Audi LMP1 Discussion

[roderick]

Originally Posted by Articus

I think you guys are thinking about this battery power and life expectancy in the wrong way. A battery that is designed to only deliver max power for a race weekend or even a 60 minute race is going to be the lightest battery.
To make it last longer, you can build a battery with more total energy (i.e more mass) and only discharge it to 50% capacity every time. I imagine the race teams have lighter batteries (power cells) which are drained to very low capacity each time at a high rate, and then recharged at a high rate. For most types of lithium cells, this leads to increased internal resistance and reduced capacity when this cycle is repeated so lower max output, and less storage capacity. You tune it to the duration of the event.

There is no incentive to make a battery that can last more than 1 race. They will design the cells and battery management strategy (how long the system tolerates undervoltage, overvoltage, high temperatures of indivudual cells as well as cell balancing) to suit the duration of the event. Batteries deteriorate in a somewhat predictable way, with these teams, it will have atleast been tested in a lab, and they know what battery management stratgeies are required to run the battery for 24 hours.

I hate to point out that some one is wrong...but here are mixed up facts with both posche and toyota:
They use their capacity of between 80~90% to 20~30%. (Soc wise)
Their battery system without cooling weights about 60~80KG (very heavy!)
The difficulty with 24 hrs is to manage the cell temperature (keeping their cells balanced is easy)
Porsche this year sees to be having some trouble with keeping the cell cool (guessing 40~70C)
Toyota hasnt reported any battery problems. However, I'm guessing they have gained some weight compared with Capacitor.

PS: their charge and discharge system is regulated by software mostly likely doing distance traveled vs allowed total discharge per lap.

Oh, and the fun part is...in the qualifying, They can keep the battery at almost full capacity and use as much as they can on the last corner to gain speed till the finish line.(this will reset the allowed battery energy at the finish line)That's how they get super fast time.

sorry about the long post

[Articus]

Originally Posted by roderick

I hate to point out that some one is wrong...but here are mixed up facts with both posche and toyota:
They use their capacity of between 80~90% to 20~30%. (Soc wise)
Their battery system without cooling weights about 60~80KG (very heavy!)
The difficulty with 24 hrs is to manage the cell temperature (keeping their cells balanced is easy)
Porsche this year sees to be having some trouble with keeping the cell cool (guessing 40~70C)
Toyota hasnt reported any battery problems. However, I'm guessing they have gained some weight compared with Capacitor.

PS: their charge and discharge system is regulated by software mostly likely doing distance traveled vs allowed total discharge per lap.

Oh, and the fun part is...in the qualifying, They can keep the battery at almost full capacity and use as much as they can on the last corner to gain speed till the finish line.(this will reset the allowed battery energy at the finish line)That's how they get super fast time.

sorry about the long post

What exactly is wrong about what I said?

Everything you posted here seems to agree. High current (recovery and deployment) causes the cell heating issue. You control it by deploying less power though a software current limit in the battery management system.

I'm not sure what the point about a 60-80 kg battery is. They have constructed a 60-80kg battery WITH cell temperature issues when running. This tells you that they are on the low end of the spectrum with regards to battery size. Lets say you need 100 amps. From a 1 Amp hour battery this is 100C. From a 200 Amp hour battery this is 0.5C. The 200amp-hour battery runs cooler but is MUCH HEAVIER assuming the same battery chemistry....extrapolate this to what porsche are doing. There cell temperature issues will go away with a battery pack double the current size and weight. But who is going to run an overweight battery in a race? They designed a system on the limit for weight reasons, and as you would expect, we see the negatives of doing such (temperature)

When you take a lithium battery and deep cycle it (80% to 20-30%) for a long time, you reduce the energy and power density of the cell over time. The way that lithium redeposits or binds to the cathode is controlled by the chemistry and kinetics so it's not always what you want and there can be side reactions producing "dead" deposits which don't hold any energy and just increase internal resistance inside the cathode. Cell manufacturers will have experimentally derived data on this specific to each program. A good designer only builds a battery to last a race distance and some change (i.e safety factor) and no longer. Any longer and it's just more weight when you fully consider the design of the pack and how it operates.

[TzeiTzei]

One race? Sounds like a terrible waste.

