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Where to get vac signal for FPR
dave_424 - 20/5/13 at 12:53 PM

I was just wondering if the FPR is supposed to see vacuum and boost, or just boost. If it sees vacuum then it would lower fuel pressure at idle and cruise speeds.

So do I get the vacuum signal from after the throttle plates or before.

I'm tuning with megasquirt BTW

Dave

britishtrident - 20/5/13 at 12:58 PM

The injectors inject into the manifold therefore the FPR works relative to the inlet manifold pressure.

dave_424 - 20/5/13 at 01:02 PM

Okay i'm using zx10 throttle bodies so I should have the reference to the FPR coming from after the throttle body plates.

I have been told that the fuel pressure of the zx10 is 44psi whilst running, so I should set it to 44 psi whilst running and the FPR is seeing vacuum? would't this give me a pretty high fuel pressure at WOT?

baz-R - 20/5/13 at 01:21 PM

if you need fuel pressure to rise and fall with inlet pressure then you connect your vac line to anywhere behind your throttle valve and if you are running multi throttles like bodies then you need to tap into all of them then use tee bits between

most bike bodies have vac points for ballancing so use thease.

if you are using a std bike ecu you need to plumb up as orignal as some bikes run fixed fuel pressure

MikeRJ - 20/5/13 at 04:21 PM

quote:
Originally posted by dave_424
Okay i'm using zx10 throttle bodies so I should have the reference to the FPR coming from after the throttle body plates.

I have been told that the fuel pressure of the zx10 is 44psi whilst running, so I should set it to 44 psi whilst running and the FPR is seeing vacuum? would't this give me a pretty high fuel pressure at WOT?


Fix it at 44 psi with no vacuum, i.e. disconnect vacuum port. When the engine is running at small throttle openings (high vacuum) the fuel pressure will be reduced to maintain a constant 44PSI pressure drop across the injectors. If using forced induction then fuel pressure will be raised under boost, either to maintain 44psi from a standard regulator, or to increase the pressure drop if it's a rising rate regulator.

[Edited on 20/5/13 by MikeRJ]