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Losing fuel pressure when hot.

Hpjunky
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Hpjunky Apprentice

Hpjunky

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Hey guys. Just want to run a problem past you all. I'm working on a r33 gtst and the aftermarket fuel is as follows. Submerged Bosch 044 to 3ltr surge tank via -8an line. Twin 044 from surge to Y piece -10an to engine bay Y piece to 2 -8an lines to top feed twin entry rail to feed 1200cc injectors. -8an return to reg and -8an to surge tank and -10an from surge to fuel cell. Problem I'm having is when the pumps and fuel warm up fuel pressure drops and pumps get very noisy. Is this just fuel temp causing this and I need a cooler? I can get the problem to happen at idle on a warm day bonnet closed. Will a fuel cooler help? The engine can run from 550hp to 850hp. Even if I stage pumps on the track it probably won't turn the second pump off. Any ideas would be helpful thanks. 

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GTSBoy Grand Master

GTSBoy

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Posted

3x 044s will beat the shit out of the fuel and make it hot. Adds heat to it every time it passes through a pump. Adds heat to it every time it passes through the engine bay, comes back, gets dumped into the surge tank (confining the heat and putting it straight back into another pump), etc etc etc.

So, yes, putting a fuel cooler in will help.

Staging the pumps will still help. The problem is greatest when you are not using much power. The pumps are all still thrashing away, and a larger quantity of fuel is going around and around. When, instead, You are using a lot of power, the fuel isn't going around and around as much. More of it is on a one way trip to the exhaust pipe. So the issue of staging the pumps is not about what happens when you're on track using a lot of power. It is about when you're on track not using a lot of power.

Even better than just staging the pumps would be to put a proper pump controller on with PWM control.

In any case, a fuel cooler will help even if you do stage/modulate the pumps.

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robbo_rb180 Grand Master

robbo_rb180

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Posted

Smaller lift pump and stage the 2 main pumps will help alot or for a cheap fix fit a cooler.
Can you monitor fuel temps with either a temp sensor or ethanol content sensor? I see temps upto 55C at track and around 43-47c on the street 

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