Quagmire Posted July 9, 2012 Share Posted July 9, 2012 Efi going on this coming weekend... question: Do I connect a vacuum line to fpr or leave open to atmosphere? Will Ms account for the variance in fuel pressure (with o2 correction) or is the likely drop in fuel pressure without vac line at WOT too much? Cheers! Jamie Quote Link to comment Share on other sites More sharing options...
Quagmire Posted July 9, 2012 Author Share Posted July 9, 2012 From googling it looks like I do need it... can anyone confirm? Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted July 9, 2012 Share Posted July 9, 2012 You have a "Ickle Hole" in the back of the plenum as std that has a Hose from the PRV to the ickle hole Add a T piece into this short hose and T off to theECU Solder / araldite closed the little Barb just above the butterfly on the top of the plenum Nige Quote Link to comment Share on other sites More sharing options...
Quagmire Posted July 9, 2012 Author Share Posted July 9, 2012 Cheers Nige! Quote Link to comment Share on other sites More sharing options...
AncientGeek Posted July 11, 2012 Share Posted July 11, 2012 I recently wondered how it would run without it (and why the V8 likes to run so rich at idle). Theoretically you would then have higher pressure and a better spray pattern at idle. You would then reduce the injector pulse width. But maybe you would have to reduce it too much and run into resolution problems...? Quote Link to comment Share on other sites More sharing options...
Dave W Posted July 11, 2012 Share Posted July 11, 2012 I've never used it, I don't think it's necessary or gives any benefit on an MS install. Providing your map is matched to it being in use or not it doesn't seem to matter. Even Land Rover ditched it on later model V8s so presumably they couldn't see any benefit in it either. MS has enough options to reduce fuelling in overrun situations that having a pseudo mechanical variable fuel pressure as well is more likely to get in the way than provide any benefit IMV. I've always assumed it was introduced on the primitive EFi systems to try and compensate for limitations in the control systems. Quote Link to comment Share on other sites More sharing options...
zoltan Posted July 11, 2012 Share Posted July 11, 2012 I run mine without vacuum on the FPR on MS1 and it runs just fine, no issues at all. I remember being told on here that that was wrong for reasons I cannot recall. Three years later, still fine! Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted July 12, 2012 Share Posted July 12, 2012 PRV is pressure relief valve. The efi designed (loosest term) by LR involved mixing bits From all sorts the orb was shoved in as the std rr hp pump can shove out 120 psi ! Too much pressure in the fuel rail can bypass closed injectoHrs and make then weep etc And if really bad can flood engine or make run rich the Prv connected to a map pip is supposed to Maintain around 38 ish psi only in the rail Eales tweaked engines to gain psi on the rail by crushing the prv to make it up to around 45 - more then this And you can have probs. it is a bit of aJ bodge some engines will be fine unconnected others will not Nige Quote Link to comment Share on other sites More sharing options...
zoltan Posted July 12, 2012 Share Posted July 12, 2012 I thought we were talking about a fuel pressure regulator? It regulates fuel pressure to a set value e.g. 3 bar. A pressure relief valve is a different animal. A high pressure pump will only make 120 psi in a closed circuit. Run it against a 3 bar regulator and it makes....... ...3 bar! Quote Link to comment Share on other sites More sharing options...
zim Posted July 12, 2012 Share Posted July 12, 2012 Agree with above. To me a PRV will open if a certain pressure is exceded. It'll then dump. Not used to regulate. G Quote Link to comment Share on other sites More sharing options...
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