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Stock FPR and Fuel Management

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  • Stock FPR and Fuel Management

    Just wanted to know what you guys are doing to modify the duty cycle of the injectors without modifying the stock ECU. A very old write up talks about crushing the FPR, but that's not something I want to do since I can't un-crush the FPR. Cartech used to sell a billet FMU, but I think it's discontinued like most Z31 performance parts. Has anyone tried a SARD adjustable fuel pressure regulator?

  • #2
    I've had bad luck with adjustable FPRs for daily driving (versus going for big power) my Z, which is a mild-but-Nistuned VG33ET. I tried an AEM and an Aeromotive. I was only trying for a little over 40 PSI and was unable to get a setup which would give me a good idle without running stupid rich the rest of the time. If I set the AFPRs up for 42-ish PSI at zero vac, at idle they'd be sending 22 PSI and the car would be banging and staggering and leaning out. And for standard highway driving the AFRs would drop to 9.8 as soon as I got into any boost. Plus the AEM shit the bed inside 2000 miles, and, like a lot of adjustable FPRs, they don't hold pressure once the fuel pump shuts off. I screwed around with resizing the injectors in Nistune but that opens up new cans of worms, and I'd rather drive the car as is this summer and fuck around with it next winter. I would say if you need to go past the stock FPR, you should probably be getting into Nistune and a wideband as well. Just my experience.

    edit: I just went back to the stock FPR for the rest of the summer for drivability's sake.
    Last edited by FrozenZ; 06-09-2017, 05:54 PM.


    • #3
      Gotcha. I know if I were shooting for 300+ horsepower, I'd need to upgrade to an aftermarket ECU and wideband 02 sensor. I don't plan to go past 10 psi right now not being inter-cooled. Even then I'd have to put 93 octane in just to make sure I don't detonate. I am using 87 right now because I am running stock boost for everyday driving. I just wish there was a way to make it so you're not running lean up top, and rich at low boost without fiddling with FP or Nistune. Some people have had bad luck with Nistune, and it's also cash I'd rather spend elsewhere. I noticed that these Turbo Z's run lean up top even if you've got a JWT POP upgrade.