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Registered User
Join Date: Dec 2006
Posts: 62
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1979 930 Fuel Injector Opening Pressure
So I've taken it upon myself to test pop test all my injectors. I noticed that 4 of my injectors opened up at 40 psi, but 2 injectors opened at 38 psi and 39 psi. Is this bad? Shouldn't they all open up at the same psi or is it that the spray pattern really matters more? I'm just curious. These injectors come from a CIS system on a 79 930.
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01-08-2007, 08:13 PM
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Since they spray continuously, I can't imagine that the opening pressure would matter much.
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2014 Cayman S 2011 Cayenne Turbo 1979 930 (475 rwhp at 0.95 bar) |
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01-09-2007, 01:44 PM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,205
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Your pressure differences are fine.
It (can) matter(s) quite a bit. According to the local guy who does injectors/tested mine, the opening pressure ("crack pressure")   coincides with injector leakage. One of mine opened way too early (about 8 psi too early and 'flowed' a ton more than the rest......and consequently dribbled profusely when the crack pressure threshold was reached on the way down.
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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01-09-2007, 02:58 PM
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Crotchety Old Bastard
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38 to 40 pounds cracking pressure is not significanly different. You should be fine as long as they are not leaking when closed.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds '78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8 |
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01-10-2007, 04:05 AM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,205
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Isn't that what I just said?
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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01-10-2007, 05:35 AM
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A fellow Pelacanite
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it's always nice to get a second opinion even if it is worded a different way.
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1981 UK 930. G50/01 shortened, 964 3.8RS Fibreglass Body Kit, 18" Alloys 8.5" F & 10" R, 225's F & 285's R, Special Colour Metallic Blue Paint, FIA Sparco Evo's, A/C and Air Pump removed, Electronic Boost Controller, GHL Headers, Tial46 WG. Fitting - New service kit. Needs Fitting - Innovate XD-16 Kit, Kokeln IC. Stephen's K27 HFS, EVO Intake Assy & his Modded USA Fuel Head. 1983 UK 911 3.2 Carrera Sport Coupe. Black, Black Leather with Red Piping, Black Alloy Gear Knob, K&N Air Filter Element, Turbo Tie rods. Needs Fitting - K&N CO Sensor, Round A/F Dial Gauge, Factory Short Shift Kit. http://www.danasoft.com/sig/Iamnotanumber.jpg |
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01-10-2007, 02:15 PM
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1979 Porsche 930 3.4
78 Porsche 911SC 3.0L, 3.3Turbo soon. 
