Testing walbro voltage/amps

[Guest]

People say to test the voltage on the fuel pump when upgrading to a walbro to ensure you are getting max out of your pump. But what does it draw? Does the factory wiring handle the extra it would draw with a walbro or is it the wiring/amperage not the voltage that limits it? Obviously rewiring with heavy cable and a relay which most do would fix either problem but which is it that restricts it? The stock wiring would be 10A max at a guess.

[Rosssub]

AFAIK the ECU sends out a 1.7v switching signal to the fuel pump relay for on/off, but imagine the pump itself would see full battery voltage? But pretty much if you\'ve got full 14.6v at the battery but only 12.8 ish at the pump with no other load then your losing amps and need bigger wiring.

Here\'s a good link on a pump re-wire/walbro upgrade:

http://forums.nasioc.com/forums/showthread.php?t=2382384

[loner]

I wired mine for 12 amps which will cover all loads and voltages... pretty sure the instructions had that info.

[Kiwi_Fozze]

Mean, been hunting for a how-to for this

[Pappu1]

On the gc8 models just wite in a big feed from the pump relay and a good ground and ur sorted. Anything 8ag wire is way more than u will ever draw (well tested in a near 300kw setup anywY)

Not so easily on the v7+ as the fuel controller gives variable voltage to pump based on load so a straight wire will cause a cel

U can remove the cel a s get round the issue or u can put a resister in the controller output to fool it

In saying that, speedsource appears to have run their 300kw Sti on stock wiring (or so the article on their Sti would suggest)

[Guest]

Max it can draw is 13A it seems being that the relief valve is set at 80psi ish so 43.5+boost youre likely to draw under 12A. I dont think power has a bearing on it as much as psi does.

[nztintin]

I\'ve just redone the fuel pump wiring in my forester, on the factory wiring the voltage at the pump dropped to 12.7v, with a feed straight from the battery the voltage was 13.7. not sure what the currents would be but at a higher voltage you will draw less current.

[loner]

There are some good resources out there in terms of calculating wire gauge required based

on amperage and length of wire... and also how much all the common fuel pumps draw based

on pressure being pumped.

http://realstreetperformance.com/store/pages/fuel-pump-comparison-test-5.html

http://radiumauto.com/media/techarticle-page.php?Radium-s-Ultimate-Fuel-Pump-Test-87

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html