ORIGINAL PAPER

Study and the effects of ignition timing on gasoline engineperformance and emissions

J. Zareei & A. H. Kakaee

Received: 1 November 2011 /Accepted: 31 March 2013 /Published online: 25 April 2013# The Author(s) 2013. This article is published with open access at SpringerLink.com

AbstractIntroduction Ignition timing, in a spark ignition engine, isthe process of setting the time that an ignition will occur inthe combustion chamber (during the compression stroke)relative to piston position and crankshaft angular velocity.Setting the correct ignition timing is crucial in the perfor-mance and exhaust emissions of an engine.The objective ofthe present work is to evaluate whether variable ignitiontiming can be effect on exhaust emission and engine perfor-mance of an SI engine.Method For achieving this goal, at a speed of 3400 rpm,the ignition timing has been changed in the range of41° BTDC to 10° ATDC and for optimize operation,ignition timing has been designed at wide-open throttleand at last, the performance characteristics such as pow-er, torque, BMEP, volumetric efficiency and emissionsare obtained and discussed.Results The results show optimal power and torque isachieved at 31°CA before top dead centre and volumetricefficiency, BMEP have increased with rising ignitiontiming. O2, CO2, CO has been almost constant, but HC withadvance of ignition timing increased and the lowest amountNOx is obtained at 10 BTDC.Conclusions In conclusion, it obtained that ignition timingcan be used as an alternative way for predicting the perfor-mance of internal combustion engines. Also engine speedand throttle position were all found to significantly influenceperformance in this engine.

Keywords Ignition timing . Performance . Emission . Sparkignition engine

1 Introduction

The performance of spark ignition engines is a function ofmany factors. One of the most important ones is ignitiontiming. Also it is one of the most important parameters foroptimizing efficiency and emissions, permitting combustionengines to conform to future emission targets and standards[1]. Since the advent of Otto’s first four stroke engine, thedevelopment of the spark ignition engine has achieved ahigh level of success. In the early years, increasing enginepower and engine working reliability were the principalaims for engine designers. In recent years, however, ignitiontiming has brought increased attention to development ofadvanced SI engines for maximizing performance [2, 3].

Chan and Zhu worked on modeling of in-cylinder ther-modynamics under high values of ignition retard, in partic-ular the effect of spark retard on cylinder pressuredistribution. In- cylinder gas temperature and trapped massunder varying spark timing conditions were also calculated[4]. Soylu and Gerpen developed a two zone thermodynam-ic model to investigate the effects of ignition timing, fuelcomposition, and equivalence ratio on the burning rate andcylinder pressure for a natural gas engine [5]. Burning rateanalysis was carried out to determine the flame initiationperiod and the flame propagation period at different engineoperating conditions [5].

A zero-dimensional thermodynamic cycle model withtwo zone burnt/unburned combustion model, mainly basedon Ferguson’s and Krikpatrick work [6], was developed topredict the cylinder pressure, work done, heat release, en-thalpy of exhaust gas, and so forth. The zero-dimensionalmodel is based on the first law of thermodynamics in whichan empirical relationship between the fuel burning rate andcrank angle position is established.

Now a day sustaining a clean environment has become animportant issue in an industrialized society. The air pollutioncaused by automobiles and motorcycles is an important

J. Zareei (*) :A. H. KakaeeDepartment of Automotive, Iran University of Science andTechnology, Tehran, Irane-mail: ja_zareei@iust.ac.ir

Eur. Transp. Res. Rev. (2013) 5:109–116DOI 10.1007/s12544-013-0099-8

environmental problem to be solved. For this purpose, find-ing new alternative energy sources in place of petroleum ininternal combustion engines is becoming a necessity morethan ever.

2 Test engine

Facilities to monitor and control engine variables (such as:engine speed, engine load, water and lube oil temperatures,fuel and air flows etc.) are installed on a fully automated testbed, experimental standard SI engine, located at the IranKhodro Company Laboratory. The first set of performancedata was taken varying timing angle, the intake manifoldpressure was 100Kpa and equivalence was held at unity.The specifications of the test engine are given in Table 1.

