Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Figure 6.24: CO emissions CI-Additional 
an optimum volumetric fraction of additive exists above which condensation processes 
occur, although, no published data on non-metallic compounds on the matter could be 
found. 
Emissions analysis for antiknock additives suggested a more complete 
combustion compared to base fuels. The CO levels reduced while increased CO
2
levels 
were experienced. Also, an increase in NO
x
emissions was observed. Although 
typically this could be explained by higher in cylinder pressures, as seen from Figures 
6.17 and 6.18, this was not the case in present study.
Figure 6.25: CO
2
 emissions CI-A 
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
20
30
40
50
60
70
80
CO
 Co
ncent
ra
tio
n, 
%
Ignition Timing, CAD BTDC
CI-Additional Base
CI-Additional1X
12.0
12.2
12.4
12.6
12.8
13.0
13.2
13.4
13.6
13.8
14.0
20
30
40
50
60
70
CO
2
Co
ncent
ra
tio
n, 
%
Ignition Timing, CAD BTDC
CI-A Base
CI-A 1X
CI-A 10X

---

6.3 Engine Testing 
155 
Figure 6.26: CO
2
 emissions CI-I 
Figure 6.27: CO
2
 emissions CI-Additional 
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
20
30
40
50
60
70
80
CO
2
Co
ncent
ra
tio
n, 
%
Ignition Timing, CAD BTDC
CI-I Base
CI-I 1X
CI-I 10X
13.0
13.2
13.4
13.6
13.8
14.0
14.2
14.4
14.6
14.8
15.0
20
30
40
50
60
70
80
CO
2
Co
ncent
ra
tio
n, 
%
Ignition Timing, CAD BTDC
CI-Additional Base
CI-Additional1X

---

6.3 Engine Testing 
156 
Figure 6.28: NO
x
 emissions CI-A 
Figure 6.29: NO
x
 emissions CI-I 
500
700
900
1,100
1,300
1,500
1,700
1,900
20
30
40
50
60
70
NO
x
 Co
ncent
ra
tio
n, 
pp
m
Ignition Timing, CAD BTDC
CI-A Base
CI-A 1X
CI-A 10X
1,500
2,000
2,500
3,000
3,500
4,000
25
35
45
55
65
75
NO
x
 Co
ncent
ra
tio
n, 
pp
m
Ignition Timing, CAD BTDC
CI-I Base
CI-I 1X
CI-I 10X

---

6.3 Engine Testing 
157 
Figure 6.30: NO
x
 emissions CI-Additional 
Figures 6.31 – 6.33 show the relationship between the time to reach peak HRR and 
ignition timing and in Figures 6.34 – 6.36 the relationship between the time to reach 
peak pressure and ignition timing is displayed. For CI-A additive at either 1X or 10X 
concentration, no noticeable change could be seen in the time to reach peak pressure 
or HRR. Although the peak pressure and HRR during knocking conditions were likely 
to be higher than non-knocking combustion, each combustion event was processed 
with a low-pass filter set below the cylinder natural frequency, thus, excluding the 
knocking behaviour from further analysis.
Figure 6.31: Time of peak HRR CI-A 
1,500
2,000
2,500
3,000
3,500
4,000
25
35
45
55
65
75
NO
x
 Co
ncent
ra
tio
n, 
pp
m
Ignition Timing, CAD BTDC
CI-Additional Base
CI-Additional1X
330
340
350
360
370
380
390
20
30
40
50
60
70
80
T
im
e 
o
f 
P
ea
k
 H
RR,
 CAD
Ignition Timing, CAD BTDC
CI-A Base
CI-A 1X
CI-A 10X

---

6.3 Engine Testing 
158 
Figure 6.32: Time of peak HRR CI-I 
Figure 6.33: Time of Peak HRR CI-Additional 
Figures 6.32 – 6.35 display the time of peak HRR and pressure with CI-I 
additive. At 1X and 10X similar characteristics could be observed and on average 
compared to the base fuel, the peak HRR and pressure were delayed by 1.3 CAD and 
1.4 CAD, respectively. Savaranan and Nagarajan [262] explain that longer residency 
of high temperature gases in the cylinder could explain increased NO
x
emissions. 
Furthermore, Sayin [263] found increased ignition delay to enable better air-fuel 
mixing that would result in reduced CO emissions. 
330
340
350
360
370
380
390
20
30
40
50
60
70
80
T
im
e 
o
f 
P
ea
k
 H
RR,
 CAD
Ignition Timing, CAD BTDC
CI-I Base
CI-I 1X
CI-I 10X
330
340
350
360
370
380
390
20
30
40
50
60
70
80
T
im
e 
o
f 
P
ea
k
 H
RR,
 CAD
Ignition Timing, CAD BTDC
CI-Additional Base
CI-Additional 1X

---

6.3 Engine Testing 
159 
Figure 6.34: Time of peak pressure CI-A 
Figure 6.35: Time of peak pressure CI-I 
Similar explanation could be used to explain the emissions from CI-Additional 
bearing gasoline, although as seen in Figures 6.33 and 6.36, the delays in reaching 
peak HRR and pressure compared to base fuel are shorter than for CI-I additive 
bearing fuel, at 0.5 CAD and 0.93 CAD on average, respectively. Similar magnitude 
percentage changes to the timings of peak pressure and HRR between the anti-knock 
additive bearing fuels and the base fuel also apply for CO, CO
2
and NO
x
emission 
characteristics.
 
360
365
370
375
380
385
390
395
20
30
40
50
60
70