Has anyone done a double pumper running Walbro 255 as a 1st pump on stock wiring and 450 as a second pump with hardwire and hobbs switch? And will this flow any more than just a single 450? Is the 450 just killing the flow of the 255 when it kicks on?

And is it safe to use stock wire plug for the 255 running E85? Asking because the E85 Wally 450 has a sealed plug and the oem hanger plug is not sealed. Maybe just better to connect the stock wires outside of the hanger and use the oem plug only for the fuel level metering.

 

If you Ned more than twin 255's, you just need to run twin 450's. And really, since the new 525 pump is out, it should be 2 of those.

 

Personally, I like your thinking. 255 for primary with stock wiring (255 should be more efficient than oem pump, i recall seeing that the 255 draws slightly less current). Then drop in 450/525 as secondary with a switch.

 

What's your power goal? Will 255 + 525 be enough fuel?

 

My power goal is 600-650whp dynojet running E85. I am running a hardwired 450 now, stock fuel filter removed, stock line and 6an + filter before aem fuel rail. I just hit 600whp with Bosch 1500 injectors (measured 1450 at 43.5 psi). The duty cycle is about 95-97% at the end of the run and afr hits 12 and floats between 11.7-12. And it blew the head gasket between cyl 1-2. I had an exhaust temp gauge in 1st runner and it didn't show more than 800 celsius. Before the injury, I had a fuel pressure gauge installed and it read 70 dropping to 62-60psi when the boost was 34.5 dropping to 28psi. So the pressure should be about 78psi to 71psi. Maybe the gauge was reading too low, but the pressure is dropping a little at the end. That's why I was thinking about installing a 255 next tor 450 and a digital fuel pressure gauge to get solid readings. If it's not keeping the pressure, then I will swap the regulator and maybe switch to bigger injectors.

Yes, I know I was playing with a fire with those duty cycles, but the afr was reading fine and the exh. temp too.

So, none done a 255+450 double pumper LOL If I put another 450 in there, I have to do another hardwiring and relay. Or do as suggested, two 255 Wallys.

 

I'd do 255 and 525. This is actually my plan with an addition of Boost-a-pump on 525. I don't need it until I build my motor.

 

Well. I have an almost new 450 in there so I don't like the idea of the 525. But as I asked in the 1st post, I wonder how much the 255 will flow when the bigger pump kicks on? Is it fighting against the bigger pump flow? That's why I asked if anyone has done the double pumper this way,

 

I have a 450 primary, running an upgraded wiring version of the factory dual voltage setup, and then a 255 as secondary on a hobbs switch. It gives me 3 levels of fuel delivery and works great.

 

Interesting. The 255 should have an easier time pressurizing up to fuel pressure than the 450 as secondary. The only reasons I'd use 255 as primary is to not have to worry about too much return fuel at idle, even with OEM dual stage. Running 450 as primary works too but I would double up on the oem fuel resistors to avoid burning them out since 450 will draw more power than oem pump when off throttle.

 

Thanks talonkev. Do you see afr dropping, when the 255 kicks on?

What do you mean with upgraded wiring version of the factory dual voltage setup? I know the dual voltage system, but how can you upgrade it? I have 3 levels now (mr fred style: stock wiring+ relay, bigger wire and hobbs swirch)and I wouldn't like to do another relay and wire (+ same hobbs switch) for the second pump.

I was thinking of doing it 255 as a primary and 450 as secondary, so I don't have to do any rewiring. I just connect the 255 to the oem wires (it's good enough for the 255) and then hobbs switch and bigger wire to the 450.

 

I started with a single 450 fuel pump on dual voltage, then when I needed more fuel it just made sense to simply add a 255 and hobbs switch as a secondary. I'm still using the factory return line. Fuel pressure stayed down at idle with the 450 on low voltage even back when I was running 93 octane. I've had this setup for a couple years now, and the factory resistor hasn't blown out yet, but now that you mentioned it I'm sure it will soon. lol

 

You're wasting your time with twin pumps. A walbro 525 with hi/voltage rewire is all you need. Don't even need to upgrade lines, rail, fpr, etc.

You could also go a bit bigger on injectors and be ok. FIC 1650 or ID 1700's flow closer to 1600cc/min. That with the ~10% extra flow from the 525 and you'll be fine.

 

Yes, I have been thinking of this too. 525 flows some more than 450 around 70-80psi and would probably be enough in my situation.

 

I try to avoid the complexity of twin pumps as much as I can. And at 600-650whp they're certainly not needed.

 

I agree 100%. I wish the 525 existed a few years ago when I was upgrading my fuel system.