The questions of water injection....

[Hypsi87]

Originally Posted by guitarXgeek

My bad, what I meant to say was those MODERATELY AGED TURBO BUICK GUYS I'm glad you guys see the tremendous benefits of water/alky injection. I don't get the whole "band-aid" idea, in my book it just doesn't hold water (pun intended ).

HELL, even moderly aged turbo buick guys..... IM 22 LOL


Zgringo, thanks for the hats off!! I have always felt that doing some research always helps. I usually don't try to make quick assumpsions on anything.

[SaabJohan]

1. Knocking is NOT the same as pre-ignition. The octane rating is the fuels resistance against knocking, but it has noting to do with pre- or post-ignition.

2. Water is the best coolant for water injection. Alcohol is sometimes added to prevent freezing of the water.

3. Water injection has serveral downsides.

4. An intercooler is a better choice than water injection (water injection is however not a real option to an intercooler). Intercoolers have been around since basicly the internal combustion engine was supercharged. Intercoolers was used on several of the WW2 airplanes, one manufacturer of these intercoolers (fitted to the Boeing B-17 for example) was Garrett which today is well known for their turbochargers. Low weight aluminum intercoolers where however Garretts first product back in the late 1930:ies. Intercoolers were of couse also used on the 5.5 bar boosted F1 engines of the eigties.

Water injection, as a separate liquid or emulsion with gasoline, or as a
vapour, has been thoroughly researched. If engines can calibrated to operate
with small amounts of water, knock can be suppressed, hydrocarbon emissions
will slightly increase, NOx emissions will decrease, CO does not change
significantly, and fuel and energy consumption are increased [113].

Water injection was used in WWII aviation engine to provide a large increase
in available power for very short periods. The injection of water does
decrease the dew point of the exhaust gases. This has potential corrosion
problems. The very high specific heat and heat of vaporisation of water
means that the combustion temperature will decrease. It has been shown that
a 10% water addition to methanol reduces the power and efficiency by about
3%, and doubles the unburnt fuel emissions, but does reduce NOx by 25% [114].
A decrease in combustion temperature will reduce the theoretical maximum
possible efficiency of an otto cycle engine that is operating correctly,
but may improve efficiency in engines that are experiencing abnormal
combustion on existing fuels.

Some aviation SI engines still use boost fluids. The water-methanol mixtures
are used to provide increased power for short periods, up to 40% more -
assuming adequate mechanical strength of the engine. The 40/60 or 45/55
water-methanol mixtures are used as boost fluids for aviation engines because
water would freeze. Methanol is just "preburnt" methane, consequently it only
has about half the energy content of gasoline, but it does have a higher heat
of vaporisation, which has a significant cooling effect on the charge.
Water-methanol blends are more cost-effective than gasoline for combustion
cooling. The high Sensitivity of alcohol fuels has to be considered in the
engine design and settings.

Boost fluids are used because they are far more economical than using the
fuel. When a supercharged engine has to be operated at high boost, the
mixture has to be enriched to keep the engine operating without knock. The
extra fuel cools the cylinder walls and the charge, thus delaying the onset
of knock which would otherwise occur at the associated higher temperatures.

The overall effect of boost fluid injection is to permit a considerable
increase in knock-free engine power for the same combustion chamber
temperature. The power increase is obtained from the higher allowable boost.
In practice, the fuel mixture is usually weakened when using boost fluid
injection, and the ratio of the two fuel fluids is approximately 100 parts
of avgas to 25 parts of boost fluid. With that ratio, the resulting
performance corresponds to an effective uprating of the fuel of about 25%,
irrespective of its original value. Trying to increase power boosting above
40% is difficult, as the engine can drown because of excessive liquid [110].

Note that for water injection to provide useful power gains, the engine
management and fuel systems must be able to monitor the knock and adjust
both stoichiometry and ignition to obtain significant benefits. Aviation
engines are designed to accommodate water injection, most automobile engines
are not. Returns on investment are usually harder to achieve on engines that
do not normal extend their performance envelope into those regions. Water
injection has been used by some engine manufacturers - usually as an
expedient way to maintain acceptable power after regulatory emissions
baggage was added to the engine, but usually the manufacturer quickly
produces a modified engine that does not require water injection.

Below a picture of the turbocharged BMW M12/13 F1 engine:


The intercooler is the one on the left side and cools the pressurised air down to around 30-40 degrees celsius. Going lower than that just results in varporisation problems due to the fuel.

According to engine designer Paul Rosche they also tested to supress engine knock with water injection, fuel developements showed however greater results and the developements where then focused on fuels.