[Victor_RO]

Originally Posted by chernaudi

F1 team's battery packs barely last a race weekend before they start to lose power. So I'm betting that between LMP1 hybrids having more power and such, It'd be stretch for them to last much longer than 24 hours/30 hour endurance test without losing potency.

They're restricted on batteries too since the new rules were introduced, they're only allowed 5 energy storage units per season. Aka a battery pack needs to last for 4 race weekends at least. (still not as long as Le Mans)

[GasperG]

Can you point me the document that says that?

in sporting regulation I have found this sentence:
"Engine use is limited to 5 engines for the complete season (all race events) per car entered."

This is specific limitation to engine only I have not found anything about ERS.

[Articus]

Originally Posted by TzeiTzei

One race? Sounds like a terrible waste.

Not so far fetched. They used to do it in F1 where they had a qualifying spec engine to put in that would last qualifying before needing a rebuild. You can imagine in the engine was lightened to reduce mass of rotating and reciprocating components as super low viscosity oils to reduce drivetrain losses (ironic because not enough lubrication will increase the drivetrain losses). They don't do this anymore, because as you said, terrible wasteful, but if given the option, and the goal is to win, if you have the budget, you'll do it, if not at least consider it.

[Victor_RO]

Originally Posted by GasperG

Can you point me the document that says that?

in sporting regulation I have found this sentence:
"Engine use is limited to 5 engines for the complete season (all race events) per car entered."

This is specific limitation to engine only I have not found anything about ERS.

I was talking about F1 power unit limitations, that was the point I think in the post I quoted. I'm not aware of any limitations on energy storage units (in terms of number of units used per season) for LMP1 though.

[roderick]

Yes, for LMP1 hybrids, They will use bran new battery pack for the 24hr race, However, they do reuse other packs for at least 2 races. Batteries they use should last more than 3000 deep cycle and even with that, they only loose capacity to 80% or original.

also, they wont redesign the pack with each race. they will use same new/old battery pack for all the races though out the season.

[sssssssss]

Originally Posted by Gingers4Justice

Porsche have had the same car for 3 years, and Toyota for 2 before their engine concept was proved out-dated - but it's not like that was unforeseeable.

The reason Audi keep having to take these radical steps between each season is, imo, because diesel compromises their design. They have the money and resources to find time in their chassis and aero to make up for the disadvantages that the diesel powerplant brings.

Traditionally, Audi prototypes have been made of concrete and have been supreme mechanical machines built to last. In recent years, they've become much more flimsy and unreliable. This isn't just because of the new technology these LMP1 cars use, but because they've had to push the envelope in a number of areas to make up for the compromises their diesel brings.

I would bet that if Porsche weren't on the scene, Audi would have switched to petrol by now. But I believe that the VAG bosses are only happy if the cousins race each other using different technologies.

In short - Audi's outrageous development curve on their R18s has more to do with VAG politics than it does the LMP1 rulebook. But this is, of course, my opinion and I invite posters to disagree.

that would be my take on the situation as well. i think the diesel aspect forces audi to really push things to the very limit, which in turn compromises their reliability and does not provide any actual performance edge over their competition, who can afford to spend a lot less and still be competitive.

[chernaudi]

Based on a piece at Motorsport Total and Audi Sport's own pre-LM roll out video, the Audi guys seem fairly confident about the test weekend and such. I just hope the weather cooperates, but there's a 90% chance of rain showers and possible thunderstorms for Sunday last time I checked the weather for LM.

As for the above post, you have to remember that Audi, as with many things German, tend to overbuild some mechanical parts, namely the engine (the old R8 3.6TT V8, and 5.5 liter V12 and V10 TDI engines were bulletproof, but a bit hefty for what they were designed for, as is probably even now the 3.7/4.0 TDI V6. An all aluminum Ford small block V8 was a bit lighter than the R8's V8, for example, and Audi's 4.2/4.0T road car V8s are comparable in weight as well). It's easier to lose weight by making lightweight bodywork and ancillary parts (and, if engine or engine/hybrid power allow for it, gears out of the transaxle, as the current R18 gearbox is a 6 speed without an actual reverse gear, too) than to get it out of the engine.

But with advancing technology, everything is being pushed to the limit to make it smaller, lighter, faster and more reliable. And as we've seen already this season, Audi aren't alone in that arena.

