This may sound stupid but depending on which lb injectors you have, that controls how much fuel is injected along with the ecm/maf. So if you have an adjustable fuel pressure regulator, wouldn't you just have it opened max all the time? What would be the point of closing the regulator if the flow is controlled by the injectors/ecm/maf? I know there's a rookie answer here I'm just not thinkin of it.
Stupid Question but I don't get it.
- Thread starter WhiskeyGN
- Start date
Welcome!
By registering with us, you'll be able to discuss, share and private message with other members of our community.
Fuel flows in a loop in these kinds of systems. The fuel pump generally is flowing the same high volume all the time (unless the voltage is ramped). There really isn't anything to hold the "extra" capactity of fuel when the demand is low, so the regulator flows the extra fuel back to the tank.
I've often wondered why the regulator isn't set to a steady 60 PSI and it just stays there instead of ramping with boost. The only thing I can guess is that idle pulsewidth of the injectors couldn't be made short enough to allow the right amount of fuel into the cylinders.
- Joined
- Aug 1, 2003
- Messages
- 9,828
fuel base pressure at 0psi is approx 45psi fuel pressure
why because injectors are rated for their flow at 45psi FP
at 45 psi FP its a known flow for the injector
if you run x psi boost and dont increase the base fuel pressure the boost pressure would push from the manifold on the injector tip and less fuel would flow out
if you ran 45 psi of boost the and fuel pressure remained at base of 45psifp then when the injector opened no fuel would flow
with a 1-1 fuel regulator as the boost rises the fuel pressure rises so that the injector flow remains constant and predictable
that allows the chip maker and the ecm to be able to control fuel flow using pulse width (the duty cycle) to the motor with less error
why because injectors are rated for their flow at 45psi FP
at 45 psi FP its a known flow for the injector
if you run x psi boost and dont increase the base fuel pressure the boost pressure would push from the manifold on the injector tip and less fuel would flow out
if you ran 45 psi of boost the and fuel pressure remained at base of 45psifp then when the injector opened no fuel would flow
with a 1-1 fuel regulator as the boost rises the fuel pressure rises so that the injector flow remains constant and predictable
that allows the chip maker and the ecm to be able to control fuel flow using pulse width (the duty cycle) to the motor with less error
turbodave231
Moderator
- Joined
- May 24, 2001
- Messages
- 2,301
As Pacecarta said, our engines vary fuel pressure based on engine load to allow the injectors to deliver enough fuel at all engine loads. This requires more hardware: Fuel regulator on the rail, vacuum plumbing to the regulator, a fuel return line (more expensive parts and more fuel connections).
Most of the current generation of engines run a set fuel pressure and have no return line. The pressure regulator is in the tank with the pump. Fuel pressure never changes even when under boost. How do they get away with this? Well, they start with an injector that is large enough to deliver the necessary fuel flow at WOT/Max Boost. They control injector on-time (pulse width) very carefully at low loads to keep the Air/Fuel correct. The modern returnless fuel system simplifies the parts required, reduces the number of connections and costs less.
Two different strategies to accomplish the same goal.
Most of the current generation of engines run a set fuel pressure and have no return line. The pressure regulator is in the tank with the pump. Fuel pressure never changes even when under boost. How do they get away with this? Well, they start with an injector that is large enough to deliver the necessary fuel flow at WOT/Max Boost. They control injector on-time (pulse width) very carefully at low loads to keep the Air/Fuel correct. The modern returnless fuel system simplifies the parts required, reduces the number of connections and costs less.
Two different strategies to accomplish the same goal.
Well this AFP Regulator I have http://www.summitracing.com/parts/HLY-512-503-5. So what your saying is then I'd end up having to running a vaccuum line to it (from where to where?) and I thought mine already had a fuel return line? Unless your saying I'd need a secondary one. This is maybe, again, another novice observation but on my buddies old 5.0 foxbody he adjusted his pressure with an allen key on his AFP Regulator. I'm assuming this is a different set up??
turbodave231
Moderator
- Joined
- May 24, 2001
- Messages
- 2,301
If you have that part installed, you should already have manifold pressure/vacuum plumbed to it. The return line attaches to the regulator. You don't need anything extra at this point. You will need a pressure gauge to attach to the fuel rail schraeder valve. With the vacuum source disconnected and the pump running, set your rail pressure to 43 psi. when you hook up the vacuum, you will see the fuel pressure drop......totally normal. That is just one way this engine management system adjusts fuel delivery for varying engine load.
Clear?
Clear?
HelloBozos
A Bozo in Buick
- Joined
- Feb 9, 2011
- Messages
- 1,047
Go out to your motor,look at the driver side fuel rail,at the front on top is the fuel regulator ,the regulator has a vacume line running to it from metal vacumelines on top the throttle body. Now look at the other side the fuel rail, at the front,thats your return line. you need varing fuel pressure so you dont blow an inj. out or at WOT suck the fuel rail dry. Your going to need some kind of fuel pressure gauge ,they make small ones that fit on the end the drivers side rail. set the Reg. with alen wrentch with the vacume line Off!
Enjoy!
