Fuel Pressure Still Dropping...
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Oh man i was just getting another 255 walboro pump in the tank Please keep us updated on your problem.
Anyone know where to get the 044 pumps for the best price? They are pretty expensive on the web. Also would one 044 pump be enough to flow 700-800rwhp SC'd car?
Anyone know where to get the 044 pumps for the best price? They are pretty expensive on the web. Also would one 044 pump be enough to flow 700-800rwhp SC'd car?
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I just found this artcile which compare Walboro VS 044 pump.. http://www.stealth316.com/2-fuelpumpguide.htm#j6
They are saying there is a 255 high pressure walboro (GSS340-341-342) and 255 low pressure (GSS307-315-317). Which one are you running now?
They are saying there is a 255 high pressure walboro (GSS340-341-342) and 255 low pressure (GSS307-315-317). Which one are you running now?
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Originally Posted by MECHAM
340's
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Originally Posted by MECHAM
i turned the ingnition on...waited a sec for the pressure to rise to ~52psi...turned the car....pressure stayed at 52psi...didnt drop any..waited a few minutes.
but if i dont turn the ignition off...the pressure starts to slowly drop.
i take it that both instances i just described are normal?
but if i dont turn the ignition off...the pressure starts to slowly drop.
i take it that both instances i just described are normal?
As far as the pressure dropping, I saw a video on hereI think of someones Procharged car with an in-car 1/4 mile video focused on his FP gauge. It dropped pretty good. If someone has the link/knows the setup maybe they can chime in.
Good luck
Andy
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Originally Posted by MECHAM
Twin 255 Walbros in tank - hot wired to run all the time
-8 Feed line to LS1 Speed Rails
60# Motos
Aeromotive FPR 1:1 at rails
50psi idle
~13 vacuum
+12psi
------------
75psi fuel pressure during WOT
pressure raises fine but towards 5k the fuel pressure drops and at redline its back to 60 or so psi..
Any1 else having fuel pressure dropping
-8 Feed line to LS1 Speed Rails
60# Motos
Aeromotive FPR 1:1 at rails
50psi idle
~13 vacuum
+12psi
------------
75psi fuel pressure during WOT
pressure raises fine but towards 5k the fuel pressure drops and at redline its back to 60 or so psi..
Any1 else having fuel pressure dropping
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hopefully the pic link works
http://community.webshots.com/photo/...76734921LxBlsP
using the stock line for return
http://community.webshots.com/photo/...76734921LxBlsP
using the stock line for return
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Originally Posted by HUGGER ORANGE SS
Not supprised.. Be careful with that 40psi of fuel pressure.
any updates Mecham...???
any updates Mecham...???
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Originally Posted by MECHAM
hopefully the pic link works
http://community.webshots.com/photo/...76734921LxBlsP
using the stock line for return
http://community.webshots.com/photo/...76734921LxBlsP
using the stock line for return
Your math is, I think incorrect, in the subtraction of the vac value, you show as 13, will only allow the FP to rise that 4-6psi, I mentioned. This will occur as the engine progresses into boost. At that point, zero vac, zero boost, the FP should read the original set point. [50]
As the boost comes on, and rises to 13psi, the FP gauge should read 62+/-, a #, or two, not 75....
You may want to consider a larger return line, as supporting that much HP with a small return, is a bit risky.
Just my $.02...
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Old G
my car has 13psi of vacuum at idle...always has from the days I was supercharged.
50psi fuel regulator (vacuum line attached to regulator)
13psi vacuum
12psi boost
-----
75psi
I am intrigued as to why I would need a bigger return line?
my car has 13psi of vacuum at idle...always has from the days I was supercharged.
50psi fuel regulator (vacuum line attached to regulator)
13psi vacuum
12psi boost
-----
75psi
I am intrigued as to why I would need a bigger return line?
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Originally Posted by HUGGER ORANGE SS
Not supprised.. Be careful with that 40psi of fuel pressure.
any updates Mecham...???
any updates Mecham...???
