Our "Formula 1 Tech Spotlight" feature articles are normally reserved for grand-prix weekends, but following Daniel Ricciardo's disqualification from the Australian GP, we felt a couple of details in the engine rules ought to be clarified.
As a refresher, the Red Bull driver had finished second, but he and the team were stripped of their points because Ricciardo had "exceeded consistently the maximum allowed fuel flow of 100kg/h" throughout the race. The announcement came hours after the checkered flag, and during the long wait, we encountered questions like these on Twitter:
Isn't the limit 100kg?
What's the right limit--100kg or 100kg/hr?
If the cars only have 100kg of fuel and a race is over an hour long, how are they supposed to complete all the laps? They'll be out of fuel in an hour!
To answer these questions, both 100kg and 100kg/hr are correct and applicable, but they don't mean the same thing. The first figure, 100kg, is the fuel limit--the maximum amount of fuel a car may use for the entire race. The second figure, 100kg/hr, is the peak fuel-flow rate allowed on the cars--the maximum amount of fuel a car may be consumed at any given time. This peak fuel-flow rate is only available from 10,500rpm and up; on slower parts of the track where revs are below 10,500rpm, fuel is fed into the engine at a slower rate.
Let's use an analogy to make the difference clearer: Say you were asked to drive 100km in two hours, and you can't go over 100kph in doing so. You don't have to run in full anger the whole way--you can vary your speed, from 1kph all the way to 100kph, throughout the trip, provided you complete the required distance within the required length of time.
It's the same with the new fuel regulations in F1. A car doesn't always have to consume fuel at a rate of 100kg/hr. If it does that, it would burn its entire 100kg fuel allowance well before the end of the race. Rather, the rate of fuel consumption may be varied up to 100kg/hr, so that the race distance is completed using the maximum amount of fuel or, if possible, less.
Engine maps and settings are used to vary the rate of fuel flow depending on factors like power requirement and fuel availability. In qualifying--where a car may be fueled as the team deems fit (with still enough left over to be submitted as a fuel sample after the session)--richer fuel-burn settings are utilized in order to max out the fuel-flow rate and extract as much performance as possible. More conservative settings are used in the race, but certain circumstances allow for the use of richer settings, too. For instance, a car is able to save fuel during a safety-car period, and that extra bit of fuel can be used to sustain a faster speed later on.
It must be noted that the monitoring of fuel consumption falls upon the team and not the driver, so Ricciardo didn't really do anything wrong. The thing is, his car's rate of fuel consumption had gone consistently over the 100kg/hr limit, and that's a direct performance advantage that may have made the difference between P2 and a lower finishing position.