So I have a stupid idea!!
This is my idea… get 2 boost referenced fuel pressure regulators and connect them is series. Set the static pressure at 45psi. When idling at 15lbs of vacuum, each regulator would be at 30psi (45psi static – 15psi of vacuum) for a total of 60psi of fuel pressure. When at 15lbs of boost, each regulator would be at 60psi (45 static + 15psi boost) for a total of 120lbs of fuel pressure. It would essentially be a 2:1 boost reference FPR.
This is theoretical of course, but if it would work, that would solve my problem of getting 8 injectors to idle on pump gas and still make 1200fwhp on E85. I attached a scribbled up drawing of my idea (hope the link works)
Any thoughts?
Last edited by smokinHawk; Jul 26, 2010 at 07:18 AM. Reason: NON SPONSER URL
Ofcourse you would want to keep the peak fuel pressure as low as possible to prevent excessive heating of the fuel, but on E85 it probably isnt that much of an issue anyway.
this is how most sport bikes on the road are setup, 4 cylinders, 4 injectors, and 4 injectors/nozzles. Keeps the primary injectors from doing all the work.
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The pintle of the injector opens against fuel pressure. Above around 100 psi, the pintle is slow to open or wont open at all, due to it working against fuel pressure. You will need to keep the fuel pressure below 100 psi.
Get an adjustable boost-referenced fuel pressure regulator, set it to a high number that satisfies fuel delivery requirments for the hp needed, and just trim the pulsewidth back at idle/low speed through tuning.
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"can you not just buy a reg that has a 2:1 ratio instead?......"
I've never been able to find one.
"or you can boost reference a fuel nozzle to come on, kind of like a TPI setup, right before the TB."
This idea would work, but their would be a concern with proper fuel distribution. Plus, I wouldn't have to mount, plumb, and wire extra injectors. This idea just sounds easier.
"An FMU would be anouther option."
A FMU only controls the pump (at least the ones I've seen). The type with "Pulse Width Modulation" like the one from Weldon is used to decrease the volume of the pump when there isn't demand for extra fuel, and the type like the Boost-A-Pump from Kenne Bell uses a boost reference to increase the flow from the pump. Either way, they only affect the volume of the pump, not the fuel pressure.
"15 psi of vac is approx 30 inches of vacuum. There's not many engines I can think of that idle with 30 inches of vac. You may have around 20 inches of vac at idle (10 psi vac)."
I meant 30psi of fuel pressure, not vacuum. Think of each FPR as a separate unit, then add the resulting pressure from each FPR to get the total fuel pressure. If one FPR would normally be at 30lbs of fuel pressure, then 2 in series would be at 60. If one would normally be at 45lbs of fuel pressure (with 15lbs of boost reference) then 2 would be at 90.
"The pintle of the injector opens against fuel pressure. Above around 100 psi, the pintle is slow to open or wont open at all, due to it working against fuel pressure. You will need to keep the fuel pressure below 100 psi."
If fuelinjectorconnection.com says they are rated up to 120psi, I don't see what the problem is.
"Get an adjustable boost-referenced fuel pressure regulator, set it to a high number that satisfies fuel delivery requirments for the hp needed, and just trim the pulsewidth back at idle/low speed through tuning."
I wish I could. The problem I have is getting 8 injectors to meet all of my fueling needs. I want to be able idle and cruise at stoich using pump gas, and when I switch to E85 meet my 1300fwhp goal. 100lb injectors at 120psi of fuel pressure would get me there, then I wouldn't have to switch to 120's or even 160's.
Has anyone run 100+ lbs of fuel pressure?




