Maximum Injector Fuel Pressure INfo...FYI

[Turbo_Nismo_EC]

Hi, I have noticed in here a few times when people ask how much you can raise the fule pressure with an FMU on turbo N/A cars with stock, or aftermarket fuel injectors. I e-mailed Bell Engineering(as in Corky Bell) and they replied back to this answer for me. I thought some of you might find it interesting also.

Question I asked...

Hi, I recently purchased your 2025 (This is the B.E.G.I., or Cartech regulator that I asked about in another thread) regulator for my 95 Nissan HardBody turbo project and I was going through your instructions and I have a couple questions real quick.

First, I was a little nervous about using a rising rate regulator because I am afraid of one of my injectors failing under the increased load. To help relieve my mind I purchased a new set of high performance injectors from Venom(Python)Performance. Still a little worried I was reading through your instructions that came with the FMU and noticed where it says about how a 90 lb. injector can take up to 100 psi fuel pressure no problem. Does this also apply to a stock sized injector? Meaning that theoretically my injectors can handle the same abuse w/o incident? I am not sure of what my aftermarket fuel pump is capable of handling, but according to the pressure calculation in your instructions I will need approximately 90 psi fuel pressure at 6 psi boost. However I do know that this fuel pump will work because it is the same pump that is used with NSport Racing's 240sx turbo kit, that they set at 7 psi.

Answer......

"Any stock injector can take approximately 1000 psi before it can physically leak or be harmed.

The possibility exists that injectors over 100 #/hr can jam at pressures greater than 100, but no physical harm is done.

The weak point in all efi systems is the diaphragm of the stock regulator. These usually can't take much more than 150 psi.

If the fuel pressure goes up to the desired number at mid-range rpm then fades at higher revs, the pump is inadequate." (Turner)

I just thought that some of you considering running an adjustable rate regulator, or FMU, would find it interesting.

Here is the link to the installation instructions I referred to..http://www.bellengineering.net/fmu2020instruc.html

Jason

Source:Turner, Stephanie. "Re:Just a couple simple FMU/Fuel Pump/Injector Questions." [email protected]. 4/28/03

[WDRacing]

Good info...

[Sil240]

do you know what the resistance one your injectors are?and do you have a sohc?

[Turbo_Nismo_EC]

No, unfortunately I don't know if they have high resistance or not, but YES, I do have a SOHC. As a matter of fact I have some NEW Venom injectors(10% over stock flow rate for a 95(maybe other years) for a federal emission HardBody truck. MY baby got stolen today:(

[AceInhole]

Quote »The possibility exists that injectors over 100 #/hr can jam at pressures greater than 100, but no physical harm is done. [/quote] Heh.... yet they neglect to mention anything about the ability of the injector to atomize fuel correctly at higher pressures.

[Turbo_Nismo_EC]

I didn't ask them anything about the ability to atomize fuel. My question was regaurding the fuel pressure and how it affects the injector itself. I wanted to know if the injector would fail at or, or near, 100 psi, since according to my calculations I would have needed 90 psi rail pressure for my 6 psi boost.

[themadscientist]

now I find it hard to beleive that an electric solenoid that was pulling the pintle back against what 45psi? would not be adversely affected by having to do the same work against 90psi. If you have to crank up fuel pressure to twice normal to get your ratios right you are in the market for larger injectors my freind. Less stress on the injectors, the regulator and the pump.

[TomsMR2]

90psi is an obsurd pressure. buy bigger injectors.

id worry more about damaging the engine, than breaking some injectors.

[Turbo_Nismo_EC]

Yo, this was just to inform you guys what I was told. That IS EXACTLY what I was asking. I didn't want to jack my engine over an injector failure. The 90 psi is just a ball park figure that I calculated according to the Cartech/ B.E.G.I. FMU instructions..it may have taken more, or less, but that was what I was going to start with. A rising rate regulator is standard on a lot of aftermarket turbo kits, including the XS Engineering kit and the N-SPort kit for the 240sx, which means that the people who designed these kits knew of the extreme rail pressures generated by an aftermarket fuel pump and an FMU. I bet if you were to ask someone who runs one of those kits on their 240 would say that they run upwards of 80-90, or more, psi rail pressure at full boost. All I wanted to know is if the FMU would cause an injector to fail under the increased load, that is ALL. I didn't care about anything else but whether or not it would hurt the injectors, or cause them to seize, which in turn would kill my engine. The only reason I posted this thread in the first place was because I thought some of you would find it interesting that an employee of Bell Engineering, who specifically deals with the FMU, says that any stock injector can take 1000 psi fuel pressure w/o failure. I didn't know that and didn't know if you did either, so I posted it, for your information only. If you want to second guess it e-mail her, the e-mail addy is in the original post.