Quote:
| Originally Posted by 1996Bmw318TI Water injection- On similar systems (Downing Atlanta) the supercharger is powerful in the morning when the car is still cold, after the car heats up, the power drops off tremendously. The reason is, the supercharger heats up, the intake manifold is almost the same temperature as the cylinder head and hot air/fuel mix pre-ignites in the combustion chamber, causing the cars ECU to retard the ignition timing and loosing power. We use a dual nozzle water injection system that is boost activated to cool the supercharger and the air charge going into your motor to maintain the HP and stop pre-ignition without having to run the car super rich. Just fill the tank with water when you pump gas.
what exactly does this mean? You put water instead of gas or what does it mean exactly? Serious responce please. |
1st, you can only increase boost (pressure) to a certain level before gas pre-detonates. This is the same as increasing the compression ratio of an engine. If you raise the compression ratio too high, pump gas will pre-detonate and cause your engine to eventually self destruct. keep this in mind for later...
working with gases (not gasoline, elements in their vapor state, like air) there's a formula to describe the relationship between pressure, volume and temperature. You can read more here
http://scienceworld.wolfram.com/phys...ealGasLaw.html The idea of an internal combustion engine is to get oxygen from the air, mix it with gas and cause an explosion that pushes the piston. To get the greatest amounts of oxygen ( n = number of moles ) in the combustion chamber ( v = combustion chamber volume, R = universal gas constant, which are both constant) (based on PV=NRT) without water injection, t would be constant (around the thermostat temp of the car) we can rearrange the equation to read P=N(RT/V) where RT/V is constant. So here you see that the most oxygen you can get in the combustion chamber is directly related to the pressure. If we could decrease T at the same time as increasing P ( P/T=N(R/V) ) it would be the same thing as increasing pressure even more, without increasing the compression ratio(explained before), preventing pre-detonation. The safest way of doing this is to add an intercooler to cool the pressurized intake air back to outside air temps, but using the manfold design of MA and DA, this isn't possible. The alternative is to spray cool water into the hot intake temps.
The explination of causing the ECU to retard the timing isn't a complete picture of what happens, I tried to explain what fully happens here, I know i over simplified it, but I'm just trying to prove concepts here.