As a follow up to this topic. Perhaps there will be an ever increasing level of interest in using 91 octane unleaded auto fuel in our Lycoming engines going forward.
This increasing interest may be driven by a multitude of factors: 1) The political debate over 100LL (environmental, closing airports due to lead, etc). 2) A desire on the part of owners to gather the benefits to their engines by getting the lead out. 3) The potential of larger economic forces pushing the issue (cost of 100LL vs 91 unleaded). And other factors.
With these potential driving forces, and the prospect of many folks involved doing their own "testing" -- to understand more about the risks, benefits, best management procedures, of using 91 unleaded, would it make sense to start a new forum on 91 unleaded auto fuel?
Some of the questions and discussion might include: Implications of compression ratio on fuel decisions. How to manage fuel sources for different compression ratios. Different approaches to using 91 unleaded such as: dedicated fuel tanks vs blending. If different tanks are used, how to manage the source to avoid detonation or other adverse events.. If blending is used, what is the best ratio for different types of missions. If using dedicated tanks, when to switch from 100LL to 91, and back to 100LL (what altitude, what type of flight operations, are leaning procedures used with 91 unleaded, if leaning is used are there best management procedures, etc)? What are the different considerations for EFI vs Carb type fuel systems? Does the use of 91 unleaded result in any adverse effects on engine (valve guide wear, valve recession, etc)? How about vapor lock, and best practices to avoid this risk? What steps should be taken to document this testing, and decisions on how to manage the fuel system (modifications to the "POH" - at least the POH as referenced on VAF)? How about the use of advanced ignition systems that are mapped to MP? And many more questions and nuances.
Rather than each of those that are interested in this topic, pursuing their own "testing", and randomly sharing their efforts on various forums, perhaps a more strategic approach would be to have a focused forum (maybe something like "Using 91 unleaded auto fuel") under one of the main headings. Under this scenario, folks that have already made some headway on this topic could share their approaches and lessons learned, and those that are "testing" can benefit from their wisdom, as well as contribute to the cause. Maybe there is already a forum that could host this type of discussion, but in my review, in my humble opinion, I couldn't find any forum titles that would automatically draw my attention to this topic.
FWIW - I personally don't buy into the whole environmental/human health risk dialogue that is being used to shut down 100LL and close AIRPORTS. The risk assessment methodology used in the 100LL analysis is just too full of leap of faith assumptions and very casual cause and effect assumptions. But, once the narrative gets started, it's very difficult to bring common sense (and reasonable science) into the discussion. On the other hand, if a Lycoming will run cleaner, and longer (ie, more TBO), while at the same time costing less to run, then I'm on board that train.