[sssssssss]

i hope they solved the low grip issues they had at spa, for whatever reason. other than that, the car seems pretty fast: they were faster than last year at paul ricard, with noticeably higher top speed (although they had by far the highest top speed last year as well, which counts for le mans), faster than last year at silverstone, again with noticeably higher top speed, while at spa, the tire problem hit all the manufacturers, but audi more than anybody, probably because of some extra handling issues. yet they still managed incredible top speeds. they also had the least reliability problems at spa, which basically handed them the win. i think if they solved that issue, they're in a really good position for le mans at this point. i expect them again to be fastest in race pace, if the handling issues don't occur again.

[MyNameIsNigel]

Originally Posted by J Jay

Haha, time for Racecar Engineering!

Some new information, but mostly confirmations. The quotes within the article come from Jorge Zander (LMP1 Technical Director) and Thomas Laudenbach (Head of Electronics and Energy Systems).

Chassis
- The weight distribution is significantly rearwards compared to the 2015 R18, largely thanks to the cockpit being moved further back.
- The high nose (which contains the battery pack, next to the driver's legs) was designed to free up the airflow around the front wing.
- To keep as much weight on the front axle as possible, the battery was mounted far up in the high nose.
- A further focus of the aerodynamics is to keep the airflow as clean as possible at the front of the car, which has led to routing the airflow through and underneath the car rather than over and around.

Suspension
- The suspension is "closer in mechanism" to Porsche's, but Audi focused on generating heat in the front tyres to combat the low front grip issues encountered in its 2014-15 LM-spec cars.
- Although the 2016 R18's Linked Suspension System (LSS) is still inspired by F1 FRIC systems, the front and rear heave springs are now hydraulically linked.
- There is no longer a roll-heave link as there was in the 2015 R18. The link between damping and springing has also been decoupled, to allow for independent adjustments.
- There are no wishbones; only linkages. The geometry rework has also resulted in better kinematics overall and an improvement in the tyres' load cycles.
- The major effects of the revised suspension were to be and are in transition, as Audi wanted to keep aerodynamic benefits the FRIC suspension gives in "quasi-static" conditions.

Engine
- The updates to this year's engine also include measures to account for further reductions in fuel allowance, beyond this year's 10MJ cut.
- Despite Baretzky's best efforts (!) in increasing efficiency, the 2016 engine is down on power/torque compared to previous years.
- While there have been some weight reductions, the better (lower) weight distribution of the engine is also due to rearranging the components to better fit the bodywork. The engine is also mounted lower within the car.
- Even though Audi have been working with Sentronics on a more accurate, including increasing the sensor frequency to 2.2mHZ, they have remained with Gill sensors as they are now working in a "relatively stable" manner.

Hybrid
- The battery system weighs approximately 40kg more than the flywheel system. The cell supplier remains confidential.
- The 2016 R18 is the first version of the car to run traction control on the front axle, similarly to the Porsche 919.
- To reduce the weight of the cell (by reducing the current and therefore the amount of copper needed), the cells are run at as high a voltage as possible, given the 1000V limit stipulated by the FIA.
- Audi looked at a super capacitor system as used by Toyota in 2013-15, but chose batteries even though the handling (weight distribution) "would have been easier" with a super capacitor.
- The flywheel system was considered for an uprating to 6MJ, but the weight would have been greater than that of the current battery system.
- The front mounted KERS is also placed in the cockpit, which led to an oil leak within the cockpit at Spa when the unit failed under high loads.
- A second ERS was considered but the single front-mounted KERS remained because it was felt that the motor could still recover energy fast enough to charge the battery under braking.

Other
- Given the fuel reductions from the total allowance restriction and the move to 6MJ, the target was for the 2016 R18 to match the 2015 R18's lap times.
- Unlike last year's electromagnetic steering, and probably as a result of hiring more F1 engineers, the steering, gear change and other systems are now activated from a centrally with a hydrualic system.
- The central reservoir can deliver 3000psi, which is enough to use actuators with much lower inertia compared to the motors/actuators used in the EM system(s), increasing responsiveness.
- When factoring the jump in energy class and 10MJ fuel reduction, the target was to set the same lap times as last year.
- Although there is some concern about the 6-8MJ petrol EoT values being unfairly incentivized compared to 4-6MJ diesel, Audi are discussing the 6-8MJ diesel values with the FIA and are confident of a satisfactory outcome.

