hey if someone happens to run across it i have one question.
okay, say i upgrade the injectors and fuel pump and get the ecu tuned. am i still going to need an FMU? is the FMU necessary or is it just a little insurance against failure?
Safe boost levels for KA-T w/ stock fuel delivery
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gingerbredman
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C-Kwik
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Talk about resurrecting a thread from the dead.
Anyways, an FMU simply allows an injector to flow more than it's rated flow as it increases the fuel pressure during boost.
A factory FPR or any 1:1 FPR simply maintains a constant relative pressure between the fuel and the manifold. In other words, if the system is set to run 43 psi of fuel pressure, then under boost, it will increase fuel pressure by the same amount as the amount of boost present at that time. Conversely, when the motor is operating under vacuum, it will decrease fuel pressure by the same amount. This maintains the same amount of pressure relative to the pressure in the intake manifold so that fuel metering remains linear at all times.
An FMU or Rising Rate Fuel pressure regulator (RRFPR) increases fuel pressure at a higher rate than a factory FPR. For an 8:1 RRFPR, when 1 psi of boost is seen, it will increase fuel pressure by 8 psi instead of one. At 2 psi, it will increase fuel pressure by 16 instead of 2. So on and so on until the fuel pump can no longer increase pressure and flow. It will not affect fuel pressure when the engine operates under vacuum. It is installed inline, after the factory FPR.
Typically, if larger injectors are used, there is no need for a RRFPR provided the injectors are able to flow an adequate amount of fuel for the application. A RRFPR can still be used with larger injectors, but I've never heard of anyone doing this as injector upgrades are more accurate and the hardware to run even larger injectors is usually already in place.
Anyways, an FMU simply allows an injector to flow more than it's rated flow as it increases the fuel pressure during boost.
A factory FPR or any 1:1 FPR simply maintains a constant relative pressure between the fuel and the manifold. In other words, if the system is set to run 43 psi of fuel pressure, then under boost, it will increase fuel pressure by the same amount as the amount of boost present at that time. Conversely, when the motor is operating under vacuum, it will decrease fuel pressure by the same amount. This maintains the same amount of pressure relative to the pressure in the intake manifold so that fuel metering remains linear at all times.
An FMU or Rising Rate Fuel pressure regulator (RRFPR) increases fuel pressure at a higher rate than a factory FPR. For an 8:1 RRFPR, when 1 psi of boost is seen, it will increase fuel pressure by 8 psi instead of one. At 2 psi, it will increase fuel pressure by 16 instead of 2. So on and so on until the fuel pump can no longer increase pressure and flow. It will not affect fuel pressure when the engine operates under vacuum. It is installed inline, after the factory FPR.
Typically, if larger injectors are used, there is no need for a RRFPR provided the injectors are able to flow an adequate amount of fuel for the application. A RRFPR can still be used with larger injectors, but I've never heard of anyone doing this as injector upgrades are more accurate and the hardware to run even larger injectors is usually already in place.
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gingerbredman
- Posts: 543
- Joined: Sat Jun 09, 2007 11:36 am
- Car: 93 SE hatch, ~260k miles on the clock, 15" Enkei 92s, still stock. 2009 Sonata bouncing on Eibachs.
Re: (C-Kwik)
cool, thanks. mucho gracias senior
When we did my car about 3.5 years ago. We had the IAP kit on it... we ha the Walbro fule pump with stock injectors ( 260cc )'s and it was giving us RICH conditions without any corrections ( safc ).. I ahve a .48 a/r 57 trim t3/t4oe turbo. When the 370cc injectors were installed, they were about 85% duty cycle at 9psi with just the walbro fuel pump and STOCK FPR. BTW, we have the same FPR as an SR20DET.
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gingerbredman
- Posts: 543
- Joined: Sat Jun 09, 2007 11:36 am
- Car: 93 SE hatch, ~260k miles on the clock, 15" Enkei 92s, still stock. 2009 Sonata bouncing on Eibachs.
Re: (GEO)
wait, so on that turbo kit you ran stock injectors with a fuel pump and it was running rich.. and then when you ran 370cc injectors, they were almost peaking out??