What Is It?

Wire under carpet near fuel computer

Wire under carpet near fuel computer

If you have the carpet out to access the main power panel under the passenger's toeboard, and you happen to notice a disconnected wire on your computer - DON'T connect it!

There is a wire with an inline connector located on the end of the computer located on the right kick panel on MY84, MY85 and MY86 cars. This wire is the "Performance Switchover for Low Octane gasoline". If you connect it, the computer map is changed to accommodate low octane gasoline, noticeably degrading performance. The intended usage, of course, is for those occasions when you must operate the car on what is usually called "locally available fuel" in order to make it back to civilization.

Wally Plumley
928 Specialists

PLEASE yell me that this is the small (maybe 16gage) brown wire with red dots on each connector end! It is up and back (as viewed from the driver seat) and is connected on my car.

To think that all my complaints about lackluster performance could be corrected by simply disconnecting this has me fairly excited!

I'll be up all night now thinking about this!

86.5 Indischrot 5-speed

[the next day ...]

I decided to unplug the inline conector found at my computer per Wally's tip, not knowing if it was the correct one or not. The car ran a bit rough at first (then again, it has been running rough anyway), and went for a spin.

I have a nice dead-end road leading to my plat, and use it as my "test track" when needed. On all previous occasions, I have been able to press the shark up to the 95-100 mark before prudent braking is necessary. Today, I hit the century mark nearly 200 yards sooner than normal!

To say it has been transformed would bit an understatement. Since purchsed by me this past fall, the car has been very flat at WOT until it got up to around 4k on the tech...no more! Strong all the way from 2k up. Even smokes the tires in first which it has never done.

Given mechanics' proclivity for reconnecting anything that appears disconnected, I'd encourage fellow sharksters to look into this.

Thanks Wally, and Wooohooo! Got to find a reason to go cruising this afternoon.

86.5 Indischrot 5-speed

If anyone is interested in documentation for this plug, it can be found on page 28-64 of the factory manuals. It is called the "Octane Loop" and has a picture of the wire (mine is green) with a square single-pin plug at the end. It says that when the plug is connected, the "ignition timing will be retarded apptox. 3 degrees at full load and high partial load. (Provision for adaptation to poor grade gasoline.)"


Jason Butler
85 928s Euro (unplugged)

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