Fuel
For the first time since I started this project, fuel feels like an integrated game mechanic. Fuel has been in the game for a long time in various forms. None of those forms has played well enough for me. Because of this, I’ve had remove fuel as potential change for almost as long is had fuel in the game.
In going to talk through the changes, where we are at now and what is next.
The idea for fuel started off as a way to increase the number of viable strategies available to players. To shift the game from picking different tires and playing them off against each other, to factoring in stopping for fuel and then the option of going faster at the cost of more fuel or conserving fuel at the cost of speed.
I wanted to allow strategies where a driver takes the most durable tires and just enough fuel for the race and then drives as conservatively as possible. Or, the driver can take fast tires, burn more fuel and stop more often to try and counter the no-stopping strategy.
Fuel Modes
The more fuel you have, the slower you go. This is a fixed amount so that each additional unit of fuel adds the same amount to your lap time. This is different to the real world where each additional unit of fuel slows you down more than the prior unit did.
There are three fuel modes. Standard where you burn fuel at track defined rate. Slow where your lap times are increased by 300ms but you burn less fuel per lap and Fast where your lap times are decreased by 300ms at the cost of more fuel consumed per lap.
Pit Stops
Adding fuel also increases the duration of your pit stop. The more fuel you add the longer your pit stop. Just like in the real world.
Each track has a pit length measured in seconds, the shorter the pit stop the less impact stopping has. The shortest pit length is currently 10 seconds. This base amount of time is the minimum cost for all pit stops. Then you add time-based on the work being done.
When you change tires then you’re going to add between 1.5 and 4 seconds to that time. When you add fuel you have the choice of taking 30 or 60 units. 30 units is going to add another 3.5–4 seconds to your stop. 60 units will add between 6.5 and 7 seconds.
The shortest stop adds 1.5 seconds if only add tires and the longest pit stop can add 7 seconds. So when the pit length is 10 seconds you have a range of 11.5 and 17 seconds. That’s a big range.
So here the strategy comes in. You can choose to start the race with more fuel in the tank. This slows you down from lap 1 onwards but your pit stops are shorter. While having less fuel in the tank at the start means you can go faster and your pit stops will be longer — as you need to add fuel.
Each track has a different pit length, a different fuel burn rate and different tires available. This means what works for one track, won’t necessarily work for another.
That’s the premise behind it, now to look at the implementations we’ve had so far.
Immediate Toggle, Flexible Fill
The first iteration allowed the driver to change fuel modes whenever they wanted. You want to go faster, turn it on. You want to save fuel, turn it off and go slowly. This is how F1 drivers work now. The key difference is that they cannot add more fuel.
I also gave the players a slider and let them control exactly how much fuel to add. This resulted in always taking sufficient fuel to make the next pit stop.
The result was that it was best to run the fast mode all the time. My feeling is that if the best strategy is for everyone to always do the thing, then that’s not a great game mechanic.
Fixed Fill Amounts
I changed the intervals when choosing your start fuel and adding fuel during the race. So to start you can have 30, 60 or 90 units of fuel and during the race, you can choose to add 0, 30 or 60 units during a stop.
This forced the player to think about how much to add instead of exactly what is required for the next tire change.
Incentivised Modes
In this version I wanted to get people to commit to running a fuel mode for longer and when you do that the negative impact of a fuel mode is reduced. The caveat here is that you can’t change modes once set until it has expired.
If you run a fuel mode for only 3 laps the fuel benefit or penalty is reduced when compared to running for 7 laps or 13 laps.
This, in hindsight, did not change anything. It’s a more interesting system but if you have people running a particular mode all the time then at the end of the 13th lap they will turn the mode back on again. Which is what they did.
Cooldown
How do you stop someone from spamming a mode? One way is to apply a cooldown. After your 3, 7 or 13 laps of running a particular mode, you have to wait the same amount of time before running that mode again. This also helps bring out more interesting decisions around which mode to run. If you run rich for 3 laps, then you consume more fuel over those 3 laps but your cooldown is shorter.
Now we’re starting to get somewhere with the fuel mode mechanic.
Increase the penalty from 10-20% to 20–30%
The next change was to increase the cost/savings of a particular fuel mode across the board. I’m doing this because there wasn’t enough thought going into running a mode or not. It still made sense to run a particular mode all the time to get the speed benefit. So if I increase the cost of a decision, then I force the player to think more about it.
This is especially important for tracks that have a high fuel burn like Monza. When your cost per lap of fuel is high, then running a fuel mode at 30% may be cost prohibitive. Then again, you do need to catch up to that car in front.
Change percentage speed boost to fixed change
The chart below shows the impact on lap times for the fastest and the most durable tires. The top three lines are the fastest tires when running the fast fuel mode, standard and slow fuel mode. The bottom three lines are the same but for the most durable tires.
Take a look at lap 20 can you see how the three lines converge and then separate again?
This is because the because the speed benefit is proportional. A 20% change to 1000 is 1200. While a 20% change to 10 is 12. So you get less speed benefit from running different fuel modes on the more durable tires. It does mean you get less speed penalty when running different fuel modes on the more durable tires. So that’s an advantage over the better tires.
I don’t want this. I want fuel modes to be somewhat independent of tire choice. Tires will provide the minimum and maximum performance while fuel modes will give you a benefit within that range.
So if I change the benefit from 20% to 300ms. Then I get a new chart with no convergence.
This will help incentivise running different fuel modes on the more durable tires.
When I originally switched from proportional to linear I wasn’t sure if I wanted this. The proportional approach penalises running rich on durable tires more than faster tires. But it also penalises running lean on faster tires more than running lean on more durable tiles. The linear change gives the same benefit across the board.
I did the only thing I could do. I put it into production and we’ve been running with it ever since. And it works well.
Now that I have players making the kinds of decisions I want, it’s time to design some tracks to emphasise this aspect of the game.
High fuel cost and a very long pit length. This was the first track where it was not possible to complete the race without stopping. However each time you stop it costs you at least 30 seconds.
Low fuel cost and a very short pit length. You use up very little fuel in this track and the ultra-short pit length means that the cost of adding fuel is low as well. This encourages stopping more often, using faster fuel modes and quicker tires. The best strategy at Monaco requires 4 stops.
Bahrain lets you run the most durable tires from start to finish without stopping, if and only if you use in the slow fuel mode as often as allowed. It’s not the fastest strategy but it certainly is one that can win.
What Next?
We may not be done yet. The fuel mechanic works well but there are some variations that I may play with in the future.
- No refuelling — this is likely to be on a per track basis
- Set number of fuel mode changes — let’s say you can only set two fuel modes over the course of a race. This is a variation on the cool down in that you need to think a bit harder about when to use the different modes.
- Non-linear fuel weight cost — the more fuel you carry the slower you go just like in real life. I’m reluctant to do this at the moment as it would mean rebalancing the existing tracks
Get the beta here. I’ll post updates on the project here and on the game twitter account.
