Le Mans Test Day 2018 - Engineering Discussion

With just over a week until the on-track action starts at Le Mans for the race week, the official test has been completed providing new drivers and new car updates to be put through their paces. This article will have a look at anything new the teams have brought to the table and the standout performances of man and machine from the day. 



Before I go any further I will offer the disclaimer that this is testing and is not necessarily representative of what we will see during qualifying/the race. The teams historically keep their cards close to their chests. I like to look at the best sector times set per car as it is a marker for what the car has proven it is capable of doing, even though it may not have completed that lap as a personal best - for example it got held up by traffic later on in the lap. That said, the setup may change after personal best sector times are set as time may be lost more significantly elsewhere through the lap. This personal best sector time in practice for the Toyotas is not as good a method for analysis as the deployment of hybrid energy and where on the lap they use it can differ lap by lap – I will touch on that later on when looking at their top speed.

I will also be looking at the top speeds achieved, as the teams can be using the test to stress their engines along the straights – this is a lap consisting of the highest percentage of time on full throttle for the season and a real test for engines.

LMP1 

The only class with in season development is LMP1. The non-hybrid cars are permitted an unlimited number of rehomologations throughout the season and can theoretically bring updated to each race. Toyota however have two aerokits permitted throughout the season. 

Toyota

During the test day their low downforce aerokit featured a small Gurney on the rear wing that did not cover the full span. This is expected to maximise the performance of the central portion of the wing whilst reducing the magnitude of the tip vortices at each end which contribute to the drag. This reduction in vortex strength is due to a slightly lesser pressure differential between the upper and lower wing surfaces compared to using a full span Gurney flap. The Dallara LMP2 cars have used this setup in the past for higher speed events in the ELMS or WEC whilst being stuck with the high downforce bodywork through the season.

The number 7 Toyota was measured with the highest top speed of the day. I do not believe this Toyota was using its hybrid deployment as usual (the same as in qualifying/the race) on this lap however as it is 10kph faster than the best speed the #8 Toyota achieved all day (23rd overall) despitethe 8 setting the fastest overall lap time. For example, it may have been stressing its Hybrid system to see if it would fail, or how it operates while near top speed.

Toyota using a near-half span Gurney flap with its limit marked in red

SMP Racing

After the unfortunate accident at Spa where Matevos Isaakyan flipped over Raidillon corner in the number 17 BR1 car, some changes have been made to reduce front lift. This is primarily around the front wheel wells and how the pressure within the wheel well is treated. 

At Spa, the front end had a flat top surface on each fender upstream of the big holes – these are nicknamed Big Honking Holes (BHH for short). The BHHs are there for yaw conditions and to reduce the chance of a lift off event caused by high pressure inside the wheel wells. 

SMP BR1 at Spa Francorchamps. This is the design that experienced front lift issues

To control the pressure in the wheel well, the top surface of the fender has been changed in the form of a new panel. They have lowered the surface creating a channel aligned with the BHH opening and added a small lip/ramp on the front edge of the hole to introduce upward momentum to the airflow. This will help draw more air from out of the wheel well in its wake reducing any pressure build-up contributing to front lift. There are reports of the hole being larger than at Spa also (taking it over the minimum size in the rules). The hole edge is set into the panel rather than on the edge of the panel. Please open the images in a new tab/window to view at full resolution. 

Left: Side on view with the new panel, and lip added.        Right: New panel in bare carbon showing its depth before the lip is added

Close up of the small element. The profile is highlighted in red as the image is focused on the Toyota behind

This does however have drag a penalty as it would be detrimental to the wake structure the BHH creates increasing its height; a BR spokesperson saying “It will have some negative effect on performance, Just a few tenths, a few kilometers per hour – we need to see”. 

As for top speed measured at the test day, the SMP didn’t disappoint managing 337.0 and 336.0 kph for each car just behind the 7 Toyota with 338.1kph. During the race, I expect the SMPs to be the fastest cars on track. 

A more simple way of covering the brake ducts is used by SMP racing - some tape. I much prefer Rebellions solution below.

The SMP BR1s retained their upper dive planes used at Spa for some laps to keep some front downforce in the test but also were spotted with them removed to find extra top speed. They may lean towards keeping them for the race to make up more time in sectors 1 and 3 which contain the higher speed corners or remove them to affirm their strength in top speed, we will have to wait on what direction the setup goes from the data collected.

Rebellion 

It appears the Rebellion R13s have not had visibly significant changes made to their bodywork used at Spa Francorchamps – there may be a lower profile front wing underneath the nose out of view to correspond with the removal of the large Gurney flap on the rear wing since Spa however. 

This car had the fastest sector 1 time (start line to Tetre Rouge), so must have some good downforce through the Dunlop chicane and Esses. 

The fastest Rebellion was only 4 kph slower than the fastest SMP top speed, a promising number considering its times through the high-speed corner sections within sectors 1 and 3. The R13 has a good balance between drag and downforce and a strong engine – hence why it achieved the second fastest lap of the day splitting the Toyota TS050s at the top around half a second slower than the number 8 car. It is the only car to have multiple drivers to lap below 3:20 however, another positive to take forward.

#1 on the left with a smaller brake duct orifice and the #3 on the right. This can be easily changed by removing the two fasteners

The modular front brake duct system is adjustable, both cars deciding on slightly different orifice sizes on the day. As this is easily changed, this can be tuned to the conditions based on temperature.

I look forward to seeing whether it can repeat this performance in qualifying during race-week. It certainly is looking like the best non-hybrid outfit at this stage.  

Dragonspeed

The team have opted to use the low downforce aerokit for the whole test for the BR1. Unfortunately mechanical issues held them back from completing many hot laps. The car was well down the order on the top speed chart. I expect this car to have a better showing at Le Mans proper, as the Rebellions that share the same powerplant managed some high speeds, and it shares the same silhouette as the SMP.   

