International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 04, April 2019, pp. 455–463, Article ID: IJMET_10_04_044
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=4
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
THE EFFECTS OF AIR-FUEL RATIO ON
AUTOMOBILES VIBRATIONS
Sayel M. Fayyad, Abdeslam Al-Sabagh, Fadi Alfaqs,
Nehad A. Darweesh and Ahmad S. Awad
Department of Mechanical Engineering,
Faculty of Engineering Technology, Al-Balqa Applied University
Amman – Jordan
ABSTRACT
This paper studies the effect of the change in air-fuel ratio on the engine and
automobiles vibrations. Principle of vibration analysis is used to determine the system
behavior. Air-fuel ratio is studied, as an input parameter, for stoichiometric, rich and
lean fuels. Such changes in air-fuel ratios makes the engine and so the automobile to
vibrate significantly. A benzene automobile with1800 CC - 4 cylinders engine is tested
and an accurate vibrometer is used to sense such vibrations. It is found that there is
an effect for the air-fuel mixture on the vibration of the engine and on the car as a whole.
Rich mixtures have the highest frequencies at most record time. It is theoretically expected
due to the high energy released by the combustion in which all of the oxygen is consumed.
Key words: Air-Fuel Ratio, Vibrations, Rich Mixture, Lean Mixture, engine,
Automobile. Stoichiometric.
Cite this Article: Sayel M. Fayyad, Abdeslam Al-Sabagh, Fadi Alfaqs, Nehad A.
Darweesh and Ahmad S. Awad, The Effects of Air-Fuel Ratio on Automobiles
Vibrations, International Journal of Mechanical Engineering and Technology 10(4),
2019, pp. 455–463.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=4
1. INTRODUCTION
Automobiles bad vibrations cause many difficulties to drivers and passengers comfort. The
automotive manufacturers are trying to adapt more from the directives of the competition on
the market. To meet these requirements the best, they need to find the best compromise
between the price, the operational safety, the fuel consumption, the emission limits and the
performance. The performance can be influenced by the air-fuel equivalence ratio which can
be resulted in the examination of the pollutant emission or the validation of mathematical
models. Several references describe this kind of research works based on ICEs [1]-[3].
Besides of the air-fuel ratio, the engine characteristics and operation can be influenced with
various types of fuel as well [4]. Nowadays, because of the environmental awareness,
experimentally friendly fuels are used also. In [5] an experimental study can be seen on a
direct injection diesel engine operated with Kapok methyl. An internal-combustion engine
has several physical values which can be measured and the results characterize the state of the
http://www.iaeme.com/IJMET/index.asp
455
editor@iaeme.com
The Effects of Air-Fuel Ratio on Automobiles Vibrations
engine. Vibration analysis is applied frequently as the basis of expert systems. Some of these
systems are used for condition monitoring and fault diagnosis [6]-[8]. A very interesting
research can be seen in reference [9] where the combination of the vibration and acoustic
emission was applied. Frequency-based analysis is often used in the vibration diagnostics of
ICEs. Lin et. al [10] represents a vibration diagnostic technique based on the correlation of
discrete spectrum. In reference [11] the combination of the time and frequency domain
analysis can be seen. It can be concluded from the literature that the vibration analysis of the
ICEs is quite common and the research trends are very diverse over and above the relation
between the vibration and the air-fuel ratio is not a frequently discussed topic. However, the
applied diagnostic methods are becoming more complex and the simple ones being forgotten
or will be not applied anywhere. This study will go back to the basic vibration diagnostic
methods which made us also possible to determine correlation between the numerical results
of vibration and the actual Air-Fuel equivalence ratio. The sources of noise, vibration and
harshness in a vehicle can be classified as:

Aerodynamic (e.g. wind, cooling fans of HVAC)

Mechanical (e.g. engine, driveline, tire contact patch and road surface, brakes)

Electrical (e.g. electromagnetically-excited acoustic noise and vibration coming from
electrical actuators, alternator or traction motor in electrical cars). Table 1 shows some
sources of noise in cars with its percentages [12]-[13].
Table 1: the percentage contribution of parts of automobile in total automobiles’ noise
Vibrations in engine are generated due to the reciprocating mechanism used for
converting the energy into rotary motion. The forces producing the engine vibrations are:
Combustion, Engine geometry, Air/Fuel equivalence ratio, Type of fuel, Reciprocating and
Rotational Forces. Engine noise is caused by various types of force generation within the
engine and is transmitted to the radiating outer surfaces. The transmission path properties are
determined by the vibration modes of the structure. The properties of the outer surface will
also influence the sound radiation. Number of ways in which the final sound radiation may be
influenced:
1) Reduction at the source of combustion forces and mechanical forces.
2) Reduction of the vibration transmission between the sources and the outer surface.
3) Reduction of the sound radiation of the outer surface.
