I'm wondering how all these different fuel rails work. I noticed on my s3 fuel rail there is a regulator on it connected to vacuum source from the intake. I'm guessing that it adjusts the fuel pressure in the rail depending on the amount of vacuum/boost in the manifold so that the pressure differential between the two always stays the same? The stock rail doesn't have one of those regulators, does it just stay at a constant pressure regardless of the manifolds pressure?
yes and yes. s3 is a returnless regulator, stock is steady. aftermarket kits usually are set up as a rising rate as well, although some cars seem to do better at a static pressure, it all depends on the car.
So does stage 3 always have a 75 psi differential? From idle to on boost? And the stock always has what like a 58 psi static pressure? Is that what you call an s3 rail a rising rate fuel rail? And stock is a steady rate fuel rail?
no matter what the car a big turbo setup will do better with a rising rate system. although the stock is a steady state regulator pressures will fall in the higher rpms if you are running bigger injectors. if you are running the s3 fuel pump and you turn the boost up a considerable amount one of two things will happen, the pump will fail altogether trying to keep up with the pressure, or the pump will not be able to keep up with the pressure to begin with and you will run lean. if you are shooting for big numbers the best bet is to go with a walbro/aftermarket FPR setup.
i think its the only thing i don't like about the srt, the returnless system.. i know they are considered 'better' but not for tuning/modding im still a little unclear on the S3 regulator.. is it also static, just adjusted to a higher pressure? im guessing it is, since its still a returnless system.
