Porsche 993 air cooled tuning

[Gavin Magee]

Hi,

I currently have a Porsche 993 in the workshop, (last of the air cooled I believe) and it's up and running with G4x Monsoon.

What I am trying to familiarise myself with is the engine cooling or temperature measurement and control.

These engines are also largely cooled by their dry sump oil system.

Firstly, does anyone have a calibration for the OEM engine temp sensor? This sensor is mounted directly in the head, close to cylinder 3, however it is tricky to impossible to get the laser thermostat anywhere near it to be able to create a decent sensor cal.

Also, if anyone has any experience with these engines... could you give a brief idea of the normal temps expected from this sensor? What is acceptable, what is too hot etc?

 

Lastly, I would suggest that running these engines a little richer than the average water cooled engine may help slightly to keep temps down... has this been others experience?

 

Of course any other relevant info is always useful.

 

Many thanks.

Gav.

[Adamw]

Most of the Porsche cyl head temp sensors use the Std Bosch NTC calibration.  I have come across one earlier car (mid '80s) that appeared to use the 0280130017 calibration.  Set it to Std Bosch NTC to start with, if it isn't correct it will be quite obvious if it doesnt report a realistic room temp with a cold engine.  

As for typical temps, I found them to be quite sensitive to ambient temp.  We have quite mild temperatures in the city I live, say 0°C on the coldest winter day Vs 30°C on the hottest summer day.  The most recent one I tuned in summer acted pretty similar to a water cooled engine on the dyno - it sat around 100°C most of the time, it would creep up to 120ish when idling after a full power run, but I didnt have any trouble keeping temp under control even without a lot of airflow through the engine bay when tuning.  Temp would come back down quickly at RPM a bit higher than idle.  But the owner rang me a few months later because in winter when cruising on the motorway he found the head temp would drop so low that the warmup enrichment would kick back in.  From memory we had to drop the warmup enrichment out at about 60°C which was a bit of a compromise.  

[koracing]

Possible suggestion/idea: Use engine running time as an axis on the warmup table warmup after some period of running.  Feasible?

[Adamw]

Yeah there are certainly options we could have tried if needed, he was happy enough after just some small adjustments of a relatively typical-looking warmup strategy.  I suspect there was possibly some part of the cooling system not as originally intended as this seemed to run very cold considering it is relatively mild temperature here.  I know it had all the cabin heater stuff removed which may have originally had some sort of throttling or air bypass to control temperature better, It's not a platform I know very well.