Just as aside, why do the newer LS motors run with the fuel pressure so high, ~58psi? Does this affect fuel atomization in any way? I know you can sometimes up the fuel pressure to e able to fuel high horsepower if you don't want to buy bigger fuel injectors, but that will also max out the injectors pretty quick.
Manageable? Sounds like another word for compromise to me. Jmo. 61636- increasing the pump pressure will max out the pump not necessarily the injectors. When you increase pressure to the injector you increase their output, but at the same time you decrease the output of the pump. You're right they run higher pressure for better atomization, which also allows them to run smaller injectors for better low speed fuel control. It's all about emissions.
Supremeefi said it 100% correct. Best way to imagine this is a pressure washer vs a standard hose nozzle. Something not mentioned is if you raise the fuel pressure too high you can actually stick an injector open. For obvious reasons this is bad. I believe this happens at about 80psi give or take a few. If you choose to piece together a EFI system you should pay extra attention to your injector selection. Beside the fuel flow rate you should also pay attention to high and low impedance injectors. Depending on the system you have you will need to use the correct style. There are also different nozzle patterns.
For someone like you or me there are never any issues. I can make any engine run like butter, but for the guys that don't have the knowledge or experience it becomes increasingly difficult to solve little drivability issues. For example I could haveTheone61636's car fixed up in a day, and that's time to allow for the motor to completely cool down 3 times.
actaully that doesent help the mpg that much as you think.most people have that tuned out and really dont loose any mpg. it may make it get 1 mpg better if that, helps the emissions though.
The DOD is hugely influenced by driving behavior. If you seem to get better mpg's than other's with the same vehicle, your mpg's will go up 3-5mpgs, if you seem to get dismal mpg's, then you will continue to get dismal mpgs because it'll rarely shut down the 4-cylinders. My friend has a 2008 Pontiac GPX with the DOD 5.3L. It gets the exact same mpg's as the '99 Olds Alero with the 3.4L it replaced. High 20's were pretty common, maybe into the low 30's a time or two on the highway.
