Q — I just bought a track car, a one owner 88 Carrera and I am looking forward to this year’s DE without sweating the damage I could do to my GT3. So I have a number of questions.
1) The former owner installed headers and has the oxygen sensor still installed in the left header but it is unplugged. Should I leave it unplugged or should it be connected.
2) The sway bar mounts in the rear are showing signs of cracking and I was told that a revised bracket is available. What should I do about it?
3) The AC does not work and I need to replace an oil line underneath the compressor anyway. Can I just remove the compressor and leave it off? Mike
Wow Mike, this is what I call “living large”. While you are at the track with the Carrera, I would gladly exercise the GT3 for you. You really should not let these cars sit around.
But seriously, on item 1, the OXS sensor is an electronic “nose” that constantly monitors the fuel mixture and adjusts it based on “smell”. Do you notice that funny odor that you detect after a hard run at full throttle? That is raw un-burnt fuel. And although $4.00 a gallon gas is a factor, there are other considerations.
With the sensor wired into the fuel injection system, the amount of fuel compared to oxygen is constantly adjusted by the Motronic computer for peak engine efficiency except at full throttle. At full throttle, the computer ignores the sensor signal and uses a different “computer map” to give you maximum power. Or you might say “engineered maximum power”. This is where chips come in. A chip will give you more power by re-engineering the map to provide more advanced spark and a richer fuel mix. Simply unplugging the sensor causes the fuel mix to go “full rich” without the benefit of advanced spark timing. So the engine runs great at full throttle and ironically, it would do that anyway if the sensor were plugged in.
The other considerations have to do with increased engine wear by dumping all that extra gas into the engine when it does not need it and the comment by your better half: “why does your car stink?” My dear old Dad also claimed up to 10% better fuel economy in both of his chipped Porsche’s (when he drove for economy).
My advice: Chip it, adjust the fuel mixture to base settings, plug the sensor back in, have it tested, and enjoy the best engineering that Bosch and Porsche built into the car.
On question two, the sway bar mounting brackets were poorly engineered from the start. By my rough guess, they are broken or cracked on better than half the cars I inspect. There are three methods of dealing with this: 1) If the bracket is completely broken, Porsche offers an updated stronger design that is priced at under $100.00 each (plus labor) 2) If the bracket is cracked, it can be reinforced before it breaks and this is equal to the updated bracket at a much lower labor cost. 3) There are aftermarket brackets that attach to that large round tube called the torsion bar housing. Although I consider these ugly, they work and they are cheap.
On question 3: Should you delete the AC compressor? On this model there is no down side to removing the compressor. There is only one wire to disconnect, the compressor is heavy and who needs it at the track? Before you remove it however, make sure any remaining coolant (Freon) is recycled. I suggest that you cap the AC hoses if you ever want to reinstall it. If you want to take this project a step further, that AC condenser under your turbo tail is not improving air flow to the engine either. –MC