I'm a fan of endurance racing, where single-lap pace on its own isn't enough to win races. Making the most of your tire and fuel strategies is critical if you are to finish at the top after several hours. So with that in mind, I decided to do some data collecting on GT Sport's Fuel Mixture feature to see just how effective it is. I also wanted to compare it to other fuel-saving techniques, such as short shifting, or lift-and-coast. I will share those results here, so you can work out what is best for making the most of every drop of fuel.
All testing was performed with a Group 3 BMW M6 Race Car, on Racing Medium tires, with entirely stock settings (except in one test, where the gear ratios were modified). I chose this car because it's one of the easier Gr. 3 cars to drive (It's more understeery than most) and thus was easy to get consistent lap times with it. Additionally, tire wear was set to “off” in all tests, fuel consumption was set to 10x at Blue Moon Speedway, 5x at Dragon Tail Seaside.
I've put all my data in a Google spreadsheet here (Not particularly well organized, and no fancy formatting. Just the raw data)
TL;DR
Generally the best way to save fuel is to do the following:
Power vs Fuel Consumption of different Fuel Mixture settings
First I wanted to know just how much power is lost, and fuel consumption drop, there was with each Fuel Mixture setting. To test this, I went to Blue Moon Speedway. I measured the top speed the car would reach at the end of the front strait at each of the 6 fuel mixture settings. Then, in the tuning menu, I would see what power level I'd need to drop to in order to match each of the fuel mixture's top speeds. I've put the results in the table below
Next, to test fuel consumption, I simply tested how far the car would go before the fuel ran out. Based on the distance covered, I could work out how much the fuel consumption dropped.
Here is the basic rule for fuel mixture settings: Each step of Fuel Mixture will reduce power by 4%, and fuel consumed by 8%. The full table is below:
It's important to note here that the fuel consumption figure measures fuel consumed over distance (not over time). This is an important difference, as fuel consumed over time appears closer to a 9% or 10% reduction per step. But since your laps are also slower, this somewhat offsets that gain when measuring it over distance. (Imagine you cut your fuel-consumed-per-unit-time in half, but your lap time became twice as long. In this case, your fuel consumed per-lap would still be the same)
As you can see, fuel mixture 6 is actually pretty incredible. For only a 20% drop in power, your fuel consumption is cut nearly in half. It is worth noting at this point, that reducing power in the tuning menu does not improve efficiency. If you reduce power by 10%, it will cut fuel consumed by 10%. Whereas the fuel mixture settings do improve efficiency.
Lift and Coast
Next, I wanted to test fuel mixture settings compared to other fuel-saving techniques to see what works best for balancing lap times and fuel distance. So I headed to Dragon Tail Seaside, and established lap time and distance averages for each fuel mixture setting. First, I tested a technique that is used most often with LMP1 cars in the WEC (as these cars have very strict fuel-flow requirements). Lift-and-coast involves lifting off the throttle pedal a couple seconds before you start braking for a corner. I tested 3 different lift-and-coast distances: 1, 3, and 5 seconds before braking points (5 seconds may not sound like much, but in the case of the final corner at Dragon Tail, this means your lift-and-coast starts while still in the tunnel!)
The data here isn't super-accurate, as I'm an imperfect human (you can see the exact results I gathered in the spreadsheet) but from what I could notice, using lift-and-coast offers similar fuel gains per lap time reduction as fuel mixture settings. (3-second lift-and-coast with Fuel Mixture 1 offers similar lap times and fuel consumption as no-coasting with Fuel Mixture 3) However, lift-and-coast only works up to a certain point. It seems that the ideal coasting time is about 2-3 seconds before braking. Any longer than that, and you start sacrificing too much lap time for the amount of fuel you're saving.
Short Shifting
First of all, I'm going to distinguish 2 terms here: Redline and Rev Limiter. Redline is where your tachometer (RPM gauge) starts flashing, while the Rev Limiter is the point where the engine cuts out temporarily.
Next I tried simply shifting earlier than normal, and thus keeping the RPM of the engine lower throughout the lap. For all prior tests, I went well above the redline and would change gear immediately before hitting the rev limiter. For my first test, I simply shifted before hitting redline, which meant shifting about at about 10 mph lower speed for each gear. This result was particularly surprising. I only lost about half a second of lap time by shifting earlier, but fuel consumption was cut by 20%! This is a huge fuel efficiency gain for such a small loss in lap time. This also strongly suggests the a car's fuel consumption skyrockets when it's above redline.
Beyond this, and shifting even earlier before redline, again seems to offer similar gains to fuel mixture settings. In my more extreme tests, I did have to adjust the gear ratios to ensure the engine RPM always stayed below a certain point, but this is the only setup change I made to the car throughout the tests; everything else was just changes in fuel mixture and driving style. Like lift-and-coast, short shifting also only works up to a point. It is possible to get your RPM so low that the engine starts bogging down. Do not let this happen, as it's just slowing you down a ton and not saving you any fuel.
This in particular would imply that cars which reach peak power well before their redline will have a significant advantage when it comes to balancing lap times and fuel flow.