#35
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Originally Posted by MECHAM
Old G
my car has 13psi of vacuum at idle...always has from the days I was supercharged.
50psi fuel regulator (vacuum line attached to regulator)
13psi vacuum
12psi boost
-----
75psi
I am intrigued as to why I would need a bigger return line?
my car has 13psi of vacuum at idle...always has from the days I was supercharged.
50psi fuel regulator (vacuum line attached to regulator)
13psi vacuum
12psi boost
-----
75psi
I am intrigued as to why I would need a bigger return line?
I suggest you look at the gauge reading with the engine idling, vac line off, and blocked. If you do this, you will see that the 13" of vac has only a 4-6PSI effect on the pressure reading you will see, not 13 PSI.
Let's look at doing a "test" setting.
Base pressure desired is: 50PSI
So, engine idling, vac line off, and plugged, we set the regulator to 50PSI, lock it down.
Reattach the vac line, and the PSI will likely drop to 44-46.
Take the car out, and run WFO. If the 1:1 regulator is working correctly, AND the pumps are working correctly,
at 13# boost, the FP should be 62, +/- a #.
As for the fuel line sizing:
A. An OEM line that was sized to support an engine at 400HP, could be on the borderline when used on a modified system. [Except at WFO, that OEM line is expected to flow nearly twice it's intended volume.] May work, but most aftermkt systems recommend return lines near the size of the supply line.
B. Return line restrictions can cause backpressure at the regulator, pump[s]. [Causes heat, and may cause incorrect FP readings]
I'd suggest you modify the wiring to the pumps, so that off boost, you run with 1 pump. Here's a part # for a GOOD quality HOBBS switch.CCS Model 607GK.
Last fone # I had was 818-341-4610.
1 pump operation will cool things down, when you are not at "WFO"....
Lastly... Be sure your gauge is accurate. I flow check alot of the little, "mini gauges", and find them off as much as 5 psi, +/-. The best I've seen were only a # off, the worst, 7#.
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Don't always trust what you read here... I have never had a problem with running out of fuel pressure..
I'm pushing about 14psi with my setup and over 700RWHP..
Keep us updated Mecham. Depending on how you have your pumps setup, you could just pull the fuse to the primary pump to see if you still get fuel pressure from the 2nd pump..
Good luck.
Clint
I'm pushing about 14psi with my setup and over 700RWHP..
Keep us updated Mecham. Depending on how you have your pumps setup, you could just pull the fuse to the primary pump to see if you still get fuel pressure from the 2nd pump..
Good luck.
Clint
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Originally Posted by MIGHTYMOUSE
your running too much fuel pressure, kick it back to say 3 bar (43psi) key on engine off and then re trim your injector flowrate.
less pressure will allow the pumps to flow more
less pressure will allow the pumps to flow more
But wouldnt less pressure make the injectors flow less? The way i understand is that the more FP u run the more the injectors would flow. I understand that the pump will flow better at a lower FP, but what about the injectors. For example, the 60lbs injectors will flow that much at 43psi of FP and could go to being a 85lbs injectors at 87psi of FP.
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Originally Posted by LSs1Power
But wouldnt less pressure make the injectors flow less? The way i understand is that the more FP u run the more the injectors would flow. I understand that the pump will flow better at a lower FP, but what about the injectors. For example, the 60lbs injectors will flow that much at 43psi of FP and could go to being a 85lbs injectors at 87psi of FP.
But, the pressure you MUST deal with is called "delta P".
That is the NET PSI the injector is working with.
IE:
Set the base, line off, to 60PSI. Reconnect reference line.
13# boost.
The FPR, if working at 1:1, should show operating PSI as 73PSI., at 13# boost.
Remember, that the outlet end of the injector is seeing the same 13# boost. Therefore, the NET, or DELTA P, is still 60PSI, and that's the flow, in #/hr, that the injector will flow.
BTW, the increase to 87PSI, from 60PSI, will not make a 60# inj flow 85#. It will flow 72.25#, if it will work at that elevated PSI....Some will not.......
Last edited by Old Geezer; 04-26-2006 at 01:35 PM.