Fuel Pump Relay?

[Saint_]

I don't follow you, rotates inside the tank? Do you mean rotates through the pump and fuel not used is dumped back without circulating to the engine compartment?[/b]

Exactly. This is Mazda3 setup:



And in milly it rotates the whole car.

[ken inn]

Exactly. This is Mazda3 setup:



And in milly it rotates the whole car.[/b]

the loop system in the millenia has been used for many years, on every fuel injected car. however, lately, only fuel that is needed is sent to the rail. the biggest reason is heat. as fuel goes to the engine bay, and excess is returned to the tank, it transfers heat back to the fuel in the tank. this increases the vapors, and makes more emissions. less vapor, more fuel, better fuel economy. also, cooler fuel makes more power. not a whole lot, but with the high sophistication of fuel injection systems, every little bit helps. bmw started this type of system back in 2000.

[yel-low]

That certainly adds a new level of difficulty in increasing fuel pressure if you ever planned on boosting. I wonder if it is still vacuum controlled or electronic.

[SteveSter]

Ken inn is right on the money. We learned this in school. Its all about emissions now days.

[ken inn]

That certainly adds a new level of difficulty in increasing fuel pressure if you ever planned on boosting. I wonder if it is still vacuum controlled or electronic.[/b]

if you are boosting, you dont want increased fuel pressure, you want increased volume. the international standard for fuel flow is at 3 bar pressure. some idiot us manufacturers like delphi(gm-assholes) go to like 60(4bar) psi, and even higher. these are substandard injectors, and they are just upping the pressure because they cant build a good injector. fuel injectors are either saturated(on the full pulse), or peak and hold. i dont know much about saturated, they are generally for smaller loads. but i do know that peak/hold injectors have a duty cycle, and above about 90% duty cycle, the injector becomes unstable, and fuel delivery will vary. increasing fuel pressure will increase duty cycle, and it is a cheap but unreliable way to increase fuel flow. peak and hold injectors also must have a dead time, and here again, delphi has their own ideas(and they dont work) about dead time. i believe delphi is in bankruptcy. you build ****, eventually everyone finds out, and stops buying.