Laurence Edmondson F1 Editor
Although most of the focus of the 2017 rule changes has been on the chassis and aerodynamic side, Formula One’s new regulations have also impacted power unit development.
In a video on Mercedes’ YouTube channel, the head of the team’s engine division Andy Cowell explained why more downforce and wider tyres would lead to higher fuel usage and some new challenges for his engineers.
“The power unit’s principal aim is to propel the car down the straight,” he said. “Now, if the tyres are stronger and if the aerodynamics are stronger, the straight actually starts a little bit earlier because the driver can get on full power sooner and the straight actually finishes a little bit later because the driver can come on the brakes later, so the period of full throttle increases and it’s increasing considerably.
“It’s increasing by just over 10 per cent, which equates to just over five seconds of full throttle time. Now, the engine is limited in fuel-flow rate to 100kg/hour, but if the time is going up by 10 per cent then the total amount of fuel that will be used per lap is going to go up by 10 per cent. Now, last year the limit for the race distance was 100kg of fuel. That’s a limit that was set in 2014 and maintained through 2014, 2015 and 2016 and through efficiency improvement of the manufacturers we all ended up at a point where typically for a race distance we needed less than that.
“So, the starting point is less than that, the increase amount for this year is plus 10 per cent and where the regulations are set to is 105kg of fuel for the race. It still means that you need to be efficient with the aerodynamics and efficient with the power unit, but we won’t have all the ridiculous fuel saving scenarios that we had in 2014. So that’s a major change for the power unit.”
The increased workload of the power unit in 2017 will also see greater demands on cooling, which will in turn affect the aerodynamics of the car. Cowell said Mercedes has put a lot of effort into improving the cooling system on the new W08 to ensure the most efficient package possible.
“One of the consequences of having an extra 5kg of fuel and an extra 10 per cent used per lap is that the waste energy — the engine is very efficient but not 100 per cent efficient, so there is some waste energy — how do you get rid of that waste energy? We have put a lot of effort into the cooling system on the engine to get that waste energy out of the piston, out of the cylinder head, out of the crankcase and out of all the bearings, transmit that to the car and the cooling packages on the car need to increase as well.”
Now that the calendar is back down to 20 races, teams are only allowed four power units before getting a grid penalty, rather than the five power units they were allowed last year. Combined with the increased cornering forces and use of full throttle, Cowell said Mercedes has had to pay even more attention to the reliability of its power units this year.
“The last change, although not regulated, is the durability of the engine, and this is in terms of both the number of revolutions you can do, the number of qualifying laps you can do but also the structural load. If the car goes through the corner quicker because the tyres are stronger and the aero is quicker, the lateral load on the car is higher and the power unit is a critical structural element of the car, right in the middle of the car with engine mounts front and rear connected to the chassis and the gearbox.
“We have had to do a lot of detailed analysis on those and the engine is a little bit heavier as a consequence of that, but the structural stiffness has been maintained and the strength of the car has been maintained. This year, also, we are going from five power units before we get a grid penalty to four, so there is a big extra demand on each of those power units both in terms of the heat that’s going through it, the structural load and the kilometres that the power unit needs to do.”