You aren't running the stock regulator are you?

Andrew mentions issues with the dw300 and a stock regulator. Deatschwerks Fuel Pumps (DW100/200/300)

Additionally, the stock NB regulator tries to achieve 60 psi in the feed line no matter the conditions. If you add 27 psi of boost to the intake you effectively have 33 psi of fuel pressure. That's how you max out ID1000s and a dw300 at your power.

Yeah, you've got effectively 30 psi at WOT and an unregulated 80-90 psi at idle. You need a proper regulator.

--Ian

Ah right , that entire ditty. I suppose I'll run into that if I push too much harder as well.

You should probably put your wallet away and do some reading on converting to a return style fuel system.

This.

The stock regulator is in the fuel tank. You can't easily put an AFPR in there, so you're looking at doing at least some rework of the fuel system no matter what. There's basically two options:

A) convert to a return system like an NA.

B) move the regulator down next to the charcoal canister and use it to drive the non-return line from there like FM does in their "big fuel kit".

If you do B, you will probably need fuel pulse damper(s) up in the engine bay.

--Ian

What about what Savington did with his 452hp NB?

To your questions:

1. and 2. The idea of a referenced FPR is that, as boost goes up, so does fuel pressure. That means more flow. The non-referenced (or atmosphere referenced to be more precise) flows more up to roughly 15 psi boost. After that, the manifold referenced system provides more fuel.

It is a misnomer to say that the NA is "vacuum referenced". It is "manifold referenced". Therefore, it is vacuum referenced only when there is less than one atmosphere (100kPa) in the intake manifold.

3. Yes.

You can also look in my build thread for how I did the conversion. I did use a full size return line, and I did not add extra pressure beyond the NA FPR (or, more precisely, a FPR from a UK NA). Depends on how much more fuel you need. Since you have the big injectors, and you are running quite a bit of boost,

Whether your pump is over-powering your regulator, or would the NA regulator, I don't know, but it has been discussed how big you can go before you need an aftermarket FPR.

The problem with the pump overwhelming the FPR is that the fuel is then unregulated. Yes, you can compensate for higher pressure by shortening the idle, but an unregulated pump does not produce a consistent pressure. As things like voltage and temperature change, the pump performance changes, so the fuel pressure at idle changes, and thus the amount of error is not consistent.

As an example, say you have the regulator set to 60 psi, but the pump produces so much fuel when it's at 14.5 volts that the regulator can't keep up, so the pressure spikes to 80 psi. You go into the VE table and change the cells around idle to compensate. Then a few months later it's December. Temperature has dropped, so the fuel is more viscous and the pump has a harder time pumping. You're running the heater, blower motor, and defroster, so there's a lot more demand on the alternator. With the lower temperature the battery is also not performing as well, so you're only get 13.0 volts at idle. The pump performance sags, it can only do 60 psi, and now your VE tables are 25% too lean at idle, and the car starts stalling at stoplights.

Overwhelming the FPR isn't going to blow the motor up, but it will make it a PITA to get the car running consistently well around town. It hurts drivability.

--Ian

You can get a real regulator and set it to stock base pressure 60psi. When you make 30psi of boost, you will have 90psi of fuel pressure because of the real regulator you bought (probably around $150.) As Ian and Andrew taught me.

There are two unrelated problems with your setup. Pressure regulators work by mechanically comparing the pressure on two sides of a diaphragm. One side of the stock regulator has pressurized fuel on it, the other is the "reference", and the regulator opens or closes a relief valve in order to have those two pressures be equal. Your first problem is caused by the fact that the factory regulator has this reference open to the ambient pressure inside the fuel tank, meaning that it always produces a fuel pressure that is ~ 60 psi higher than whatever the ambient air pressure is.

Injectors work off a pressure difference -- subtract the pressure in the intake manifold from the pressure in the fuel rail, and that's how much pressure there is trying to squirt fuel out when they are open. With a naturally aspirated engine, the max pressure in the intake manifold is the same as ambient, meaning that there is always at least a 60 psi difference (and more than that when the manifold is in vacuum). With a turbo car, you have the ability to raise the manifold pressure above ambient. 27 psi of boost means that the manifold is 27 psi above ambient, and if the manifold is only 60 psi above ambient then you only have 33 psi pushing fuel out. Since you've only got half the effective fuel pressure, your id1000s will only flow half as much fuel as they would if you had 60. This is why you're running lean, the system as currently set up simply cannot supply enough fuel.

The factory setup on an NA, and what most people use for aftermarket regulators is to have the reference side of the regulator connected to a vacuum line, so that it is the same pressure as the intake manifold. This means that the regulator will produce a fuel pressure which is always a fixed delta higher than MAP. This means that as the turbo adds boost pressure to the intake manifold, the regulator adds fuel pressure to the fuel rail to balance it out. Your injectors thus always see the same relative pressure and you don't lose fuel capacity.

The second problem with your current setup is the "overwhelming the regulator" one. It is a problem that manifests not with high power loss of capacity, but with unpredictable low power response, and thus drivability problems.

To fix both problems you need to install a MAP-referenced regulator which is larger than the stock NB one and can handle the larger volume of fuel that the aftermarket pump produces. I don't know if a stock NA regulator will do that or not, I have an AEM. You then need to mount that regulator somewhere, because it can't go in the tank.

On a stock NB, the in-tank pump pressurizes a line that exits the tank, flows to the filter (mounted down by the passenger rear wheel), and then splits into a tee. One half of that tee goes back into the tank and to the stock regulator, the other half goes forward through the hard line to the engine bay, to the fender-mounted pulse damper, and then to the fuel rail where it dead-ends. You have two choices about how to set this up:

- The first is to put the new regulator up in the engine bay, on the firewall for example. To do this you need to remove the tee at the back, run the outlet of the filter to the hard line, drill/tap a second port in the rail, run a line from there to the regulator input, then run the regulator output to a new return line that you run underneath the car. That new return line then goes to the port on the tank that isn't being used any more. This is how the fuel routes on an NA.

- The second is to put the regulator next to the fuel filter, just after the tee, in the return line to the tank and leave everything going forwards with the same config. This is how FM does it with their "big fuel kit" (except that they also replace everything going forward with -6 AN for more fuel flow. It's somewhat debatable as to at what power level you need that -6 line, vs the roughly 5/16 stock line).

Note that except for the steel hard lines, the stock lines are all plastic with quick disconnect fittings. They don't really bend to new routings and you can't easily shorten them, so to change them you're basically replacing them with rubber and getting hose-barb-to-quick-disconnect fittings from Dorman. You need high pressure fuel injection hose.

Most people on this forum recommend adding the return line. The FM-style routing works (that's what's in my car), but it's not clear if it'll work with all regulators or if the AEM that they supply is special in some way. It also tends to produce pressure pulses when the injectors open, this is what the pulse dampers are for, they smooth them out.

In either case, you need a lot more than a $30 AFPR kit from ebay. Note also that you need to remove the stock regulator from the tank, and if you're going to run the car on track you need to replace it with a short piece of submersible fuel hose (not regular hose) in order to return the fuel to the baffled area that the pickup goes into. Otherwise it'll go lean in hard left-handers when you drop below about half a tank of fuel.

--Ian

I run the returnless setup and drivability is good. Savington has a nice regulator, and it's a good deal, I bought my pump from him too. Best to follow Sav's advice IMHO, even though I did it slightly different. I wanted a 90, and I blocked one port on the regulator meant for a return system. But mine is unusual and I am comfortable making/working with the PA12 line.