Audi LMP1 Discussion

[bobec]

Originally Posted by sssssssss

while the slower times compared to porsche (and very similar to toyota's) at spa could well be due, at least partly, to the non-specific aero setup - in fact, given that what toyota call a HD package seems to be more of an interm package, i suspect audi were the only ones this weekend not to use a spa-oriented aero setup, hence the slightly slower lap times, although, even so, they were quite similar to toyota's. their package seems extremely slippery, with really low downforce.

It seemed like Audi wasn't good at the corners at all, and if the cause was less downforce, then it must have been considerably less downforce than the rest, with a little bit less drag. Then why this complex high-nose front-end design? Isn't superior cornering performance the whole point? The cornering disadvantage seemed too big for a sophisticated aero design even in LD trim. And if the downforce really isn't there, they might as well have gone low nose with low air resistance.

But as has been mentioned here, maybe the issue was not downforce, but instead set-up and suspension issues.

[GasperG]

I would say that complex aero design is for low drag first, but as noted above we will see if it works at LeMans. If top speed will be as good as last year with less engine power and cornering speed in the same ballpark, then this will be clear indication that radical nose design works.

[MyNameIsNigel]

Another series of shots of the Audi R18 front end, nose section removed, have been posted on the motorport.com website. These shots were apparently taken during one of the interventions on the #7 car during the race:



(source: Spa photo gallery / race)

It seems that the last shot above shows the damage sustained by the #7 car which required repairs.

[joeb]

Originally Posted by MyNameIsNigel

Another series of shots of the Audi R18 front end, nose section removed, have been posted on the motorport.com website. These shots were apparently taken during one of the interventions on the #7 car during the race:


It seems that the last shot above shows the damage sustained by the #7 car which required repairs.

I missed what was said to be the cause of the damage. Was it contact?

[Artur]

Originally Posted by bobec

It seemed like Audi wasn't good at the corners at all, and if the cause was less downforce, then it must have been considerably less downforce than the rest, with a little bit less drag. Then why this complex high-nose front-end design? Isn't superior cornering performance the whole point? The cornering disadvantage seemed too big for a sophisticated aero design even in LD trim. And if the downforce really isn't there, they might as well have gone low nose with low air resistance.

I think that Toyota's Spa aero that is bad.

Audi were ~8kmh slower than Toyota, on qualifying, through Pouhon but an awful lot faster on the straights.

Toyotas were slower than Porsche on S2, despite having quite lower top speed. That's poor aero, not necessarily Audi's.

As GasperG said, the main reason for adopting a high nose is to get the front less obstructed, for less drag. Then, for a high downforce sprint spec, you just fill it with flaps and you'll end up with more downforce than the blocked front end cars as well.

I still don't know what was Audi's biggest problem at Spa, and it's aero still needs to be proved, but you can't dismiss it as of now.

My guess right now is that Audi's spec was too low drag/downforce, for Spa, and it made them look slower than they actually are. As Davidson said, with the LM spec, you can't go high enough(on downforce) for Spa but if you trim down the sprint spec, then it's low enough(drag) for the Belgian circuit.

In 2014, because Audi was on 2MJ, they had much more ICE power allowed, so that should play in top speed's favour. However, the HD Audis reached ~ 280kmh while the LM spec third car had ~297 on the speed trap. That compares very poorly to this year's top speeds.

Last year, the Audi #7 had a ridiculously faster S2(~20kmh faster than the Audis, this year, on Pouhon) than everybody else and it's top speed on it's best QLF, and race, lap was 292kmh(versus 314 of this year). The #8 was much slower on S2 and on it's two 1.56.5 laps, it reached 295 and 300kmh. You see that a few more kmh on top speed can take away quite a lot of downforce and overall pace.

If you look into the 2016 best race sectors, you'll see that the #8 was less than 2 tenths slower than the #2, on S2. Not bad for a much more slippery car. With this year's levels of Toyota's top speed, previous Audis were an a lot faster on high speed corners, so it's definitely Toyota that has a bad aero. But then again, Toyota says they are almost entirely focusing the aero development on the LM spec, so it understable that their trimmed down sprint package is not great.

[Akrapovic]

Originally Posted by joeb

I missed what was said to be the cause of the damage. Was it contact?

I think Ben said it happened in Eau Rouge.

[bobec]

Originally Posted by GasperG

I would say that complex aero design is for low drag first, but as noted above we will see if it works at LeMans.

Wasn't the high nose design developed specifically to increase downforce? It doesn't seem less draggy than a more regular Le Mans nose, like on the 919s, TSO40/50, 908s.

[MyNameIsNigel]

Originally Posted by joeb

I missed what was said to be the cause of the damage. Was it contact?

DSC report that driving over a curb led to the damage to the front part of the underbody.

Better avoid those "sausages" at Le Mans...

[joeb]

Originally Posted by MyNameIsNigel

DSC report that driving over a curb led to the damage to the front part of the underbody.

