Driving style vs fuel usage in 2014

[timbo]

There's no such thing as "coast" in an F1 car. When you lift your foot at 300+ kph the car slows down at 1G due to drag alone.

As for fuel saving some corner combinations can be tacked with different combination of lift/brake/throttle. I remember Petrov said that in Hungary there was a corner where you could just lift, carry more speed into it and accelerate later, or you could brake and accelerate earlier. Petrov said he preferred former while Kubica used latter way.

[Roland Ehnström]

There's no such thing as "coast" in an F1 car. When you lift your foot at 300+ kph the car slows down at 1G due to drag alone.

Oh, I know that the car will slow down at that rate from drag alone, but it's still technically "coasting" since you are using 0% throttle and 0% brake. In my calculations, I stated that when "coasting" for two seconds, the drag will slow the car down from 334 to 320 kph. I'm not sure how many G's this equates to, could someone do the maths for me? Perhaps the car will slow down to well below 300 in two seconds - then the lost time would of course be a lot more than 0.053 seconds. Perhaps it could be worth it to only lift to, say, 50% throttle for the final 200 meters of the straight as a compromise.

[timbo]

Oh, I know that the car will slow down at that rate from drag alone, but it's still technically "coasting" since you are using 0% throttle and 0% brake. In my calculations, I stated that when "coasting" for two seconds, the drag will slow the car down from 334 to 320 kph. I'm not sure how many G's this equates to, could someone do the maths for me? Perhaps the car will slow down to well below 300 in two seconds - then the lost time would of course be a lot more than 0.053 seconds. Perhaps it could be worth it to only lift to, say, 50% throttle for the final 200 meters of the straight as a compromise.

That's easy. 1G for 2 seconds is about 20m/s (18.6 to be a little more precise) so the loss would be around 70kph. Of course as the cars slows the drag decreases, so it would be less than that. But I guess 40-50kph would be about right.

[Roland Ehnström]

All right, that's a lot quicker deceleration than I expected. So, if the speed decreases from, say, 334 to 284 kph when "coasting" for two seconds, the time lost is almost two tenths, rather than just over half a tenth as in my previous (wrong) estimate. Doing this four times a lap (in order to save ~12% fuel, as mentioned before), costs a total of around seven tenths a lap, rather than the two tenths I expected.

Still, seven tenths a lap to save 12% fuel is not bad - might still be worth it. Especially if you can do this while you are anyway stuck behind a slower car. As mentioned it also cools the engine and saves the brakes, in addition to saving a full lap of fuel every eight laps.

[timbo]

Still, seven tenths a lap to save 12% fuel is not bad - might still be worth it. Especially if you can do this while you are anyway stuck behind a slower car. As mentioned it also cools the engine and saves the brakes, in addition to saving a full lap of fuel every eight laps.

Yeah, on this I agree. I imagine that everyone would be trying something like this. However there is a question whether driver can just tune down fuel mix so that he saves 12% of fuel. How much it would cost in laptime? I think the optimal strategy would be to accelerate on full fuel flow and than tune down mix when the car is already around 300kph or so.

[Roland Ehnström]

Still, seven tenths a lap to save 12% fuel is not bad - might still be worth it. Especially if you can do this while you are anyway stuck behind a slower car. As mentioned it also cools the engine and saves the brakes, in addition to saving a full lap of fuel every eight laps.

Yeah, on this I agree. I imagine that everyone would be trying something like this. However there is a question whether driver can just tune down fuel mix so that he saves 12% of fuel. How much it would cost in laptime? I think the optimal strategy would be to accelerate on full fuel flow and than tune down mix when the car is already around 300kph or so.

Agreed - the best place to save fuel is clearly when you are already at or near top speed. What I am saying is that the closer you get to the braking-point, the less useful it is to keep the throttle down - you are about to brake in a matter of seconds anyway, so why keep burning fuel?

I believe that a skilled driver can do this dynamically in a more effective way than a fuel injection system can, especially when running in heavy traffic. Tuning down the engine might make you a sitting duck in such a situation, but a skilled driver can still save a bit of fuel here and there by lifting off early when the situation warrants it.

[timbo]

I believe that a skilled driver can do this dynamically in a more effective way than a fuel injection system can, especially when running in heavy traffic. Tuning down the engine might make you a sitting duck in such a situation, but a skilled driver can still save a bit of fuel here and there by lifting off early when the situation warrants it.

