Craig:

One thing you can do now is compare the TSIO-550 and it's operating parameters to the TNIO-550 which has 8.5:1 CR. The differences are significant and address the issues you are asking about. Lower TITs and higher efficiency. As a result, the TNIO-550 can be operated continuously at higher power settings. I routinely operate mine at 87-90% power, LOP.

Also, high CR engines will be much easier to operate when PRISM is available so that the ICP/thetaPP issues are directly measured and the spark timing is altered accordingly in real time, rather than by a look-up chart based on MP and RPM. Since mixture plays such a significant role in the EFFECTIVE timing, it is very helpful for it to be factored in. Rather than trying to calculate the variables, why not just MEASURE the parameter that matters and adjust accordingly?

Walter


On May 12, 2005, at 10:24 AM, Craig Berland wrote:

"I put those two pieces of information together and reach the conclusion that if there are ways to operate the engine at high power but minimize the peak torsionals,  then that method ought to be used. I’m not sure I answered your question.  If not, let me try again. Regards,  George"

Yes you did answer my question...thanks.  One more.  How much of a tight rope are we walking with the TSIO550 trying to balance peak pressure and TIT?  Well, two questions.  I have discussed with some the advisability of raising the compression ratio on the TSIO550 and I advised against it. The quest for efficiency is outweighed by the quest for durability. What do you think?  A similar question.  Would you advise retarding the timing if Scot's engine was stock CR?  Retard 2 to 3 deg's more at 9 to 1 and 5 to 7 deg's more at 10 to 1???  If this is so, then stock CR is the way to go. Finally let me say I believe there are lots of variables that affect engine durability like oil type and viscosity, engine component balance and prop balance to name a few. So this is not a discussion on whether or not Scott or someone else should run a given CR. I'm trying to isolate and understand a given engine calibration feature and I'm most interested in the TSIO550.

Craig Berland