Water injection improves MPG?

[cRiPpLe_rOoStEr]

Originally Posted by Doc Joe

I had a 2001 7.3 diesel and if it was raining or better yet missing, my truck would run like it had two turbo's. It was amazing, I did notice on my wife's Colorado, it runs better when it is raining or misting. I think it is because of the added water grains in each intake stroke.

In a Diesel, which already runs pretty much leaner than a gasser, the higher humidity does increase the air density since it requires a higher air mass to reach the latent heat of evaporation and increasing the internal pressure on the combustion chambers (even though it won't harm the engine itself because the evaporated water content stores the extra thermal energy during the compression stroke and releases it more effectively in a more homogeneous way across the combustion chambers due to the high thermal conductibility of water), thus leading to a more accurate combustion of the fuel. Meanwhile in the gassers, it does allow a leaner AFR without the risk of melting a piston.

[ProDigit]

I would believe that on a hot engine, water vapor increases performance, especially on a turbo car.
Since the added mass, creates added expansion, your turbo should rev higher.

Routing the AC drain pipe to a sponge in the air intake (or wetting the filter), is a great idea to both increase filter effectiveness, as well as cooling down the intercooler, and at the exhaust point, revving up the turbo.

If you have an eco turbo engine, you can expect a little more torque at lower revs.

If you are running a performance engine, and can choose between 2 types of turbo, it might benefit to take the larger size turbo (lag, but also much higher HP), if your engine can handle the increase in power.

The water vapor of the AC unit is too little to make a big difference, but might actually benefit eco turbo engines, in hot summer days.

Cons of water injection is:
Much faster exhaust rusting.
Water coming out of the tailpipe.
White smoke coming out of the tailpipe (might not pass regulations on some places)
Not much is known about how the water interacts with engine oil, and engine bearings and rods.
AC drain pipe does not supply a steady stream of water (which is why you'll need a spongy kind of material, to soak up any water splashes, and transfer the water into the air intake, as much as a vapor as possible).

[oil pan 4]

You run gallons per hour of water.
If your exhaust rusts faster, you get white smoke and have emwater in your oil you are running way too much water.

[Galane]

Some fighter planes in WW2 used water or water and methanol injection to boost power for takeoff and when engaging enemy aircraft.

https://en.wikipedia.org/wiki/War_emergency_power

Bonus points if your car's water injection switch is labeled WEP.

[cRiPpLe_rOoStEr]

Originally Posted by ProDigit

I would believe that on a hot engine, water vapor increases performance, especially on a turbo car.
Since the added mass, creates added expansion, your turbo should rev higher.

Since the higher humidity added to the intake stream is likely to retain more of the heat that would otherwise be wasted through the engine cooling system, it would benefit basically every engine, not just the forced-induction ones.

Routing the AC drain pipe to a sponge in the air intake (or wetting the filter), is a great idea to both increase filter effectiveness, as well as cooling down the intercooler, and at the exhaust point, revving up the turbo.

If you have an eco turbo engine, you can expect a little more torque at lower revs.

If you are running a performance engine, and can choose between 2 types of turbo, it might benefit to take the larger size turbo (lag, but also much higher HP), if your engine can handle the increase in power.

The water vapor of the AC unit is too little to make a big difference, but might actually benefit eco turbo engines, in hot summer days.

No wonder BMW is already messing with a similar setup.

Cons of water injection is:
Much faster exhaust rusting.
Water coming out of the tailpipe.
White smoke coming out of the tailpipe (might not pass regulations on some places)

Exhaust rusting depends on many factors, ranging from the material to the amount of vapor that would end up condensing inside the muffler. Under normal operation, it would not be too likely for water to come out of the tailpipe in liquid phase. When it comes to white smoke, if it doesn't have that typical smell like burnt oil we usually notice in poorly-mantained beaters it might not lead to a fail on inspections.

Not much is known about how the water interacts with engine oil, and engine bearings and rods.

As long as it doesn't condensate inside the engine, which by the way sounds quite unlikely to happen, there would be no contamination to the engine oil. Even during the expansion at the power stroke, piston temperatures might be high enought to prevent the water to condense.

[ctmaybury@yahoo.com]

Piston blowby might bring water to the crankcase. Cooling the iat on a turbo engine might be worth the extra oil changes, though my truck does hold 10 quarts of oil.

The water might be better used externally on the intercooler. Evaporation would dramatically increase intercooler efficiency.

[ProDigit]

Originally Posted by ctmaybury@yahoo.com

Piston blowby might bring water to the crankcase. Cooling the iat on a turbo engine might be worth the extra oil changes, though my truck does hold 10 quarts of oil.

The water might be better used externally on the intercooler. Evaporation would dramatically increase intercooler efficiency.

The water can also cool the intercooler internally, and transfer the heat to the engine. It doesn't have to be used on the outside of the intercooler.

Although I'm not 100% sure if the water droplets would vaporize easier in the hot intercooler, since they're under pressure, and we know that for every bar on pressure, water boiling point goes up by almost 10 degrees.

As far as piston blow by gasses, engine oil is often run at temps that would evaporate the water easily. Oil and water don't mix, and water vapor will be floating in the air pockets in the engine. Not sure how much engine oil will trap water, how much water will sink to the bottom on a turned off (cool) engine, and how much gets sucked back in the lifters via the oil pump when starting.
If too much water enters the car, it might seize.
Then again, many cars ran Chevron's over-ethanolized fuel, which attracted so much water that every time you started from a stop, so much water would come out of the tail pipe, that you could water plants and flowers with it!

[ar5boosted]

Originally Posted by ProDigit

Then again, many cars ran Chevron's over-ethanolized fuel, which attracted so much water that every time you started from a stop, so much water would come out of the tail pipe, that you could water plants and flowers with it!

I'm convinced that when the fuel companies sell a 'Premium' fuel with 'Cleaning Agents' that it's just a water-emulsion that they're using.

It would be so cheap for them to produce, I find it hard to believe they wouldn't.

There's no harmful effects of water-injection unless done wrong. Oil soaked metal blocks won't absorb water. Exhausts on newer vehicles are all stainless steel so they won't be rusting.

There is enough engine heat to evaporate all water out of the engine.

Hypothetically you could get water in an oil channel which would cause a lubrication failure and then a catastrophic-engine-failure but I always use anti-sieze of some type to avoid that.

I was a bit busy on other things and I'm working through installing a system again and will be posting some results when I have them.

Fooling the computer is the main problem with an EFI car.

Water drops the engine operating temperature which the computer interprets as an invitation to go rich on the air-fuel mixture - kindly negating your efforts.

[JockoT]

I used to do a quick engine overhaul by removing the air filter then dribbling a glass of water through the carb. You had to keep the revs up, but the steam produced during combustion would scour the exhaust valves and ports and blow everything out the exhaust.
Got that tip from a US book from the 60's, with 100 tips to improve fuel consumption. Seemed to work and never done any harm to the engines I used it on. After all, for every gallon of petrol you burn it produces 1.52 gallons of water.

[ctmaybury@yahoo.com]

It does seem unlikely for water to collect in the cranckcase given the heat and cranckcase vent. Haven't tried this yet, but some type of material to hold the water on the outside of the intercooler like wool blanket or something similar. This is for a water to air cooler I want to design. I want to get ride of much of the friction the air sees going through the tortured path from the compressor to the engine. I'll use a watertank instead of collecting condensate from the ac though. I haven't measured yet, but I'll bet there's a 3 or 4 psi drop I can get back.