Originally Posted by ksa8907
Its only going to do any good on a high compression engine, more than 11:1, or forced induction. Putting water injection on a stock engine with stock tune is not going to do any good.
I think the idea has some merit. But you would have a lot of experimenting to do.
It would be a fun experiment, that might yield better FE. Most people don't have the skill, patience, or time/money to carry it out (including me).
The increased compression ratio and cylinder pressure might give you better efficiency from the given engine, the 'fog' introduced at the right time under the right conditions, could keep combustion temperatures and detonation in check under heavy load. Gaining efficiency while cruising at a constant speed and relatively low load, yet keeping engine killing detonation and Nox production under control under heavier loads.
I'll add to that: raising the compression ratio of most any normally aspirated gasoline (street) engine will increase power, and usually efficiency. The oem's have know this for a long time, and as of the last 15 years or so, have been able to take advantage of that through better fuel metering and ignition timing controls. Standard compression ratios for passenger cars used to be in the neighborhood of 8 or 9:1. These days, 10 or 10.5:1 are common in normally aspirated passenger cars that burn 87 octane fuel. You could have never gotten away with burning 87 octane in a 1960's 9.5:1 compression mild performance V8. 87 octane in a 1960's performance V8 like a factory optioned 11:1 Chevrolet V8, would have ruined the ring lands and beat the rod bearings up, not made much power and would have run very hot.
If a guy had a car to experiment with, and lots of spare time, I'd start by doing the required machine work and increase the compression ratio by an entire point. Say, from factory 10:1 to 11:1 for example, then adding a computer controlled Snow or similar system.
I tried something like this on an air-cooled VW back in 1981. The guy I bought the car from warned me it had higher than factory 9:1 compression, and said I needed to burn premium fuel in it, or it would ping and overheat (death to an air-cooled engine). I cobbled together a primitive water injection system copied from a magazine article of the day, and was able to burn regular octane fuel, without running hot, had good power, and decent FE while I was commuting back and forth to college. When it ran out of water, it would ping and rattle so bad you could hear it over that aweful music I used to listen to back then