The engine is mounted on a fully automated test bed andcoupled to a Schenck W130 eddy current dynamometer,having load absorbing and motoring capabilities. There isone electric sensor for speed and one for load, with thesesignals fed to indicators on the control panel and to thecontroller. Via knobs on the control panel, the operator canset the dynamometer to control speed or load. There is also acapability of setting the ignition timing from a switch on thecontrol panel. The coolant and lube oil circulation isachieved by electrically driven pumps, with the temperaturecontrolled by water fed heat exchangers. Heaters are used tomaintain the oil and coolant temperatures during warm upand light load conditions. Figure 1 is the control panel andtest engine on dynamometer.

3 Method

3.1 Exhuastgas analisis aparatus

The exhaust gas analysis apparatus consists of a series ofanalyzers for measuring soot, NOx, CO and total unburned

Hydrocarbons (HC). The smoke (soot) level in the ex-haust gas was measured with an ‘AVL Di Gas’ thereadings of which are provided as Hart ridge units (%opacity) or equivalent smoke (soot) density (milligramsof soot per cubic meter of exhaust gases). The nitrogenoxides concentration in ppm (parts per million, by vol-ume) in the exhaust was measured with a ‘Signal’Series-4000 analyzer and was fitted with a thermostati-cally controlled heated line.

3.2 Experimental errors

No physical quantity can be measured with perfect certainty;there are always errors in any measurement. This means thatif we measure some quantity and, then, repeat the measure-ment, we will almost certainly measure a different value thesecond time.

However, as we take greater care in our measurementsand apply ever more refined experimental methods, we canreduce the errors and, thereby, gain greater confidence thatour measurements approximate ever more closely the truevalue [7].

3.2.1 Combining errors in calculations

When several measurements are taken and combined informulas, the resultant error will be a combination of indi-vidual errors. Although errors may cancel, we must calcu-late the maximum possible error assuming that errors areadditive [8, 9].

First convert absolute errors to % errors, The maxi-mum possible error is determined by adding the %

Table 1 Engine specifications

Engine type TU3A

Number of strokes 4

Number of cylinders 4

Cylinder diameter (mm) 75

Stroke (mm) 77

Compression ratio 10.5:1

Maximum power (kW) 50

Maximum Torque (NM) 160

Maximum speed (rpm) 6500

Displacement (cc) 1360

Fuel 97-octane

Fig. 1 Control panel and test engine on dynamometer

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errors together, If a reading is raised to a power in acalculation, then the % error for that part is the powertimes the % error. Generally, errors can be divided intotwo broad and rough but useful classes: systematic andrandom.

Systematic errors are errors which tend to shift all mea-surements in a systematic way so their mean value isdisplaced. This may be due to such things as incorrectcalibration of equipment, consistently improper use ofequipment or failure to properly account for some effect[10].

Sources of systematic errors are external effectswhich can change the results of the experiment, butfor which the corrections are not well known. In sci-ence, the reasons why several independent confirmationsof experimental results are often required (especiallyusing different techniques) is because different apparatusat different places may be affected by different system-

atic effects. So should be considered errors of apparatusbefore testing.

3.2.2 Calculation combined error

Rate of probable error in each means obtain from combina-tion errors of each part. Assuming M is u1, u2, …un inde-pendent variable n function of quantity [11, 12]

