Thread: Boost springs
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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
If you don't have a mechanical boost gauge you don't really know what your boost is.
The factory boost gauge and sensor are not accurate and even less so after 20 years or so.

The spring and diaphram in the stock electronic boost gauge sensor fatigue and become inaccurate after time so it takes less pressure to compress the spring in the sensor and it gives higher readings.

Also, the stock sensor is reading boost pressure from the intermediate manifold or intercooler above the throttle body, not below the throttle body in the intake manifold where you have slightly lower boost pressure.
This is the only place you can really get an accurate boost pressure reading that the engine is seeing because of the air flow restriction of the single throttle body.

Another thing that can happen is if a lazy or hung over mechanic ever cleaned the intermediate blow off valve housing in parts washer without removing that sensor, the solvent could get inside it and swell the diaphram in the sensor making it softer and it may give optimistic readings after that. Same thing goes for the overboost switch.

Good chance the one in yours is a stock spring.
Old 03-08-2008, 02:24 PM
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