It is a question. I am not sure if a driver can be precise with a throttle in a partial position. Of course they are teasing the pedal when they accelerate, but to lift say like 90% and hold it along the straight is not easy. Not least because of all the shake in a car. I remember reading some magazine (maybe "f1 racing" not sure) where they tested Toyota F1 car on Le Castellet and the writer found it hard to hold the feet on the pedals because of vibration (and the track has pretty smooth surface reportedly).
So maybe we would see some fast dials for fuel flow settings.

[Roland Ehnström]

This is also partly why I think it's best to lift off completely at the very end of the straight, moments before you start to brake. But maybe this could be combined with a "fuel save button" than cuts the engine power to 90% once you hit top gear, or something like that. The best solution in practice is probably a combination of the two.

[ringo]

You may be right, but I still think that's not the most effective way to do it. Tuning down the engine costs time in acceleration as well as top speed, while backing-off just before the braking-zone saves a measurable amount of fuel with a very minimal loss of time.

Instead of using fuel to accelerate from, say, 334 to 336 kph in the last 200 meters of the straight, you coast, and, as a result, drop from 334 to, say, 320 kph in the same 200 meters. So the average speed over these 200 meters will be 327 kph instead of 335 kph. So it will take 2.202 seconds to cover the distance, compared to 2.149 seconds while going flat out. That's a total of 0.053 seconds lost while spending 2.2 seconds on 0% throttle instead of 100% throttle. Do this four times a lap, and you lose in the region of two tenths a lap while spending 8-9 seconds less on full throttle. Instead of using full throttle for, say, 70 seconds during the lap, you will only use full throttle for, say, 61-62 seconds. That's a reduction of 12%, which should mean you spend 12% less fuel. 12% better fuel milage for just over two tenths a lap. I am sure that tuning down the engine to save the same 12% of fuel per lap will cost a lot more than two tenths a lap in performance.

What you say is true, but would you consider coasting a driving style?
And in the same breath the driver can still turn his dials right before the braking zone to enhance the coasting lol.

[chip engineer]

Oh, I know that the car will slow down at that rate from drag alone, but it's still technically "coasting" since you are using 0% throttle and 0% brake. In my calculations, I stated that when "coasting" for two seconds, the drag will slow the car down from 334 to 320 kph. I'm not sure how many G's this equates to, could someone do the maths for me? Perhaps the car will slow down to well below 300 in two seconds - then the lost time would of course be a lot more than 0.053 seconds. Perhaps it could be worth it to only lift to, say, 50% throttle for the final 200 meters of the straight as a compromise.

I ran my simple simulator (http://www.f1technical.net/forum/viewto ... 11#p491611) on your numbers and mostly support your speculation (losing very little time for that much coasting). According to the simulator (assuming using full power including MGU-K until coasting), coasting down from 335 km/h to 321 only takes 0.6 s and average deceleration is 0.66g. Braking to the same speed (initially at 5.2g) takes just 0.1 s.


The difference in time between these scenarios to get the same distance down the track at the same corner entrance speed is very small: 0.01 s (I should probably improve the simulator time resolution to be more accurate). At these speeds, even just 0.01 s is still about 1 m on the track.
See tables below (upper is coasting, lower is braking) at times (5th column) 11.00 to 11.14 sec.

Difference in fuel used is about 6% (15 grams and 10 kJ from the energy store out of a braking total of 273.7 g to accelerate from 72 km/h and go 743 m until slowing to 321 km/h).


If anyone sees any errors here or would like to see other scenarios, please let me know.

[Per]

Do F1 engines cut the fuel completely when coasting? Because if they don't it will influence your results in terms of fuel saving. But that's great stuff. I've been wanting to have something like this for quite a while.

[beelsebob]

Lovely to see someone using actual real simulation, however corse, rather than just yelling "I THINK THIS BECAUSE I'M RIGHT". +1.

[chip engineer]

Do F1 engines cut the fuel completely when coasting? Because if they don't it will influence your results in terms of fuel saving. But that's great stuff. I've been wanting to have something like this for quite a while.

Most of the speculation I've seen on the engine thread assumes engines will cut the fuel completely when no power is needed. Direct injection should make that relatively straightforward.

[ringo]

I think the ferrari is doing this more noticeably.