ENERGY, ENVIRONMENT, ECOSYSTEMS, DEVELOPMENT and LANDSCAPE ARCHITECTURE
Impact of altitude on the fuel consumption of a gasoline passenger car
EFTHIMIOS ZERVAS*
Department of Environmental Engineering
Democritus University of Thrace
Vas. Sofias 12, 67100 Xanthi
GREECE
[email protected]
Abstract: - Engines of new passenger cars are tuned at the sea level. However, in several countries, a
significant part of the engine operation is performed at higher altitudes than that of the sea level. The different
air density can have a significant impact on fuel consumption. In the case of gasoline engines, the higher
altitude theoretically leads to lower fuel consumption due to lower throttle frictions due to the wider throttle
opening. From the other side, as the air is less dense at higher altitudes, the vehicle aerodynamic is changed
and this also leads to lower fuel consumption. This work studies the impact of high altitude on the fuel
consumption of a gasoline passenger car. The impact of higher altitude is studied on three regulated driving
cycles. The impact of changed vehicle aerodynamics of higher altitudes, through the change of deceleration
times, on fuel consumption is also estimated.
Key-Words: - Altitude, fuel consumption, gasoline, passenger cars
regulated driving cycles. Also, the change of
aerodynamics through the change of deceleration
times is measured here and the fuel consumption of
the higher altitude is estimated.
1 Introduction
Engines of new passenger cars are tuned to operate
with the lowest possible fuel consumption having
the same time the highest output power and torque
and respecting the regulations for exhaust emissions.
This engine tuning is usually performed at the sea
level. However, in several countries, a significant
part of the engine operation is performed at higher
altitudes than that of the sea level. This has a
significant impact on the local atmosphere quality of
many cities, as for example Mexico City which is
found at an altitude of 2200m above sea level, and
on fuel consumption. Some authors study the impact
of altitude on exhaust emissions [1, 2]; however no
work studies the impact on fuel consumption.
In the case of gasoline engines, the lower density
of air at higher altitude leads theoretically to a
decrease of fuel consumption due to the lower
negative loop of engine operation due to the
decreased frictions due to the wider throttle opening.
The case of Diesel engine is less evident.
From the other side, as the air is less dense at
higher altitudes, the vehicle aerodynamic is
changed. For this reason the deceleration times of
the vehicle increase and that have also an impact on
fuel consumption.
This work studies the impact of high altitude on
the fuel consumption of a gasoline passenger car.
The impact of higher altitude is studied on three
ISSN: 1790-5095
2 Experimental section
A Renault Clio equipped with a Euro3 gasoline
engine of 1400 cm3 was used for these tests. The
inertia of this vehicle is 2250 lbs and its SCx of
0.685.
Two kind of testes were performed for the fuel
consumption measurements: one almost at the sea
level (altitude of 70m) and one at an altitude of
2200m which is the altitude of Mexico City. A
commercial Euro3 fuels was used for these tests.
The above tests were performed on three
regulated driving cycles: the New European Driving
Cycle (NEDC) and two driving cycles from USA,
the FTP and the Highway one. Figures 1-3 show the
profiles of those driving cycles. More details about
those driving cycles can be found elsewhere [3].
The deceleration times were also measured at the
altitude of 70m, but due to technical reasons, it was
not possible to measure them at Mexico City. For
these reason, the deceleration times were measured
at an altimetric vehicle test bench, using the altitude
of 700m.
197
ISBN: 978-960-474-125-0
ENERGY, ENVIRONMENT, ECOSYSTEMS, DEVELOPMENT and LANDSCAPE ARCHITECTURE
1st part: urban (ECE): 4,052 km
140
NEDC Cycle
Max. speed = 120 km/h
Average speed = 33.6 km/h
Duration = 1 180 s
Distance = 11.007 km
120
2nd part: extra-urban (EUDC): 6,955 km
Speed (km/h)
100
80
60
Elementary urban cycle
40
20
0
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Time (s)
Fig 1. The New European Driving Cycle (NEDC).
100 Phase 1: 505 s (5,8 km)
Cold phase
Phase 2: 866 s (6,3 km)
Steady phase
Engine stop closed hood
10 ± 1 min
Phase 3: 505 s (5.8 km)
Warm phase
90
FTP 72 or LA4 cycle
Speed (km/h)
80
Cycle City or FTP 75
70
Max. speed = 91.2 km/h
Average speed = 34.2 km/h
(stop excluded)
Duration = 2 479 s
(stop included)
Distance = 17.86 km
60
50
40
30
Weighting factors:
Phase 1 : 0,43
Phase 2 : 1,00
Phase 3 : 0,57
20
10
0
0
500
1000
1500
2000
2500
Time (s)
Fig 2. The FTP driving cycle.
ISSN: 1790-5095
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ENERGY, ENVIRONMENT, ECOSYSTEMS, DEVELOPMENT and LANDSCAPE ARCHITECTURE
120
Highway Cycle
Speed (km/h)
100
80
60
Max. speed = 96.4 km/h
Average speed = 77.4 km/h
Duration = 765 s
Distance = 16.5 km
40
20
0
0
100
200
300
400
500
600
700
800
900
Time (s)
Fig3. The Highway driving cycle.
altitude on
cartography.
the
complete
engine
operation
3 Results and discussion
70m
2200m
120
3.1 Driving cycle results
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CO2 emissions (g/km)
Figure 4 shows the CO2 emissions on the three
driving cycles tested at the sea level altitude (70m)
and the altitude of 2200m, which corresponds to the
altitude of Mexico City.