Better avoid those "sausages" at Le Mans...

I was wondering if it was self inflicted, and given the fragility the factory cars have demonstrated so far this year, avoiding curbs sounds like a good plan!

[MyNameIsNigel]

Originally Posted by bobec

Wasn't the high nose design developed specifically to increase downforce? It doesn't seem less draggy than a more regular Le Mans nose, like on the 919s, TSO40/50, 908s.

Higher nose allows more air to be channeled around the front wheels and to the underbody feeding the rear diffuser, which in turns creates more downforce for similar if not less drag.

It's quite amazing to see how tight this package is at the front. The Porsche 919 looks like a fat lady in comparison in this area.

We will see if Audi have initiated the future trend in terms of aero design at the front. If the aero efficiency is there at LM, the competition may have no other choice than to follow.

[bobec]

Originally Posted by Artur

As GasperG said, the main reason for adopting a high nose is to get the front less obstructed, for less drag. Then, for a high downforce sprint spec, you just fill it with flaps and you'll end up with more downforce than the blocked front end cars as well.

But didn't the Audis have enough flaps under the nose at Spa?
I always thought the high nose was developed, at least in F1, to enhance underbody airflow. Lowest drag would have been to have low-profile cars, like the MP4/4.
If I remember it correctly, the first R18s from 2011 had higher and more open noses than the 908s that year, and at Le Mans the R18s had better cornering, while the 908s usually had the straightline speed advantage. Also, I think for opening up the car for low drag, Nissan had the best concept. But there was no downforce there because it was just ducts.

Originally Posted by Artur

I still don't know what was Audi's biggest problem at Spa, and it's aero still needs to be proved, but you can't dismiss it as of now.

My guess right now is that Audi's spec was too low drag/downforce, for Spa, and it made them look slower than they actually are. As Davidson said, with the LM spec, you can't go high enough(on downforce) for Spa but if you trim down the sprint spec, then it's low enough(drag) for the Belgian circuit.

In 2014, because Audi was on 2MJ, they had much more ICE power allowed, so that should play in top speed's favour. However, the HD Audis reached ~ 280kmh while the LM spec third car had ~297 on the speed trap. That compares very poorly to this year's top speeds.

Last year, the Audi #7 had a ridiculously faster S2(~20kmh faster than the Audis, this year, on Pouhon) than everybody else and it's top speed on it's best QLF, and race, lap was 292kmh(versus 314 of this year). The #8 was much slower on S2 and on it's two 1.56.5 laps, it reached 295 and 300kmh. You see that a few more kmh on top speed can take away quite a lot of downforce and overall pace.

If you look into the 2016 best race sectors, you'll see that the #8 was less than 2 tenths slower than the #2, on S2. Not bad for a much more slippery car. With this year's levels of Toyota's top speed, previous Audis were an a lot faster on high speed corners, so it's definitely Toyota that has a bad aero. But then again, Toyota says they are almost entirely focusing the aero development on the LM spec, so it understable that their trimmed down sprint package is not great.

That's very interesting, thanks. I'm definitely not dismissing Audi's concept before Le Mans.

[bobec]

Originally Posted by MyNameIsNigel

Higher nose allows more air to be channeled around the front wheels and to the underbody feeding the rear diffuser, which in turns creates more downforce for similar if not less drag.

It's quite amazing to see how tight this package is at the front. The Porsche 919 looks like a fat lady in comparison in this area.

We will see if Audi have initiated the future trend in terms of aero design at the front. If the aero efficiency is there at LM, the competition may have no other choice than to follow.

Yes, it is very compact. When you think of it, it's not just a high nose, it's a more compact, F1-style nose (circa 2012), so some of the front has been cut out. So less drag definitely. But I expected more downforce. Efficient, low-drag downforce.

[MyNameIsNigel]

(source: Spa photo gallery / race)

Also looks like the front brake drums have been substantially revised compared to the previous iterations.
2014-15 car:

(source: RCE)

Brake calipers have now been moved to the rear part of the brake drum assembly:

(source: RCE)

[Artur]

Originally Posted by bobec

But didn't the Audis have enough flaps under the nose at Spa?

Audi had flaps there but the angles of these things make a huge difference in downforce levels. The rear wing had an almost flat flap, so it's pointless to run high downforce on the front. Also, the fenders were totally for ultra low drag and those will affect the whole airflow around the car.

It seems that the flow conditioners and vortex generators were removed for Spa and those can massively increase the floor's downforce as well.

Compared to last year, Audi lost ~20kmh on the faster corners(+200kmh) while gaining the same ~20kmh on top speed. It might have been simply a poor choice of aero spec,something that Audi often did, last year, after LM.

[Adam43]

Direct comparisons are hard between years at the best of times This year it might be a little worse as the Audi driver's did comment they thought the track had less grip than the previous year.

