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Old 03-08-2010, 06:51 AM   #97
jeremyk
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Joined: Aug 2008
Location: Novi, MI
Oddometer: 91
Not sure if this has been mentioned yet, but running at a lower pressure will screw up air/fuel ratios under "open loop" operation (i.e. full throttle). In closed loop, the O2 sensors will likely detect the lean condition created by not enough fuel (~40 PSI vs ~ 50 PSI) and may be able to correct. However, most FI systems go into an open loop mode under full throttle and no longer use O2 feedback. They use "fixed" look-up tables in the ECU to determine proper air/fuel ratio and those tables are based on a assumption of 50 PSI fuel pressure.
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