Downside of bumping pressure via FPR?
10-20-2009, 10:07 AM
#1
Downside of bumping pressure via FPR? Quick background on my fuel system real quick. Twin walbros in tank, stock feed, boost reference Aeromotive FPR, FAST rails, 95lb/hr Precision Turbo low impedance injectors, acceleronics driver box, -6AN braided return.
I'm pretty sure I'm maxing out the stock feed line, injectors are at 97% duty cycle, but A/F is solid, doesn't go lean and responds to fuel addition/subtraction as it should, also, when I switched from the 75's (after I found out they were 115% at 5300 RPM) the A/F didn't move at all, so in my mind that is telling me that the tuning is on. The shop has ordered me an -8AN line and fittings to upgrade the feed. I'm hoping that will lower my duty cycle because I don't see how I'm maxing 95's out, but the car does have a lot of drivetrain loss so it may have more power at the flywheel then I'm taking into account.
My question is, what is the downside of bumping fuel pressure via the regulator from say 43, to 50psi? Is there a downside, assuming the pumps can keep up? In short, I don't want to band aid a problem, if I need new injectors I need them and I'll get them, just checking out the options. Thoughts, opinions, and objections welcome. Thanks guys!
I'm pretty sure I'm maxing out the stock feed line, injectors are at 97% duty cycle, but A/F is solid, doesn't go lean and responds to fuel addition/subtraction as it should, also, when I switched from the 75's (after I found out they were 115% at 5300 RPM) the A/F didn't move at all, so in my mind that is telling me that the tuning is on. The shop has ordered me an -8AN line and fittings to upgrade the feed. I'm hoping that will lower my duty cycle because I don't see how I'm maxing 95's out, but the car does have a lot of drivetrain loss so it may have more power at the flywheel then I'm taking into account.
My question is, what is the downside of bumping fuel pressure via the regulator from say 43, to 50psi? Is there a downside, assuming the pumps can keep up? In short, I don't want to band aid a problem, if I need new injectors I need them and I'll get them, just checking out the options. Thoughts, opinions, and objections welcome. Thanks guys!
10-20-2009, 11:23 AM
#2
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Walbro's start to struggle around 75psi on their flow curve. If you're boost referenced at 1:1 I would keep 75 as a max and bump your base fp up to get there. example...if your running 20psi boost max 75-20 = 55 max base pressure.
10-20-2009, 11:24 AM
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PS: I would be surprised if the stock line is a problem...at these pressure levels...the stock line can flow enough fuel for 1000rwhp and has done it over and over....never hurts to upgrade it though....
10-20-2009, 01:58 PM
#4
Hmm, interesting info on the line. I've ran a few calculations and from what I can see, 1000HP at the crank I'd need a 93.75lb/hr injector at 80% duty cycle. I'd be surprised if the motor is over 1000 or really that close to it. What do you think?
10-21-2009, 08:59 AM
#5
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What's you AF ratio? That plays a big part. What kind of mph does it run? How much boost and what system?
10-21-2009, 03:55 PM
#6
I've heard about Speed Inc. making good power on the stock line, but theoretically could you not add more injector than you would need with a suitable feed to make up for lack of line?
AF is 11.8-11.9 at the tail pipe, 11.5 on the scanner. MPH isn't going to be much help, 130-134 with the converter slipping. 19.5 psi, D1-SC ProCharger kit.
AF is 11.8-11.9 at the tail pipe, 11.5 on the scanner. MPH isn't going to be much help, 130-134 with the converter slipping. 19.5 psi, D1-SC ProCharger kit.
10-21-2009, 04:02 PM
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"95lb/hr Precision Turbo low impedance injectors"...who is the manufacturer? Confirm the manu number on the injector to be sure they are 95's...
D1 should not max a true 95.
A larger than needed injector can mast an insufficient line or pumps with a proper tune.
D1 should not max a true 95.
A larger than needed injector can mast an insufficient line or pumps with a proper tune.
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10-21-2009, 07:31 PM
#9
Idle PSI on the reg is 45psi.
10-21-2009, 10:16 PM
#10
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Did you flow test them or Precision? At what pressure were they tested?
Only a few companies actually manufacture injectors....a lot of companies rebrand them as their own...nothing wrong with that at all...just good to know a 95lb "Brand x" injector is rated at 43psi.....not 58psi....
Bosch, Standard, Siemens, and a few others.
Only a few companies actually manufacture injectors....a lot of companies rebrand them as their own...nothing wrong with that at all...just good to know a 95lb "Brand x" injector is rated at 43psi.....not 58psi....
Bosch, Standard, Siemens, and a few others.
10-21-2009, 10:32 PM
#12
Did you flow test them or Precision? At what pressure were they tested?
Only a few companies actually manufacture injectors....a lot of companies rebrand them as their own...nothing wrong with that at all...just good to know a 95lb "Brand x" injector is rated at 43psi.....not 58psi....
Bosch, Standard, Siemens, and a few others.
Only a few companies actually manufacture injectors....a lot of companies rebrand them as their own...nothing wrong with that at all...just good to know a 95lb "Brand x" injector is rated at 43psi.....not 58psi....
Bosch, Standard, Siemens, and a few others.
10-22-2009, 07:14 PM
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If they flowed 95 at 43.5 they are fine. You have a supply problem. Since you're going to do the feedline anyway, that's a start....I'd question the pumps myself. Does the fuel pressure rise at a steady rate when under boost? You should be seeing 65ish psi at max boost.
