Pit stop strategy advice (6 hour pro/am team event)

Hey Drivers,

I'm participating in a two man, 6 hour race at Nurburgring and was wondering if anyone better at Math than me could give me a hand with strategy?

The reason I can't just use a normal calculator is that there is no max stint length, but a max total driving time of 3.5 hours.

So the plan is to have the pro driver in the car longer, but our problem doing a simple 4 stop 5 stint run is that my partner would be in the car 7 minutes too long.

So are there any strategy geniuses out there that could work out the optimum strategy? I've been giving it some thought but this is my first team race and I suck at math.

To summarize the variables.

6hour race at Nurburgring
No max stint time
3.5 hours total driving time
No mandatory pitstop amount
Lexus
3.24ish fuel/lap
120L tank
Around 1:57:5 to be safe, though my partner is more often in the 56's


What's the quickest way of doing this do you think? Any help would be greatly appreciated!

 

If my calculations are correct it's 120L/3.24L, which means you can do a maximum of 37 laps.
37 laps with laptimes of 1:56 is 37x116 = 4292 seconds = 71.5 minutes.
3x70 minutes = 3.5 hours
So 2 pitstops for fuel and tires, and on the 3rd pitstop you do the driver change.

That leaves you with 2.5 hours left in the car.
2x71.5 minutes stint = 143 minutes. There's a total of 150 minutes you'd need to drive. Meaning you'd have to come in for a splash and dash with 7 minutes left.

Fuel saving:
7x60 = 420 seconds.
420/117 (laptime) = 3.5 laps = 4 laps.
4x3.24L (Liters) = 12.96L

If you can manage to fuelsave about 13-ish Liters in your 2.5 hour stint, you could save yourself from a 5th pitstop.
150 minutes x 60 seconds = 9000 seconds
9000/117 (laptime) = 77 laps
13Liters /77 laps = 0.17L per lap of fuel saving.

 

Those calculations won't take into account the fuel economy getting better as the car gets lighter so there's a chance I won't need to fuel save at all right?

Thanks!

We were looking to do a stint each swapping back and forth, would that still work or would we NEED to double stint?

This is just what i've been looking for.

 

I'm not 100% sure if the amount of fuel drops when the car gets lighter. Even if it does, I'm quite sure it will not be enough to save 13L over 77 laps.
Fuel calculations in general don't take this into account, so I think any difference in fuel consumption would be very little.
Again, I'm not 100% sure.

I don't think it would matter if you switch seats after each stint. As long as he does 70 minute stints and you save fuel throughout your stints. Keep in mind tho that he shouldn't be saving fuel in his stints because he will go over the maximum allowed driving time.

Also, I don't know how beneficial it would be to even save fuel throughout 2 entire stints. Maybe it's faster to just come in for a splash and dash. Refueling 13L takes 5.6 seconds in total (3 seconds to start refueling + 0.2 seconds per Liter). If the pitlane is around 15 seconds, it would cost you around 22 seconds.
Plus, it's more fun to be able to drive full out. And saving fuel means you're not able to be as competitive in terms of fighting for position.
Also, 13L is pretty much the bare minimum you'd need. If the race goes 1 lap longer because the leader is doing 54s, you'd need 16L. So it might also be more safe to come in and refuel.

But that's something for you guys to figure out

 

With a light car it goes down to about 3.03 I think? I'd need to double check.

We'll work it out, we know the timings for the stints now so should be ok from here.

Thanks a lot, you've been invaluable. If we don't punt out and actually finish we'll dedicate it to you haha. It won't be the win but it'll be something.

 

I really doubt it's .2L difference, that would mean a noticeable difference in total amount of fuel needed, which I have never experienced myself. You really ought to double check this.
Also be aware that the average fuel consumption you see in the setup menu is not always accurate! I don't know why, but sometimes it shows a rather huge different value than what it really is. I think this only happens when it switches from 1 session to another tho.

No need to dedicate it to me Just have fun!

 

the beauty of endurance

 

You can also consider the pitstops.. that will add to your total time.. Outlap and in lap will be longer with the pit transit time ~20 seconds and stationary time (0.31 seconds per litre filling) @ 110 litres = 33 seconds.. So say depending on track 50-60 seconds additional time used per stop.
Over enduro thats 4 minutes spent in pitstops.. (which may equate to 2 less laps total needed) @ 3.5ltr/lap = 7 ltrs saved

Depending on the legue you may have a full warmup lap to add (At low pace) - (2 litres extra needed)

But the first 3-4 laps you will also be slower (10 or so seconds) - unless your in the top 5-10.. as the field consatinas.. and you fight in traffic for first few laps.. This would add 30-40 seconds to total race time(so maybe 0.5 ltr saved).

Net effect you should need aroud 5.5ltrs less than the above.

I have spreadsheets for strategic planning if you need. (Google sheets)

 

Quick update for everyone. Was able to do 2 1hr 15min stints easily, with a few L left over. We did 5 stops overall, but only because we forgot to put fuel in the car at the end of the first stint. Otherwise it would've been 4. No fuel saving needed, though I tend to use the progressive throttle setting with the Lexus.
Thanks for all the help!