While the car was being assembled for the first time at the circuit, it gave us a nice view of the front wing normally hidden under the nose bodywork. It works with the front diffuser under the splitter acting like a big multi-element wing. 

The splitter behind the mechanics shows the front wing affixed. This is usually hidden by the nose above

The upwash from this wing is worked either side of the tub into the sidepods for cooling and out the side of the car with the help of the fins there(this would help with the working the front tyre wake outwards like what bargeboards do in F1) The wing is a different chord and angle of attack along its span because of the proximity to the tub in the centre and to help work the air outwards - giving the nice curved shape.

ByKolles 

The ENSO-CLM had promising top speeds, passing the timing beam at 333.9 kph, only 3 down from the best of SMP. This is a slippery machine on the straights and must have good power coming from their NISMO V6 unit. They are losing time through sectors 1 and 2 based on the best sector times achieved on the day; so could be struggling with downforce dependent corners.

ByKolles used some narrower dive planes than the ones used at Spa. These are flush with the fenders and do not feature an extension outward. 

Manor Ginetta

This is the first race event that CEFC TRSM completed multiple laps in a single session after their unfortunate financial situation around the Spa round. They have stuck with the high downforce package while waiting for the low downforce aerokit to be finished at the factory – this should arrive for race week at Le Mans where a final decision on its use will be made. To find some extra top speed with what they’ve got, the dive planes have been removed completely. 

The rear brake ducts on the wheel fenders have reappeared since Spa due to the large braking loads across the lap - the rear bodywork at Spa may not have been race spec however. We will have to wait to see if that bodywork is used again in future. 

Class Recap

The results of the class as a whole are positive with close times at the top spread between multiple manufacturers. The times will fall during the qualifying sessions, especially for the Toyotas – we’ll have to wait and see if the privateers also have some pace up their sleeves. In addition, the EoT may change for race week, either to boost or hold back the privateers relative to the Toyota. 

LMP2 

LMP2 cars are allowed a low downforce package but just for Le Mans with their designs consistent through the whole season elsewhere. Due to the Oreca’s superior performance last season, the other chassis have been granted upgrades to catch up in addition to any BoP adjustments applied to the Oreca. 

Dallara

The Dallara cars have an aerokit similar to the one used last year, as it allowed the car to take fastest overall top speed at the test last year. Unfortunately, there were stability and downforce issues with this kit, such that the normal aerokit was used with the dive planes removed. 

Left: 2017 Low Drag Kit      Right: 2018 Low Drag Kit

This year there is an addition of an upper dive plane to improve the downforce, and there may be a tweak to the front wing outlined above. 

This added downforce has reduced their top speeds, with the car slower than some of its class rivals through the speed gun. The laps times are less promising overall with the best Dallara time 8th in class

Ligier

The Ligier has a more significant differences over last year. The cooling for the front brakes has changed slightly, with the inlets opened up.  The more significant changes are made for the low drag spec bodywork, around the front end. The leading edge of the bodywork around the duct inlets is lowered. This will increase the share of air over the upper surfaces of the car compared to the air through the car.

Left: High downforce kit with high bodywork     Right: the brand new low drag kit with lower bodywork

The shape of the front fenders is also changed – they have been brought forward, just like most le mans aerokits. Overall this is a large step forward compared to last year as Ligier teams used the high downforce bodywork like Dallara in 2017. Top speeds can be good with the Panis Barthez Competition Ligier passing the speed gun 4th fastest overall. 

Considering lap times, the Ligiers were consistently at the bottom of the class. 

Left: 2017 Ligier Le Mans front end with high downforce nose       Right: New Le Mans aerokit seen testing at Monza

Tyres

Michelin has entered this class to create the only tyre war at Le Mans this year, and with it have topped the time sheet. The Dragonspeed and IDEC Orecas both on Michelin tyres provided the best lap times of the day in P2. This tyre may be good on one lap pace, but didn’t feature in the top 5 at Spa at the end of the race. These two are the only Orecas on Michelin tyres, the other cars are the Racing Team Nederland Dallara and the Larbre Competition Ligier at the foot of the field. The rest of the class use Dunlops. 

GTE Pro

This class includes multiple new cars for the Superseason, which bring aerodynamic upgrades for Le Mans that have never been used before at a race event. The modifications permitted apply to:

• The lower surface of the front splitter 
• A redesign of Dive planes or removal thereof 
• Rear wing Gurney flap height can be changed or removed altogether 
• Rear Wing supports can be changed
• Rear Wing range of angle can be changed

Through the speed gun, the Fords were all together at the top, with the rest of the competition mixed around behind. The Aston Martin Vantages were well off the pace, at least 15kph down from the fasted Ford. Their lap times were also not impressive, being well within the Am field on the timing screens five seconds behind the fastest lap of the day, set by Pilet in the #93 Porsche. Hopefully they aren’t deliberately holding back to gain a favourable BoP setup come race day. 

GTE Am

For the Am field, the fastest time was set by the Dempsey Proton Porsche 911 RSR. Behind is a good mix of Porsches and Ferraris, they are balanced well based on lap times. The Aston Martins are at the bottom for the time sheets despite the TF Sport Vantage having the highest top speed - probably with too shallow a wing providing not enough downforce on that lap. Curiously the AMR run Vantage was the slowest through the speed trap, probably due to the engine change that was required. Hopefully they were not holding back deliberately alongside the Pro cars from the same team.  

In Summary

As I mentioned at the start of the article, this all may change depending on BoP/EoT adjustments and drivers going full attack around the course. I certainly cannot wait to see these cars in action, not too long to go now! 

If you’d like to look at the data for yourself, you can access it at fiawec.alkamelsystems.com