Fuel system for KAT

[raging panda]

Ok, ive been through a lot of this forum, and I can't seem to understand what exactly needs to be done to the fuel system to turbo my KA. I'm looking for the absolute basics so that I may build upon that with more information later. I understand that you must introduce more fuel to the engine due to the increase of air, but I dont understand how exactly a FPR works, or even if it is absolutely necessary. Also, the SAFC (i think thats the one), what exactly can it do for me, is there a simpler, cheaper version of it? I really just want a small amount of boost at first, I am in the process of trying to put together a turbo kit and I am just stuck on the fuel system. thanks guys.

[Structure240sx]

FPR works by restricting the amount of fuel that leaves the rail thus increasing the pressure. its not neccessary for low amounts of boost

if u are stickin to boost less than 7psi then an FMU will work for you if ur going for the basic route.

take a look at nsports kit on their website http://www.nsport.com work off of that for ur setup. and search more the answers can be found

[I am Technoman]

The fuel system for a turbo engine is the most important “system” that you need to know about. Read, read, read about how a fuel injection system works and how fuel is metered to the injectors and fuel rail. After you have a complete understanding of how a fuel injection system works. Understand that then you add boost to any engine you need to increase fuel pressure and alter and widen the injector pulse. Pulse meaning how long the injector says open and sprays fuel sprays into the cylinders. After you have this down the rest will follow.

[raging panda]

OK, well how would one go about controlling the injector pulse? Is that the purpose of the FMUs or what? So if i keep the boost down, i wont have to use a FPR?

[Structure240sx]

to control the injector pulse u would need an ecu retune or like u mentioned a SAFC or similiar fuel computer to alter the signal goin to the ECU. FMU's increase the pressure goin to the fuel injectors. try findin a copy of Corkey Bell's book Maximum Boost

[C-Kwik]

OK, well how would one go about controlling the injector pulse? Is that the purpose of the FMUs or what? So if i keep the boost down, i wont have to use a FPR?

Unless you ungrade to larger injectors or run a higher pressure fuel system, there's not much a piggy-back can do for you in terms of providing more fuel than the factory injectors can already put out. Especially at higher RPM's where the available pulsewidth get shorter.

All the FMU does is raise fuel pressure in accordance to the amount of boost in the manifold. Stock fuel pressure regulators raise ressure at a rate of one psi of fuel pressure for each psi of manifold pressure(1:1). FMU's add a larger amount of fuel pressure for ech psi of boost(i.e. 8:1 FMU will raise fuel pressure 8 psi for every psi of increase in manifold pressure). There are limitations though. FPR's work by restricting flow back to the fuel tank. And the more you restrict flow, the less flow the fuel pump is able to provide. Try to raise the pressure too high and the fuel poump will not be able to pump out the pressure needed. For this reason, they can not boost too high unless you upgrade to a pump that can handle a large restriction while still being able to flow enough fuel.

[raging panda]

Ok, at low boost, say 4-6 psi, will i need to raise the fuel pressure, or will the 1:1 that i presumably have be enough.

[Structure240sx]

people have done 4-5 psi with stock fuel system but i wouldnt. for that amount of boost i would go with an FMU and walbro 255lph high pressure fuel pump

[I am Technoman]

people have done 4-5 psi with stock fuel system but i wouldnt. for that amount of boost i would go with an FMU and walbro 255lph high pressure fuel pump

I agree...

[raging panda]

whats a good fmu that doesnt cost me a small country that would work well for the small amount of boost i am trying to run? Would a 300zx pump work well in place of the walbro?

[encasemyheart]

Also I have a quick fuel question. I plan on using 370cc injectors + FPR + walbro fuel pump for 10psi with an AFC to dyno tune. (I may go JWT just for the extra benefits though)

But anyways, will the fuel system change affect off-boost gas mileage? Just wondering, sorry to hijack the thread.

[WDRacing]

Depends of how the much the injectors are trimmed down EMH. If you get them to flow like the stock one off boost then you shouldn't notice to much of a fuel mileage problem.

[WDRacing]

Use google for a search online. just type in rising rate fuel pressure regulator, or FMU. That should get you going. I believe Summit and Jegs are selling a couple cheap models.

WD

[I am Technoman]

Use google for a search online. just type in rising rate fuel pressure regulator, or FMU. That should get you going. I believe Summit and Jegs are selling a couple cheap models.

WD

Dont go cheap on the fuel system! Go cheap on the mani or the turbo hell buy a 100 dollar intercooler but do NOT cheap out on the fuel system.....

[Structure240sx]

whats a good fmu that doesnt cost me a small country that would work well for the small amount of boost i am trying to run? Would a 300zx pump work well in place of the walbro?

u can get vortech and similar FMU's on ebay for about $100. the 300ZX fuel pump will work. i would say jsut spend a couple extra dollars to get a new walbro that comes with a kit to make the install easier

[raging panda]

Not planning on going cheap on the fuel system, just not gonna spend tons of money for the low amount of boost im planning on running.