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Mikejc wrote:Have a peek at my profile for the mods to date
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Yep, I've seen that, but that would have led me down the garden path without this other snippet of info.
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Mikejc wrote:At the time the car was mapped I was infact still using the standed fuel pump, however I do not think this was causing my problem.
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How do you know?
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Were you monitoring fuel rail pressures?
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Mikejc wrote:I base this on the fact that the pump was obviously allowing me enough fuel to reach 100% injector duty cycle, there for the pump must have been doing all that was asked of it!?
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I don't see the logic there.
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So what if you're having to go up to that duty cycle? That obviously means you don't have enough fuel available.
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That could be for a number of different reasons.
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You can't do it with guess work.
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Mikejc wrote:I believe the AFR was around 11-1.
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Boost
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@ 1.2 bar.
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And in control of the show was the Apexi Power FC
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OK, 11-1 is very rich, plenty of fuel that could be taken out there.
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1.2Bar is not that much, at least not to affect the fuel pump pressure.
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You see, fuel rail pressure rises with boost.
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On a turbo car, you want to be using a 1:1 pump pressure-to-boost fuel regulator.
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Therefore, if you set base fuel pressure at 40psi, fuel rail pressure will be:
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40+14.5psi
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= 54.5psi
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(at 1Bar Boost)
40+15.9psi
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= 55.9pis
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(at 1.1Bar Boost)
etc
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Now, you have to take into account the characteristics of any given fuel pump.
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Any pump's flow capability decreases as the fuel pressure is raised.
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Some are better than others in flowing well at high rail pressures.
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Also, some pumps have an internal pressure relief valve.
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I've seen some pumps actually bypassing most of the fuel back into the tank when the fuel rail pressure reaches the pump's internal relief valve pressure.
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You sure as hell ain't gonna get the fuel flow then!
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I think that the stock pump starts to have issues in maintaining the desired fuel pump pressure at boost levels in excess of 1.3bar.
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Therefore, when you start to run more boost than this, the desired fuel rail pressure becomes too much for the stock pump to maintain.
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This is what it seems I'm experiencing at the moment, despite larger injectors, so it seems that no matter what injectors I use, I'll still have an issue with maintaining the right fuel rail pressure when on heavy boost.
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Since the guy was wondering what to do for his specific needs, I still believe that he can achieve what he's after with the stock injectors.
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An uprated fuel pump and an adjustable fuel pressure regulator are needed, IMHO.
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