2. MATERIALS AND METHODS
The main device and parts of the experiment is GM-63A type vibration meter manufactured
by BENETECH. This product adopts piezoelectric effect of artificial polarized ceramic for
http://www.iaeme.com/IJMET/index.asp
456
editor@iaeme.com
Sayel M. Fayyad, Abdeslam Al-Sabagh, Fadi Alfaqs, Nehad A. Darweesh and Ahmad S. Awad
design. It is suitable for monitoring all kinds of vibrating mechanical facility, specially the
vibration measurement of rotating and reciprocating machinery. The unit can measure
acceleration, velocity and displacement, which is widely, used in mechanical manufacture,
electric power metallurgy and general aviation etc. Figure 1 shows the device used in the
study and some of its components.
3. APPARATUSES AND PROCEDURE
The following apparatuses are used here to collect data. a. Measurement with short (S) probe
tip: this probe tip is factory default installment, adapts in wide scope vibration measurement,
and obtains good response value, as shown in Figure 1.
b. Measurement with long (L) probe tip: this probe tip is packed inside the carry box, mainly
adapts in narrow objects field, the unit will response quickly, as shown in Figure 1 below.
c. Measurement without probe tip: adapts in smooth object surface measurement to get stable
value, as shown in Figure 2.
Figure 1: Vibrometer and its probe types used in different situations to obtain the best response
http://www.iaeme.com/IJMET/index.asp
457
editor@iaeme.com
The Effects of Air-Fuel Ratio on Automobiles Vibrations
Figure 2: Data taken by scan tools
-Another device used to integrate this study that is G-SCAN 2 diagnostic scan tool powered
by GIT (Global Information Technology Co., Ltd). This device is used to give accurate
measurements of engine speed, fuel amount and injectors pulses, air amount in the intake
manifold, and every sensor feedback signal, etc. It is also used to control the mixture richness
value by making the engine run on a rich, lean or Stoichiometric mixture. This device has a
multi-task functions, two of them were used in the experiment a. Data Analysis mode: this
mode allows the user to be updated on every changing on the vehicle's sensors signals
feedback such as Engine speed and Engine temperature…etc, and also provides information
about actuators performance and pulses such as Coil charging time and Injection time… etc.
b. Resetting of mixture adaptation mode: this mode allows the user to control the Air Fuel
mixture richness either Rich, Lean or Stoichiometric, by changing the injection time and
pulses per second. The experiment will investigate the effect of Air-Fuel ratio at the vehicle's
vibrations. The experiment will investigate the following performance of: Shock absorbers,
Engine dampers and Engine Mounts. The experiment is divided into three sessions with the
same procedure, but with a different Air-Fuel mixture Richness.
http://www.iaeme.com/IJMET/index.asp
458
editor@iaeme.com
Sayel M. Fayyad, Abdeslam Al-Sabagh, Fadi Alfaqs, Nehad A. Darweesh and Ahmad S. Awad
In this study a Mercedes-Benz E-Class model 2005 car is used, with 1.8 Liters, 4-cylinder,
super charged, gasoline injected Engine, Automatic transmission, and proceeded as follows:
-Make sure that the Engine is switched OFF, and remove the Engine cover.
- Adjust the suitable probe (type L) to the vibration meter.
-The vibration meter was attached directly to the engine as in the following Figure 3.
Figure 3 Data captured by scan tools
Figure 4 Vibration meter attached directly to the engine
-Connect G-scan 2 to the Vehicle's ECU using OBD II wired connection.
-Switch on the Engine and make sure that the devices are working probably.
-Run the Engine on Stoichiometric Air-Fuel mixture using G-scan 2 at Idling (in our
experiment it is 750 RPM), and measure the acceleration and displacement.
-Apply load on the Engine (by moving the gear stick to Drive mode), and measure the
acceleration and displacement. (650 RPM)
- Fix the Engine speed at (2000, 2500, 3000 RPM) and measure the acceleration and
displacement.
-Change the running mixture to lean and rich and then repeat the procedure to measure the
acceleration and displacement.
http://www.iaeme.com/IJMET/index.asp
459
editor@iaeme.com
The Effects of Air-Fuel Ratio on Automobiles Vibrations
4. RESULTS AND DISCUSSION
The measurements were carried out on variety of Engine speeds and recorded in the following
table, so as a consequence the frequency components of the signal should have changed only
a little. Table 2 shows the change of the acceleration, displacement and the calculated
frequency with respect to the change of the Air-Fuel mixture Richness and the Engine speed.
Table 2: The change of the acceleration, displacement and the calculated frequency with respect to the
change of the Air-Fuel mixture richness and the engine speed.
The Stoichiometric mixture has the same frequency as the lean mixture at low Engine
speeds, and then the difference starts to appear at higher Engine speeds, that’s because the
Stoichiometric and the lean mixtures nearly uses the same amount of Oxygen and it's just that
the fuel amount isn't the same. At higher speeds the Stoichiometric mixture gives higher
frequencies as the large load needs a large power produced by the Engine which the lean
mixture can't do it efficiently. As a result for the experiment we can assume that the lower the
equivalence ratio (λ), and the higher the Richness of mixture, give a higher frequency and
vibrations. The trend of acceleration and frequency is the same (direct linear proportion) with
the Engine speed, while the displacement has an opposite trend, as shown in Figure 5 to 8.
