Water injection improves MPG?
 

I understand the basic idea of how water injection works: Water mist gets sprayed into the intake, intake cools off, combustion temp drops, the chance of knock decreases. But would that actually mean better MPG with no other changes? I know that water injection would allow for more ignition timing advance, which would improve MPG. But would water injection improve MPG with no other changes? Thanks

Water vapor is LIGHTER than AIR, but it does take of space nevertheless, so the amount of oxygen-containing AIR being drawn into the cylinders will go down, the equivalence of running a rich AF-ratio.

Water is definitely heavier than air. I just know this because there was a huge different in weight when my 20-litre water-tanks were filled with water compared to when they were empty or filled with air. 20kg of difference thereabouts.

Water-Injection works by the water absorbing heat and turning to steam. When water vaporises it expands x1800 times and will give additional driving force to the pistons. That is more power, so you get a lighter throttle pedal and don't need much pedal force to drive around.

I got up to using 50%-water/50% fuel. So for 20 litres of water I used 20 litres of fuel.

The EPA for the vehicle was around 17mpg and I consistently got 21 mpg and the best was 26mpg.

This was on an old Mitsubishi L300 with a 4G63 SOHC Carburator engine. yes, it can work.

Best thing was the improvement in Torque. When the water was on, the engine felt like it gained 2-cylinders because it drove like a 6. You'd turn the water off after getting used to it, and you'd be wondering if the engine was broke because it felt gutless - haha.

However, with EFI vehicles it's harder. The computer will try to thwart all your good idea's. So when I tried on my next EFI car, it didn't work anywhere near as well.

Typical water injection systems spray a mist of water droplets into the intake. This mist, consisting mostly of fine droplets of liquid water, doesn't do a whole lot by itself, because typically you'd spray at most a 1:4 ratio of water to fuel. The water mist that does vaporize will cool off the intake charge, but not by a lot. Most of the cooling occurs within the combustion chambers themselves, as the water mist absorbs heat from the charge being compressed, and then vaporizes. If you could optimize the spark and fuel maps to take advantage of this cooling effect, then you could get some modest fuel economy gain there.

Now, you could set it up so that you would inject very hot water into the intake. Although it is counterintuitive, this may also give some fuel economy gain because the hot water mist will more completely vaporize than with traditional water injection. This will displace the air in the intake such that less oxygen is being drawn in than before, and your throttle plate would have to open a bit more to compensate. This would lower intake manifold vacuum, and since the engine would not longer have to work as hard to make that intake vacuum, it would use less fuel than before.

I use a variant of the second type, but I use fuel instead. The 12-hole fuel injectors spay a very fine mist into heated intake air, which causes the fuel to mostly evaporate. This lowers the amount of work each piston has to perform to suck in the intake charge, and has the added benefit of more uniformly mixing the fuel air mixture. I saw a 11% improvement in fuel economy by switching to these injectors, and am going to press on with an auxiliary hot water injection system to verify this idea will work.

On diesel engines yes.
On gasoline engines, usually not unless the engine is specially tuned and designed around using water injection because it runs unusually high compression or something else.

In a gasser, it's all about how you fool the ECU to adjust the injection to go leaner when water injection is on.

Well, I opened the bonnet today on my V6 to inspect if I could find space for Water-Injection and it seems that I was in-luck.

Since it's a sucky V6 (a powerful one), 270hp or so it would be interesting to attempt a Water-Injection build on this car. The car was bought as a muck-around toy rather for any practical transportation use.

http://ar5boosted.com/users/david/DSC_0330.JPG

It's a 20mpg around town, 30mpg freeway. It would be good to get more.

On such a car it's worth doing. I'm pretty sure that hacking the IAT sensor is the way to temporarily go leaner. But the o2-sensors eventually reset during the calibration phase which I'm led to believe is running at constant speed 80kmh+. I've used o2-sensor extenders in the past, they did achieve a change in economy.

To come will be photo's of it having a Water-Injection system.

I might have been born in the wrong country, because I do love the Holden Commodore.

Is it manual or automatic? Those mileage figures are quite good for an engine which has around 80% more displacement than the Subaru Impreza that my dad used to have, which got similar mileage figures (only slightly better in city, even though it could get close to 35 MPG while not going faster than 80km/h).

It's a five-speed Automatic that also has like flappy-paddle select like race-car. Gearchange is steering-wheel mounted if you want to use it so not really separate paddles but close.

It also has LSD because trying to be race-car with 190kW. Feels like a Sports car and drives nicely. I just bought it to try to improve the fuel economy tbh and add turbo. It's booked in for Track days in August and September.

Before I do the Turbocharging I'll run some tests with simple Water-Injection. I checked out it's Sensors yesterday which include an AirFlow sensor which would be all I would need to calculate water-flow. I then just need to find the IAT sensor and hook into that.

Even with water injection, I hope you don't disconsider getting an intercooler.

It's there, but just in a strange way.

http://ar5boosted.com/users/david/DSC_0308.JPG

I should have guessed you were planning another rear-mounted turbo setup...

My Vaz gets better MPG in the rain. Probably due to it's swirl-type combustion

I'm not sure if the swirl-type combustion chambers should be affected in a different way to the higher humidity at the intake air stream.

It might get better MPG in the rain from lower rolling resistance, or a number of other factors.

I have found that O2 extenders fool the O2 into showing leaner than what's really in the pipe and add more fuel, actually makes the vehicle run richer.
Or us them to fool the rear O2 after a catalytic converter delete.

