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help ajusting fuel pressure

bigstu

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vx ss,vn calais 355
Hey guys just set up the surge tank with a o44 and a turbosmart fuel pressure regulater on the vn 5L and wanting to know if I should be setting the pressure at 40psi at idle with the vac line on or off.Ive got it set at 40psi at the moment with the vac line on and it seems to be running a bit weird.cheers guys
 

Cheap6

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It's always relative to manifold pressure, with the fuel pressure a constant value above manifold pressure. With the engine off (fuel pump relay bridged to run the pump) and manifold pressure at ~102kPa, it should be ~320kPa absolute. Engine idling it will be lower than that, ~250kPa, with manifold vacuum pressure at ~30kPa absolute = 70kPa vacuum, and as you open the throttle or load down the engine it will rise.

40psi is 277kPa (absolute) and too high for idle. Setting it at idle is not accurate, unless you know the manifold vacuum/pressure and can subtract that from absolute pressure to get the delta pressure.
 
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