[mwebb]

for best performance
and / OR
best fuel economy

the injectors must have about exactly the same flow relative to each other under the same conditions
if not
you will have some cylinders that are lean and some that are rich and
none that are operating at peak efficiency .

system mixture will be at stoich BUT individual cylinders can be way off stoich
because Mr 02 sensor does not see mixture per cylinder , but sees system mixture
when all injectors have the same exact flow , all cylinders will operate at as close to peak efficiency as is possible .

which is why you should never replace 1 injector OR mix and match injectors from various systems .
it is never ok to do that .

Originally Posted by Christ

The injectors used in D-series Civics are all basically 190cc or 240cc... that's about the only part that's going to make a difference in FE, really. Spray pattern might have an effect, but it's not going to be noticeable at the low power settings you're experiencing.



1988-'91 Civic Si/CRX Si Peak and Hold 240cc
1992-'95 Civic Saturated 240cc
1996-'00 Civic dx cx and lx Saturated 190cc
1996-'00 Civic ex/si Saturated 240cc

The problem could arise when someone puts 240cc injectors in the 190cc engines, but it's not likely that's the case here. Someone could have put 190cc injectors in your 240cc requirement, but that would only make the injector duty cycle increase to meet fuel requirements, and it wouldn't really even do that in your case, because you're never touching the max flow rate of the injectors.

In fact, I don't think you can really affect fuel economy too much by changing injectors at all, because the ECM just compensates for increased or decreased flow as much as it can. If it can't compensate to bring the mixture back into a reasonable margin, it will signal the CEL to come on, probably with an O2 sensor code.