There is always politicking going on in F1, this year the pre-season test was spiced up by the suspension technical directive, but less debated was the oil consumption jibes. With both a technical directive from the FIA and a comment from Christian Horner about teams may be using oil to boost engine power. As part of the new 1.6l hybrid power unit rules, fuel consumption was restricted to 100kg of race fuel and instantaneous fuel flow capped at 100kg\hr. If teams wanted more fuel to go into the engine in either the race or qualifying there is nothing that can be done. But, of course everyone wants more power and a means to do this is to burn more hydrocarbons. Petrol is one source of these, but so too is the oil circulating through the engine. If you can burn a little oil then you can gain some power, so the option is an attractive one, if difficult to achieve legally. Modern oil and race engines are not like that of an old car in need of a re-bore and trailing blue smoke along the high street. Even a high level of oil being burnt would be smokeless and undetectable to the eye or nose. Clearly the rules do not allow any overt method of getting oil injected into the combustion chamber, nor a means to alter the ratio of oil being burnt, between qualifying and the race.
The oil system in an F1 car is generally quite typical for any racecar, oil is circulated at pressure by a pump, the oil passes through galleries into the bearings and hot surfaces, were upon it lubricates and cools. With its job done, the oil passes down into the sump of the engine for recirculation. An F1 car uses a dry sump, there isn’t the deep pan holding the oil that you would see on a road car, this would raise the engine up, ruining the cars aero and CofG, while also allowing the oil to slosh around as the car moves about the lap. So, the sump is very shallow and the oil is sucked up by scavenge pumps. These pass the oil through a deaerator, that takes the air bubbles out of the oil and then it sits in the oil tank mounted in front of the engine, before being cooled and recirculated. Any oil vapour or excess pressure in the crank case must be vented into the engine airbox, where the trumpets feed air into the inlet tracts. An auxiliary oil tank is typically added to the system, to top up the small amounts circulating furiously through the main oil system, 3-5l can be stored in the spare tank and added during the race from a steering wheel control, once called ‘oil bomb’ Renault.
This is all typical race engine technology. The void inside the crankcase, between the sump and the pistons above, works best if its pressure is controlled, so the scavenge pumps can also work to draw a slight vacuum. The crankcase pressure also helps to control the oil on the cylinder walls, preventing too much oil passing up past the oil control ring on the piston. Again, this all quite legitimate. To control this pressure, teams are allowed another breather from the crankcase into the airbox, but the bypass is controlled by a solenoid valve under ECU control. With the scavenge pumps and solenoid controlled breather, the teams have the ability teams to control the oil in the crankcase either getting into the combustion chamber by the airbox or by passing the piston. Thus, the control and conditions to purposely burn oil are there and as with anything in F1 this can be exploited if someone wanted. So, if an engine performance map, also included the crankcase pressure as a parameter, then the solenoid can legally be tuned to alter the level of that can be burnt. Already F1 engine burns a lot of oil, some 3-5l may be used during a race, this consumption has gone up from about 3l under the old v8 rules, so clearly something might be going on and the technical directive has been issued to point out that oil usage will be monitored to cap any escalation. Is there any impact? one of more of the current F1 power units may well be burning oil for combustion performance. There is a small power boost for this in both qualifying and resulting fuel efficiency boost (burn more oil - less fuel) in the race. Separating the normal oil function and consumption is near impossible by the FIA in a race, but oil consumption is now effectively capped and any escalation in consumption will be seen a sign of combustion boosting oil burning and will result in penalties.