I hope this little experiment will help those of you looking to perform well in endurance races. There's some interesting data here, and I'm excited to try out some of this stuff with various pit stop strategies. Let me know if you'd like me to test other things!
All testing was performed with a Group 3 BMW M6 Race Car, on Racing Medium tires, with entirely stock settings (except in one test, where the gear ratios were modified). I chose this car because it's one of the easier Gr. 3 cars to drive (It's more understeery than most) and thus was easy to get consistent lap times with it. Additionally, tire wear was set to “off” in all tests, fuel consumption was set to 10x at Blue Moon Speedway, 5x at Dragon Tail Seaside.
I've put all my data in a Google spreadsheet here (Not particularly well organized, and no fancy formatting. Just the raw data)
TL;DR
Generally the best way to save fuel is to do the following:
- Never go above redline.
- Adjust fuel mixture to get the distance you're after; each step of fuel mixture reduces power by 4% and fuel consumption by 8%.
- A lift-and-coast here and there is good for more precise adjustments to your per-lap fuel consumption.
Power vs Fuel Consumption of different Fuel Mixture settings
First I wanted to know just how much power is lost, and fuel consumption drop, there was with each Fuel Mixture setting. To test this, I went to Blue Moon Speedway. I measured the top speed the car would reach at the end of the front strait at each of the 6 fuel mixture settings. Then, in the tuning menu, I would see what power level I'd need to drop to in order to match each of the fuel mixture's top speeds. I've put the results in the table below
Next, to test fuel consumption, I simply tested how far the car would go before the fuel ran out. Based on the distance covered, I could work out how much the fuel consumption dropped.
Here is the basic rule for fuel mixture settings: Each step of Fuel Mixture will reduce power by 4%, and fuel consumed by 8%. The full table is below:
It's important to note here that the fuel consumption figure measures fuel consumed over distance (not over time). This is an important difference, as fuel consumed over time appears closer to a 9% or 10% reduction per step. But since your laps are also slower, this somewhat offsets that gain when measuring it over distance. (Imagine you cut your fuel-consumed-per-unit-time in half, but your lap time became twice as long. In this case, your fuel consumed per-lap would still be the same)
As you can see, fuel mixture 6 is actually pretty incredible. For only a 20% drop in power, your fuel consumption is cut nearly in half. It is worth noting at this point, that reducing power in the tuning menu does not improve efficiency. If you reduce power by 10%, it will cut fuel consumed by 10%. Whereas the fuel mixture settings do improve efficiency.
Lift and Coast
Next, I wanted to test fuel mixture settings compared to other fuel-saving techniques to see what works best for balancing lap times and fuel distance. So I headed to Dragon Tail Seaside, and established lap time and distance averages for each fuel mixture setting. First, I tested a technique that is used most often with LMP1 cars in the WEC (as these cars have very strict fuel-flow requirements). Lift-and-coast involves lifting off the throttle pedal a couple seconds before you start braking for a corner. I tested 3 different lift-and-coast distances: 1, 3, and 5 seconds before braking points (5 seconds may not sound like much, but in the case of the final corner at Dragon Tail, this means your lift-and-coast starts while still in the tunnel!)
The data here isn't super-accurate, as I'm an imperfect human (you can see the exact results I gathered in the spreadsheet) but from what I could notice, using lift-and-coast offers similar fuel gains per lap time reduction as fuel mixture settings. (3-second lift-and-coast with Fuel Mixture 1 offers similar lap times and fuel consumption as no-coasting with Fuel Mixture 3) However, lift-and-coast only works up to a certain point. It seems that the ideal coasting time is about 2-3 seconds before braking. Any longer than that, and you start sacrificing too much lap time for the amount of fuel you're saving.
Short Shifting
First of all, I'm going to distinguish 2 terms here: Redline and Rev Limiter. Redline is where your tachometer (RPM gauge) starts flashing, while the Rev Limiter is the point where the engine cuts out temporarily.
Next I tried simply shifting earlier than normal, and thus keeping the RPM of the engine lower throughout the lap. For all prior tests, I went well above the redline and would change gear immediately before hitting the rev limiter. For my first test, I simply shifted before hitting redline, which meant shifting about at about 10 mph lower speed for each gear. This result was particularly surprising. I only lost about half a second of lap time by shifting earlier, but fuel consumption was cut by 20%! This is a huge fuel efficiency gain for such a small loss in lap time. This also strongly suggests the a car's fuel consumption skyrockets when it's above redline.
Beyond this, and shifting even earlier before redline, again seems to offer similar gains to fuel mixture settings. In my more extreme tests, I did have to adjust the gear ratios to ensure the engine RPM always stayed below a certain point, but this is the only setup change I made to the car throughout the tests; everything else was just changes in fuel mixture and driving style. Like lift-and-coast, short shifting also only works up to a point. It is possible to get your RPM so low that the engine starts bogging down. Do not let this happen, as it's just slowing you down a ton and not saving you any fuel.
This in particular would imply that cars which reach peak power well before their redline will have a significant advantage when it comes to balancing lap times and fuel flow.
I hope this little experiment will help those of you looking to perform well in endurance races. There's some interesting data here, and I'm excited to try out some of this stuff with various pit stop strategies. Let me know if you'd like me to test other things!
