External Fuel Pump
- Thread starter TLI
- Start date
http://www.turbobuick.com/forums/e85-technical-forum/276679-parts-way.html
most of your answers are here
most of your answers are here
You can have an in-tank pump feed an external pump, in a series configuration. What you will get is that the head pressures are additive. In other words, at any flow rate, you add the output pressures, on a flow chart. The resultant will be greater flow than a single pump alone.
turbofabricator
Well-Known Member
- Joined
- Mar 7, 2004
The in-tank pump can only supply what it is rated at. Putting a bigger pump down stream will only choke the bigger pump. It is impossible for a intank pump to flow more fuel just because there is a pump trying to pull fuel through it. Consider the intank pump an orafice. Also, the stock fuel lines on our cars are REALLY only a 1/4" in diameter. At every saginaw fitting, the tube is crimped to hold an O-ring and the ID is necked down to .257". With that being said, installing a -6AN fuel line in our car for feeding the rail is enough area to feed OVER 750 HP. There are guys running 140+ mph in the 1/4 with a single in tank pump and methanol. (using stock fuel lines) Unless you are making more than 600HP, there is no reason to go to an external pump. IMO
I ran a 1/2 tank of E-85 and 1/2 of Sunoco 94 mixed and had no issues. Turned my Alky off and car showed no signs of knock even at 22 psi. I do however have the ATR double pumpers. My injectors are 60#'s. Not an expert on E-85 but it worked in my combo. Guy at Station said my Octane rating should be close to 100 when mixed with the Sunoco 94.
A good set of double pumpers and big injectors and of course an Alky chip should be all you need. White Marine and racing sells a Red Armstrong double pumper kit complete with fuel sending unit and hobbs switch to activate the second pump. Around $600.00
A good set of double pumpers and big injectors and of course an Alky chip should be all you need. White Marine and racing sells a Red Armstrong double pumper kit complete with fuel sending unit and hobbs switch to activate the second pump. Around $600.00
Absolutely, as does any and every pump. Remove the "load" or pressure restriction by putting an external pump downstream and now the in-tank pump is delivering fuel at near zero pressure (also called free flow). The in-tank flow rate during this condition is a maximum, it has almost no restriction at its outlet. So it is delivering fuel at 0 psi, or what is at "rated at", on its pressure-flow chart.
No way. In this configuration, the bigger downstream pump is now having fuel "handed" to it, instead of trying to suck it up itself. It now has an easier time delivering fuel (because it has fuel pushed to it) and will actually outperform it's "rated at" pressure-flow chart (which was developed with the single pump configuration).
Incorrect. Ever blown in to a running fan, assisiting airflow? Have you noticed that it speeds up? Same principle. Again, the outlet restriction has been removed (the external pump is sucking fuel away) so the in-tank is in a free-flow configuration, delivering fuel to no load whatsoever. The bigger pump, pulling fuel away, is helping the in-tank pump, and in some cases, can actually cause negative suction pressures to develop and speed up the feeder pump. (This only happens when the external pump is free-flowing against no pressure load).
You will notice on pressure-flow charts, the slope of the curve at or near 0 pressure is negative (sloping down to the right). Almost always, the chart stops at zero presssure (since it would take another downstream pump to get data at negative pressures). But if you were to test with 2 pumps in-line, and develop negative suction pressures, you would see that the flow rate of the feeder pump would actually keep increasing (beyond that of free-flow) because it has fuel being pulled from it (like blowing through a fan). In this case, the p-f curve would continue upward to the left, with negative pressures on the x-axis. Seen this all the time while testing/charactrerizing multiple pump configurations.
turbofabricator
Well-Known Member
- Joined
- Mar 7, 2004
Your info is mostly correct, HOWEVER...........Why put a big external pump as a band-aid. Just do it right once and not have one pump or the other go bad and not be able to do the job. Keep it simple. BIG external near the tank and below fuel level (i.e behind and below) and you will have a reliable, easy to diagnose fuel system. Dual in tank pumps is really the best way to go if you need more fuel than a single pump can deliver. That would be on cars that make over 650 hp (with a alky system). I use to use intank and extenal together, but stopped that 18 years ago to keep it simple.
So, are saying that if a Eliminator pump will flow enough fuel to feed 1200HP, it will flow more with a single Walbro in tank? Answer: NO, because the Walbro is now the restriction. It feeds through a .250" (or so, as I don't have one in front of me right now) hole. It fits a 5/16 hose. Your info is a generalization and could cause BIG problems if the intank pump is incapable of flowing the required fuel flow (even at zero/negative delta P)
So, are saying that if a Eliminator pump will flow enough fuel to feed 1200HP, it will flow more with a single Walbro in tank? Answer: NO, because the Walbro is now the restriction. It feeds through a .250" (or so, as I don't have one in front of me right now) hole. It fits a 5/16 hose. Your info is a generalization and could cause BIG problems if the intank pump is incapable of flowing the required fuel flow (even at zero/negative delta P)
I just ordered an aluminum fuel cell and A1000 pump this weekend. Should be here Wednesday. The cell has a 90ohm sender unit, so my gas gage should work too. 
I'm tired of fooling around with stock gas tanks and questionable in-tank pumps. I'm not messin around anymore.
I'm tired of fooling around with stock gas tanks and questionable in-tank pumps. I'm not messin around anymore.
