Well it turns out that I have officially maxed out the stock fuel pressure regulator on our cars.
I am running a TD07-25 Turbocharger and a Haltech, with stock 550cc primaries, 1600cc secondaries, Walbro 255lph Fuel pump. and so far the stock fuel system so I am on the road tuning and with my G-Tech RR Properly calibrated and Actual weight of car inputed. And datalogging on my laptop. I was on the Highway doing 5th Gear tuning for high load, and then I notice that my EGTS start climbing so I adjust timing accordingly, and notice the egts went down a little but not significantly so I look at my afr's for that run in the datalog from the haltech and it turns out that the afr's went into the High 12's.... so I in turn add fuel in that area of the map and it did not good, there just isn't the fuel pressure to run the 1600's and the 550's.
Anyways the system started to top out at 15.5 PSI on my large turbo and according to the G-Tech that translates into 348 RWHP. So If anybody is looking to go much above this with your stock fuel pressure regulator, I strongly suggest upgrading to an aftermarket FPR.
I just happen to have an Aeromotive and -6AN fittings sitting in my garage ready to install I just wanted to see when the stock fuel system maxed out. And voila I have fount it approx 350 HP and 15 PSI on a larger single Turbo.

 

anybody have any experience beond that?

 

No monitoring of fuel presure? Then you can't assume it is the fuel pressure regulator.

I have made more than 350 hp with the stock FPR without issues, and your description does not sound like a fpr problem... it sounds more like a lack of fuel flow causing fuel pressure to drop.

 

Lack of fuel?
in which instance my fuel pump is good for alot more than 350, and my injectors are good for alot more than that as well, FPR is about the last thing left.
I do have a fuel pressure guage but it is the mechanical type, and I bought it to go with my Aeromotive FPR. So it isn't installed yet.

 

is there nobody else that ran a similar setup that made more power?

 

Lack of fuel flow causing the pressure to drop, not injectors.
The Walbro pump isn't exactly known for its high quality. I wouldn't be surprised if it wasn;t pumping at its full rated capacity.

 

I suspect it's the pump, too, but you might as well install the Aeromotive FPR and see what happens if you were going to install it anyway. I think your deduction that fuel pressure is dropping off is probably correct, but it would be nice to have a FP gauge you can read inside the car to be sure. You might want to get one of those, too. And be careful while tuning -- it would suck to blow the engine because of this.

Also, it might not be that the pump is running out of steam -- it could be a leak in the pump outlet hose inside the fuel tank, a pinched fuel line, etc.

-Max

 

ok so I installed my -6 and lines and my Aeromotive Fuel pressure regulator today and went for a couple of runs on the highway and Zip Tied a Digicam with video recording to the FPR in the Engine bay.
so here is what I found.
at iddle 32 PSI
at 0psi boost is see 40psi
at 15.5 psi boost I see 55 psi.
and Lone Behold I am now rich in that area of the map....
So now I stt 10.8 AFR at 15psi in 5th Gear.
and on a HP test with the G-Tech in 3rd I managed to pull off a 365 HP
So I do suspect that it was the Fuel pressure Regulator buecause nothing else was changed.

 

The FPR is mounted after the injectors, so if it's not big enough to flow the required amount the fuel pressure goes up, not down. It's a bit like a wastegate in that respect. So if you're running lean, it is not the FPR. A bigger aftermarket FPR is needed when you can't keep the fuel pressure down where you want it.

 

Back from the dead...

Ok so I'm trying to understand fuel pressure regulators. If the stock FPR is overloaded, your fuel pressure spikes. So what? Does this mean you will run rich? I mean I guess at some point too much pressure could break a fuel line or something.

The reason I say this is that I picked up a brand new aeromotive FPR and I'm wondering now if I even need it, if I'm planning on making around 350-400rwhp.

 

yes, too much flow will overwhelm the pressure regulator and the pressure will be irregular depending on loads and conditions. a number of people have run up to and probably past 350RWHP with the stock FPR but it is a good idea to replace it with something that will give you more stable readings.

 

Sure, it's a good idea. But if I understand this correctly, an undersized fuel pressure regulator in some ways has the inverse effect of an undersized wastegate. A boost spike=possible blown motor, while a spike in fuel pressure (up to a point of course) just equals the car running rich. And fuel pressure spikes usually occur under major boost. Yet that's weird to me... because when the boost climbs, so does the risk of running lean from running out of fuel.

What I gather from this thread is that the biggest danger is a drop in fuel pressure, which is usually caused by an overwhelmed fuel pump, not an overwhelmed fuel pressure regulator (despite common beliefs).