The laydown layout of the radiator and intercooler allows a small surface area with an effective cooling (you don't need a high flow velocity through the radiators).

[Zgringo]

SaabJohan,
As I have a ATP in Airplane Single engine land and sea, Airplane Multiengine land and sea, Rotorcraft Helicopter, Instrument Airplane and Helicopter.
A&P licence
Certified IA
Masters degree in Aeronautical Engineering & Metallurgy
and having been a research engineer for Wright & Patterson engine lab in Dayton, Ohio I find your comments interisting and wonder where you have found this information and what you base your theory on.
The main reason Aircraft only used water/alky injection for short periods is it was only needed for takeoffs under heavy loads or for high power settings for climbing higher quickly to avoid ground fire or enemy aircraft. The inter cooler was used because not enough water/alky fluid could be hauled aboard the aircraft as it is with the F1 racing engines. Intercoolers were used in F1 cars as not enough water/alky could be hauled onboard without affecting the weight of the car.
Now for what were talking about is a street car or a car used for dragracing, where 2 gals. well be more than enough to last for a tank of gasoline.
you've posted some figures that just don't hold water.
Both in racing as well as the avation industry it's a proven fact, not theory that water/alky injection is one of the best ways to control inlet temp. and increase power in a engine.
Please so I (we) can research your claims were you found this information.

[SaabJohan]

My quote is from:
http://www.faqs.org/faqs/autos/gasoline-faq/part1/
Which in turn have several references about water injection.

The info about the turbocharged F1 engines comes from interviews with BMW's Paul Rosche but also from technical papers from for example Honda and Garrett and articles by Ian Bamsey.

That water is the best coolant is simple to find out by comparing the specifications on water, methanol, ethanol and so on.

That knocking and pre-, and postignitions isn't the same thing one should be able to read anywhere from Bosch Automotive Handbook to Heislers Advanced Engine Technology. It should even be possible to find that out by reading the history of Kettering, Midgley and TEL.

The amount of fuel an engine can burn is limited by the amount of oxygen. With a given engine the amount of oxygen availible will be dependant on the oxygen content in the air (basicly air pressure). If we use an intercooler to cool the air we will only have air in the stream but if we use water to reach the same temperature we will also have some steam taking up place since most of the cooling is done by the heat of vaporisation.
With water, some cooling (most?) will also occur in the combustion chamber and thereby not having a positive effect on the volumetric efficiency but only on engine knock while an intercooler will only cool the charge and not directly supressing engine knock. With that given, water injection isn't a real option to an intercooler which is also probably why WRC cars use both intercoolers and water injection. In WRC the intercooler cools the charge, which can't of course go below ambient, then the water injection decrease the temperature further a bit, but it isn't that much, it do however supress engine knock effectivly and also reduce exhaust temperature making life a little bit easier for the turbine (exhaust temperature is still 1050 degC).

Saab Powertrain have also tested waterinjection (windshield washer fluid), but that wasn't as a intercooler replacement, it was more like an option to fuel enrichment at high loads.

In short the intercooler can be said to increase the oxygen content of the charge while the water injection primarily supress engine knock but it can also cool the charge at the cost of some water vapor. Water injection can be replaced by fuel injection, but the cooling effect from fuel is usually less than from water. The knock supressing funcion of the water can be replaced with higher octane fuel.

[nissanfanatic]

Thanks for your input saabjohan. I'm glad to hear someone else agrees with me.

[Zgringo]

SaabJohan,
Fact is Honda's big secret was they were using rocket fuel (toluene) and water injection to develop over 1,000HP per liter in there race cars.
As for a water/alky injected engine getting less oxygen because of the present of the water/alky in the inlet stream is absurd. A N/A 300 Cu. In. engine well take in only so much oxygen bearing air unless the air is being compressed by mechanical means. The water/alky present in this air stream cools the air, making a denser air with more oxygen. Anytime you cool air it becomes denser meaning it takes less space therefor more oxygen bearing air can be stuffed into a engine, and buy adding more fuel , make more power.
your trying to quote from old theory's that have been proven wrong and replaced with modern technology and facts not personal feelings.
Now if you'd like i'd be more than happy to setup a dyno test with the same engine being used for all testing and the turbo set at 20# boost, with and without water/alky injection and prove which will make the most power. Loser pays for the dyno time.
Thats the bottom line.