Sorry I didn't get round to doing this for the TS050/919, but one out of three isn't bad! If you have any questions I'll do my best to answer them

Thanks for the wrap-up. I just had a chance to read that article. I would have loved to see more descriptive pictures or diagrams in that article as there are still a number of areas of that car that have to reveal their secrets

As far as the battery arrangement is concerned, the following diagram that comes from Audi Sport's recently-released 2016 fact book is the only element published so far that gives some indication of how extreme Audi Sport had to go to ensure proper weight distribution. There is truly a "passager" sitting next to the driver and stretching its legs

Originally Posted by MyNameIsNigel

The 2016 Audi Sport Factbook is out.

This schematic diagram on pages 30-31 suggests that the battery cells are distributed longitudinally in a forward section of the monocoque, next to the driver, likely in an attempt to achieve proper weight distribution.

[Artur]

Originally Posted by sssssssss

they were faster than last year at paul ricard, with noticeably higher top speed (although they had by far the highest top speed last year as well, which counts for le mans), faster than last year at silverstone, again with noticeably higher top speed, while at spa, the tire problem hit all the manufacturers, but audi more than anybody, probably because of some extra handling issues. yet they still managed incredible top speeds.

that is incorrect*. The car was a bit faster, at Silverstone, but that's to be expected as now it has more downforce which compensates for the -10MJ, on such track layout.

Spa is more like LM, although not quite, in the sense that the -10MJ affects more, so that's why the cars were so slow there. The out-of-temperature tires can only explain faster degradation, not peak pace.

*the speed trap on 2015's best lap was 269kmh while this year it was 268

[MihokS5]

So Audi has two #7 cars at the test day. One is running the black trim on the windshield and one is running the chrome reflective trim.

It also appears as though they are running two different types of rear fender designs. Based on the photos below, it looks like the openings on one are smaller and sleeker than the other. The car with the chrome windshield seems to have taller and more squared leading edge/air vents:

[Artur]

At the front fender, it seems the diveplanes(right below the Michelin Man) are different and maybe even the external top edge of the fender(by the side of the BHH)

I'm very surprised the central section of the FW's flap is still there. Actually, this package looks quite like the sprint one(used at Silverstone). The front fenders surely aren't the typical boxy low drag ones(ala the one used at Spa). Even the rear wing flap seems quite high for LM standards

I'm puzzled(which is always good and a pleasant surprise, btw ) with what Audi came up to the test day

[chernaudi]

The #7 Audi with the black windshield trim was re-numbered #8 during the Audi Sport photoshoot. It's just a show car.

[MyNameIsNigel]

Originally Posted by chernaudi

The #7 Audi with the black windshield trim was re-numbered #8 during the Audi Sport photoshoot. It's just a show car.

Is it really a show car or will Audi Sport test two different aero packages ? The official picture definitely shows two different packages as this is especially visible at the front (different legality panels on either side of the nose section, different front fender shapes, different rear view mirror integration, etc.):

[chernaudi]

It's a show car it seems. It's got the launch spec bodywork, not the newer spec that Audi first ran at Monza and also used at Spa.

[MyNameIsNigel]

Originally Posted by chernaudi

It's a show car it seems. It's got the launch spec bodywork, not the newer spec that Audi first ran at Monza and also used at Spa.

Looks like it indeed

[TF110]

The new car has the vortex generators ahead of rear tires, the front suspension bumps are smoothed (bodywork connecting to the nose and the inner front fender blister), it lacks diveplanes and the rear brake intakes are reshaped. That's just what I noticed.

[Creep89]

So it looks like the #7 encountered some reliability issues. They are once again working at the front according to Motorsport Total.

[gustavobamba]

Audi nº 8

3:21.375

They are almost as fast Porsche was last year!!! UAAUU!!!

[Creep89]

So the Audi guys needed 4 hours to change the damper on the #7.

[Articus]

Safe to say they won't get away with that in the race.

[chernaudi]

At least (hopefully) it wasn't a hybrid issue. They for sure won't win if that happens due to time loss.