How much fuel do I need at 11psi?
10-02-09, 05:04 PM
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How much fuel do I need at 11psi?
Hey everyone I have a S5 'JDM' with full 3.5" exhaust, HKS intake, Haltech E6K, and ported wastegate. I have the 550cc primary and 720cc secondary at about a mile high elevation. I am aiming for around 11 psi hopefully out of the stocker, is this enough fuel for my altitude?
10-02-09, 05:32 PM
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what kind of horsepower are you looking to make
(or what does the setup of yours roughly make)
that's the main question, psi isn't the particular number you should be worried about for fuel supply.
the equation for the fuel injector size (In Cubic centimeters) is
(engine hp x BSFC x 10.5) divided by (# of injectors x duty cycle)
BSFC
rule of thumb is to use .6 for really well tuned Rotaries
to .7 or .8 for not so well tuned.
regardless, if you use the bigger (if you're unsure) number for this variable
you will just end up with some slightly larger than needed injectors
which means if you up the power of your vehicle your fuel system will be able to handle it.
Also, if you start running bigger and bigger fuel injectors
you need to upgrade your pump and grab a fpr if you start getting really large.
the only other thing to remember is that the stock fuel system has about 40psi to offer
while after market injectors are set for their 43psi so if you stick stock they'll be slightly less efficient
google one of the injector sites if you're not willing to do the math yourself
most of them have online calculators for you.
hope that helps
(or what does the setup of yours roughly make)
that's the main question, psi isn't the particular number you should be worried about for fuel supply.
the equation for the fuel injector size (In Cubic centimeters) is
(engine hp x BSFC x 10.5) divided by (# of injectors x duty cycle)
BSFC
rule of thumb is to use .6 for really well tuned Rotaries
to .7 or .8 for not so well tuned.
regardless, if you use the bigger (if you're unsure) number for this variable
you will just end up with some slightly larger than needed injectors
which means if you up the power of your vehicle your fuel system will be able to handle it.
Also, if you start running bigger and bigger fuel injectors
you need to upgrade your pump and grab a fpr if you start getting really large.
the only other thing to remember is that the stock fuel system has about 40psi to offer
while after market injectors are set for their 43psi so if you stick stock they'll be slightly less efficient
google one of the injector sites if you're not willing to do the math yourself
most of them have online calculators for you.
hope that helps
10-02-09, 05:58 PM
#3
1986 Rx-7
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Well I got a wally 255, forgot the mention that. Which is another questions. Do I need a pressure regulator for the 255? I am aiming for as close to 300 as I can with the stock turbo. I am getting a BNR stage 2 or 3 down the road so hope to hit a decent amount over 300 after that.
10-02-09, 10:49 PM
#4
Stock turbo maxed out (~12psi): 550/720cc injector combo & proper tuning
BNR hybrids: 4x720cc injectors or larger depending on the headroom you want.
You also won't be making 300 hp at the wheels with the stock turbo. But it's possible to make that much at the flywheel (mid 200s at the wheels). BNRs can make in the 300-350 WHP range.
BNR hybrids: 4x720cc injectors or larger depending on the headroom you want.
You also won't be making 300 hp at the wheels with the stock turbo. But it's possible to make that much at the flywheel (mid 200s at the wheels). BNRs can make in the 300-350 WHP range.
sad day. I just want to make as close to it as possib le.
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