Boost Deviation
The percentage difference between actual boost pressure and the ECU's requested target, measured after the turbo has fully spooled.
Why it matters
Large deviation means the boost control system isn't maintaining the pressure the tune asks for. The direction matters: over target suggests wastegate/boost creep issues, under target suggests leaks or turbo capacity limits.
What to look for
Warning at 8-10%, critical at 15%+. The P95 (95th percentile) is used instead of absolute max to filter single-sample noise.
Related terms
The boost pressure the tune is requesting. Actual boost should track this closely.
The measured boost pressure in the intake manifold at any given moment.
How hard the ECU is working to keep the wastegate closed and maintain boost. 0% = fully open, 100% = fully closed.
The turbo building up to target boost pressure from idle or cruise. During spool, boost is low, WGDC is high, and deviation from target is large. All completely normal.
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