[MyNameIsNigel]

Originally Posted by Adam43

Direct comparisons are hard between years at the best of times This year it might be a little worse as the Audi driver's did comment they thought the track had less grip than the previous year.

I would expect that loosing more than 3sec in sector 2 alone at Spa, compared to last year's times, greatly contributed to that low grip feeling.

Has there been any similar comments from the other competitors suggesting that the track appeared to provide less grip than last year ?

[Adam43]

I only heard it from an Duval, in the last hour. I'll take it at face value, what with him being aprofessional race driver and tuned to these things, even in different cars. He said it in the context of others having a problems and it might have caused a few incidents.

Originally Posted by Duval

...
Definitely the track is not as grippy as it used to be in the past years.

What I am saying is that it makes comparison harder as we can't be sure conditions were comparable. I am not saying it proves one thing or the other.

[Adam43]

FWIW, I've just finished watching qualifying and Hartley noted the higher than expected temperatures made it harder for everyone. He didn't directly say this was effecting the grip, but I guess that what he was talking about.

[TF110]

Not going to clutter up this thread with a vs. talk between Audi and it's competitors, but going on the lap times from this year and last, the temperatures could have had a big influence on that.

2016 track temperature was around 48 degrees C at race start and climbed to 52 within the first 2 hours. After that it cooled but not significantly until the last hour to below 35 degrees.

2015 track temperature was around 16 degrees C at race start and dropped to below 14 degrees at the last hour.

So the track was 3 times as warm this year than last year. That probably had a huge impact on lap time differences, not just the fuel drop. I think if you look at qualifying, the Porsche was super quick but it was also cooler, 41 degrees C for the beginning of qualifying.

[Adam43]

That is quite a difference, I didn't realise it was that much. (Although it is not really correct to say "3 times as warm with that scale")

It's all very difficult to tell the impact of each; the track, the cars, the drivers, the tyres all different.

[MyNameIsNigel]

Originally Posted by TF110

Not going to clutter up this thread with a vs. talk between Audi and it's competitors, but going on the lap times from this year and last, the temperatures could have had a big influence on that.

2016 track temperature was around 48 degrees C at race start and climbed to 52 within the first 2 hours. After that it cooled but not significantly until the last hour to below 35 degrees.

2015 track temperature was around 16 degrees C at race start and dropped to below 14 degrees at the last hour.

So the track was 3 times as warm this year than last year. That probably had a huge impact on lap time differences, not just the fuel drop. I think if you look at qualifying, the Porsche was super quick but it was also cooler, 41 degrees C for the beginning of qualifying.

Good point.

I now wonder if Michelin brought tires to the race that were really suited to those temperatures

[TF110]

Originally Posted by Adam43

That is quite a difference, I didn't realise it was that much. (Although it is not really correct to say "3 times as warm with that scale")

It's all very difficult to tell the impact of each; the track, the cars, the drivers, the tyres all different.

Haha, you're right. I was trying to point out the huge difference and I ended up thinking Centigrade scaling was like Fahrenheit! You know us backwards American's.

[Adam43]

OT: it doesn't work in Fahrenheit either. It'd still be a little odd, but it would be better to use the unit Kelvin if you want to say things like 3 times the temperature. It'd make a little more sense as there is no negative and the energy involved is proportional (by the Boltzmann constant) to the temperature in Kelvin.

Fahrenheit is still used quite a bit here too.

Whatever, that temperature difference is significant to the working range of race tyres.

[tomazy]

But Audi did deploy its hybrid system from 310 to 329 kmh, and when it stoped deploying, the speed started to fall down.

https://youtu.be/cUOJZgf2Oxw?t=3973

[MyNameIsNigel]

According to AutoHebdo, the performance of the Audi R18 at Spa was hampered mainly by two issues:
(i) the simulations suggested that the LM-spec car would be faster by 0.5sec compared to the sprint package run at Silverstone, but these simulations were assuming much cooler track conditions; the LM-spec packaged turned out to be less adapted to the hotter conditions. Interestingly, Audi were originally contemplating to race the two different aero packages at Spa, but this plan was changed after Silverstone;
(ii) Audi opted - like Porsche - for two specs of Michelin tires, soft tires for "cold" temperatures (< 17 degrees C) and soft tires for "hot" temperatures (between 15 and 30 degrees C). Both tires specs happened to be unoptimal for the actual track conditions. Toyota were the only ones amongst the manufacturers to opt for soft tires "hot" temperatures and soft tires for "hot +" temperatures (> 25 degrees C). This explains the good level of performance of the TS050s at the beginning of the race (Buemi's double-stint as the beginning of the race was apparently made using the "hot +" tire compound).

It's worth noting that the manufacturers had to make their choice of tire compounds for the Spa round back in early April. Toyota's choice at the time was quite bold and happened to be spot on. This should also be taken into consideration when analyzing the level of performance of the three manufacturers.