October 9th 2006

Firing Order on a Formula 1 V10

Pierre-Jean Tardy

Brief presentation of our 2005 World Brief presentation of our 2005 World Champion F1 Engine Champion F1 Engine

V10

3 liters displacement

Naturally aspirated

4 valves per cylinder

Variable trumpets

Max Speed : 19250 RPM

Max power : ~900 hp

Weight : ~107 kg

Engine PerformanceEngine PerformanceA good engine has to help get good lap times : peak power is not sufficient, therefore we created a lap time performance index.

Lap Time - Effect of power curve shape

707274767880828486889092949698

100102104

14500 15000 15500 16000 16500 17000 17500 18000 18500 19000 19500

Engine speed (rpm)

Engi

ne P

ower

(%)

Engine # 1

Lap Time - Effect of power curve shape

707274767880828486889092949698

100102104

14500 15000 15500 16000 16500 17000 17500 18000 18500 19000 19500

Engine speed (rpm)

Engi

ne P

ower

(%)

Engine # 1

Engine # 3

Lap Time - Effect of power curve shape

707274767880828486889092949698

100102104

14500 15000 15500 16000 16500 17000 17500 18000 18500 19000 19500

Engine speed (rpm)

Engi

ne P

ower

(%)

Engine # 1

Engine # 2

Engine # 3

Same peak power, but 0.45’’ gap on Barcelona track

Same lap time, but gap of 27 hp

Role of firing orderRole of firing orderParameters of firing sequence :

•Crankshaft design ( sequence between each cylinder on 1 bank)

•Ve angle ( sequence between 2 cylinders on 1 Ve)

•Camshaft design ( choice between firing or scavenging TDC)

The firing order impacts :• Reliability (dynamics)

• Performance, because of :•“Free” acoustic couplings between intake ports

•Acoustic coupling between ports and plenum

Therefore, it is important to understand:•Eigen modes of the plenum

•Excitability of these modes

•Influence of these couplings on volumetric efficiency

SimulationSimulationFunctional specification:

• Being able to characterize firing order and plenum design on a whole performance curve within 1 day

• Reactive design : ability to guide new evolution designs from the analysis of 3D acoustic phenomenon

Simulation tools :• Since 2000, we have been designing and evolving a specific software “GT-Mesh”able to translate a plenum CAD into a GT-Power model. It can also help the post-treatment with 3D visualizations and animations from the gp files.

• GT-mesh allows the building of specific meshes to be used on 3D linear acoustic softwares (Plenum Eigen modes and frequency responses) or Star-CD

• Fine analysis work with Star-CD / GT-Power coupled simulations

• Plenum design DOE and optimization using morphing tools

GTGT--MeshMesh

Basic firing ordersBasic firing ordersThere are 24 « basic » firing orders divided into 2 symmetric groups of 12 Firing Orders:

Firing order 1 2 3 4 5 6 7 8 9 101 1 7 2 9 4 10 5 8 3 62 1 7 2 8 3 10 5 9 4 63 1 7 2 10 5 9 4 8 3 64 1 7 2 8 3 9 4 10 5 65 1 7 2 10 5 8 3 9 4 66 1 8 3 7 2 10 5 9 4 67 1 7 2 9 4 8 3 10 5 68 1 8 3 7 2 9 4 10 5 69 1 8 3 10 5 7 2 9 4 610 1 8 3 9 4 7 2 10 5 611 1 9 4 7 2 8 3 10 5 612 1 9 4 8 3 7 2 10 5 613 1 8 3 10 5 9 4 7 2 614 1 9 4 10 5 8 3 7 2 615 1 8 3 9 4 10 5 7 2 616 1 10 5 9 4 8 3 7 2 617 1 9 4 8 3 10 5 7 2 618 1 9 4 10 5 7 2 8 3 619 1 10 5 8 3 9 4 7 2 620 1 10 5 9 4 7 2 8 3 621 1 9 4 7 2 10 5 8 3 622 1 10 5 7 2 9 4 8 3 623 1 10 5 8 3 7 2 9 4 624 1 10 5 7 2 8 3 9 4 6

Firing Sequence

Simulated Power CurvesSimulated Power CurvesFiring order

80%

85%

90%

95%

100%

19500185001750016500155001450013500Engine Speed (rpm)

FO1FO2FO3FO4FO5FO6FO7FO8FO9FO10FO11FO12

Simulated performance indexSimulated performance indexAs expected from high speed power figures, lap time performance index shows 3 groups of firing orders.

RS25 GT-Mesh / GT-Power Simulation : performance offset with base plenum

0

0.1

0.2

0.3

0.4

0.5

0.6

18000 18250 18500 18750 19000 19250

max engine speed (rpm)

Lap

time

perf

orm

ance

inde

x ga

in (%

)

delta between FO4 and FO1

In the first group N°4 gives the best results: compared with RS24 firing order (N°1), the performance gain increases with max speed.

0A1 0A2 0A3 OA4 OA5 OA6 OA70A8

0A9OA10

OA11OA12

V

103.4103.3 103.3

103.9

101.7

101.4 101.6101.5

100.8

100.5 100.6

100.2

98.0

99.0

100.0

101.0

102.0

103.0

104.0

Perf

orm

ance

inde

x G

Tpow

er

Firing Order

V10 - RS25 : max speed = 19000 rpm

Volumetric efficiency Volumetric efficiency cylcyl. to . to cylcyl. FO4 vs. F01. FO4 vs. F01

80%

85%

90%

95%

100%

19500185001750016500155001450013500

Engine Speed (rpm)

FO1FO4

AnalysisAnalysisCorrelation between performance at high revs and number of consecutive firing neighbors on 1 bank (free acoustic couplings).

For example, FO9 (1-3-5-2-4) is the worst whereas the ideal one is FO4 (1-2-3-4-5).

High revs power = f(firing order)

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8 9 10 11 12Firing order number

Pow

er c

ateg

ory

0

1

2

3

4

Nr o

f suc

cess

ive

firin

g ne

ighb

ours

19000 rpm power category

number of successive firingneighbours on a bank

Analysis Analysis Nevertheless, the correlation is not perfect: free acoustic couplings between ports do not explain all!

For example, firing order N°12 (1-4-3-2-5) and N°1 (1-2-4-5-3) have very different performance whereas they both have 2 consecutive firing neighbors.

This is due to other acoustic couplings between ports and plenum.

AnalysisAnalysisCoupled Star-CD / GT-Power simulation allows to confirm that a port can help the volumetric efficiency of his neighbor when the later fires next

ConclusionConclusion

The simulations were confirmed on the dyno, with a good power and performance index improvement.

Therefore, despite increased external vibrations, Firing Order N°4 was adopted on the RS25, which was a little step (among many others) towards the world championship…

Thank you for your attention

Pierre-Jean Tardy