Figure 4 shows that there is a gain of 3.5% in the
case of NEDC, when the vehicle is used at the
altitude of 2200m instead of the seal level altitude.
However, this trend is not confirmed from the two
US cycles. The gain on the FTP driving cycle on the
2200m comparing to the sea level altitude is lower
than that of NEDC: only 2.6%, while the Highway
driving cycle shows the opposite trend: an increase
of 6.2% of fuel consumption at the altitude of
Mexico City comparing to the sea level one.
The above results show that the impact of higher
altitude than that of sea level on fuel consumption is
not evident and there is not always a decrease of fuel
consumption according to theory. The impact of the
driving cycle used, and consequently of the driving
profile used, on fuel consumption is quite
significant. More work is necessary to clarify this
change. Our future, more detailed, work includes
tests on each engine operating point and also on
several transition points to analyze the impact of
80
40
0
NEDC
FTP Highway
Fig4. CO2 emissions on the three driving cycles
tested at the sea level altitude and at the altitude of
2200m.
3.2 Deceleration tests results
As shown before, the lower air density at higher altitude
changes aerodynamics of the vehicle and thus changes the
deceleration times. Due to technical reasons, the measure
of deceleration times was not possible at the altitude of
199
ISBN: 978-960-474-125-0
ENERGY, ENVIRONMENT, ECOSYSTEMS, DEVELOPMENT and LANDSCAPE ARCHITECTURE
NEDC on the sea level emits 126.7 g of CO2/km, while
the altitude of 700m gives an emission rate of 124.85 g of
CO2/km. This difference is about 1.5%. It is evident that
this gain will be higher a the altitude of 2200m above sea
level.
2200m above sea level. These times were measured in an
altimetric vehicle test bench at an altitude of 700m.
Figure 5 shows the deceleration times as a function of
the vehicle speed for the two altitudes of 70 and 700m
and figure 6 the difference between these times. These
figures show that there is a significant difference on
deceleration times between the two altitudes. This
difference depends on vehicle speed: it is quite small at
low speeds (less than 1%), but increases significantly
with speed to reach 6% at the speed of 120 km/h.
130
CO2 emissions (g/km)
70m
2200m
50
Deceleration time (s)
70m
700m
40
30
120
115
20
110
Altitude
Fig7. CO2 emissions on NEDC at the sea level
altitude and at the altitude of 700m for the two
different deceleration times.
10
0
0
40
80
120
4 Conclusion
Vehicle speed (km/h)
Fig5. Deceleration times at the sea level altitude and
at the altitude of 700m.
This work studies the impact of high altitude on the
fuel consumption of a gasoline passenger car. The
impact of higher altitude is studied on three
regulated driving cycles. Also, the deceleration
times are measured and the fuel consumption of the
higher altitude is estimated.
Even if there is a gain on fuel consumption of
3.5% in the case of NEDC in the case of higher
altitude, other regulated driving cycles do not show
the same tendencies. The gain on the FTP is only
2.6% on the 2200m, while the Highway driving
cycle shows the opposite trend: an increase of 6.2%
of fuel consumption. The above results show that the
impact of higher altitude is not evident and there is
not always a decrease on fuel consumption and more
work is necessary to clarify the impact of higher
altitude.
0
Diff. on the deceleration time (%)
125
-2
-4
-6
From the other hand, an altitude of 700m decreases
deceleration times of the vehicle. This decrease is a
function of speed and can reach up to 6% at the speed of
120 km/h, leading to a decrease in fuel consumption on
the NEDC of about 1.5%.
-8
0
40
80
120
Vehicle speed (km/h)
Fig6. Difference of the deceleration times between
the sea level altitude and the altitude of 700m.
References:
The deceleration times of the altitude of 700m were
used on the vehicle test bench and a new NEDC is
performed. Figure 7 shows the fuel consumption
(expressed as CO2 emissions) of the two altitudes. The
ISSN: 1790-5095
[1] Schifter I., Díaz L., López-Salinas E., Ramos F.,
Avalos S., López-Vidal G., and Castillo M.,
Estimation of Motor Vehicle Toxic Emissions in the
200
ISBN: 978-960-474-125-0
ENERGY, ENVIRONMENT, ECOSYSTEMS, DEVELOPMENT and LANDSCAPE ARCHITECTURE
Metropolitan
Area
of
Mexico
City,
Environonmental Science and Technology, 34
(17), 2000, pp 3606–3610
[2] Gamas, E.D., Diaz, L., Rodriguez, R., LópezSalinas, E., Schifter, I., Ontiveros, L., Exhaust
emissions from gasoline- and LPG-powered vehicles
operating at the altitude of Mexico City, Journal of
the Air and Waste Management Association, 49
(10), 1999, pp 1179-1189.
[3] Zervas E., Bikas G. (2008), Impact of the
driving cycle on the NOx and PM exhaust
emissions of Diesel passenger cars, Energy and
Fuels, 22 (3); 1707-1713.
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ISBN: 978-960-474-125-0