How would you like your F82 M4 to have the same great looks, but even more power? It could happen—in fact, it has already happened for the BMW M4 coupes that will serve as 2015 MotoGP safety cars in the world-championship motorcycle-racing series.
Where will the added power come from? Water.
BMW M engineers will use water injection to not only increase performance but also decrease fuel consumption. Injecting a fine spray of water into the collector is supposed to lower the engine’s tendency to knock, thereby creating a more effective and efficient combustion process and lowering combustion temperatures. Cooler air is more dense, which translates into more oxygen in the combustion chamber at the time of ignition, which translates into higher combustion pressure and more performance and torque. A side effect is that lower temperatures will increase the longevity of engine components. At least that’s what BMW M is saying.
An additional liquid in the combustion process has to come from somewhere, and in the case of the M4 safety cars, it will come from the trunk, which is probably okay, since not many MotoGP safety car drivers will have their golf clubs back there.
The water will start in a frost-proof five-liter tank in the trunk. The tank will also contain the system’s water pump plus some sensors and valves, with the whole thing being controlled by the engine’s computerized management system.
The pump will send water to the injectors at a pressure of about 10 bar, or 145 psi. The volume of water will depend on the load, engine speed, and temperature. It’s not a magic tank, so someone will have to refill it occasionally. BMW M says that time would be before any "rigorous action out on the racetrack,” or once every five fuel stops during normal driving on public roads. We’re guessing that drivers who perform “rigorous actions” on public roads will probably have to figure a refill schedule by trial and error.
Using water to increase power in a combustion chamber seems to be counterintuitive, but it’s been around for a long time. Certain fighter planes in World War II were equipped with a form of water injection sometimes called “war emergency power,” or WEP. When the P51D Mustang was equipped with WEP, the horsepower increased from 1490 to 1720 when the pilot called for it. However, employing the WEP rapidly used up the engine to the point where pilots were cautioned to use it only in emergencies. Hence the name.
Getting back to cars, here is the interesting news. According to Worldcarfans.com, BMW claims it will be offering water injection soon on a production model. It didn’t say which model, but since more power is involved and it’s already going to be on the MotoGP safety car M4, why wouldn’t that production model be an M car?—Scott Blazey
See the system in animated action in this video.
[Photos and video courtesy of BMW M via worldcarfans.com.]
