jon88se

How come nobody is using 660cc injectors on our cars? 4 of these for primaries and secondaries can be controlled by an SAFC and should provide a bit more fuel than the standard 550/720 combo everyone runs. The bigger primaries also won't max out as soon as the stock 550's will before the secondaries come on.

I run 4 660cc's on my Galant VR4 with an SAFC and I only mention it because I know several people use 4 stock FC 550cc's on their cars as bolt on upgrades meaning that 660's are available and can be used easily.

Any ideas?

YearsOfDecay

Basically because its easier to tune the SAFC if you only upgrade the secondaries.

The staging point between the primary only and secondary kick on isn't going to change with the addition of an SAFC. Therefore, adding bigger primaries is going to add more fuel before the staging point, but you are just going to have to take it out because its not needed there, its needed AFTER the staging point after you get beyond the stock boost levels. If you are needing more fuel at this point than the 550/720 combo can provide.. its time to step up to another form of fuel control that an SAFC anyway.

Also, most guys will find that they are taking fuel OUT of the curve at idle and lower RPM/boost levels. This is much easier if you leave the stock injectors in place.