Stock Cobalt SS/SC injectors ...

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Dec 16, 2005 | 08:34 PM

#26

Jmc007

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From: Quebec City, Quebec

Posst deleted, see post #1.

Dec 17, 2005 | 11:46 AM

#27

korax123

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From: Arizona City, AZ

So we have 36lb injectors???

Dec 17, 2005 | 12:16 PM

#28

Bad GTP

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From: Westerville OH

Quote:

Don't forget that the stock LSJ fuel pressure runs somewhere between 50 and 62 PSI (highest numbers at WOT). For those who want to make some calculations, since this car is a forced induction one, you MUST use the differential pressure (I mean if there is 62 PSI in the fuel rail at WOT with the stock supercharger pulley running at 12 PSI, the differential pressure through the injectors (bone stock) to be used for calculation is 62-12 = 50 PSI).
Some notice that the fuel rail pressure can increase up to 70 PSI when running a 2.9" pulley, giving a differential pressure of 55 PSI.

We asked the guys at Hoosier Performance to measure this, and they're seeing 66 psi at idle, cruise and WOT - always the same regardless of boost. This seems to indicate that these cars use a constant fuel pressure, which is not referenced to boost in any way (mechanically, electronically, etc.). Remember that this is a returnless fuel system, and this is the 'norm' for returnless systems. For example, the 2004-2005 Grand Prix GTP and GTP CompG are the same way with constant fuel pressure of 58 psi.

Quote:

The results gives 380 cc / min (36,2 lb/hr) @ 43,5 PSI, as I saw on the flow bench.

That's a pretty close starting point. We have come up with anywhere between 36 and 42 pounds/hour using actual dyno results and fuel injector pulsewidths in conjunction with estimates for drivetrain loss and B.S.F.C. We plan to post a lot more information on this topic next week...

Dec 17, 2005 | 01:37 PM

#29

Jmc007

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From: Quebec City, Quebec

EDITED ENTIRE POST : Hi ! You can be sure that I'm very glad to get some help from you guys.

About the constant fuel pressure of 66 PSI, it has been achieved with a smaller than stock supercharger pulley don't it ???