lmp1 race engineering

LMP1 RACE ENGINEERING

JOSEPH DOUGLAS PEARCE

INTRODUCTION

The aim for this project is to use vehicle simulation software to compare three different

setups for a LMP1 car. The simulation software was AVL VSM, the engineering software was

MoTeC i2 Pro.

Table 1 - LMP1 Energy/Power regulations (FIA, 2015, p. 55).

Three VSM files were assigned to us representing three different setup variations:

Setup 1 Setup 2 Setup 3

LMP1h Class 6 MJ 8 MJ 8 MJ

Aerodynamic Forces % DF and Drag 100% 90% 100%

Weight Distribution % Front 53% 52% 53%

ICE Power kW 420.5 416.1 416.1

e-power kW 164 175 175

KERS kW 240 240 240



The race simulated was a 6-hour event at Silverstone:

Figure 1 - 2011 Silverstone Grand Prix circuit (AlexJ).

In each section we include a speed/distance trace to pinpoint where we are on the circuit:

Trace 1 - Speed/distance trace with position markers.



AERODYNAMIC DRAG VS. FUEL CONSUMPTION

GENERAL

Trace 2 – Drag/Total Consumption/Fuel Flow (Red = 6MJ 100%; Green = 8MJ 90%; Blue = 8MJ 100%).

𝐹𝑑𝑟𝑎𝑔 =1

2∗ 𝜌 ∗ 𝐶𝑑 ∗ 𝐴 ∗ 𝑉2, so drag rises with speed. Fuel consumed per lap fluctuates

through slower corners, constant at speed. All cars hit the maximum fuel flow after leaving a

corner, indicating strong traction.



6MJ 100%

Trace 3 - Drag/Total Consumption/Fuel Flow (6MJ 100%).

We see a flattening of drag at high speed due to lower Vmax. The 6MJ car consumes the most

fuel; the lowest e-power:ICE-power ratio forces the engine to work harder. Lower Vmax

means the car spends more time at full throttle before braking (blue circles).



8MJ 90%


The 8MJ 90% car generates less drag at high speeds (green circles). This gives the lowest fuel

consumption. Less drag means higher speed, so this setup needs to brake earliest (blue

circles). We also see a big lift through Chapel, suggesting a lack of high-speed aero grip

(yellow circle).



8MJ 100%


The drag is similar to the 6MJ car; the values do not trail off as rapidly at high speed. The

fuel consumed middles the other setups. This setup also displays similar fuel-flow

characteristics to the 6MJ (with the exception of braking), lifting at the same points.

COMPARISON

Setup Fuel Consumed (kg) Δ Fuel consumed (kg)

6 MJ, 100% 1.514 +0.064

8 MJ, 90% 1.450 0.000

8 MJ, 100% 1.486 +0.036

We see that the fuel consumption difference due to drag reduction is greater than the

difference due to e-power:ICE-power ratio.



TYRE SATURATION VS. ACCELERATION VS. THROTTLE

GENERAL

Trace 6 - Tyre Saturation /Acceleration/Throttle Position – Black line = 100% Saturation.

We see that throttle > 0 represents positive acceleration and throttle = 0 represents

negative acceleration. We see the highest saturation values when cornering at speed; the

driver is using all available grip when cornering. G force under braking is higher than

acceleration; most LMP1 cars have some form of traction control fitted (FIA, 2015, p. 6). This

is reflected in tyre saturation.



6MJ 100%

Trace 7 - Tyre Saturation /Acceleration/Throttle Position (6MJ 100%).

The 6MJ car has less KERS power at the front axle. We can see this when accelerating out of

corners (blue circle). We see high saturation (> 100%) at the slowest sections of the track

(Arena, Brooklands, Vale), suggesting a mechanically balanced car that gives confidence.

Peak G-forces are 3.2 G laterally (Maggots) and +0.9/-1.0 G longitudinally (Arena).



8MJ 90%

Trace 8 - Tyre Saturation/Acceleration/Throttle Position (8MJ 90%).

