Hi, just wondering if anyone is running twin walbro 485s? I was thinking that running two feeding to a -8an Y piece so you then run a single -8an feed and 6-an return. could have the second 485 come on with a hobbs switch at say "X" psi? thoughts? supra another zed one
If you ran the second one off a psi switch, will this then double the fuel pressure, requiring also an adjustment at the fpr?
The point of the fpr is exactly that: to regulate the pressure of the fuel. So regardless of the pressure from the pump/s on the inlet side it maintains a certain pressure on the outlet side. Thats my understanding of it anyway
Yeah I don't know, is the adjustment based on a set pressure at the incoming side, so if you double the incoming pressure, will this affect the outgoing pressure for the same adjustment? Actually I've got that backwards haven't I lol. But same point. I don't know. Too much thinking for this time of day :rofl:
The fpr is located in the return line, after the rails, the fuel comes into the rails and builds pressure against the regulator until the reg opens at what ever pressure its pre set to. No matter what the pressure from the pump, or pumps is, the reg will open at the set pressure.
It's a regulator not a tap, it's operation is proportional IE: if you provide lots more flow than is required it is open a lot more than if you have just enough flow. As far as the two pumps go, don't mount the two of the side by side in the tank as per the pictures if you want to do any track work, in short it doesn't work & you get serious fuel surge. If you are trying to draw that much fuel from the tank & want to go around corners as well you are going to need something better than the plastic tank the factory provided. (see my thread about the fuel tank mod I started but aborted) I've had twin pumps in the car for a little while and use the Link ECU to control the second pump based on injector duty cycle, once it hits fifty percent duty on the injectors the second pump kicks in on a PWM setup, that way we can adjust how much extra fuel we get so as not to overpower the FPR & increase fuel pressure. New setup has a surge tank feed by the stock TT fuel pump then twin Bosch 044 pumps, one running full bore all the time, the other via PWM as required.
Elegant like a show pony Works well for dyno queens or drag racing but zero use for track work so depending on what the intended use for the car is it's possibly not actually a solution but more of a sideways step - solve one issue & create another.
Something I was looking at with the 2+0, it appears the hole and bolt pattern for the passenger side sender is the same as the driver side pump/sender assembly. Could you mount a second factory pump assembly in the passenger side, either then teed together or feeding a surge tank? Would this be a better option for circuit work? A pump either side in the main tank? Rather than the 2 pumps mounted together on one side only?
Mark that setup is pretty much the same as my twin walbro 255's. As long as they fit back into the tank its a good setup. My second pump is off a 2psi hobbs in the intercooler which grounds the second relay trigger. Check out racetronix for proper fuel resistant in tank looms etc and bulkhead plugs
So long as both intank pumps are located within an internal "swirl pot" then all is good. This reduces chances of fuel surging and pressure drops which will really ruin your day. However, its always a little marginal at lower tank levels as no matter what, your going to get splashing and surging of fuel. Best practice is a stock intank as a lift pump to an external surge tank and then feeding whatever pumps you need. Its also perfectly acceptable to run 2 pumps in series. Or stock intank feeding a second external inline (helper) pump. This is the simplest upgrade to do. Think VL turbos. You still need to ask yourself the question, "Why do I think I need twin pumps?" 040/044's deliver near 700Hp worth of petrol. Not too many of you will go anywhere near that. Boosted up on corn juice, I get that. E
I thought it was closer to 600hp? Is why I ended up going with two, one would have done the job JUST but been right on the brink of disaster at the top end. The trouble with the stock tank is this: The pumps sit in nothing more than a glorified bucket & when you go left fast the bucket suddenly becomes empty, I had fuel surge with 3/4 tank of gas - doesn't lend to many laps out on the track before having to pit when you're burning ~3L per lap. A pump mounted on each side would solve this so long as they both have check valves BUT each pump MUST have the ability to deliver the full volume of fuel required at peak demand otherwise you could be in for a bit of an issue
Question, how does the stock pump located on one side of the hump in the fuel tank pickup fuel from the other side once the levels get low, ie below the hump?
There's a tube that runs across to the bottom of the other side, on the pump side that tube is connected to a valve assembly that uses return fuel to draw fuel from that tube & drops it in the LHS. Ironically if you get low on fuel & have little to no return from the engine you will loose the fuel supply from that system :rofl:
I need two pumps as I will be running 35psi on slightly larger turbos and a 150 shot on top of that pending how it runs on 100. So a fair bit of fuel at WOT and it will all be on e85
Ahh well, thats different. So shooting for circa 600 Kw then. Thats reasonably serious goalposts in the really big league and your asking such questions??? 10mm fuel lines (min) for you as well. Dont go dicking around with funky arsed pressure switches and so-on sport. K.I.S.S. principle. Simple and foolproof. Just run your pumps flat out. Make sure you have good dedicated power supplies to the pumps as well. Override one pump manually if you must. Big red flashing light when its overidden so you cant forget. Have fun. E