[SaabJohan]

Originally Posted by Zgringo

SaabJohan,
Fact is Honda's big secret was they were using rocket fuel (toluene) and water injection to develop over 1,000HP per liter in there race cars.
As for a water/alky injected engine getting less oxygen because of the present of the water/alky in the inlet stream is absurd. A N/A 300 Cu. In. engine well take in only so much oxygen bearing air unless the air is being compressed by mechanical means. The water/alky present in this air stream cools the air, making a denser air with more oxygen. Anytime you cool air it becomes denser meaning it takes less space therefor more oxygen bearing air can be stuffed into a engine, and buy adding more fuel , make more power.
your trying to quote from old theory's that have been proven wrong and replaced with modern technology and facts not personal feelings.
Now if you'd like i'd be more than happy to setup a dyno test with the same engine being used for all testing and the turbo set at 20# boost, with and without water/alky injection and prove which will make the most power. Loser pays for the dyno time.
Thats the bottom line.

Toluene isn't rocketfuel (one old myth that never seems to die).

The Racingfuel Honda used did contain 84% toluene and 16% n-heptane. The fuel was developed by Honda together with ELF for F1. They did not use water injection, but they did however use two air to air intercoolers.

When you add water to the airflow there will be water in in, as water vaporise it will cool the charge but the steam will also take up some place (as there is a huge expansion when the water goes from liquid to steam). If the water do not vaprise before entering the cylinder the cooling effect will be small and the charge won't be that much denser. This is just plain thermodynamics which you can't escape from, no matter what.

The reason for the higher power made by the engine which has water injection is mainly because the water supress engine knock and the engine can therefore be optimised for a higher power output with for example higher boost or more ignition advance. Just like ERL, the supplier of waterinjection systems for the Prodrive-Subaru WRC team, states on their homepage:

The main function of these systems
is to suppress detonation caused by
high temperature and pressure developed
within the combustion chamber when
the effective compression ratio has
been taken beyond the auto-ignition point
by either a turbo or a supercharger.

[Zgringo]

Originally Posted by SaabJohan

Toluene isn't rocketfuel (one old myth that never seems to die).

The Racingfuel Honda used did contain 84% toluene and 16% n-heptane. The fuel was developed by Honda together with ELF for F1. They did not use water injection, but they did however use two air to air intercoolers.

When you add water to the airflow there will be water in in, as water vaporise it will cool the charge but the steam will also take up some place (as there is a huge expansion when the water goes from liquid to steam). If the water do not vaprise before entering the cylinder the cooling effect will be small and the charge won't be that much denser. This is just plain thermodynamics which you can't escape from, no matter what.

The reason for the higher power made by the engine which has water injection is mainly because the water supress engine knock and the engine can therefore be optimised for a higher power output with for example higher boost or more ignition advance. Just like ERL, the supplier of waterinjection systems for the Prodrive-Subaru WRC team, states on their homepage:

Rocket fuel isn't a myth but a name for a fuel we were using at that time. Moths don't have balls, and i've never seen a housefly. There nothing but names attached to a thing, like golfballs, what's a golf?
As for Honda/ELF developing rocketfuel, sorry we were using it before Honda was a company. Honda's GP or F1 efforts didn't come into play till many years we were using toluene (paint thinner) as a base for racing fuel. And they did use water injection when qualifying with power settings above 5 bar as the IC couldn't handle the hot inlet air temp., but didn't use it for the race as they couldn't haul enough water.
Lets get this vapor, steam thing straight. First water will turn to vapor by evaporation, but to turn it to steam you need to apply 212F to the water.
Water injected into the intake air stream turns to vapor not steam as the tempature of the intake air isn't 212F. but this water vapor upon entering the combustion chamber, wow, lots of neat things happen.
It turns to steam because of the combustion chamber temp. it starts expanding very quickly, absorbing combustion chamber heat, steam cleans the combustion chamber, and assists the A/F mixture thats also building pressure on top of the piston make more power. Isn't that cool? Now we have a gas fired steam engine.
Because of the steam cleaning effect ( no carbon hot spots) and lower combustion chamber temps. We can now run more timing, more boost or for those using nitrous not have to run radical retarded timing and claim more power which is the name of the game.
Water/alky injection isn't a band-aid for a poorly setup engine, it's a power adder.

[beef_bourito]

I'm just wondering, wouldn't the water add some compression to the engine? water doesn't compress so wouldn't that take up some space and compress the af ratio more than normally?

p.s. great info, i'm really enjoying this flame-free conversation

[Zgringo]

Originally Posted by beef_bourito

I'm just wondering, wouldn't the water add some compression to the engine? water doesn't compress so wouldn't that take up some space and compress the af ratio more than normally?

p.s. great info, i'm really enjoying this flame-free conversation

Does gasoline compress? No liquid well compress.

