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Adjusting the Fuel-Quality Switch (FQS) - Technical

click to enlarge photo The Fuel-Quality Switch allows minor fuel and ignition adjustments in the event one runs across a batch of sub-standard gasoline. It does not yield any appreciable performance benefits. Improper adjustment of this switch may actually destroy your engine; use with caution!

click to enlarge photo To access the FQS:
  • Pull back passenger-side carpeting under glovebox
  • Remove plywood panel
  • Remove two plastic screws at top and two sheet-metal screws at bottom of DME computer bracket
  • Pull out computer bracket.
Adjusting the Fuel-Quality Switch
The hole at the bottom of the DME computer (see photo above) can then be accessed. On some computers, the hole is covered with a metal cover; gently pry it off. Make three-sided tool to fit (trimmed-down golf tee works well).

When making frequent changes, you can just re-install the two top plastic screws loosely and leave the bottom ones off completely. This allows you to pull the bottom of the bracket forward enough to adjust the rotary switch without removing it completely.

Porsche 944 (1982-1985) Porsche 944 (1985.5 +) Porsche 944 Turbo (951)
Position Fuel Adjust Spark Adjust Position Fuel Adjust Spark Adjust Position Fuel Adjust Spark Adjust
Stock 0 0 Stock 0 0 Stock 0 0
1 +4% 0 1 +3.1% 0 1 +3.1% 0
2 -4% 0 2 -3.1% 0 2 -3.1% 0
3 -6% 0 3 +6.3% 0 3 +6.3% 0
4 0 -4.15 4 0 -2.77 4 0 -2.72
5 +4% -4.15 5 +3.1% -2.77 5 +3.1% -2.72
6 -4% -4.15 6 -3.1% -2.77 6 -3.1% -2.72
7 -6% -4.15 7 +6.3% -2.77 7 +6.3% -2.72