injection (for the fuel, I assume water injection wouldn't require quite the controls/pressure issues, but you never know once the air hits the compression cycle.)

[wumpus]

I can't seem to edit the above, but obviously it would require nearly a fully hacked fuel injection system, presumably megasquirt. Reusing non-DI fuel injection wouldn't avoid this issue.

[oil pan 4]

You can try it on a wankle.
I don't know if any one has, or at least I haven't found anything on it being tried.

Diesel and turbines have a long history of gains with water injection.

[kirkerik]

Originally Posted by oil pan 4

You are correct.
No one has come up with a way in theory or practice to inject water on a gasoline engine at light load and increase fuel economy.

The only other way water might be used to increase fuel ecomomy is to use steam in place of or in addition to EGR.
As far as I can tell no one here is about to do that.

i had the same thought on the EGR and i have one sitting idle on my motor. Any tips on hooking up a simple system?

How to produce the steam is the question. Would atomized water have the same effect?

I would think if there is no direct benefit then how about injecting water in a gas ICE just to keep it clean? A clean engine alone could help fuel economy. No?

Originally Posted by maxc

Ive done that and increased engine power 10% with only steam on a na engine.

I would like to see more info on your testing...

Again, how is the steam aquired?

[kirkerik]

BTW: i know this an old thread, but the question occured to me just last night about water injection when i was driving home in a thick fog.

i noticed my engine was running noticeably smoother and seemed to have an inrease in acceleration or power with less throttle applied than when there is no fog. I know that others have experienced this and i have experienced this more than once in more than one vehicle. So there must be something to it. But what is it?

Can anyone here explain this phenomonon?

[pete c]

Yes, even gas engines like a littl ebit of water injection. I just think that they don't benefit enough to go through the trouble of water injection, whereas diesels do.