I have an awesome F2T powered machine ('89 Probe GT) have reason to to suspect the factory fuel pump is on its way out. I have a chipped ECU, Manual Boost Controller, 2.5" exhaust, and low restriction intake filter. The engine had slightly higher (8.6:1) Pistons, is installation of a Walbro 255lph pump gonna cause this thing to run like poo? It's my DD, and I just got the pump, just curious is its gonna cause an issue before I stall it. Input from the hive?
In reply to dansxr2:
No difference, the fuel pump doesnt add any more fuel to the engine just adds fuel availability. I put a walbro 255 in a 113hp Volvo and noticed nothing other than it stopped sputtering because one of the stock pumps was dead. Now its at 200hp and still fine
The only way a fuel pump can be too big for the car is if your pressure regulator can't flow enough to bring pressure down to the correct pressure. It's happened to me before, but only on setups with two pumps in series with each other.
Done with two!
I've added a secondary fuel pressure regulator and return line to a system where the factory return line posed a restriction at idle. This was a really, really weird circumstance, though, and the pump was way bigger than a Walbro 255.
The FUN part was that the problem only presented itself after rewiring the pump with 8 gauge wire bac to the tank and then 12 gauge wire from the close-mounted relay to the pump. Now that the pump wasn't underperforming due to voltage drop (it actually had burned the pins in the sending unit) it was causing 85+psi at idle and low load. So fixing one problem showed where another one was occurring.
In hindsight, a better fix might have been to set up a resistor through a relay and a vacuum switch, when engine is under vacuum the relay closes and power goes through a resistor wired to pin 87a to slow the pump down, vacuum goes away and relay opens and pump gets full voltage from pin 87. But I'm not sure if running a pump at lower voltage would pose any longevity issues.
Awesome! I have installed a 195lph with no ill effects, but someone tried to tell me it would make it run super rich. I appreciate the input!
As long as you don't overwhelm the return, you are good.
I have one fuel setup that pumps almost 3gpm and min fuel pressure is 58psi with a huge regulator and 1/2" return line. So its possible but hard to have issues.
In reply to Knurled:
The 3SGTE motors have a fuel pump resistor. It drops the voltage to the pump in low load conditions. In high load conditions, the resistor is either switched out of the circuit (up through 3rd gen) or bypassed (4th gen), giving full B+ to the pump.
FWIW, even a walbro 255 will overwhelm a stock NB Miata fuel pressure regulator at idle. Been there, measured it. :)
If you don't want an aftermarket regulator an alternative is to PWM the pump. You don't need a closed loop PID algorithm, just a few speeds that you select based on engine load/injector duty cycle and let the regulator do the rest.
I came here to say what codrus said - you can indeed overwhelm a stock FPR. If you're going to start messing with pumps, fuel pressure gauges are cheap.
I know some OEs do it (FC and FD RX-7 do it, too) but I feel kinda funny about doing it with aftermarket pumps. They aren't always made to the same level as OE pumps.
If'n I had my way, I'd just use two or three Bosch 044 pumps and be done with it, but the people who write the checks tend to balk at the expense 
In reply to Knurled:
Two or three 044? Jeebless what are you trying to supply?
The next one I will be involved with will probably be something in the 10 liter range and 900-1100hp, unless the schedule for that one gets pushed back again. It's probably 1-2 months out from plumbing and wiring the fuel system. (IIRC it's going to be an XFI with a FAST dashboard, which will be something new for me)
But it will be nice to work with something that isn't forced induction for once.
I like overkill on fuel pumps. All it takes is one time with hot pumps for fuel flow to sag and boom. Sure, many EFI systems can compensate for fuel pressure loss in real time, but that tends to show its ugly head right when duty cycle is getting right on up there too, so that won't be much help. And fuel pumps are cheaper than REALLY BIG injectors...
2 hp per liter per hour.... (1.7 if under boost) this is a quick and dirty method of fuel pump sizing (correct way is injector volume, and duty cycle, wear, etc and it comes pretty close to 2hp per lph)
You don't want extra fuel... EVEN IF the FPR can handle it... you don't want to push the fuel around the system for no reason... this is because by pushing excess fuel you add heat into the fuel... and most systems CAN'T handle the volume screwing seriously with idle, and off idle character there is no reason to run a Walbro 255... unless you are pushing 450 - 500hp.
450-500hp isn't out of reality in an F2T.... but in that case I'd look to run staged injection(2 injectors per cyl)... OR a very fast injector driver so you can run very short injector timing for idle and off idle
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