The throttle application at higher speeds is less aggressive (green circles). At elevated

speeds, traction is dependent on aerodynamic load. At these points on the track, we see

higher tyre saturation than on the 100% aero cars; the tyres are being worked harder. We

reach a high peak lateral acceleration (3.5 G, Maggots) and longitudinal acceleration (+0.9/-

1.0 G, Arena). We see that peak saturation events due to braking occur earlier.



8MJ 100%

Trace 9 - Tyre Saturation/Acceleration/Throttle Position (8MJ 100%).

Throttle behaviour is almost identical to the 6MJ car. The peak G-forces are 3.3 G laterally

and +0.9/-1.0 G longitudinally; all our cars have similar acceleration/braking characteristics.

We see that losing KERS leads to a drop in force and front tyre saturation (yellow circles).

Trace 10 - Front Saturation/Acceleration (Red/Orange = 8MJ 100%, Green = 6MJ 100%).



FUEL CONSUMPTION VS. STINTS VS. TOTAL RACE TIME

MATHEMATICS

A script was written in MATLAB to calculate the number of pit-stops and total distance. It

assumed constant lap time throughout the race distance (no tyre/fuel degradation). This is

covered in Appendix 2.

COMPARISON

The two variable inputs are Fuel consumption and Lap time. Running the solver with these

values gives us the following outputs:

Setup 6 MJ, 100% 8 MJ, 90% 8 MJ, 100%

Fuel consumption (kg) 1.514 1.450 1.486

Lap time (s) 103.610 103.940 103.380

Stint length (laps) 34 35 34

Number of stops 6 5 6

Laps completed (@ 6 hours) 204.71 204.68 205.17

Total laps completed (@ flag) 205 205 206

Fuel remaining (kg) 50.53 8.56 49.87

Fuel remaining (laps) 33 5 33

Comparative position 2 3 1

Chart 1 - Lap chart over the 6 hours (Blue = 6MJ 100%; Orange = 8MJ 90%; Yellow = 8MJ 100%).



Chart 2 - Lap chart over the final hour (Blue = 6MJ 100%; Orange = 8MJ 90%; Yellow = 8MJ 100%).

Setup 6 MJ, 100% 8 MJ, 90% 8 MJ, 100%

Δ Lap 0.03 0.00 0.49

Δ distance (m) -2714 -2891 0

Estimated Δ time (s) +48.00 +51.00 0.00

This represents a time difference of 0.2-0.3%.

STRATEGY OPTIMISATION

The 8MJ 90% car is optimal – finishing the race with a buffer of 5 laps in the tank. Both of

the other cars are actually required to pit on the penultimate lap. In a real-world race, a

decent engineer would call for a few laps at reduced speed to save fuel and avoid an extra

pit stop.

Our results are similar to some real-world strategies (Porsche #18).

Figure 2 - 2015 6 Hours of Silverstone results (FIA WEC, 2015).



AERODYNAMIC BALANCE

GENERAL

Trace 11 - Aerodynamic Balance (Red = 6MJ 100%; Green = 8MJ 90%; Blue = 8MJ 100%) – Black line = 50%.

As speed rises so does the proportion of downforce generated at the front. 50% balance

marks the car moving from stable/understeer to unstable/oversteer. Through slower

corners (circa 150kph) the cars have rear-lead tendencies. Above this, the cars are

cornering at exactly 50% balance; the stability limit.



6MJ 100%

Trace 12 - Balance (6MJ 100%).

We see a sudden rise, followed by a flattening off of the balance at Vmax (blue circles).

Through the most challenging section – Maggots-Becketts-Chapel – we see how finely

balanced the car is; flitting between front-lead and rear-lead balance (green circle).



8MJ 90%


We see a big difference through the Becketts complex (green circle) – we don’t see the third

pronounced spike that the 100% cars have indicating a large braking event. This suggests

that the overall speed through the corner is reduced. In general, the aero balance at

medium speed is further rearwards than on the 6MJ, increasing towards Vmax and under

braking (blue circles).



8MJ 100%


The behaviour of the 8MJ 100% car is very similar to the 6MJ car, with the biggest difference

being a continued rise in forward aero balance at high speed (yellow circles).

