Which fuel upgrade injectors, fuel pump, or both?
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Cadillac STS-V Series Forum Discussion, Which fuel upgrade injectors, fuel pump, or both? in Cadillac V-Series Forums; I've upgraded my exhaust with a home fabricated Dynamax cat back system, D3 stage 1 & 2 intake, frozone/flexlite intercoolers, ...
  1. #1
    Zzapp's Avatar
    Zzapp is offline Cadillac Owners Fanatic
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    Which fuel upgrade injectors, fuel pump, or both?

    I've upgraded my exhaust with a home fabricated Dynamax cat back system, D3 stage 1 & 2 intake, frozone/flexlite intercoolers, 160 thermostat, my car is currently apart as I have sent my blower pulley snout to TimmyC, and I have a D3 lower OD crank pulley I'm putting on while waiting for my TimmyC upgrade... Should I upgrade the injectors, fuel pump, or both before I get a Dyno tune... What injectors should I use, and which fuel pump???

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  3. #2
    Psycho-albanian is offline Cadillac Owners Fanatic
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    TimmyC or coach would be the guys to ask.

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    PGA2B's Avatar
    PGA2B is offline Cadillac Owners Connoisseur
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    I don't know what pump you could get other than a boost a pump. With that you could wait to change injectors (I think). Talk to Tim about the BAP. I changed my injectors to a set of Seimens 73lb Ford Racing and scaled my tune for them. The problem is that our tune limits the Injector Flow to a point we have to scale it to use anything above 63.5lb. Before my injectors I was running 98% duty cycle, now with them I am only running 55% so I have plenty of headroom for my pulley.

    The other guys that upgraded their injectors just had their stock injectors redrilled.

    I will be very interested in your results with the lower and upper combination and your numbers.

  5. #4
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    Stock injectors with a BAP and a boost referenced fuel system are good for around 550rwhp. I made 575 with this setup but it was leaning out at the end of a dyno pull. Stock injectors with just the BAP are good for 430. My car makes more than that but it starts to lean out at 6000rpm.

    The stock fuel system is 58psi no matter what the pressure in the manifold is. In vacuum there is a greater pressure difference across the injector than in boost. A boost referenced fuel system uses a pressure regulator that references the pressure in the intake manifold and keeps the fuel pressure 58psi above that. That way fuel pressure increases with boost and the injectors can flow more. Conversely, the fuel pump's output drops as fuel pressure increases so you need the BAP.

    I think the stock fuel pump will go at least 460rwhp with bigger injectors. Bigger injectors flow more fuel at stock pressure to a point.

    BAPs are around $270 I think and I could make boost reference kits for $250 so this route might cost more than bigger injectors. However, even with bigger injectors the fuel pump is going to be the limiting factor. I prefer a BAP to an aftermarket fuel pump for two reasons. One is that aftermarket pumps are not as reliable as oem pumps. Two is that the fuel tank in an STS is a pain in the ass to remove. You have to partially drop the rear suspension cradle.

    These are the reasons I kept the stock injectors with a BAP and referenced fuel system.

  6. #5
    Zzapp's Avatar
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    BAP? what's that?

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    PGA2B's Avatar
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    Boost A Pump- It increases the voltage to the fuel pump.

  8. #7
    Zzapp's Avatar
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    With the increased voltage to the stock fuel pump have there been any longevity issues?

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    PGA2B's Avatar
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    There have been no issues on other applications but only Tim has tested it on ours.

  10. #9
    Carlosg's Avatar
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    What do u mean by the fuel reference system?

  11. #10
    TimmyC is offline Cadillac Owners Connoisseur
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    Re: Which fuel upgrade injectors, fuel pump, or both?

    Quote Originally Posted by Carlosg View Post
    What do u mean by the fuel reference system?
    Read paragraph two of post four in this thread.

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