Water Vapour Jet - WTF.

[itz_baseline]

Just bought an Integra Type R and it came with a water vapour kit fitted:

http://www.invoauto.co.uk/Products/Water%20Vapor%2...

Never really heard about these before so I'm more than likely going to take it off as it seems like a bit of a swizz....unless of course people can confirm they are actually effective? Anyone had any experience of these? Apparently it gets great reviews by Max Power

[Davi]

never had any experience of them but was told by someone that I have reasonable faith in that they can actually be quite effective! Certainly wouldn't write it off without a bit of research.

[trickywoo]

These have been used on forced induction engines for years with good results.

[RobM77]

Standard on certain mk1 Imprezas I think.

[kambites]

The principle of injecting water into the cylinders to increase expansion is certainly sound. Whether it works in practice and/or breaks your engine, I have no idea.

[Richard-G]

RobM77 said:

Standard on certain mk1 Imprezas I think.

i think thats the intercooler spray.

this system sprays vapour into the cylinder bore directly. I'm pretty sure that its only really of benifit to turbocharged cars.

[kambites]

Richard-G said:

this system sprays vapour into the cylinder bore directly. I'm pretty sure that its only really of benifit to turbocharged cars.

Why would it make any difference? The principle is simply that water expands more than air when heated from below 100 degrees to over 100 degrees. That will happen just as well in a N/A car as a turbocharged one.

[edo]

I cant get my head round the idea of injecting water into an engine - sounds like a horribly crap idea to me!

[trickywoo]

My understanding is that it is useful in preventing pre ignition combustion, which can be a problem in cars running high boost.

[Richard-G]

kambites said:

Richard-G said:

this system sprays vapour into the cylinder bore directly. I'm pretty sure that its only really of benifit to turbocharged cars.

Why would it make any difference? The principle is simply that water expands more than air when heated from below 100 degrees to over 100 degrees. That will happen just as well in a N/A car as a turbocharged one.

In a piston engine, the initial injection of water cools the fuel-air mixture significantly, which increases its density and hence the amount of mixture that enters the cylinder. An additional effect comes later during combustion when the water absorbs large amounts of heat as it vaporizes, reducing peak temperature and resultant NOx formation, and reducing the amount of heat energy absorbed into the cylinder walls. This also converts part of combustion energy from the form of heat to the form of pressure. As the water droplets vaporize by absorbing heat, it turns to high pressure steam (water vapor or steam mainly resulted from combustion chemical reaction), that would add engine output. The alcohol in the mixture burns, but is also much more resistant to detonation than gasoline. The net result is a higher octane charge that will support very high compression ratios or significant forced induction pressures before onset of detonation.

wiki

http://en.wikipedia.org/wiki/Water_injection_(engi...

[Richard-G]

the black smoke trails on this are due to water injection, in fact i have a book on tupelov bombers at home that goes very in depth wrt water injection and how they used it as opposed to RATO (Rocket assisted take off)

[Slade Alive]

Saab were offering water inj back in 1977. Nothing new and it does work!

[munroman]

I had a Nissan with a failed head gasket, the cylinders into which the coolant leaked were spotless, and I have heard that a poor man's decoke involved dumping water into the intake of a high revving engine with spectacular results!

[anonymous-user]

On a normally aspirated engine, which does not run into detonation at peak power rpm, then a water injection system will "decrease" BMEP when used. On a highly tuned forced induction engine, which generates it's high output from high cylinder filling rather than high rpm (NA = many small bangs, FI = fewer big bangs effectively), the WOT operating range is generally detonation limited across a wide expanse. In this case, the derating slope of the "BMEP vs ignition retard" characteristic is so steep, that you can gain output by cooling the end of combustion temperature (to avoid detonation) but regain performance by increasing overall mass flow (more boost)

On a NA engine, without detonation limiting, and the inability to increase engine Mdot through increasing intake density, a water injection system will just reduce power (due to reduced combustion temp/pressure (PV=nRT)).

(only case for water injection on a NA reciprocation engine is where you have a very high static compression ratio and only operate the engine at "slow" speeds in the hgihly knock limited zones)


(there is realistically no gain from increase intake charge density, as that is fully offset by the volume of charge displaced by the water volume in the intake charge)(unless you have catastrophically high intake charge temps, eg > 100degC, which on an NA would be pretty unlikely)


(don't confuse water injection on axial flow turbojet engines with that of reciprocating engines, on the turbojet, thrust is directly increased by increasing the massflow of the engine cycle (because thrust is the change in momentum of that Mdot) On your car, you'd have to pretty drastically increase Mdot to be able to "blow" your car down the road on the thrust from the tailpipe...;-)

[rhinochopig]

WI dates back years. It was used to great effect in a number of WWII fighter engines.

[RobM77]

Richard-G said:

RobM77 said:

Standard on certain mk1 Imprezas I think.

i think thats the intercooler spray.

That's the one

Richard-G said:

this system sprays vapour into the cylinder bore directly.

I didn't realise that!

[RobCrezz]

edo said:

I cant get my head round the idea of injecting water into an engine - sounds like a horribly crap idea to me!

Many people do 50% Water 50% Methanol. Its very effective in highly tuned forced induction cars.
You can use it as a safeguard to prevent detonation, or tune the car to take advantage of the increased detonation resistance and gain power and torque - downside of this is that if the water/meth injection system runs out or fails, you could suffer detonation and a chance of blowing the engine.

[Tango13]

rhinochopig said:

WI dates back years. It was used to great effect in a number of WWII fighter engines.

The Luftwaffe used MW50 which was a 50:50 mixture of water and alcohol injected into the supercharger to reduce inlet temperature.

Honda tried water injection on their 500GP bikes a few years back, the difference being they injected the water into the exhausts to try and alter the resonance in the expansion chambers.

[Richard-G]

Max_Torque said:

On a normally aspirated engine, which does not run into detonation at peak power rpm, then a water injection system will "decrease" BMEP when used. On a highly tuned forced induction engine, which generates it's high output from high cylinder filling rather than high rpm (NA = many small bangs, FI = fewer big bangs effectively), the WOT operating range is generally detonation limited across a wide expanse. In this case, the derating slope of the "BMEP vs ignition retard" characteristic is so steep, that you can gain output by cooling the end of combustion temperature (to avoid detonation) but regain performance by increasing overall mass flow (more boost)

On a NA engine, without detonation limiting, and the inability to increase engine Mdot through increasing intake density, a water injection system will just reduce power (due to reduced combustion temp/pressure (PV=nRT)).

(only case for water injection on a NA reciprocation engine is where you have a very high static compression ratio and only operate the engine at "slow" speeds in the hgihly knock limited zones)


(there is realistically no gain from increase intake charge density, as that is fully offset by the volume of charge displaced by the water volume in the intake charge)(unless you have catastrophically high intake charge temps, eg > 100degC, which on an NA would be pretty unlikely)


(don't confuse water injection on axial flow turbojet engines with that of reciprocating engines, on the turbojet, thrust is directly increased by increasing the massflow of the engine cycle (because thrust is the change in momentum of that Mdot) On your car, you'd have to pretty drastically increase Mdot to be able to "blow" your car down the road on the thrust from the tailpipe...;-)

Exactly what i was thinking

that pretty much answers the question

[The Wookie]

munroman said:

I had a Nissan with a failed head gasket, the cylinders into which the coolant leaked were spotless, and I have heard that a poor man's decoke involved dumping water into the intake of a high revving engine with spectacular results!

Poor man as in they'll be poor by the time they've finished rebuilding the engine after hydraulicing it?