Trace 15 - Balance comparison (Red = 8MJ 100%, Green = 6MJ 100%).



AERODYNAMIC LOAD VS. CORNERING SPEED

We created an Excel sheet comparing velocity, drag and downforce across the circuit:

Graph 1 - Cornering speed per setup per corner.

0

50

100

150

200

250

300

Vel

oci

ty (

kmh

)

6MJ 100%

8MJ 90%

8MJ 100%



As we expected, the 90% aero car is slower through the corners – max Δ velocity = 6 kmh –

with the difference increasing as speed and dependency on aerodynamic grip increase. At

low velocity the cars corner at similar speed. The same is true in curved acceleration zones

such as Woodcote or Club suggesting that these corners are traction limited. Overall, the

two 100% aero cars corner at roughly the same speed.

Graph 2 - Drag per setup per corner.

Graph 3 - Downforce per setup per corner.

0

500

1000

1500

2000

2500

3000

3500

Dra

g (N

)

6MJ 100%

8MJ 90%

8MJ 100%

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Do

wn

forc

e (N

)

6MJ 100%

8MJ 90%

8MJ 100%



Downforce and drag are proportional to velocity; it is logical that through the slower corners

our Δ drag/downforce is lower than through higher speed corners. We can confirm that the

90% aero car loses most of its grip and time through high-speed corners. We can also say

that Luffield and Club are not downforce-limited corners as the 90% car has the same

cornering speed at reduced load. The two 100% aero cars have incredibly similar behaviour,

confirming that the 8MJ 100% car gains its time through the straights compared to the 6MJ

100% car.



DRAG VS. STRAIGHT LINE SPEED/TIME VS. ACCELERATION

GENERAL

Trace 16 – Drag/Longitudinal Acceleration/Velocity (Red = 6MJ 100%; Green = 8MJ 90%; Blue = 8MJ 100%).

Longitudinal acceleration is proportional to the gradient of velocity/drag. During slow

sections (blue circles), the similar acceleration of all three cars suggests similar low-speed

traction. The major difference under acceleration is KERS application (black lines).

Setup 6MJ 100% 8MJ 90% 8MJ 100% Location

Vmax (kmh) 302.7 320.0 314.0 Hangar

Drag @ Vmax (N) 3851.6 3882.4 4133.0 Hangar

G Long @ Vmax 0.05 0.01 -0.01 Hangar

Max G Long 0.96 0.96 0.96 Arena

Min G Long -2.33 -2.27 -2.38 Brooklands



6MJ 100%

Trace 17 – Drag/Longitudinal Acceleration/Velocity (6MJ 100%).

A big difference between the 6MJ and the 8MJ cars is high-speed acceleration (black lines).

The 6MJ car has the lowest Vmax and drag of the trio. Acceleration at Vmax (yellow circle) is

higher than the other cars, suggesting that it has not reached terminal velocity.



8MJ 90%


The 8MJ 90% car brakes earlier from Vmax. It also brakes harder to balance through Abbey

and Luffield (green circles). The low acceleration at Vmax shows that the car is appropriately

geared. It has the highest Vmax and middling drag force of the three; representative of the

‘low drag’ setup. It has the lowest braking capability of the three cars.



8MJ 100%


The 8MJ 100% car has the highest drag and second highest Vmax. The acceleration follows

the 8MJ 90% car up to around 250 kmh where drag takes effect. This high drag gives the car

the strongest braking. It loses speed as KERS is removed (negative acceleration). The

power/drag ratio has been improved by the KERS application and temporarily ‘boosted’ the

car over theoretical Vmax.



BIBLIOGRAPHY

AlexJ. (n.d.). Silverstone Grand Prix Circuit - Wikipedia. Retrieved from Wikipedia.org:

https://en.wikipedia.org/wiki/Silverstone_Circuit

FIA. (2015). 2016 Technical Regulations for LMP1 Prototype.

FIA WEC. (2015). Retrieved from www.fiawec.com



APENDICIES:

APPENDIX 1



APPENDIX 2

lmp1 race engineering

Documents