I have purchased a 2001 Type R fuel pump under the guidance of some one saying that it supplies more fuel volume and pressure. Since I plan on modding the engine considerably, I got it because it was only$10. Will this help or not? Thanks
you size the pump for your flow needs. if you are adding a significant amount of air delivery or have increased your CR, you go to a bigger pump.
the injectors need suffient amount of priming from the fuel pump before they "spray" or atomize the fuel into the chamber. So the fuel pump delivers enough "head" or priming to the injector itself.
the injectors atomised provide flow into the chamber.
The fuel pump provides enough bulk flow to the injector and so that means you must overcome the resistance of the fuel lines, EVAP, FPR, and fuel rail.
If your injectors need a high FP to maintain enough flow, then you will need a pump that flows enough to overcome the high FP first in the lines to the injector and ensure enough flow gets to the injector (i.e. prime the injector).
So it's not a simple matter of getting both injector and pump, or injector alone, or pump alone. It depends on what you need.
I'll give you a more concrete example:
Let's say you just got your headported with new moderate spec cams and added some 11.5:1 CR pistons to your LS. You do a dyno tune and find that at 42 psi FP that your air fuel is running dangerously lean at 14.8:1 air fuel ratio in the upper rpms. Even though this is near ideal 14.7:1 stoichiometric, you are worried that when you cycle through the engine up to the redline often. It may lean out further under more stressful engine loading or unforseen circumtances and put you at risk for detonation and damage. So you want to play it safe and give yourself more of a margin of error...you want to run a little richer.
You have stock 240 cc/min injectors unfortunately.
You first crank up your Apex AFC or VAFC fuel settings in that upper rpm range by the maximum allowable (14% increase). The air fuel ratio for some reason does not richen the air fuel ratio in that area to richer than 14.5:1 air fuel.
Next, you try to richen even further by cranking up your FPR so that the FP is now 70 psi to see if you can richen the mix. You realize that this will cause the lower rpms to also richen up by the same amount and therefore you may lose a bit of power down below but you have no choice.
the flow rate on the injectors now should be equal to:
SQRT (70/42) x 240 = 310 cc/min (Prelude injectors flow at 280 cc/min at 42 psi FP!!).
that's a 29% increase in flow but you have exceeded the max limit considered safe for increasing the FP. This means the injectors are running above 90-95% duty cycle (when you look at your ECU emulator or datalog) at the upper rpms. They are getting strained. The stock fuel pump is getting strained, since it has to pump against almost a third more fuel pressure.
A buddy of yours has a second hand Walbro pump he wants to sell that flows twice as much as your stock LS fuel pump. You also hear on T-I.net that they sell aftermarket injectors that flow 310 cc/min injectors at 42 psi FP.
Do you get the 310 injectors and lower your FP back to 42 psi and keep your stock fuel pump?
Do you get the Walbro fuel pump to support the extra oomph you need to deliver flow to the 240 injectors with 70 psi FP but are running 95% duty cycle at WOT?
Or do you get both the injectors and pump and turn down the FP?