Titanium Wrist Pin

this research paper shows that increasing the compression ratio from 7:1 to 9:1 increases the combustion pressure 22%:
http://rescomp.stanford.edu/~efroeh/papers/RDH_Engine_Performance.pdf
Picture 28.jpg
 
but beyond 9:1 becomes fairly negligible. spark advance is always a much bigger concern than compression in regards to combustion pressure.

the facts are that my steel pin survived and my titanium pin didn't in an engine with nearly stock timing and one of the most common aftermarket cylinder heads
 
It seems that there is titanium and titanium - rubbish product sold at bargain basement prices and the good stuff, that at very least, matches steel for strength and wear resistance.

I guess it's just a matter of finding a 10mm titanium wrist pin with a high grade materials specification; applicable to internal combustion operation and without any thought to the cost.
 
combustion pressure vs spark timing

you are right about timing being a critical factor in the combustion pressure that a wrist pin and its bearing have to tolerate.
Picture 13.jpg
The degrees listed below the graph are the spark timings which match the graph by the color coding.
 
A readily available titanium alloy wrist pin will fail before one made of readily available hardened steel. Even at normal compression. Titanium has greater hardness and is more elastic. This may explain the 'slop'.

The property that limits the use of titanium is fatigue strength. The graph from THIS steel manufacturer shows their steel (SP-700) as requiring greater Max stress than a common Ti alloy. This is at least in the data range provided - four data points for their steel is not many and, there are no error bars.

When reading about wrist pin applications for titanium vs. steel you will see that Ti does not have the long term wear characteristics and requires frequent replacement.
e_graf_hiro4.gif
 
I never got into the titanium wrist pin hoo-ha, because the stock standard steel wrist pin has never failed on any of my engines, and, i have installed external modifications to boost low and midrange torque; allowing the engine to use lower rpm's for the same road speed; giving much less vibration to the point where vibration isn't even an issue.
 
ok good to know..so coating the pin is wise huh...ok and i need another cdi..jag id have to find a place that isnt sold out
 

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