[beef_bourito]

but when you inject water into the cylender, aren't you cramming the same a/f into a smaller area thus increasing the compression and giving more power?

[Zgringo]

Originally Posted by beef_bourito

but when you inject water into the cylender, aren't you cramming the same a/f into a smaller area thus increasing the compression and giving more power?

Lets see if we can see what effects compression ratio. A/F mixture and water/alky vapor don't seem to fit into the equasion. You think it's possible because it's negledgeable when it comes to the sweep volume of the cylinder and part of the mass air flow of the intake air? Nice point beef_bourito, glad you mentioned that.

Displacement = (Bore ÷ 2)2 x 3.14 x Stroke x 16.387
Head Gasket space = (Bore ÷ 2)2 x 3.14 x Gasket thickness x 16.387064
Deck Height space = (Bore ÷ 2)2 x 3.14 x Deck Height x 16.387064
Compressed Volume = Head Gasket space + Deck Height space +
Piston Top volume + Combustion chamber volume
Uncompressed Volume = Compressed Volume + Displacement
Compression Ratio = Uncompressed volume ÷ Compressed volume

[-Jayson-]

i thinky alky injection is a great idea. I plan on using it this summer on my setup. I have a roots blower, so its attached directly to the engine, i have no room for an intercooler. I plan on running 8 lbs of boost with the alky injection.

[Zgringo]

Originally Posted by -Jayson-

i thinky alky injection is a great idea. I plan on using it this summer on my setup. I have a roots blower, so its attached directly to the engine, i have no room for an intercooler. I plan on running 8 lbs of boost with the alky injection.

Jason, I think you'll be happier than pigs knee deep in poop running that combination.

[SaabJohan]

That the F1 fuel of the eighties was called "rocketfuel" has its roots in the special fuel used by BMW. According to a myth the fuel was old nazi rocket fuel which of course it wasn't. The fuel BMW used was fully synthetic and made by Wintershall, the petroleum division of BASF (which was one of the companies in IG Farben).

The intercoolers used by Honda did their job quite well and got the temperatures down below 40 degC (from about 250 degC). They were infact fitted with bypass valves so the inlet temperatures didn't got too low (the temperature was supposed to be kept at 40 degC) which resulted in vaporization problems and a higher fuel consumption (these engines where fuel consumption limited). Later even the fuel was preheated by the coolant and the temperature of the incoming air was increased to 70 degC.

Steam can be defined in several ways. In either case it will be nothing more than water vapor (water in gas state). Water can vaporize at temperatures lower than 100 degC, but the vaporisation will be quite small.

Even liquids can be compressed, the compression is however that small that it's often ignored (for good reasons). Water for example decreases its volume by about .3% when going from 1 to 70 bars pressure.
In the case of water injection the amount of water in the chamber is very small so that as a liquid it won't take up much space.

Let's assume that we inject water with a ratio of 40 kg air per kg water (about 30% of gasoline flow). With that ratio the heat of vaporization will result in a cooling effect of 56 kJ/kg air. If methanol is injected as a fuel with a ratio of 7:1 it offer a cooling effect of 133 kJ/kg air, and gasoline about 36 kJ/kg air injected with a ratio of 12.5:1. 56 kJ/kg air is enough to cool the charge with around 70 degC, but most of this cooling will occur in the combustion chamber. The charge itself isn't cooled with much more than around say 15-20 degC with an initial temperature of the air by 70 degC. The cooling effect will however increase if the air temperature increase and decrease if the air temperature decrease. As for increasing the density of the charge, water injection alone isn't a good idea, but most supercharged racing cars using water injection where also fitted with an intercooler for that purpose.

In addition to the cooling provided by the heat of vaporisation, water will consume 4,18 kJ/(kg*K) as liquid and around 2 kJ/(kg*K) as vapor. The specific heat as water vapor is about twice that of air.

The real advantage of the water is that well inside the combustion chamber it can cool the chamber itself but also the gas during combustion resulting in lower temperatures and a slower heat release. The water do not provide additional pressure on the piston (as sometimes stated), but it supress engine knock due to the reasons mentioned above and the engine can therefore be used with higher boost pressures, more ignition advance and leaner fuel mixture giving possibilities to increase engine power/save fuel with those methods. The injection of water alone will most likely cause a small drop in engine power.

It's also very important that the water injection system provides the correct amount of water just like with fuel injection. Too little water and detonation can occur, too much water and the engine will lose power but it can also take damage by for example contaminate the lubricant.

The effects of "boost fluids" or "water injection" was mainly studied around the 1930:ies by sir Harry Ricardo, which is documented in his book "The High-Speed Internal Combustion Engine".