A few days ago while I was walking around the neighborhood I noticed the amount of water drained from the air-conditioning of a small bus at a stoplight. It does seem like a waste that it wasn't reused into some water injection system, since it could eventually at least overcome the fuel-consumption penalty inherent to the air-conditioning.

A self-perpetuating evaporative cooler (wink,wink)?

Well, sort of. Since the water would evaporate either in the intake stream or during the compression stroke while retaining latent heat and decrease the heat irradiation through the cylinder walls :D

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.

I have always wanted to add some kind of water injector upstream of the sensors and make it so I could turn it off before I shut the engine off to clear the system of any extra water.

I still feel with the right set up it would help and improve both power and fuel economy.

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.

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).

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.

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. ;)

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.


No wonder BMW is already messing with a similar setup.


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.


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.

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!

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.:mad:

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.

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.

Gotta have to agree on that. Anyway, since the humidity embedded in the intake stream during a rainy day actually retains more residual heat that would otherwise irradiate through the cylinder liners to the cooling water jacket (or the cooling fins if we were looking at an air-cooled engine), it doesn't sound likely that any small amount of steam would condense and fall through the pistons. Steam also tends to go upstream, so it would also pick more residual heat from the cylinder head and eventually escape easier when the exhaust valve opens.

Seems like a good mod to try. I'm already doing lpg fumigation with good results. I have 3 stages that key on boost pressure. I'm going to add a few more stages. I think you would need high pressure and good nozzles to get the best atomisation you can. Big drops of water wouldn't help much. If you drop the combustion heat with water, you pobably increase the hydrocarbons in the exhaust and reduce the nitrogen oxides.

What vehicle are you doing the LPG fumigation? Is it Diesel-powered?


Atomisation is the key, and adding some alcohol (methanol, ethanol, whatever) usually also helps vaporising the water at the intake stream.


Sure it reduces the NOx, but any increase in HC emissions is quite arguable. Dropping the intake temperature with water injection usually leads to a denser air flow, with a higher concentration of oxygen which then leads to a more accurate combustion. OTOH we also may remember it's likely to also involve a leaning of the air/fuel ratio, while the water helps cooling down the pistons instead of relying on a richer mixture for that matter. Anyway, since the water has a higher thermal conductibility than air, it retains some heat that would otherwise be wasted instead of turned into motion.

Lpg fumigation now is on my 98 dodge 2500 24v cummins 5sp. Before lpg, it regularly got 17 plus mpg and a best tank of 20.15 mpg. My tanks are true mixed driving with about 30 percent highway and the rest mountain dirt roads, sometimes with trailer always with tools and building materials. I don't want to report my mileage with lpg yet as I just hooked it up again after several years without. Burned up about half a tank so far and it looks like a good one based on odometer and fuel gauge, but you never know until the fill up.

Water/methanol is a common mod for these trucks. I'm still dialling in the lpg so won't mess with water yet.

My other work truck is going to be the true experimental platform. The 98 has an ecu that controls injection timing, fuel duration and a whole host of parameters that make it difficult to mod one aspect and pinpoint cause and effect. My 99 dodge is also a 24v cummins, but I recently put in a p7100 injection pump from the previous generation dodge. Injection timing is fixed but adjustable. The engine is entirely mechanical. I put arp head studs on to handle the extra cylinder pressure from the lpg. Right now I'm running about 3% lpg, but will slowly increase to about 15% or so. I'll start a thread when I have more to report on lpg.

Sorry about hijacking the thread.

I have actually never seen LPG and water injection being used simultaneously.

It would be an either or not simultaneously.

There was at least one member of this forum who was trying to add steam to the intake of an LPG-powered Mercedes-Benz.

Lpg only or lpg fumigation on a diesel engine? Lpg by itself doesn't have the btu content other fuels have, but it is cheap, so might be economical. A small quantity in a diesel engine is supposed to speed up the burn and help burn some of the diesel fuel that would otherwise go unburned out the tailpipe. There is definitely room for improvement on my old dodge trucks. If it's true, I should see an increase in efficiency and a decrease in hc out the tailpipe. I already have a dramatic power increase and a few subtle improvements like sound reduction and smoke reduction. The smoke reduction points to a more complete burn.

I'm going to search out the mb steam thread. Sounds interesting.

Spark-ignited converted from gasoline-only to bi-fuel gasoline/LPG.


Even though it doesn't have an outstanding BTU content, the cooling effect it proportionates when fumigated at the intake stream is worth, acting quite like a chemical intercooler. And since it's more volatile than Diesel fuel, sure it's likely to increase the flame spread throughout the combustion chambers, leading to a more accurate burn which not just decreases overall emissions but also take more benefit of the energy content of the Diesel fuel. Considering that Diesel usually runs leaner for the sake of economy, that extra amount of fuel supplied through LPG fumigation won't be too much of a problem. Eventually, if you were not into LPG fumigation as a power booster, could trim the Diesel fuel injection down a little without any decrease to performance or any side-effect on emissions compared to stock.


I'd only consider adding steam in a Diesel if you do it as a replacement to EGR. You might know, hot gases flowing through the intake tract while still expanding are likely to decrease the dynamic compression, which may affect the ability of the Diesel engine to generate enough aerodynamic heating of the intake charge.

The chemical intercooler effect is part of what I'm after. I'm going to take further advantage of that effect and use an evaporator style regulator from a forklift that uses the liquid propane and requires warm water to keep the reg from freezing. The water will come from the water to air intercooler I'm planning. No sense in wasting all that free cold from the evaporation of the propane. I'll get less restriction on my intake air stream and a more efficient intercooler. The custom header I'm going to build will further reduce pumping losses and increase the efficiency of the turbo.

Wish I could start on all that tonight.