2017 tyre testing cars

[turbof1]

Clear explenation, thanks.

I updated my previous post with an example. It involves a lot of simplification, but it does give a somewhat mathematical view.

but wouldn't the lesser loss of speed also signify you dont 'need' to regain that speed lost, which costs more fuel in comparison, or am i way off here?

Only if you'd stay at the same speed as if you did not have the extra grip (you'd leverage that extra speed for lift and coast). If not, you'd be earlier on the throttle, longer on the throttle and longer in the higher, more fuel consuming range of rpm.

Example: I exit the same corner with a 2016 car, and with a 2017 car. Say I have 500m of a straight right after the corner. Fuel flow limiter is Q (kg/h) = (0.009 x RPM) + 5. Just for simplification's sake, imagine rpm increases linear by 500 over 10m acceleration, and by decreases linear by 1000 over 10m deacceleration.

-Imagine I exit the corner at 6,000 rpm in the 2016 car, and need 20m before I can rev up higher. I also need 60m to sufficiently reduce speed for the next corner which I can take at 8000 rpm. That leaves me with 420m that I can use full throttle. My average fuel flow will be 93,56, for those 420m.

-Now Imagine I exit the corner at 7,000 rpm in the 2017 car, and only need 10m before I can rev up higher. I also only need 40m to sufficiently slow down to 9000 rpm (because my corner can handle higher cornering speeds, and slows quicker down due aerodynamics). That leaves me with 440m to use full throttle. My average fuel flow will be 96,94 over 450m.

So not only would I have a higher average flow, I also spend 30m longer on that higher flow.

[Manoah2u]

In other words, fuel saving will be even worse next year?

[turbof1]

In other words, fuel saving will be even worse next year?

Not necessarily. The total amount of fuel allowed (not the same as fuel flow! That remain 100 kg/h) goes from 100kg to 105kg. It's quite unclear at this point how much more fuel these cars will be spending.

I also realised a small error in my calculation. The average fuel flow was calculated in both cases across the full 500m, not the length they spend full throttle.

[bhall II]

but wouldn't the lesser loss of speed also signify you dont 'need' to regain that speed lost, which costs more fuel in comparison, or am i way off here?

Only if you'd stay at the same speed as if you did not have the extra grip (you'd leverage that extra speed for lift and coast). If not, you'd be earlier on the throttle, longer on the throttle and longer in the higher, more fuel consuming range of rpm.

Increasing the amount of time spent at 100kg/hr actually increases fuel economy, because it inherently means cars are covering more ground for the same fuel flow.

In F1, fuel flow is a function of time, not distance.

[turbof1]

but wouldn't the lesser loss of speed also signify you dont 'need' to regain that speed lost, which costs more fuel in comparison, or am i way off here?

Only if you'd stay at the same speed as if you did not have the extra grip (you'd leverage that extra speed for lift and coast). If not, you'd be earlier on the throttle, longer on the throttle and longer in the higher, more fuel consuming range of rpm.

Increasing the amount of time spent at 100kg/hr actually increases fuel efficiency, because it inherently means cars can cover more ground for the same fuel flow.

In F1, fuel flow is a function of time, not distance.

If both went up linear, then yes. But that is not the case. your speed increase deaccelerates with increased fuel flow. We can assume that deacceleration in speed increase, will be higher next year due more drag.

Again, I made huge simplifications to get something clear out of it, but the conclusion is not wrong. You will spend more fuel with more performance. Arguably, you might have indeed better efficiency when looking at keeping the same performance across the lap due you'd be able to do more lift and coasting. So what you are saying is perhaps neither wrong: keeping your time parameter constant, you might indeed be more efficient. But then you are not driving at 2017 speeds, but at 2016 speeds. And you need 2016 drag levels as well.

[bhall II]

That's irrelevant. Unlike aero, there's zero ambiguity here, but I'm not even remotely the best person to explain why.

[Juzh]

Remember alonso in germany this year? He's catching up jenson who's doing regular fuel saving, then suddenly falls off massively when he had to save even more fuel himself. So yeah, saving fuel will almost always make you go slower, and using more fuel will make you go faster. I don't see how this changes next year in any way. I'm not really sure where people got onto the myth this is somehow not true.
Back in old days of refuelling, no one would fuel save to somehow go faster. Lift and coast didn't exist for that purpose. There's literally not a single video on youtube where you could hear someone doing lift and coast.

[turbof1]

That's irrelevant. Unlike aero, there's zero ambiguity here, but I'm not even remotely the best person to explain why.

Not in the context of fuel saving. Fuel efficiency will go up despite no lap loss due hypothetical higher l/d coefficiency, ironically because of more fuel saving.

[Paul]

I'm not sure about existence of videos, but there definitely used to be fuel saving and tyre saving with refuelling, which allowed to overtake the car in front after it pits by doing a couple of fast laps on low fuel.

If your car is faster in the corners, you will brake less, accelerate less and do faster laps while using less fuel per lap. Only with perfect kinetic energy regeneration can this be irrelevant.