f u1 �Δu1; u2 �Δu2; …; un �Δunð Þ ¼ f u1; u2; …; unð ÞþΔu1

∂ f∂u1

þΔu2∂ f∂u2

þ…þΔun∂ f∂un

þ 1

2Δu!ð Þ2 ∂

2 f

∂u1þ…

� �þ…

ð1Þ

M ¼ f u1; u2; u3; …ð Þ ð2ÞProbably error

σM ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi∂ f∂u1

σu1

� �2

þ ∂ f∂u2

σu2

� �2

þ…þ ∂ f∂un

σun

� �2s

ð3ÞProbably error in the measurements obtained

prob x−1:96σffiffiffin

p ≤S≤xþ 1:96σffiffiffin

p� �

¼ 0:95 ð4Þ

Probable error of each measurement

S ¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiXni¼1

x−xi� �2

n−1

vuuutð5Þ

Average amount of probable error with 99 % confidence

q ¼ � 2:54Sffiffiffin

p ð6Þ

Table 2 Accuracy of measurements and uncertainty of computedresults

Measurements Accuracy

Soot density ±1 mg/m3

NOx ±5 ppm

CO ±3 ppm

HC ±2 ppm

Time ±0.5 %

Speed ±2 rpm

Torque ±0.1 N m

Computed results Uncertainty

Fuel volumetric rate ±1 %

Power ±1 %

Specific fuel consumption ±1.5 %

Efficiency ±1.5 %

Fig. 2 The relation betweenIMEP & BMEP and ignitiontiming- Wide open throttle;Equivalence ration of one

Eur. Transp. Res. Rev. (2013) 5:109–116 111

Average amount of probable error with 95 % confidence

q ¼ � 1:96Sffiffiffin

p ð7Þ

Once there are some experimental measurements, theyusually combine according to some formula to arrive at adesired quantity. To find the estimated error for a calculatedresult one must know how to combine the errors in the inputquantities. The simplest procedure would be to add the errors.This would be a conservative assumption, but it overestimatesthe uncertainty in the result. Clearly, if the errors in the inputsare random, they will cancel each other at least some of thetime. If the errors in the measured quantities are random and ifthey are independent can be obtained from a few simpleformulas. In this research, average amount of probable errorwith 99 % confidence have obtained.

3.2.3 Condition and parameters tested-experimentalprocedure

The series of tests are conducted using variation of ignitiontiming with the engine working at a speed of 3400 rpm at a

ignition timing (advance) of 41 crank angle before TDC andat full load. Owing to the differences among the calorificvalues and oxygen content of the fuels tested, the compar-ison must be effected at the same engine brake mean effec-tive pressure, i.e. load, and not at air/fuel ratio. in this alsotests are considered accuracy of measurements and the be-low table shoes accuracy of measurements and uncertaintyof computed results.

In each test, volumetric fuel consumption, exhaust smok-iness and exhaust regulated gas emissions, such as NitrogenOxides (NOx), Carbon monoxide (CO) and total unburnedHydrocarbons (HC), are measured. From the first measure-ment, specific fuel consumption and brake thermal efficien-cy are computed using the sample density and lowercalorific value. Table 2 shows the accuracy of the measure-ments and the uncertainty of the computed results of thevarious parameters.

4 Results and discussion

The first adjust of performance data was taken varyingthrottle position. By changing the Position of the throttle,

Fig. 3 The relationshipbetween exhaust temperatureand In cylinder peak pressureversus ignition timing-wideopen throttle; equivalenceration of one

Fig. 4 The relationshipbetween BMEP and ignitiontiming. Engine speed of 3400RPM, intake manifold pressureof 100 kPa

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the intake manifold pressure was varied to 100 kPa- onposition wide-open throttle. Speed was held at 3400 RPMand equivalence ratio was held at unity.

The results show that Brake Mean Effective Pressure(BMEP) tends to increase with ignition timing till 31°Before Top Dead Centre (BTDC) and then drop off.Best performance will be achieved when he greatestignition 31° BTDC. If ignition timing isn’t advanceenough, original portion of the maximum pressure willcreative in the expand stroke and in this case we loseuseful efficiency and decreasing performance.

The maximum BMEP is at an ignition timing31°BTDC minimum advance for Maximum BrakeTorque (MBT) is defined as the smallest advance thatachieves 99 % of the maximum power.

It should be noted that MBT will vary with boththrottle position and engine speed under more throttlecondition; the density of charge in the cylinder in lessdense mixtures, a not very large ignition timing advancewill be required. In this case ignition occurs and gives asuitable performance (Fig. 2).

