Hello fellow rotor heads,
My turbo vert has been running rich ever since I upgraded the fuel pump to a walbro. I tried to correct the problem by installing a rising rate adjustable fuel pressure regulator(RRAFPR), but it still was running rich since the RRAFPR wouldn't allow me to drop the fuel pressure below 45psi(7 psi higher that stock) at idle.

Why can't I lower that fuel pressure anymore than 45psi? Is it the FPR I bought? My guess is that the stock fuel return line is too small, what do you guys think?

 

I'm guessing, but I wouldn't think that the return line would be creating so much back pressure that it "overpowers" the FPR. If in doubt, just route the fuel flow around the FPR (for test purposes only, obviously) and see what your supply side pressures are. I would bet it's WAY on the low side.

Reducing the voltage to the fuel pump during idle conditions always works...

 

Just an observation: the fuel rail pressure (at idle), on a stock RX-7 is closer to 29psi. Most see approx 31psi, quite a bit lower than 45.

The fuel pump output on a stock RX-7 IS close to 70-90 psi on a turbo. Non turbo close to that figure.

 

Is the regulator hooked to a port that is seeing vacuum? You should get 42psi with no vacuum signal. What kind of regulator did you get and how much pressure does it add per psi of boost.

 

My FPR is hooked up to a vacuum line, and it raises fuel pressure with boost in a 1:1 ratio.

Have any of you been able to keep your 7's from running rich with a Walbro installed using a AFPR? Everybody keeps telling me to use an afc, but I know that the problem would be fixed if I could just find some way to lower the fuel pressure.

Does anybody know why our cars run rich with a walbro? Is it because of the stock FPR or is it because of overall resistance of the fuel system. I wish somebody could give me a definite answer about this, because it would be a big help.

 

The fuel pressure regulator should solve your problem, what kind of regulator did you get? An SX or Aeromotive?

 

Just curious. Can you describe where the vacuum nipple is that your feeding the fpr off?

 

Or when you pull the line off the fpr does your fuel pressure go up?

 

LT8TurboII- I bought a cheap FPR off of ebay, I'm not sure of the brand. I will try pulling the vacuum line off the FPR to see if my fuel pressue goes up.

Hailers- I plugged the original FPR vacuum nipple. The nipple I am using now is below and to the side of the stock FPR. It's a large nipple on the side of the UIM pointing toward the fire wall.

 

You did remove the stock FPR right?

If so, and and removing the vacuum line does raise the pressure get a real FPR, use an aeromotive.

 

Problelm solved. On a series four turboii, there is only ONE nipple on the back of the upper intake manifold that is a source of vacuum. That is the very bottom one. The others are all connected to a source of air from the FRONT of the throttle body.

You'll never get a vacuum on those. BUT you will get boost pressure since the pressure is before the front of the throttle body.

 

exactly, that nipple you used is ported to the front of the throttle body.

 

Thanks! I don't know what would I do without you guys.

I will route the FPR to the nipple my boost gauge, Pressure sensor and blow off valve are hooked up to, what other nipples could I use?

Would there be any drawback to using this one vacuum nipple and a bunch of splitters to run everything requiring vac/boost?

 

The very bottom of the three (four in some cases) on the back of the upper intake manifold will probably do. The original slanted one on the intake manifold would have been better.

I think you might consider running your aftermarket boost gauge to the lowest nipple on the back of the throttle body and the fpr one to where the aftermarket boost gauge goes now.

That should drop the fuel pressure at idle. At least lower than what you now see. I think it'll still be higher than what a stock car will see, which is around 28-31psi at idle.

 

i have the same problem but i have 50psi at idle with walbro and stock fpr..

 

If I install the RRAFPR using the proper vacuum nipple, what psi shold I set it to? 30psi?

I have my twin scroll hooked to the bottom nipple of the trottlebody, is it ok to run the boost gauge and the twin scroll off of the same nipple?

 

Pull the vacuum line off the fpr at idle and see if it goes up. If it does not go up, then see if you really have vacuum at the fpr.