Fuel Pump Sizing Tips

[walbrofuelpumps]

Wondering if your stock fuel pump can handle the performance mods you've thrown at your ride? Let us give you some ideas of how to solve that dilemma.

The stock fuel pump in an '89-'94 USDM 240SX flows approximately 143 liters per hour against a pressure of 43 PSI. There are two magic numbers to remember: .38 and .47. If you're still naturally aspirated and haven't boosted your fuel pressure then your engine can produce up to 376 horsepower before you lean out and blow your engine. (143 lph divided by .38 is 376 HP.)

But what if you've added a turbo? Well, turbocharged engines need more fuel per horsepower. So use that second magic number (.47) and you'll see that your stock fuel pump can only support 304 turbocharged horsepower.

Let's throw in another variable. Say you're boosting so you increase your fuel pressure to compensate. The challenge is that fuel pumps that flow 143 LPH against 43 PSI of pressure will flow less at a higher pressure. So now your fuel pump that might have supported 304 HP might only support 260 or 270.

So let's work the other direction. Let's say your goal is to make 400 horsepower with your new turbocharger kit pushing 12 psi of boost (all strictly hypothetical.) You already know you need a bigger pump. But do you need 255 LPH? More? Less?

Use your magic number of .47 again but this time multiply it by horsepower. 400 * .47 tells you that you need 188 LPH. Did you know that we make 190 LPH pumps? Perfect! Or--is it?

Again, don't forget about the fuel pressure. If you're running 12 psi of boost you're likely going to want to add about 12 psi of pressure to the fuel system. But where are you going to find out how much fuel a Walbro 190 LPH pump flows at 55 PSI? Right here:

http://walbrofuelpumps.com/fuel-pumps-pressure-charts

And, as you see, while it flows 190 LPH at 43.5 psi, it only flows about 170 LPH at 55 PSI. That means it's not going to work. Better go with the 255 LPH.

But what if you're going to run E85 and not gasoline? Then everything changes. You need about 40% more fuel if you're running E85 instead of gasoline. So use the same magic numbers as above, but then divide by .72 to get the new flow. In our most recent example, the 400 HP turbo engine making 12 psi of boost and burning E85 will need 261 liters per hour of E85 (188 LPH / .72 = 261 LPH.)

But there's something else to remember...very few high performance fuel pumps can survive E85. It's really nasty stuff. Zero lubricity and incredible corrosive nature turns good fuel pumps into a chunk of junk in hours. Our only high-performance fuel pump rated for both E85 and gasoline: the TIA485-2 fuel Pump, that flows a staggering 450 LPH at 43.5 PSI with a maximum system operating pressure of 87 PSI.

And, as always, we should close by saying that lots of forgeries abound. Know that the pump you're getting is a genuine, made-in-the-USA Walbro Fuel Pump by TI Automotive. The $30 you save might cost you your engine.

[e30gangsta]

TIA485-2 is legit. Hardwire it to the batt and it will support 500+ rwhp. I love mine.