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Porsche Crest 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.
Old 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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Old 01-09-2007, 01:44 PM
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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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Old 01-09-2007, 02:58 PM
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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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Old 01-10-2007, 04:05 AM
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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
Old 01-10-2007, 05:35 AM
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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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Old 01-10-2007, 02:15 PM
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