was wondering if everyone was leaving their vacuum ports on the regulators open to atmoshere or hooking up to manifold vacuum/boost? just curious which would be easier and more reliable to tune with the emanage. i'm gunna say hooked to vacuum, but making sure.

 

I was under the impression that FPRs generally required vacuum to operate properly. IE the amount of fuel that is allowed to return is directly related to vacuum.

I might be wrong.

 

Without a vaccum reference, your raising rate FPR becuase a steady state FPR. For F/I applications, you should attach the vaccum line. It will make tuning much easier, as you will be maintaining a steady pressure...at the injector nozzle, even though total system pressure is rising.

 

it depends on what exactly you are doing. Using vacuum reference has a huge advantage when running a larger injectors with high HP goals.

In vacuum (such as at idle) the drop in FP will help you idle the injectors and run them thru closed loop cycle without nearly as much MAF voltage % drop, meaning your ignition timing will be more precise and true to how nissan intended it to be thru these load sites.

In boost, FP differential will stay equal rather then fall off, increasing overall power potential of your current fuel injectors versus a falling pressure differential.

dynamic fuel pressure is the way to go if you using substantially larger injectors and going for big power.

 

alright then, question answered. i have run it both ways on my n/a cars and didn't notice much difference as the vacuum range is rather low (2-15") but just wasn't sure about doing it f/i because your vacuum and boost range is much greater (-16-+20psi) but yes i do see now how tuning would be easier due to not having to make up for fuel requirements entirely off the emanage or whatever you are tuning with and gaining a good part of your fuel off raising rate fuel pressure. thanks

 

Should you set your base pressure with the vacuum hose attached or not? I have mine set at 52 PSI @ idle, showing about 18" of vac. If I detach the hose, it shows about 56 psi, under boost, it rises to 62 PSI. Is this right?

 

Base fuel pressure should be set with the vaccum line disconnected. This becomes your differential fuel pressure, and the net pressure you will be seeing under boost conditions.

 

Thanks Sharif, that is what I was thinking, but wasn't sure.

Still waiting patiently, for the EU.

 

I set mine up..at 52 psi...with the vacuum line hooked up . What would be the difference .....bad ?....no harm ?

 

Bad....you the man...its on the way today. Check your email later today.



Booger, there is no harm. If you have a good tune at 52psi with line attached, then no worries. 52psi with line attached is about 55-56psi without the line attached.

 

would it cause the bigger injectors to squirt more fuel in at start up than needed ? [ 550 injectors ] My car does start hard some times and when it does , I get the misfire CEL

 

Yes that too. But that is more of function of having the return system...vs. the particular pressure you are running. To get my car to start cleanly when warm, I would need to run 40psi of differential fuel pressure....which is too low for the power I am running.

So I take the easy way out, and just blip the throttle while cranking...it fires right up.

 

It went out 2day air at no extra cost. You'll have it in your hands on Friday, just in time for the weekend!

 

Thanks Sharif, something to do this weekend.

 

Now with my new forged motor with cams, I have to do this as well. A little blip up to 1500-2000rpm won't hurt a thing!