why do you inject water into the chamber?

[leadstriker]

I am new to this area and would like your help!
why is it that you inject water into the chamber when using NOS?

also what is a comprex supercharger( pressure wave supercharger)?

[454Casull]

Well, for starters, you don't inject it into the chamber, but somewhere before the intake port. Second, it isn't necessary to inject water.

If the intake charge is lean, the additional water can help prevent detonation by slowing down the temperature increase of the charge.

[SaabJohan]

Comprex is a pressure wave compressor developed by Brown Boveri. It used the exhaust pulses to compress the intake air. The "comprex wheel" is however driven by the engine crankshaft (but the energy which compress the air comes from the exhaust).

[Mshkttck]

won't injecting water into the intake port hydrolock the engine?

[SaabJohan]

Originally Posted by Mshkttck

won't injecting water into the intake port hydrolock the engine?

no, the waterflow is too small for that

[2turboimports]

it's more of a mist. nothing like hooking up a garden hose..

[GTR2b]

An interesting by-product of doing this is that it's a great way to clean carbon deposits from around your valve stems and seats.

Back in the caburator days, (I feel so old) we would do that by holding the engine at 3k rpms and pouring small amounts of water down the carb. It blows a ton of steam out the tail pipe but gives your combustion chamber one hell of a "steam clean".

[rollo]

Since water injection helps to prevent knocking by cooling the air-fuel mixture down, can the same result be achieved by just cooling or chilling the fuel before it gets mixed with the air?
If that works, running on lower octane grade fuel should not be a problem, shouldn't it?

[Reed]

adding water to the chamber aslo increases the dynamic compression ratio. (I think dynamic but not entirely sure)

[Danny Demon]

I use a Netti Pot to inject warm salt water into my Nose to keep my sinuses clean. If that doesn't work I put the Lime in the Coconut and drink them both together for one hell of a Launch. My best ET within the confines of the space-time continuum is instantaneous. It ain't easy being me but I'm all I got, baby. Say goodnight Felix.

DD (alias, Rocket Man)

[SaabJohan]

Originally Posted by rollo

Since water injection helps to prevent knocking by cooling the air-fuel mixture down, can the same result be achieved by just cooling or chilling the fuel before it gets mixed with the air?
If that works, running on lower octane grade fuel should not be a problem, shouldn't it?

Cooling of the incoming air is quite common on forced induction engines, on NA engines it's almost never used since it would require a heat pump to cool it down below ambient temperature.

Cooling of the fuel has also been used.

Water injection was used for a while under the turbo era in F1 during the 80:ties, but it was found that it was difficult to get an even mixture in the chamber. So one had two options; use more water and lose some power or use less water, gain power but risk engine knock. Therefore a third option was developed, fuel which was mixed with water.

[rollo]

If I am not mistaken, during the turbo era in F1, McLaren Honda used not only just intercooling but also toluene based fuel to prevent detonation. Because toluene does not vaporize easily, they had to heat it up prior to injecting the fuel, not cool it.

I don't think water injection was practical with a F1 turbo race car because it could not carry a sufficient supply of water to last that 50 over laps in a single race.

[SaabJohan]

Originally Posted by rollo

If I am not mistaken, during the turbo era in F1, McLaren Honda used not only just intercooling but also toluene based fuel to prevent detonation. Because toluene does not vaporize easily, they had to heat it up prior to injecting the fuel, not cool it.

I don't think water injection was practical with a F1 turbo race car because it could not carry a sufficient supply of water to last that 50 over laps in a single race.

The heated fuel (it also used an intercooler bypass for hotter air) was only used on Hondas low fuel consumption engine. This was in the end of the turbo era where they had both boost limitations and fuel limitations. This low fuel consumption engine lacked power compared to earlier F1 turbo engines (it had only 600-700 hp) but was more powerful than the NA that had started to show up and it had a low fuel consumption compared to the other turbo engines used.

Water injection wasen't used anymore since it was diffucult too effectlivly supress knock with it without loosing power of too much water.

[rollo]

Yeah, that was interesting. Toluene has good anti-knock properties but its vaporization for combustion is another matter. In contrast, plain gasoline is easier to vaporize but has comparatively lower resistance to knock. Had been thinking that cooler gasoline would help resist knock.

I believe water injection was first used as anti-detonation injection in the days of WW2 era aero piston engines. These engines were either supercharged or turbocharged and their intercoolers or aftercoolers seemed inadequate to cool the air-fuel charge further to prevent detonation at higher boost, and thus, that's how water injection came into the picture. However, it was only used for short spurts of extra power due to the limited amount of water the plane could carry at one time for this purpose.

[Evil Result]

Alot of those planes where Turbo-Super charged and i don't think that Knock would be that much of a problem because of the altitude and air temperatures involved, I think the water was used during take off where the air was thicker, hoter, and boost was higher which could cause knock.