Technical Assistance

[Gregbbrd]

Joined and willing to lend help with questions or
Issues. Start a thread and let's see what we can figure out.

[Tom]

Awesome to have 'da man' in the house! Welcome!

[Tom]

While we wait for the 928 crowd to arrive, any thoughts on my head gasket options. See video in this thread.
viewtopic.php?f=4&t=21

[Gregbbrd]

While we wait for the 928 crowd to arrive, any thoughts on my head gasket options. See video in this thread.
viewtopic.php?f=4&t=21

Although it has been many years since I used/tested Raceware head studs, I was, along with several other builders at that time, never able to make these studs perform well.
Head gasket failures were extremely more prevalent with these studs than when using the factory studs....even when going to the trouble of retorquing.
In the 12mm size range, the factory studs always worked best.
The conclusion we reached was that these studs were actually of too high a quality steel, which did not stretch nearly enough, in the 90 ft.lb. range, leaving the head not under enough preload. And, unfortunately, higher torque was not successful, as the threads in the block were not capable of holding increased torque.
As we increased power levels, we were forced to increase stud diameter. John Millege made some fantastic 14mm pieces and Porsche Motorsports used monster studs in the GTR program with huge tightening torque (so high that GTR heads would crack occasionally.

[808c2s]

Hi Greg,

Any thoughts on replacing the intake temp sensor on an 86.5 928S with a faster sensor to allow quicker adjustments to IAT to improve on performance?

[dr bob]

I'll stick my nose in... Greg will reply separately.

In my limited experience, a faster sensor won't help. The situation where actual intake air temp might drop quickly is the transition from hot idling (increased intake temp) to cooler due to higher flow with larger throttle opening; you still end up waiting for all the metal in the intake to cool down as heat is shed into that intake air stream. The sensor itself sits in the bottom of the plastic air cleaner housing, so it biases the MAF reading into the LH controller in anticipation of a change in charge temperature. The actual change in charge temp to the cylinders is relatively slow, to the point where a lower-mass temp sensor with faster response is as likely to hurt as to help.

My background for this is in combustion controls, focused these days on industrial prime movers like large frame gas turbines. So not directly applicable to ICEs. In other words, take this with a grain of salt. The physics of the sensors and measurement stays the same, but the effect seen in ICE performance is dependent on several factors like the mass and speed and temperature of the airflow, and the mass, heat transfer and temperature of the intake metal. In other words, there are a few things to consider.