Impact of fuel weight on GT3 cars

Does anyone know what the impact of fuel weight is on GT3 cars irl?

I did some testing in hotlap mode with 60 l and 20 l fuel without fuel consumption. All with the same setup (safe preset).
I did about 40 laps with 60 l and just hit a limit I couldn't improve upon.
After that I did 5 laps with 20 l and was 0.6 s faster. There might have been 0.2 s more improvement possible, but I got hungry.

These results would indicate 10 l = 0. 15 s and perhaps up to 10 l = 0.2 s. On Nurburgring at least.

So does anyone know how this corresponds to real life GT3 cars and the impact of fuel weight on their lap times?

 

I don't know. But. I would guess that your experiment results are correct. In F1 cars it is something like 0.025s per liter, or something like that, I suppose an impact on heavier car than F1 would be smaller. So because of that I think your results are good.

Also, I think, you are always quicker and physically more capable with an empty stomach Well maybe not too empty, but just about empty.

 

https://www.blancpain-gt-series.com/results?filter_season_id=8&filter_meeting_id=104

Lets presume qualis are low ammount of fuel and race is 60l of fuel(or max i belive they are full tanks when they race?) how does your times compare to theirs?

 

It's too difficult to compare qualifying times to race times because track conditions can change and you don't know if they were pushing as hard in the race.
Like in that example, there is already a 0.5 s between both qualifying sessions and between both races and those fastest times were set by different drivers and cars as well.

 

Unless there is a specific reason to go all-in in a race the times from qualy and race can't be compared since you have to preserve tyres for the stint and avoid making mistakes in a race.

 

My numbers may be unreliable because I keep finding more time with 60l.

Would be cool if some alien who can consistently push the limits would test the impact of fuel weight on lap times.

 

There are quite some information known about that in F1, beginning from Gordon Murray. GT3 cars are heavier so it will obviously relatively mean a little less for them.

If you became faster with 60L, then maybe you became faster in general ?

Also maybe the setup is good for large amount of fuel ?

 

I did a lot more testing today and these are the results.
Using the safe setup and 60 l my best time was a 1:54.699 in a mega lap. I don't feel I can go much faster than that.
Using the safe setup and 20 l my best time was a 1:54.189 in a good lap, but not mega. I feel a 1:54.0 is possible.

From this I would conclude that 40 l = roughly 0.6 s to 0.7 s per lap.
So 10 l = 0.15 s and perhaps a bit more than that.

It felt much more difficult to hook up a good lap with lighter fuel load. Heavier fuel load probably makes the car more planted, making it easier to push and find stability in corners.
This was mostly noticeable to me in the first few corners (especially turn 3 and 4 where the car just slid more easily, immediately resulting in huge time loss when this happened).

Also very noticeable was how much time I lost versus an older lap on straights.
On the long straight (after turn 12) I lost about 0.15 - 0.16 s with 60 l fuel. With 20 l of fuel this time loss was only about 0.08 s.
On the start/finish straight when starting a lap the delta was neutral (perhaps stuck at 0, but really slightly negative) with 60 l of fuel. With 20 l of fuel I was 0.005 to 0.015 s faster before reaching the first corner.

Of course all these results could be influenced by me not being able to really push the limits of the car under different fuel loads.

Here are both hotlaps so everyone can judge for themselves.
With 60 l (delta/ghost was not a representative lap):


With 20 l (delta was also a lap with safe setup and 20 l):