Fuel pressure
09-20-24, 10:37 AM
#1
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Fuel pressure
I have an 1985 Mazda rx7 12a rotory fb 1st Gen it has a holloy 4 barrel carburetor it's also street ported, I'm having trouble figuring out how much psi I need for my carb it says no more than 4psi but I can't seem to figure out how much psi for a Street Port and what fuel pump is best and fuel regulator it's not pushing enough fuel to the front my filter is half fuel upfront i heard its supposed to be full im not mechanicaly inclined it cranks but doesn't start. And will loose fuel hose if it's not correctly sealed properly on my connector on my cell will that cause no pressure? Either way I want to replace my fuel pump and fuel regulator as they're old. Thanks
09-20-24, 12:18 PM
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the factory manuals have tests for both volume and pressure, both are pretty simple
the volume is easy. you put the fuel line in a container, and you turn the pump on and see how much fuel you get in either 30 seconds, or a minute.
the stock pump does about 700cc in 30 seconds, or 1400cc in 60 seconds. if you're doing the 60 second test you need a pretty big container, 2 liters.
i use something that was supposed to be for juice, and its only a liter, but its marked every 100cc, which is nice. but its only 1 liter, so i need to do 30 second tests.
the factory pump 1400cc minute, is plenty for quite a bit of power.
for pressure tests you need a gauge, the factory pump does about 2.75psi, which works pretty well for most setups. if your spec is less than 4psi, you'd be there.
the volume is easy. you put the fuel line in a container, and you turn the pump on and see how much fuel you get in either 30 seconds, or a minute.
the stock pump does about 700cc in 30 seconds, or 1400cc in 60 seconds. if you're doing the 60 second test you need a pretty big container, 2 liters.
i use something that was supposed to be for juice, and its only a liter, but its marked every 100cc, which is nice. but its only 1 liter, so i need to do 30 second tests.
the factory pump 1400cc minute, is plenty for quite a bit of power.
for pressure tests you need a gauge, the factory pump does about 2.75psi, which works pretty well for most setups. if your spec is less than 4psi, you'd be there.
09-28-24, 08:58 PM
#3
welcome to the board. 
where did you get that number from? i'm curious.
that said, as far as i know RB recommends 6 PSI for Holley setups. i can confirm that a Holley will run with the stock pump, but it does really weird things when you get you get on it. at times, it might do weird things even if you're not getting on it. ultimately, you will need more pump. i don't know what the "go-to"-pump is these days, but back when my brother and i were working on his car, he was running a Holley Red. it was a huge step in the right direction.
where did you get that number from? i'm curious.
that said, as far as i know RB recommends 6 PSI for Holley setups. i can confirm that a Holley will run with the stock pump, but it does really weird things when you get you get on it. at times, it might do weird things even if you're not getting on it. ultimately, you will need more pump. i don't know what the "go-to"-pump is these days, but back when my brother and i were working on his car, he was running a Holley Red. it was a huge step in the right direction.
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