The above figure shows that Indicated Mean EffectivePressure (IMEP) tends to increase with ignition timing ad-vance between 21 and 41° BTDC. It is expected that IMEPshould increase with timing angle advance to a point, and thendrop off. Best performance will be achieved when the greatestportion of the combustion takes place near top dead center. Ifthe ignition timing is not advanced enough, the piston willalready be moving down when much of the combustion takesplace. In this case we lose the ability to expand this portion ofthe gas through the full range, decreasing performance. If theignition timing is too advanced, too much of the gas will burnwhile the piston is still rising. The work that must be done tocompress this gas will decrease the net work produced. Thesecompeting effects cause there to be a maximum in the IMEPas a function of ignition timing advance.

As is evident in Fig. 3 the peak pressure increases withincreasing ignition timing before top dead center. Maximumpressure would be reached if all of gas were burned by thetime the piston reached TDC. But pressure decreases with lessadvanced ignition timing because; gas doesn’t burn complete-ly until the piston is on its way down on the expansion stroke.

Fig. 5 The relationshipbetween BSFC and ignitiontiming at 3400 RPM andequivalence ratio of unity

Fig. 6 The relationshipbetween O2 and HCconcentration versus ignitiontiming at 3400 RPM and intakemanifold pressure of 100 kPa

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The Above figure also shows that the exhaust tempera-ture decrease with close to TDC and ATDC. IMEP repre-sents the work done on the piston. The exhaust gastemperature represents the enthalpy of the exhaust gas forideal gases. The enthalpy is a function of temperature onlyand energy released by combustion of fuel must go intoexpansion work. The temperatures of the exhaust gas alsodecrease if energy is to be conserved (Fig. 4).

The results show that BMEP increased with ignitiontiming advance. This expected that BMEP decrease withclosing ignition time to top dead center. If the ignition isnot advanced enough, the piston will already be movingdown when much of the combustion take place. In this casewe lose the ability to expend this portion of the gas anddecreasing performance. If the ignition is too advance, muchportion of gas will burn while the piston is still rising; thework that must be done to compress this gas will decreasethe net work produced. Also, results show that maximumBMEP is between −21° to 41° and the date has a maximumBMEP at ignition timing at 31°BTDC.

Figure 5 Shows that Brake Specific Fuel Consumption(BSFC) tend to improve with increase of ignition timing

before top dead centre. It should be noted that when BMEPincrease, BSFC follows inversely.

Figure 6 shows O2 and HC concentration as a function oftiming angle. Advance timing angle causes higher in cylin-der peak pressure. This higher pressure pushes more of thefuel- air mixture into crevices (most significantly the spacebetween the piston crown and cylinder walls) where theflame is quenched and mixture is left unburned. Additionally,the temperature late in the cycle, when the mixture comes out ofthese crevices, is lower atmore advance ignition timing. The latertemperature means that the hydrocarbons and oxygen do notreact. This increase the concentration of oxygen in the exhaustand unburned hydrocarbons.

In above figure carbon monoxide, oxygen and carbondioxide concentration change very little with ignition timingin the range studied (Fig. 7).

In here, the equivalence ratio was held constant and at ratioof unity, so there was enough oxygen to react most of carbonto CO2. CO concentration increased and CO2 concentrationdecreased when there isn’t enough oxygen. Some carbonmonoxide does appear in the exhaust due to frozen equilibri-um concentration of CO, O2 and CO2.

Fig. 7 The relationshipbetween O2, CO and HCconcentration versus ignitiontiming intake manifold pressureof 100 kPa and equivalenceratio of unity

Fig. 8 The relationshipbetween NO concentrationsversus ignition timing. Enginespeed at 3400 RPM and intakemanifold pressure of 100 kPa

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Figure shows NO concentration in the exhaust gas versusignition timing. NO formation is function of temperature.With advancing the ignition timing, the in- cylinder peakpressure increase. The ideal gas law tells that increase inpeak pressure must correspond to an increase in peak tem-perature, and higher temperature causes the NO concentra-tion to be higher (Fig. 8).

The results show that power tends to increase with sparkadvance between 17 and 35°CA BTDC. It is expected thatpower should increase with spark advance to a point, andthen drop off. Best performance will be achieved when thegreatest portion of the combustion takes place near top deadcentre. If the spark is not advanced enough, the piston willalready be moving down when much of the combustiontakes place. In this case, we lose the ability to expand thisportion of the gas through the full range, decreasing perfor-mance. If ignition is too advanced, too much of the gas willburn while the piston is still rising. As a result, the work thatmust be done to compress this gas will decrease the network produced. These competing effects cause there to be amaximum in the power as a function of spark advance.

