FSE - Fuel Presure Regulator and Vems

[Agriv8]

On one of the other forums I frequent I mentioned that I have disconected the vacume pipe between the plenumn and the variable fuel presure (FSE valve).

I have retained the FSE valve ( and presure gauge ) for fault finding ( and bling value ) and is set to arround 39psi ( IIRC ).

My reasoning is that the Vems can make a better decsion about how much fuel to add ( injector opentime ). If the vacume pipe was attached surly this is changing the fuel presure and therfor unknown constant into the mix.

So question am I right in my assumption  ? or is it Hummble Pie ?

Regards

Agriv8
 

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If the fuel pressure varies with manifold pressure then when the fuel table is mapped against pressure it will take the pressure changes into account.

[Agriv8]

If the fuel pressure varies with manifold pressure then when the fuel table is mapped against pressure it will take the pressure changes into account.

Thanks for the response Rob,

yup still on Manifold presure fuel Map so

are you saying it is better to leave the vacume pipe attached ?

This would mean variable presure on the fuel rail and therfore variable amount of fuel injected  ( given a constant injector opening time ) seems strange to add another unknown when its easier just to leave the Vems ECU to open the injector a little longer for that extra fuel.

Yours Confuesed

Agriv8

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If you have a clean MAP signal then keep the vacuum pipe connected to the fuel pressure regulator.
The pressure change is consistant so it makes no odds, if you disconnect the vacuum line then the pressure is consistent and you'll have to adjust your fuel map (or let the wideband trim it up as I dont expect you'll see huge changes).

Rob

[dnb]

It makes no difference which way you do things.  You just change the VE table to suit.

In the first case, you reference fuel pressure to manifold pressure (the idea being keeping a constant pressure drop across the injectors - well, not constant as FSE regs are usually 1.7:1 rising rate...)

The other way is that the fuel pressure is relative to atmosphere, so as MAP changes, fuel pressure effectively changes.