Originally Posted by rongawer
Originally Posted by N941WR
Remember, auto engines are not designed to run at 75 or even 55 percent power all the time. The normal duty cycle for an auto engine is up and down, never continuous at one power setting. Even on the highway, with the cruise set, an engine is very lightly loaded.
Aircraft engines, on the other hand, are designed to make TBO while spinning on the redline at 75% power. That is a HUGE difference in duty cycles.
This statement is not true.
Even more so, what wears an engine out is not the continuous at-power operation, but the duty cycles themselves. If operated at a continuous rpm and load, just about any engine will last longer due to the stabilized oil film and temperatures of components.
That is exactly my point. I may be being pedantic, but the idea that "airplane engines can maintain 75% power for long periods but car engines can't" is a load of manure, and it's that part specifically that I'm objecting to. Pretty much any piston engine in normal use will sustain rated power for ridiculous periods of time, so long as fuel and ignition are properly set, and you maintain sufficient lubrication and cooling. Go look at the testing done on mass-production car engines and you'll see them running wide-*** open for hundreds of hours.
You may be interested to know that Part 33 requirements for piston engines, and specifically 33.49, only specify a 250 hour endurance test--a series of cycles between full power and various cruise settings.
The rest of my statement is not intended to encourage or discourage anyone. I'm merely trying to show that there's a lot of work that goes into designing and building a proper firewall-forward installation. Using a traditional engine, and especially the engine supported by the kit manufacturer, means that builders can leverage all of the work done previously by others throughout the industry, over many decades.
What I'm trying to get at, is if you're going to try and encourage someone to go the traditional engine route, then cite the right reasons instead of repeating old wives' tales.
For full disclosure, I will be using an O-360 with an electronic fuel injection package. As interesting and professionally challenging as I would find it to work on an engine conversion, I've chosen to use a traditional engine as the "base" plus a popular alternative fuel/spark system, because I can leverage others' past experience with both and get many of the benefits I want without having to go whole hog on a conversion.
On the topic of the engine that never went into production: something a lot of people don't realize is that you don't just have to get the design itself certified. You also have to get the production line
certified*, to include maintaining incredible volumes of records and paperwork, and setting up entire portions of your production and quality-control groups the way the FAA wants you do do them. Liability concerns may have played a part, but I suspect a large portion of the decision probably hinged on the FAA not allowing this company to just divert engines off their normal production line for aircraft use. The FAA would probably want an entirely separate and isolated line, with completely different QC and recordkeeping procedures than the rest of the company used. And I suspect all of the supplier components and subcomponents would be subject to similar restrictions, or at least face more severe ones relative to auto-industry norms.
*okay, well, technically you don't have
to get a production certificate, but not doing so likely becomes more expensive once you get out of single-digit production numbers...