Also it shows that the torque increases with increasingignition advance. This is due to increasing pressure in thecompression stroke and consequently more net work isproduced. It is necessary to mention that by further increasein spark advance, torque will not rise largely due to in-cylinder peak pressure during compression period and adecrease of pressure in expansion stroke. For this reason,determining the optimum ignition timing is one of the mostimportant characteristics for an SI engine (Fig. 9).

Figure 10 presents the predicted results of thermal effi-ciency in comparison with experimental data. Thermal effi-ciency is work-out divided by energy-in. It can be seen thatthe net work increases with rising ignition advance to apoint, and then reduces slightly. This is due to increasingfriction at high values of ignition advance and thereforereducing net work. According to Fig. 6, the highest amountof the net work occurs at 31°CA BTDC.

5 Conclusion

The aim of this paper was effects of ignition timing of aspark- ignition engine using different initial timing andengine speeds on engine performance by experimental.The overall results show that ignition timing can be usedas an alternative way for predicting the performance ofinternal combustion engines. In this paper, the best resultswere obtained at 31°BTDC for 3400RPM. Also enginespeed and throttle position were all found to significantlyinfluence performance in this engine. Volumetric efficiency,BMEP have increased with rising ignition timing. HC withadvance of ignition timing increased, O2, CO2, CO has beenalmost constant and the lowest amount NOx is obtained at10°BTDC. For future work, it recommended ignition timingand valve timing be controlled together and change throttleposition in different speeds.

70

75

80

85

90

95

100

105

110

115

120

20

25

30

35

40

45

50

-50 -40 -30 -20 -10 0 10 20

To

rqu

e(N

m)

Po

wer

(Kw

)Ignition timing(BTDC)

Power

Torque

Fig. 9 The relationshipbetween power and torqueversus ignition timing

46

48

50

52

54

56

58

60

62

-50 -40 -30 -20 -10 0 10 20

Eff

icie

ncy

(%)

Ignition Timing(BTDC)

Fig. 10 The relationship between efficiency versus ignition timing

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References

1. Golcu M, Sekmen Y, Salman MS (2005) Artificial neural-networkbased modeling of variable valve-timing in a spark-ignition engine.Applied Energy 81:187–197

2. Chan SH, Zhu J (2001) Modeling. Int J Therm Sci 40(1):94–103

3. Soylu S, Van Gerpen J (2004) Development of empirically basedburning rate sub-models for a natural gas engine. Energy ConversManage 45(no. 4):467–481. doi:10.1016/S0196-8904(03)00164-X

4. Chan SH, Zhu J (2001) Modeling of engine in-cylinder thermody-namics under high values of ignition retard. Int J Therm Sci40(1):94–103

5. Soylu S, Van Gerpen J (2004) Development of empirically basedburning rate sub-models for a natural gas engine. Energy ConversManage 45(4):467–481

6. Ferguson CR, Krikpatrick AT (2001) Internal combustion engines-Applied thermo sciences. Wiley, New York

7. Choia GH, Chungb YJ, Hanc SB (2005) Performance and emis-sions characteristics of a hydrogen enriched LPG internal combus-tion engine at 1400 rpm. Int J Hydrogen Energy 30:77–82

8. Teter WD (2007) Instruments and Controls Professor, Departmentof Civil Engineering, College of Engineering, University of Dela-ware. Section 16

9. UKAS publication M 3003 (1997) The expression of uncertaintyand confidence in measurement Edition 1, December

10. Harrison MD (2011) Error analysis in experimental physical science11. Taylor JR (1997) An introduction to error analysis: the study of

uncertainties in physical measurements, 2nd Edition, UniversityScience Books

12. Bevington PR, Robinson DK (1992) Data reduction and erroranalysis forthe physical sciences, 2nd Edition, WCB/McGraw-Hill

116 Eur. Transp. Res. Rev. (2013) 5:109–116