i bought a b16 with skunk2 stage 2 cams and valvetrain but the guy has stock injectors. fuel pressure is set at 56psi at idle and leaned out the upper portion of the fuel map with a VAFC. I need to get the car properly tuned but I need to drive it as my daily. Should i reset the VAFC and lower the pressure? What do other people with the cams run with stock injectors...

with a stock pump i thought more pressure mean less flow. anyone have a map of a stock EF fuel pump at different PSI?


Modified by civickid03 at 6:34 PM 12/19/2007

 

if you are already leaning out, then lowering fuel pressure will make it worse.. more pressure will give you more flow.

a fuel pressure regulator performs the same function as the **** on the garden hose. turning up the pressure increases the flow.

 

turning up the pressure does not increase the flow...esp with a stock pump...think about your garden hose example...your restricting flow to increase the pressure...if it were me I would put a walbro in it and tune it with the vafc for stock fuel pressure settings...esp if your still running stock injectors

 

cracking a valve with 200psi of static pressure for half a second will release more material than cracking a valve with 100 psi of static pressure for half a second. the same theory applies to fuel injectors.

You will run into the upper limit of the fuel pump's flow if the pump cant maintain constant pressure, which might happen on the stock pump, as someone mentioned.

 

who do i believe?

say the theory about the valve at 200 psi is true, wouldnt the pwm time also affect
pressure?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 92_civic &raquo;</TD></TR><TR><TD CLASS="quote">turning up the pressure does not increase the flow...esp with a stock pump...think about your garden hose example...your restricting flow to increase the pressure
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That is the dumbest thing I have ever heard. That has nothing to do with how fuel pressure works.

It all depends on how much the pump can flow but if the pump isn't being maxed more pressure = more fuel. If the pump is maxed out turning up the pressure wont really do anything.

I cant see how more fuel pressure can actually produce less fuel no matter what the circumstances are. The pump always flows the same.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spun Vtec &raquo;</TD></TR><TR><TD CLASS="quote">
It all depends on how much the pump can flow but if the pump isn't being maxed more pressure = more fuel. If the pump is maxed out turning up the pressure wont really do anything.

I cant see how more fuel pressure can actually produce less fuel no matter what the circumstances are. The pump always flows the same.
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exactly.

the time the injector is open at a given rpm and atmospheric pressure is the same if you dont change the fuel map which changes the injector pulse. The opening and closing of the injector would effect the static fuel pressure in a system where the pressure was being supplied by a pump that flowed at a similar rate to amount of fluid released from the system per increment of time. This is NOT the case on the fuel system in a stock honda, IE 240cc injectors and ~79 L/h stock fuel pump. whether or not you are running a stock fuel system remains to be seen, but in most cases, since the injected fuel volume is probably much lower than the flow rate (volume/time) of the fuel pump, the pressure drop would be negligible, and therefor not worth worrying about.

 

3rd calculator down to show new pressure vs old pressure in flow rates:

http://kgparts.com/index.php?page=fuel-calc