Effect of Gasoline Fuel Additives on Combustion and Engine Performance

IM
E
P
, 
ba
r
Ignition Timing, CAD BTDC
CI-Additional Base
CI-Additional 1X

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6.3 Engine Testing 
150 
nature of the antiknock additives that could have reduced the reaction rates. CI-I 1X 
and 10X exhibited very similar behaviour throughout the investigated range. CI-
Additional at ignition advance angles of more than 55 CAD seemed to improve IMEP 
compared to base fuel. 
In-cylinder peak pressures measurements are presented in Figures 6.16 – 6.18. 
It can be seen that CI-A at neither of the treat rates affected the pressures reached, 
while both CI-I and CI-Additional reduced the measured peaks. The reductions could
Figure 6.16: Peak in-cylinder pressure at different spark retardation angles for CI-A 
Figure 6.17: Peak in-cylinder pressure at different spark retardation angles for CI-I 
25
30
35
40
45
50
55
20
25
30
35
40
45
50
55
60
65
Pre
ss
u
re,
 b
a
r
Ignition Timing, CAD BTDC
CI-A Base
CI-A 1X
CI-A 10X
25
30
35
40
45
50
55
25
30
35
40
45
50
55
60
65
70
P
re
ss
ure,
 ba
r
Ignition Timing, CAD BTDC
CI-I Base
CI-I 1X
CI-I 10X

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6.3 Engine Testing 
151 
Figure 6.18: Peak in-cylinder pressure at different spark retardation angles for CI-
Additional 
have been caused by slower pressure rises caused by ignition inhibiting properties of 
antiknock additives. This would have caused more of the combustion to occur in the 
expansion stroke where increasing volume would mean lower peak pressure. 
However, the reduced IMEP values suggest that this was not the case. 
Peak heat release rates displayed in Figures 6.19 – 6.21 seemed not to have 
been affected by the additives either. The unaffected peak pressure accompanied by 
reduced IMEP and increased KI for CI-A additive could be explained by the low