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WinRice WinRice is offline
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Join Date: Jun 2005
Location: Colorado
Posts: 702
Originally Posted by T77911S View Post
i dont think you can just add .8 (spring) to .8 atmosphere and come up with 1.6bar. i think more goes into it than that. for one exhaust pressure has an effect too. you also have to be careful and not get psia and psig crossed.
That's 1.6 bar absolute pressure, you have to subtract out the atmospheric pressure. If the gage is zeroed at atmospheric pressure of 0.8 then it reads 0.8.

As others have pointed out, depending upon back pressure, exhaust design, etc, a 0.8 spring might give you 0.8 bar boost, but it might be higher or lower. You really need to make sure your gage is calibrated to zero before determining your actual boost pressure.

If everything is constant, and no changes have been made to the exhaust system, and you have the system set for 0.8 bar of boost regardless of spring, controller, etc. It's pretty consistent that the boost is 0.8 bar above atmospheric pressure, if (a big if), the turbo has the reserve capacity. As you increase altitude with the same boost pressure your pressure ratio goes up.

I ran these tests at 5200 ft, 6400 ft, 8000 ft, 10,000 ft, resetting zero on my Zeitronix at each altitude and the results were consistent.

Like Gumba, to compensate for the altitude, I run more boost where I'm at. Guys at sea level run 1 bar, I run 1.15 bar without issues with my EVC-V controller.
1986 911 Turbo
3.3L, K27HFS, Tial 46mm, TurboKraft Intercooler, 964 Cams, Monty Muffler, MS3Pro Evo, M&W Ignition, Zietronix WBO2 Data Logger, Wevo shifter, coupler and motor mounts.

Last edited by WinRice; 06-02-2014 at 09:35 AM..
Old 06-02-2014, 09:30 AM
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