What to look for at Beijing, the first race of the Formula E series

 

The first Formula E race is just a few days away and, as, one of the team principles at e.dams Renault, Alain Prost says, "To be very honest, we don't know what's going to happen".

 

What do we know? What might one expect to see and why?

 

The scenario below is predicated on: 1) Formula E cars being able to draft closely and 2) gaining an energy benefit from drafting.

 

We are also assuming that when two or more cars draft, the one in the front will gain a small energy advantage (over a car running alone) and the car behind will gain a substantial energy benefit.

 
Why does this matter?
 

Whether the Formula E cars can draft effectivly matters because in electric racing, the car always has less stored energy than the driver could use. Batteries are heavy, so the car's performance is always limited by the amout of stored energy. So going fast, using less energy by drafting or being drafted, will give a significant edge over the competition.

 

Conversely this means that it is a disadvantage to lead any lap except the last lap (last lap before the pit stop and the final lap of the race) since the leader has no one to draft.

 

Practice

 

The teams must accomplish three things during the two practice sessions.

1) The drivers must master a brand new street course with the challenges of changes in grip on different pavements, bumps and gratings, and the ever present threat of the barriers.

2) The teams must try to determine the best car set up, which might not be the fastest.

3) The teams must collect power usage data at different engine power settings to determine race strategy.

 

This series gives the teams an original tactic to help them accomplish all these tasks in the short practices. The teams can evaluate their data and get feedback from the driver while he or she is on the track. The mechanics then can make the adjustments on the second car. The driver will then pit and swap cars and get back out on the track to test the changes. This should occur multiple times during the test sessions. The additional benifit is the driver and pit crew get practice for the crucial mid race car change.

 

It will be difficult to evaluate relative competitiveness from practice times. There was a difference of around six seconds a lap at Donington between the highest power setting and the lowest power setting, so a slow car might just mean the team is working on evaluating an energy conservation pace. A fast lap might be set at a power consumption level that would not allow the car to complete the race distance.

 

Qualifying

 
Pole position is worth three championship points and a certain amount of glory, so teams will compete for it. They have ten minutes and only four other cars on the track, so getting clean laps should not be a problem.
 
Assuming around a minute and a half lap (average speed of 85 MPH), drivers should get in five timed laps. Drivers are not allowed to pit and make any changes during qualifying. There is some question whether in five laps, at the full 200 kW qualifying power level, the motor might overheat and automatically reduce power.
 
We might see drivers put in a banker lap at full race power, 150 kWs, and collect valuable data on power consumption for the race and then go to full qualifying power, 200kW, and try for the pole.
 
Race start
 
While in theory, the pole sitting driver might plan to be slow off the line and try and tuck into the more favorable second position, I doubt very much that we will see this. With twenty race cars jockeying for position, there is a lot of risk of an accident in the first corner. It is more likely that we will see the pole sitter lead a lap or two and then try for a more tactical position.
 
What is the best position to be in? This is where it gets tricky. Running all alone costs the most energy. Running in the very front has the next highest cost. Running behind the lead car saves more energy than running in front but what about compared to the third place car? What about five cars in a row? What about a block of cars side by side?
 
The test days in Donington might have given some hints but until the cars are in action on an actual street course, the teams will just be guessing. It will be up to the drivers to try and find what drafting position gives them the most benefit and then fight to stay in that position.
 
Watch out for Safety cars
 
With 20 racers competing hard on a tight barrier lined track, a major crash that brings out the safety car is quite possible. This could change strategies. A couple of laps behind the safety car will save a large amount of energy which might allow teams to run full race power for the rest of the stint. Then the limiting factor might not be power consumption but rather engine temperature. This would change the best strategy to staying out of the draft to allow clean air flow to the radiators.
 
Cars will only pit under a full course yellow if it is very close to the half way point. Pitting a car with energy still in the battery pack will mean having to go farther in the second car forcing the driver to use less power per lap.
 
The pit stop to change to the second car
 
A basic electric racing guideline is 'if all other things are equal, the vehicle that is able to maintain a speed closer to it's average speed will need to overcome less aero drag and thus be able to maintain a higher average speed with the same energy than the vehicle who's speed fluctuates more widely'. The math behind this rule is explained here. Based on this rule, the optimum pit strategy is to complete half the race with the first car and half the race with the second car. We should see the majority of the cars pit at the half way mark.
 
If any cars pit before the half way point, they will be at a disadvantage. It will probably only happen if their driver used more energy than he or she should have and is forced to pit early. It might look like a Formula 1 strategy called 'under cutting' but getting the car out of traffic by pitting early also removes the opportunity to draft and the second car then must run more laps on the same amount of energy.
 
On the other hand, a driver who has saved energy through drafting, smooth driving and lots of regenerative braking, might choose to go an extra lap beyond half way with their first car. If they are the only car to do so, this will probably be an unsuccessful strategy. If they have another car, perhaps a team mate to draft with, they might gain advantage. They will be able to run their second stint at a higher power since their second car will have one less lap to complete and the same amount of energy.
 
A driver who has not had a good first half of the race can gain places with a fast car change over. A driver near the front can take the lead in the pits. Coming out in front at this point is not a tactical disadvantage. Since the lead driver running alone would be caught by the following cars drafting each other, we are likely to see the lead driver run a slower energy conservation pace that trades track position for building up an energy reserve for the final laps of the race.
 
The other cars will quickly catch the leader and everyone will jockey for the optimum position. Not in the energy draining lead but close enough to the front to fight for the win.
 
The cars to keep your eyes on at this point is the lead pack and perhaps the smaller pack behind that is made up of cars that stretched their pit window and pitted a lap later. Since they have less laps to cover with the same size battery pack, they should be running a faster pace and closing on the lead pack.
 
The lead pack will be made up of cars trying to decide what pace will give that individual the best opportunity to win. Do you do better to run hard all the way and not be able to muster a sprint at the end or run a conservative pace and save power for an all out sprint for the last few laps?
 
This decision will be affected by what the other drivers do. If the lead pack goes too slow for a driver's strategy, he or she might decide to take the lead and try and break the draft.
 
The other drivers in the pack must then quickly decide; speed up and stay with him or her, or maintain their pace and hope to catch him or her before the finish.
 
We might see a couple of cars decide to break from the pack. It might be cars that work together taking turns in the energy costly lead (look for team mates coordinating their move) or cars trying to piggy back off another car's break way attempt.
 
The Finish
 
The finish will finally tell us who got it right. Will the pack of late pit stoppers catch the main pack? Will the main pack catch the break-away cars? Who will slow the final lap, short on power? Will a final sprint steal the lead?
 
This will be challenging and exciting racing. The drivers will have to think and drive, while in the middle of a scrum of racing cars. They will have to decide when to work with other drivers and when to go it alone. The teams will have to interpret the data quickly and make good strategy calls. The mechanics will have to work fast and hard to keep the cars running through the condensed one day schedule.
 
If the Formula E cars work well in the draft, these are some of the tactics that the teams could employ but it might take a while for teams to work out how to race these cars. No one knows how this will play out- and that makes it interesting.
 
 
 
 
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