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Old 06-17-2011, 08:26 AM   #1
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Car diagnostic tricks which works on 1997- 2000 boxsters.

There is some sort of serial data stream or CAN interface that allows the AC (manufactured by Audi) unit to display engine parameters. Here is a list of what can be seen:

To switch from F to C:
Hold down the recirculating button then push both the temperature + - buttons.

To access diagnostics:
Hold down the Recirculating & Air up buttons for 5 seconds.
The + - buttons go up and down through the list of "c" codes.
The center vent button switches the left display between the "c" code and its actual value.
Press the Auto button to exit.

0c - ERL
1c - Oil Temp?
2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash.
3c - Outside temp. Sensor located inside the air inlet of the A/C unit.
4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temp. sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp.
5c - Outside temp. (matches with OBC outside temp display)
6c - Coolant temp.
7c - Footwell discharge temp.
8c - Sun sensor (dash top)
9c - Sun sensor.
10c - Passenger compartment fan speed.
11c - Passenger compartment fan voltage.
12c - Temperature mix Flap command 1=COLD, 100=HOT
13c - Temperature mix Flap position
14c - Central Flap command
15c - Central Flap position
16c - Footwell/Defrost Flap command
17c - Footwell/Defrost Flap position
18c - Recirculation Valve command 1=OFF, 100=RECIRC
19c - Recirculation Valve position (feedback)
20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer)
21c - Engine RPM in hundreds. This too only updates once per second.
22c - ?
23c - ?
24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum.
25c - ?
26c - ?
27c - ?
28c - Fan speed?
29c - ?
30c - Engine run time in seconds (255 max.)(=0xff)
31c - Timing counter
32c - Displays test
33c - Software version? Mine states 3.4
34c - ?
35c - Outside temp. from inlet sensor (filtered?)
36c - temp?

Happy Boxstering,
Pedro
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Old 06-17-2011, 11:08 AM   #2
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An aluminum skid plate is very doable, we can design it with air vents to help get rid of the heat from the manifold. If its fuel lines those don't get that hot anyway usually.

There is another advantage to running a skid plate, Improved aerodynamics.

Most of the drag created by a car is created under the chassis. The smoother and flatter you can make the chassis the more down force the car will generate, and the more stable it will be at high speeds. Thats why the underside of a 911 is so flat.

In theory a flat belly should make a significant difference.

Timothy, thank you I'll send you a pm to get your contact info. I'm going out of town for a little while but Andrew (by partner) will call you and set up a meet

harryrcb, I just sent you a Pm thanks for the help


Edit: oh I just remembered something, with exhaust you want the pipes to be as hot as possible so trapping the heat may actually be a good thing. The hotter the pipes the hotter the exhaust gases, the hotter the exhaust gases the greater the flow velocity inside the pipes. This will create more power, theoretically.

This is why header heat wraps and thermal coatings make power.

The danger would be transmitting heat to other components, but thats something we would compensate for during the design phase.

also this is a pretty cool shot from one of the tests we did. Its basically showing the temperature distribution through the tube.

This is assuming oil temperatures of 400 degrees and direct heat of 1075F on the tip.


Its not accurate because after we did it we found some other things we didn't factor in, in reality this part will never see any temperatures remotely close to this, because the heads are cooled by the cooling system. The idea behind doing this test is to make sure the part will not melt or expand under usage.

Last edited by rayner@r2specracing; 06-17-2011 at 01:18 PM.
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Old 06-18-2011, 08:46 AM   #3
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Regarding the underbody trays, since we're talking aerodynamic advantages, how about seeing if one of your alternate designs can involve some diffusers that blend well with the rear of the car? Since we've got a center exhaust that leaves plenty of room on either side for some functional diffusers
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