Calculation Basis; Road Load - MAHA POWERDYNO MSR Series Original Operating Instructions

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2.10

Calculation Basis

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2.10.1

Road Load

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Equation
P
=
Air
F
x
with
• v
ref
• v
• P
air
• P
flex
• P
Roll
• a.m
Air resistance power P-Air [kW]
The air resistance power is proportional to the surface of
the vehicle front and air resistance coefficient c
with e.g.
• Air density
• air resistance coefficient
• Front surface
• Driving speed
• Head wind speed
results:
• P = 0,5 · 1,1 · 0,38 · 2,5 · 25
air
Flex power P-Flex [kW]
Flex power or resistance is defined as the power loss
which occurs due to the flexing of the tire on the road
surface and/or roller.
Generally speaking the flex power does not have a relevant influence on the test results due to the
minimal flex resistance coefficient.
⋅ ⋅ ⋅ ⋅
2
3,6 v P 3,6 v
+
Flex
3 2
v v
ref ref
Reference speed for resistance performance values - normally 90 km/h.
Driving speed
Air resistance performance [kW]
Flex performance [kW]
Roll resistance performance [kW]
Vehicle mass
(VEH-width x Height)
⋅
P 3,6
+ + ⋅
Roll
a m
v
ref
.
w
r (rho)
c
W
A
Front
v
v
0
· 25
2
r
= ⋅ ⋅ ⋅
P 0,5 c A
Air W
= 1.1 kg/m
3
= 0.38
= 1.7 m · 1.47m =
= 90 km/h =
= 0 m/s
= 8.164 kW at 90 km/h
m
= ⋅ ⋅ ⋅
P m g v
Flex w
37
⋅ + ⋅
2
(v v ) v
Front 0
2.5 m
2
25 m/s
BA053101-en