Does fuel pressure from stock frp rise during boost?
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Does fuel pressure from stock frp rise during boost?
Quoted from the Helms manual:
"When the difference between the fuel pressure and the manifold pressure exceeds 43psi [for b18b], the diaphragm is pushed upward, and the excess fuel is fed back into the fuel through the return line."
This enables the fuel pressure to be 43 psi at atmospheric pressure. But at say 9 psi, the fuel pressure would be 51 psi, right?
Just checking to see if I have this right.
"When the difference between the fuel pressure and the manifold pressure exceeds 43psi [for b18b], the diaphragm is pushed upward, and the excess fuel is fed back into the fuel through the return line."
This enables the fuel pressure to be 43 psi at atmospheric pressure. But at say 9 psi, the fuel pressure would be 51 psi, right?
Just checking to see if I have this right.
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Re: Does fuel pressure from stock frp rise during boost? (00SilverLS)
I also was wondering how the stock fpr acted under boost. I was told I should leave it open to atmosphore, because with a 12:1 fmu I would run really rich, also that I want the 12:1 fmu to react to the boost and the stock not to see boost. What do you guys think?
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Re: Does fuel pressure from stock frp rise during boost? (DeeJay)
Also, couldn't I run check valves to it to make it not see boost? I'd rather not up the pressure so that I can keep the pump flowing as good as possible.
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Re: Does fuel pressure from stock frp rise during boost? (00SilverLS)
Mine rises under boost 1:1, some people say they don't some do. I've verified mine with a in car fuel pressure gauge.
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Re: Does fuel pressure from stock frp rise during boost? (LsTurbo91)
yeah.....that sounds right.....thats what I figured it would do....thanks.
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Re: Does fuel pressure from stock frp rise during boost? (00SilverLS)
best way to verify is with an in-car gauge. the FPR on the '99-00 civic Si only rises from vacuum up to atmospheric, and does NOT rise under boost, but it's quite possible that the LS FPR acts differently.
-Xerxes
-Xerxes
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Re: Does fuel pressure from stock frp rise during boost? (Xerxes)
very interesting. if my FP gauge went high enough, or my cartech had a marking ont he rise rate adjustment, i would check this out. there is probably a certain point beyond which it is incapable of raising the pressure...
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Re: Does fuel pressure from stock frp rise during boost? (Xerxes)
XERxes, how can a regulator not rise under boost 1:1 if it has a line hooked up to the manifold. that doesnt make sense
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Re: Does fuel pressure from stock frp rise during boost? (TurboInteg95)
I think the question is:
Is the the stock FPR's diaphragm already fully closed at atmospheric pressure or is there more room to block the fuel to the return line with positive boost pressure?
Is the the stock FPR's diaphragm already fully closed at atmospheric pressure or is there more room to block the fuel to the return line with positive boost pressure?
#11
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Re: Does fuel pressure from stock frp rise during boost? (00SilverLS)
correct. the stock sping in the frp is pretty weak so the fuel pressure does raise. I see about ~56psi of fuel pressure at 15psi with the stock fpr. Its pretty much 1:1.
liam
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Re: Does fuel pressure from stock frp rise during boost? (liam821)
I was looking at the design in the Helms manual more and it HAS to go up 1:1. Thats just how it works: it compares fuel pressure to air pressure.
[Modified by 00SilverLS, 4:04 PM 11/28/2001]
[Modified by 00SilverLS, 4:04 PM 11/28/2001]
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Re: Does fuel pressure from stock frp rise during boost? (00SilverLS)
Right, but it is limited. The FPR will eventually close the return line off completely and the pressure will not be able to further rise with boost pressure. In other words, the fuel pressure will stay at a fixed psi (in liam821's case 56psi) until the boost pressure falls back down.
[Modified by quick108, 1:13 PM 11/28/2001]
[Modified by quick108, 1:13 PM 11/28/2001]
#15
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Re: Does fuel pressure from stock frp rise during boost? (00SilverLS)
My stock FPR does not rise under boost. I verified it with an in-car fuel pressure gauge. I've seen the same behavior on 3 other 99+ Civic Si's as well as 1 2000 ITR. Yours may rise under boost....the only way to tell is to test.
Sonny
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Re: Does fuel pressure from stock frp rise during boost? (Sonnyballs)
i have a greddy fuel in-car fuel pressure gauge...and the pressure does increase with boost. Although i have a sohc engine. Maybe the fpr in the b-series engines are stronger? Anybody know?
liam
liam
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Re: Does fuel pressure from stock frp rise during boost? (liam821)
You guys do understand that the 1:1 FP increase is not enriching fuel right? It is just compensating for pressure in the manifold to keep fuel delivery constant.
Dustin
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