Need to know if my 1:1 boost referanced fuel pressure regulator is supposed to be hooked up to the manifold vacum, or just boost like off the turbo.

Alex

 

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your vaccum off the intake manifold or the turbo should work as both will have a boost source. ( unless your vac source for some reason uses a check valve)

however, itll be more accurate at the intake manifold to what boost you're actually running.

reason for this- out of the turbo you will normally experience from inefficiencies such as boost dropping off from restrictions at the intercooler.

while your turbo outlet will run 10 psi. the restrictions from the intercooler and size of the pipe may only register 8 or 9 psi at the actual throttle body.

 

Easier to tune with a boost only reference. Set the fp to 58psi and it will climb 1:1 under boost. Hook it to a vac /boost source off the manifold and it will drop the fp at idle 1:1 with the vac signal.....20 vac = 58-20=38psi fuel.

 

Not true, 20 vac is not -20psi, its inches of vacuum. 20" of vacuum is actually about -9.8ish psi.

So 20" of vacuum with a base pressure set at 58psi should be close to 49ish psi.

Ryan K.

 

Hmm, I was told it was easier to tune by running the intake manifold as reference for the 1:1 FPR.

FWIW, I plan to do the above. My FPR will be hooked up to the intake manifold. Guess I will find out how hard it is to tune in a few days.

 

The boost referenced FPR will only increase fuel pressure with boost. It does not take away any fuel at all under vacuum. If you set it to 58psi at 20 vac, it will still be 58psi at 0 vac.

So in short, hook it up to the intake manifold source.

 

When connected to the intake manifold, fuel pressure will be reduced when there is vacuum present there.

This is the normal way a boost referenced FPR would be connected.

And indeed the way almost every OE reg works with a vacuum attachment. A reduction of circa 7-8psi FPR would be normal at idle etc.

 

All I can say is that my fuel pressure is at 58psi at 20 vac and it is at 58psi at 0 vac. At 10psi of boost, it is at 68psi. Mine is hooked to the intake manifold.

 

weird FPR then lol...

What make is it ? ive never seen one like that before.

Where on the intake have you taken the signal line from ?

 

putting it in front of the throttlebody makes it a 1:1 fmu instead of a regulator. If you like your tune but just need a crude way to add more fuel at WOT.. this is one of those ways.

with a stock computer the injector flow rate table is on a slant to simulate having a manifold pressure reference. hook a 1:1 regulator to the intake and you can now make this table flat.. one number straight across. EASY

lets also say that you are having trouble with minimum pulse width or 0 duty cycle / offset time problems of large injectors but you still NEED the max output of them. letting the fuel pressure drop under vaccum will help this problem significantly

 

aeromotive 13155

I set it to 58psi at idle and the fuel pressure doesn't start raising until I get into boost. I will have to double check what my vacuum is at idle, but i think it is in the 15-20 range.

 

Actually, negative pressure is negative pressure...you're assuming I meant inHg

You can assign different units of measure to negative pressure....using 20 was not a good example but I was trying to keep the units constant to make the example easy...so... 20inHg = 9.7954psi on a 60 degree F day or there abouts for the Hermione's.

Regardless, if you hook most regulators to a manifold reference you will get a greater delta in the fuel psi since it reduces the setpoint under negative pressure and increases it under positive pressure. I'd rather go from 58psi to 73psi than swing from 48psi to 78psi.....but it's just a personal preference...many different ways to kill the cat.

 

base fuel pressure is always set with vac disconnected too.....

Where on the intake is the signal line connected ?

Last time I out I was running 4 bar base pressure ( 59psi ), which sees 3.5 bar ( 51psi ) at idle, and 5.5bar ( 81psi ) at full boost

With my new rebuild, I'll bump that back up about 4psi

 

I set my base pressure with it hooked up to the vacuum line. I am using the line that comes out of the back of the manifold. The one that originally went to the EVAP solenoid...

I was looking at my fuel pressure today when i left work. idle is at 58psi with 15vac By 0 vac it is at 60psi, but I also have my switch for my second pump on the most sensitive setting (screw all the way backed out) so I don't know if it is actually kicking the second pump on and that is whats causing the pressure increase. I suppose I could disconnect the switch and drive it on a short trip without going into boost and see if pressure still rises. But even if it does, it is only going up 2psi with a delta of 15vac. That is definitely not 1:1.