Adjusting Fuel-Quality Switch (FQS)

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!

Finding the Fuel-Quality Switch
The FQS is located at the bottom of the DME box under a covered hole.

- pull back passenger-side carpeting under glovebox
- remove plywood panel (nice high-tech material)
- remove two plastic screws at top and two sheet-metal screws at bottom of DME computer bracket
- pull out computer bracket

Ajusting the Fuel-Quality Switch
The hole at the bottom of the DME computer (see photo right) 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)
- turn rotary switch fully counter-clockwise to reset to stock position
- turn switch clockwise as many turns as needed to set adustment according to following tables
- re-install computer bracket and carpeting

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 (early '82-'85) Porsche 944 (later '85.5+) Porsche 944 Turbo (951)
position fuel adj. spark adj. position fuel adj. spark adj. position fuel adj. spark adj.
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°

WARNING! Do not use the FQS settings from the Porsche 944FAQ. It is for a 911 and is not correct!