The questions of water injection....

[Zgringo]

Saabjohan, since you insist on posting old theory and mytholgy, I'll try and correct your error with proven usage and modern fact.

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).

"Rocketfuel" was used back in the 1920's and I learned of it's use in the late 40's and was using it in the 50's. This was long before the Germans were even into rocket development. BMW did have a fuel that was toluene base but the fillers added to it were very toxic and dangerious and was outlawed. Some claimed it was the old German V2 rocket fuel, which it wasn't.

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.

Honda's IC were very good but couldn't do there job at very hi-boosts, water injection was used to aid in cooling the inlet air. Under normal racing conditions water injection wasn't needed.
Toluene doesn't like to vaporise when cold and because of the high percentages of it present in "rocketfuel" had to be preheated to maintain good vaporazation.

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.

When water vaporizes at temps lower than 100C it's called, "Evaporation".

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.

What this has to do with the subject matter, I have no idea, other than water expands when heated or frozen.

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.

Tell this to the guys that run methanol and have frost on there intake manifolds. Anytime you decrease the inlet air temp you increase the density of the 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.

One gram of water heated to 350F has enough energy to lift a 3,000 lb. car 2 inches, so tell us how this water vapor heated to 800F+ has no energy.
Water alone and the power won't drop, the engine won't run. Trust me, you need alittle air and gasoline also.

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.

Same thing holds true for the gasoline, to little and you'll start damaging shit, too much and you'll lose power, wash down the cylinders and contaminate the oil.

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".

Sir Harry Ricardo's book was based on theory and equipment for it's time and very little of it applys to the modern engine as we now have or know.

I suggest Saabjohan, being you have a desire to learn and read, find some books on applied science and the modern automobile. You might even hang out at a tuners shop or try and apply some technology to your car then write reports on your findings. We need people like you with this desire to update old theory.

[Franko914]

Originally Posted by 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.

The octane rating is the fuel's resistance to detonation which in turn causes knocking. When the spark jumps the gap, the fuel-air mixture begins to ignite and the flame front propagates through the combustion chamber. If the octane rating is too low, rather than the flame front propagating throughout the combustion chamber, the remaining/unburnt fuel-air mixture detonates from the increased combustion chamber pressure. This causes the "knock."

Pre-ignition (ignition before the spark ignites the fuel-air mixture) can be caused by (a) low-octane fuel detonating as the cylinder pressure increases while approaching the top of the compression stroke, or (b) poorly seating exhaust valve which retains the heat rather than conducting it to the head thereby causing the being-compressed fuel-air mixture to ignite prior to spark sequence. In both cases, pre-ignition can cause knocking.

Originally Posted by SaabJohan

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

Yes, for cooling the charge air, water is the best. Many use water injection for cooling the charge air and also for keeping the combustion chambers and vavles "clean." Still others add alcohol, off-the-shelf H2O2 and even acetone to achieve what they perceive to be better performance.

Originally Posted by SaabJohan

4. An intercooler is a better choice than water injection (water injection is however not a real option to an intercooler).

Lowering the charge air temp is better than not lowering the charge air temp. Lowering the charge air temp by 100 degrees F is better than lowering the charge air temp by 30 degrees. If a combination of intercooler/water-injection (whether spraying water into the plenum or spraying the water onto the intercooler fins) lowers the temperature even more, then so much better, especially for diesel applications as they are not constrained by the 14.1 stoichiometric ratio of gasoline engines.