effect of fuel pressure on injector rating

[kismetcapitan]

if the stock fuel pressure is 3 bar and stock injectors are rated for 444cc flow per minute at that pressure, is there a formula by which one can work out what the flow would be at 3.5 bar or 4 bar? I've got a Nismo fuel regulator and when remapping I'd like to know so I can calculate what's actually going on and going through my injectors.

[kismetcapitan]

got this from the UK board:

The flow is a square root factor of the pressure (To double flow you have to quadruple the pressure):

((new pressure/old pressure)^0.5) x old flow= new flow

444cc at 3 bar is
480cc at 3.5 bar
513cc at 4 bar.

That old Nismo fuel regulator may just yet come in handy

[GTE]

Most are rated at 43 psi, if you lower that, you lower the rating, if you go above that, the rating does up

This may make life easier for you

http://rceng.com/technical.htm#WORKSHEET

[tyndago]

The flow does go up by pressure......HOWEVER

fuel pump flow goes DOWN with pressure.

Put that in your pipe and smoke it for a while........

[kismetcapitan]

well then, a stock fuel pump pushing stock 444cc injectors at 90% duty cycle is operating at what percent of its total flow capacity?

I'm getting a headache, I just need bigger injectors but the missus will cut my balls off if I spend the money to get them....

[GTE]

It depends on boost pressure (which correlates to fuel pressure)

As the pump has to create more pressure, it's efficiency in doing so decreases

Originally Posted by kismetcapitan

well then, a stock fuel pump pushing stock 444cc injectors at 90% duty cycle is operating at what percent of its total flow capacity?

I'm getting a headache, I just need bigger injectors but the missus will cut my balls off if I spend the money to get them....

[RHDS14]

Most married men have already lost their balls, with that in mind I say you order those 1000cc injectors you have been dreaming of.

Originally Posted by kismetcapitan

well then, a stock fuel pump pushing stock 444cc injectors at 90% duty cycle is operating at what percent of its total flow capacity?

I'm getting a headache, I just need bigger injectors but the missus will cut my balls off if I spend the money to get them....

[kismetcapitan]

I love enablers, thank you

so which Nismo injectors are a direct drop in for an RB26 and stock fuel rail?

[EDTHEMANJP]

Kissmecpt

I don't know about Nismo fuel injectors but these Sard 700's will fit into your stock fuel rail.
http://www.nengun.com/catalogue/product/4

[kismetcapitan]

the web rumors lately have been that Sards are "hard to tune" for an RB26; figured going Nismo would be a pricey but safe route...

[EDTHEMANJP]

Rumors? where have you heard this?

[tyndago]

Heres more issues with raising fuel pressure. Base stock pressure is 43 psi. Pump relief valves open around 70-100 psi depending on the pump.

Raise base pressure 25% to get 25% more flow. 54 psi base. +20 psi of boost - 74 psi- and you might be in the range of the relief valve opening.

444 cc 25% more flow is the same as a 555 cc injector. Safer to throw a 720 cc injector at it. Trust me at 8000 rpms you start to run out of time to fire the injector.

http://www.stealth316.com/2-fuelpumpguide.htm

Fuel Pump Flow Tests Comparisons Pump VR4 used
195130-0810 Bosch
10208 Mazda RX-7
195130-0782 Mazda Cosmo
195130-0771 300ZX
17042-40P05 Walbro
GSS341 HKS
1407-001US Supra MKIV
195130-1020 R33 Skyline
GT-R stock A'PEXi
BNR32 Volts 13.5 13.5? 13.5 13.8 13.5 13.5 13.5 13.5 13.5 13.2 PSIG Tested Flow in liters per hour (lph) 35 175.54 - 240.62 266.90 249.58 274.06 286.60 286.60 253.16 302.12 40 167.18 ~213 229.28 254.36 243.01 265.10 277.64 281.23 259.73 297.35 45 159.42 - 219.13 244.21 240.03 259.13 268.69 273.46 246.59 294.96 50 149.87 201.90 209.58 239.43 236.44 251.37 256.75 265.10 244.80 294.36 55 140.91 - 199.43 225.70 230.47 244.21 250.18 256.75 240.03 294.36 60 128.37 ~195 191.66 217.34 228.09 238.24 237.04 248.98 240.03 289.58 65 119.42 - 177.93 205.4 223.91 231.07 228.09 234.06 235.85 276.45 70 96.73 189.2 164.79 193.45 219.13 223.31 213.76 219.13 232.86 258.54 75 - - 155.24 171.96 202.41 216.74 200.62 197.63 228.09 240.03 80 - ~179 138.52 154.64 186.29 191.66 185.10 184.50 202.41 - 85 - - 117.63 131.36 167.18 179.72 167.78 164.20 180.92 - 90 - ~168 100.91 111.06 135.54 162.41 157.63 152.85 11.34 - 95 - - 77.62 - 120.61 149.27 134.34 127.18 - - 100 - 157.7 58.51 - - 128.37 115.83 - - -