Figure 5 Vibrations amplitude and acceleration as a function with engine speed at Stoichiometric mixture
http://www.iaeme.com/IJMET/index.asp
460
editor@iaeme.com
Sayel M. Fayyad, Abdeslam Al-Sabagh, Fadi Alfaqs, Nehad A. Darweesh and Ahmad S. Awad
Figure 6 Vibrations amplitude and acceleration as a function with engine speed at Lean mixture
Figure 7 Vibrations amplitude and acceleration as a function with engine speed at Rich mixture
Figure 7 Engine frequency at variable RPM and mixture type (all frequency values/10)
http://www.iaeme.com/IJMET/index.asp
461
editor@iaeme.com
The Effects of Air-Fuel Ratio on Automobiles Vibrations
It can be noticed that at low engine RPM values the rich mixture the engine has more
frequency values than that of Stoichiometric and lean mixtures and this is continued to the
2000 RPM then the values of frequencies are of equal values till 2500 RPM then the values of
frequencies return to be scattered the rich mixture has more values of frequencies (18 Hz),
and 12.8 Hz for lean mixture while it is about 15.3 for Stoichiometric.
5. CONCLUSIONS
The experimental results showed that with the increase of the air-fuel equivalence ratio of a
gas engine operating at a constant speed, the amplitudes of the measured signals and spectrum
decreased as well as their RMS values – the power content. This means that numerical results
of the basis vibration diagnostic methods are able to show correlations and trends between the
air fuel ratio and the vibration of a gasoline engine. Based on this observation it can be
concluded that the high frequency vibrations caused by the combustion may be detectable
with proper algorithms related with the amount of oxygen used in the combustion.
REFERENCES
[1]
C-W. Wu, R-H. Chen, J-Y. Pu, T-H. Lin, “The influence of air–fuel ratio on engine
performance and pollutant emission of an SI engine using ethanol–gasoline blended
fuels,” Atmospheric Environment, vol. 38(40), pp. 7093-7100, 2004
[2]
F.Y. Hagos, A.R.A. Aziz, S. A. Suleiman, “Effect of Air-fuel Ratio on Combustion
Characteristics of Syngas (H2:CO) in Direct-injection Spark-ignition Engine, “Energy
Procedia, Vol. 61, pp. 2567-2571, 2014
[3]
R. Ebrahimi, “Performance analysis of an irreversible Miller cycle with considerations of
relative air-fuel ratio and stroke length,” Applied Mathematical Modeling, vol. 36(9), pp.
4073-4079, 2012
[4]
Y. Huang, C.J. Sung, J.A. Eng, “Effects of n-butane addition on reformer gas combustion:
Implications for the potential of using reformer gas for an engine cold start,” Proceedings
of the Combustion Institute, Vol. 29(1), pp. 759-765, 2002
[5]
T.S. Kumar, P. S. Kumar, K. Annamalai, “Experimental study on the performance and
emission measures of direct injection diesel engine with Kapok methyl ester and its
blends,” Renewable Energy, vol. 74, pp. 903-99, 2015
[6]
Z. Geng, J. Chen, “Investigation into piston-slap-induced vibration for engine condition
simulation and monitoring,” Journal of Sound and Vibration, vol. 282(3-5), pp. 735-751,
2005
[7]
L. Barelli, G. Bidini, C. Buratti, R. Mariani, “Diagnosis of internal combustion engine
through vibration and acoustic pressure non-intrusive measurements,” Applied Thermail
Engineering, vol. 29(8-9), pp. 1707-1713, 2009
[8]
Z. Geng, J. Chen, J. B. Hull, “Analysis of engine vibration and design of an applicable
diagnosing approach,” Int. J. of Mechanical Sciences, vol. 45, pp. 13911410, 2003
[9]
J. D. Wu, C-Q. Chuang, “Fault diagnosis of internal combustion engines using visual dot
patterns of acoustic and vibration signals,” NDT&E International, vol. 38, pp. 605-614,
2005
[10]
H. Lin, K. Ding, “A new method for measuring engine rotational speed based on the
vibration and discrete spectrum correction technique,” Measurement, vol. 46(7), pp. 20562064, 2014
[11]
O.M. Boaghe, S.S. Bllings, L.M. Li, P.J. Fleming, J. Liu, “Time and frequency domain
identification and analysis of a gas turbine engine,” Control Engineering Practice, vol.
10(12)m pp. 1347-1356, 2002
http://www.iaeme.com/IJMET/index.asp
462
editor@iaeme.com
Sayel M. Fayyad, Abdeslam Al-Sabagh, Fadi Alfaqs, Nehad A. Darweesh and Ahmad S. Awad
[12]
S. Vulli, J.F. Dunne, R. Potenza, D. Richardson, P. King, “Time-frequency analysis of
single-point engine-block vibration measurements for multiple excitation event
identification,” Journal of Sound and Vibration, vol. 321, pp. 1129-1143, 2009
[13]
G. Gardonyi, G. Manhertz: Vibration diagnostic algorithms for studying electromotive
drive train (in Hungarian), Proceedings of 16th Spring Wind International PhD
Conference, Sopron, vol. 1, pp. 169-177, 2013
http://www.iaeme.com/IJMET/index.asp
463
editor@iaeme.com