If you’re into racing and you’re not watching MotoGP, stop reading this and set your DVR—or VHS machine if you’re like our father-in-law—as the racing is fantastic. While we have an undying allegiance to four-wheeled machines, the wheel-to-wheel action of a MotoGP race is unparalleled in motorsports. Plus, come March 29 and the season-opener in Qatar, you’ll get a glimpse of the latest BMW M4 MotoGP safety car, which, aside from the M-tastic graphics, has one rather notable deviation from its production brethren: water injection.
So while the car is awesome—you need only to scope the photos to gather that—we’re very interested in the underhood addition. Injecting H2O into an engine’s intake plenum or directly into the cylinder cools the intake charge via the evaporative properties of water; it’s the same principle that makes air feel like ice when you get out of a pool on a windy day. Aircraft engines and racers have been using water injection for years to cool the intake charge, which reduces knock. By reducing knock, the engine’s timing can be advanced and the engine cylinders can run at a slightly higher pressure, whether that be with a compression-ratio change or more boost in a forced-induction engine. Additional side effects of cooling the intake charge are reduced emissions and marginal gains in fuel consumption.
This all sounds great, right? Well, not really. Running higher cylinder pressures usually means a stouter and heavier engine, as the potential for perforating a piston, block, or head is higher. Plus, if you get the injection amount wrong and all the water doesn’t vaporize, the engine runs the risk of grenading because liquids do not compress. It’s for these reliability reasons that we banned water injection from our series of Supertuner challenges we ran in the past.
BMW begs to differ and says H2O will be pumped into the cylinders of a factory-built, production M car in the near future, and this MotoGP pacer is demonstrating just that. Water is stored in a 1.3-gallon tank in the trunk and an electric pump sends it to three injectors in the intake plenum, downstream of the air-to-liquid intercooler. When the engine is running at full load for extended periods of time, reducing the intercooler’s effectiveness, these injectors start adding atomized water to the mix and by the time it gets to the combustion chamber—and we’re talking fractions of a second—the vaporization of water cools the intake charge to increase the density of the charged air. Boost goes up, timing is advanced, and more power and torque result. BMW hasn’t released specific gains, however.
There’s a lot to work out before water injection is in showrooms. Aside from finding an H2O additive that’ll prevent freezing and not interfere with combustion, there’s a whole lot of programing, validation, and durability testing that needs to take place. If BMW water injection is indeed billed as an “emissions play” (we’re thinking “M Wasser Power” has a nice ring to it), the EPA will have concerns about how often H2O must be added to the system. For now, BMW says the system would have to be refilled with every tank of fuel and that if the trunk well runs dry, provisions are put in place to keep the engine running. In other words, this pace car would run the regular programing that we already enjoy from the 430-hp twin-turbo inline-six of normal M4s.
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