[Juzh]

I'm not sure about existence of videos, but there definitely used to be fuel saving and tyre saving with refuelling, which allowed to overtake the car in front after it pits by doing a couple of fast laps on low fuel.

This was done with lower engine settings, not lift and coast. And even then it wasn't done to actually go faster in those laps.

[Paul]

Why the difference? Has something changed now with maps that they used to be more efficient at fuel saving, but now lift and coast is better? I was under the impression that lift and coast generally has the best fuel saved/lap time lost ratio, which is why it is being used by everyone.

[bhall II]

Remember alonso in germany this year? He's catching up jenson who's doing regular fuel saving,...

Not in the context of fuel saving...

I didn't say anything about fuel saving. My point is that increasing the amount of time spent at 100kg/hr will improve fuel economy, because it inherently means the cars are doing more with a fuel flow rate that's unchanged. Ultimately, that means next season is unlikely to be significantly different than this season, even with cars spending more time at full-throttle.

In other words: what's good will stay good, and what's bad will stay bad.

Like I said, though, I'm nowhere near fluent enough with this stuff to explain it coherently.

[mrluke]

Remember alonso in germany this year? He's catching up jenson who's doing regular fuel saving, then suddenly falls off massively when he had to save even more fuel himself. So yeah, saving fuel will almost always make you go slower, and using more fuel will make you go faster. I don't see how this changes next year in any way. I'm not really sure where people got onto the myth this is somehow not true.
Back in old days of refuelling, no one would fuel save to somehow go faster. Lift and coast didn't exist for that purpose. There's literally not a single video on youtube where you could hear someone doing lift and coast.

Pretty sure current cars are setting outright lap records at some tracks despite using much less fuel than previously.

If we want to really take it to extremes the current cars are much faster than the 80s turbos but use significantly less fuel despite being heavier.

Looking at a real world example the Mexico Grand Prix last weekend lasted 71 laps and was completed in 1:40:00 at an average fuel flow rate of no more than 60kg/hr

Next year the same race is expected to be 5s per lap faster which equates to 5.92 minutes or 5:55. So lets call that 1:34:00 total race time giving an average fuel flow rate of no more than 63.83kg/hr

Taking the extra 5kg available we get 67.02kg/hr

So based on the assumption that in Mexico this year the cars were completely brimmed on the start line, they will have around 10% more fuel per hour available.

In practice we know that the cars are typically short fuelled as they get a lower overall race time to undertake some fuel saving during the race than they do from carrying the extra ballast.

Even with no fuel limit we will likely see some fuel saving.

[turbof1]

@Ben: Well, the question posed by manoah was about fuel saving. I do get for the record what you are getting at, it's not like your point is not getting across. And I do agree with it in the context you put it in. But the discussion at hand is from a different one.

Lap times in the race will certainly go down. Normally this would have been coupled with more lift and coast (which in the context of the aerodynamic changes is not synonimous to slower laptimes), but they are allowed to spend 5kg more fuel across the race. Very interestingly enough race time will go down as well due faster laptimes , so your average fuel flow will go up as simply evident by +delta fuel/-delta racetime.

Edit: ah, mrluke beat me to it.

[Juzh]

Remember alonso in germany this year? He's catching up jenson who's doing regular fuel saving, then suddenly falls off massively when he had to save even more fuel himself. So yeah, saving fuel will almost always make you go slower, and using more fuel will make you go faster. I don't see how this changes next year in any way. I'm not really sure where people got onto the myth this is somehow not true.
Back in old days of refuelling, no one would fuel save to somehow go faster. Lift and coast didn't exist for that purpose. There's literally not a single video on youtube where you could hear someone doing lift and coast.

Pretty sure current cars are setting outright lap records at some tracks despite using much less fuel than previously.

If we want to really take it to extremes the current cars are much faster than the 80s turbos but use significantly less fuel despite being heavier.

Looking at a real world example the Mexico Grand Prix last weekend lasted 71 laps and was completed in 1:40:00 at an average fuel flow rate of no more than 60kg/hr

Next year the same race is expected to be 5s per lap faster which equates to 5.92 minutes or 5:55. So lets call that 1:34:00 total race time giving an average fuel flow rate of no more than 63.83kg/hr

Taking the extra 5kg available we get 67.02kg/hr

So based on the assumption that in Mexico this year the cars were completely brimmed on the start line, they will have around 10% more fuel per hour available.

In practice we know that the cars are typically short fuelled as they get a lower overall race time to undertake some fuel saving during the race than they do from carrying the extra ballast.

Even with no fuel limit we will likely see some fuel saving.

You're missing the point entirely. You're comparing apples to oranges. Old versus new technology. How much TOTAL fuel was consumed in any particular era is irrelevant to this discussion.

Even the manufacturers themselves knew beforehand fuel saving will go trough the roof unless extra allocation was to be permitted for next year. In fact the original proposal was 110 kg. After a strong opposition from the merc, who as we know has the least thirsty engine, a compromise has been reached at 105 kg.
If fuel wasn't an issue at all they'd never bother with it, but they did.