FMU Question
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Joined: Aug 2001
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From: Jersey, USA
FMU Question
I was looking at the Vortech FMU's online and notice the different ratios available(8:1, 10:1, etc...). What would be appropriate for my setup?
Stock Block
Stock injectors
Walbro 255--in tank
Garrett t3/t04e
Tial 35mm--stock spring .45 bar
Stock Block
Stock injectors
Walbro 255--in tank
Garrett t3/t04e
Tial 35mm--stock spring .45 bar
Joined: Jan 2003
Posts: 51
Likes: 0
From: Fords, nj, USA
Re: FMU Question
FMU Operating Description
In Summary, the FMU backs up line pressure at the given rate for this example 10:1, therefore if the original regulator still in place holds a rail pressure of 40psi, it will take 4psi of boost for the FMU to raise pressure to 40psi. At this point there still will be no effect at the rail pressure simply because most factory regulators also raise fuel pressure at 1lbs of fuel pressure per 1lbs of boost. So you would have 44 lbs in the fuel rail and 40 psi between the FMU and the original Reg. But at 5lbs of boost you would then have 50psi held by the FMU thus raising the rail pressure by 5psi. Then at 6lbs of boost you would have 60lbs at the FMU and 46lbs held by the original reg, thus raising the fuel pressure by 14psi. This proccess will increase as boost increases. CAPA does not reccomend running fuel pressure any higher than 90psi. Precautions must be taken to ensure that all fuel system components are capable of operating at these high pressures. Hope this helps
In Summary, the FMU backs up line pressure at the given rate for this example 10:1, therefore if the original regulator still in place holds a rail pressure of 40psi, it will take 4psi of boost for the FMU to raise pressure to 40psi. At this point there still will be no effect at the rail pressure simply because most factory regulators also raise fuel pressure at 1lbs of fuel pressure per 1lbs of boost. So you would have 44 lbs in the fuel rail and 40 psi between the FMU and the original Reg. But at 5lbs of boost you would then have 50psi held by the FMU thus raising the rail pressure by 5psi. Then at 6lbs of boost you would have 60lbs at the FMU and 46lbs held by the original reg, thus raising the fuel pressure by 14psi. This proccess will increase as boost increases. CAPA does not reccomend running fuel pressure any higher than 90psi. Precautions must be taken to ensure that all fuel system components are capable of operating at these high pressures. Hope this helps
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