Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Figure 6.10: Knock intensity CI-A 
Figure 6.11: Knock intensity CI-I 
KI properties for CI-Additional are displayed in Figure 6.12. CI-Additional 
was found to be the more effective antiknock improver between the two tested gasoline 
additives. At 65 CAD spark, the reduction in KI was 81.1 %. An anticipated likeness 
in KI characteristics for CI-I 10X and CI-Additional 1X was observed. As seen in 
Table 6.1, CI-I at 10X treat rate was expected to produce comparable RON changes 
to CI-Additional at 1X.
0
10
20
30
40
50
60
70
80
90
100
20
30
40
50
60
70
Inte
ns
it
y
, 
%
Ignition Timing, CAD BTDC
CI-A Base
CI-A 1X
CI-A 10X
0
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50
60
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90
100
20
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Inte
ns
it
y
, 
%
Ignition Timing, CAD BTDC
CI-I Base
CI-I 1X
CI-I 10X

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6.3 Engine Testing 
148 
Figure 6.12: Knock intensity CI-Additional 
Figures 6.13 – 6.15 display the IMEP results for all the tested fuels. CI-A at 
both 1X and 10X treat rates caused a reduction in the values. A probable cause for this 
was a reduction in ignition delay. As a result of an increased presence of ignition 
promoting radicals in the air-fuel mixture, it is likely more of the combustion occurred 
in the compression stroke. Furthermore, as KI investigations demonstrated, advancing 
spark timing beyond 35 CAD BTDC caused end gases to auto-ignite at higher rate 
than the base fuel. This would have additionally increased the proportion