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Tech Talk Technical Discussion About The Nissan 240SX and Nissan Z Cars


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Old 08-31-2007, 03:16 PM   #1
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what does manifold pressure have to do with with injector inlet pressure? I GUESS I"M DUMB. 14.7
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Old 08-31-2007, 03:47 PM   #2
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Quote:
Originally Posted by ronin207 View Post
what does manifold pressure have to do with with injector inlet pressure? I GUESS I"M DUMB. 14.7
Think about this... The fuel injector is just a pipe that connects two pressurized areas, the fuel rail and the intake manifold. Fuel injectors flow a certain rate of fuel, at a certain rail pressure. So whenever the intake manifold pressure changes, you have to add or subtract that same amount of pressure to the fuel rail, otherwise your fuel injectors will flow different rates... Adding 10psi of boost to the intake manifold without adding more fuel pressure would effectively lower the fuel rail pressure to 33.5. This is why we have 1:1 fuel pressure regulators, to bump up the rail pressure by the boost amount and keep the injectors flowing the same rate regardless of manifold vacuum or boost pressure..

Guitaraholic pretty much answered your question here:
Quote:
Originally Posted by Guitaraholic
Under boost, if fuel pressure was constant, did not rise w/ boost,, say 3 at bar of fuel pressure, under boost would you actually flow less fuel because of the increased manifold pressure. So at 4bar under 1 bar of boost,, you would actually only flow 3 bar's worth of pressure though the injectors, again given that the fuel pressure did not rise.
Why did you put '14.7' at the end of your post??
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