An interesting thread so far
A certain shop has said that not only can they tell immediately if you've been running LOP, they'll void the warranty if you do. Also that people in the LOP crowd are keeping their shop packed with top overhauls.
Sig, my first comment is thats just rhetoric, anecdotal rubbish, unless its back by hard factual data. I bet they did not have any. Did they show you a properly set up engine Dyno with the ability to monitor ALL the parameters necessary to prove their claim. Of course not, if they did they would suddenly change their tune.
Frankh .....so true.
humptybump
I'm still flying with a traditional O320 (150hp) normally aspirated engine. I may be naive so I'll just ask - is it reasonable / possible to run this setup LOP?
Yes it is, you need all 4 EGT probes accurately positioned at the same distance (typically 2-3") from the head, and 4 CHT probes and an engine monitor with fuel flow. They you can experiment safely. If you know what you are doing you can do it but numbers.....but thats a mental exercise too big for this post.
Sailvi767........you need more detonation margin than us
, so more ROP or more LOP....... Attend an APS seminar....NOW!!!
Now here is a can of worms
For instance, you certainly can not run LOP without risk of damage during low altitude WOT take off's.
Lets think about this for a minute, WOT say 29.5"MP, say 2500RPM, and lean of peak at a suitable temp LOP.
Now apart from the fact the time it would take to get to something like 100LOP or whatever the number would need to be is going to take longer than the runway allows, so its impractical, compare that to a turbo IO550 or IO540 in the cruise or gentle LOP climb?
What you cant do is do it at 10-20F LOP.........
So the real question to all this then is, what role does fuel play with the valves as far as cooling. Seems to be the guides/seats that are taking the punishment LOP depending on who you talk to.
I'd just really like to find ONE engine shop/builder to corroborate the LOP philosophy. The arguments make sense, but I've yet to find any real data to back it up.
OK so lets have a look at your real question. What role does fuel play with the valves as far as cooling is concerned. Answer is simple. NONE, it actually provides heat, otherwise your engine would not run. now before you get all cranky at my seemingly wise guy answer, think about this for a minute. Fuel makes heat in the combustion process, not cooling. No arguments, end of story. Evaporative cooling if you pour it on your skin is not inside your running engine.
So lets look at the combustion process. Adding more fuel into the mix seems to drive CHT's down, but why? Well the best way to drive CHT's up is through detonation, getting a perfectly correct mixture and firing it at the worst possible time so the peak pressure pulse happens nead TDC. In your motor car you have knock sensors and all sorts of things to control fuel delivery (mixture) and spark delivery (timing). So in your IO-XXX you have fixed 25deg BTDC timing so to slow down the combustion event and get the peak average pressure on the downward stroke and avoid detonation you can retard the event by what means? Timing=No, so the only other option is fuel volume. Two way's, more fuel will make it hard to go bang so richer retards the event, or leaner, which is harder to get the bang going and then does so with less heat (because less calories inserted).
So fuel does not cool. But by varying the mixture we control the combustion event.
Now back to valves......which of the three has a higher heat content? The lean of peak, low calorie, slow moving combustion event, The really good volatile bang event or the even higher calorie but slower rich event? The answer now is obvious, the big bang or near detonation has the highest, the ROP is next and the LOP is the least amount.
So which is better for your heads valves etc? LOP of course, but LOP enough to be out of the detonation zone.
I do not have an engine shop like GAMI, but I have proven this myself with engine data from the Dynon D180. Its simple once you know what is truth and what are Old Wives Tailes peddled by these head in the sand engine shops, flying instructors, chief pilots and engine manufacturers.
Now you would think I am on commission, and I am not, but I will keep saying this for as long as people keep asking, whether you believe or not, the best $900 or so Yankee greebacks you have ever spent on your education, engine preserving, fuel saving and life saving is by attending an APS seminar.
Go in with a non believer attitude if you wish, they will not berrate you with anecdotal rhetoric, they may make a few jokes, but seriously they will give you HARD FACTUAL DATA, and whats more if you do not understand what you see they will explain it all. Then you make up your own mind.
If I have made mistakes above....I apologise, its 1am, I have been up since 4am, and its zzzzzzzzz time now.
Hope this helps.
PS if you want to read about leaned not enough or not rich enough causing engine failures and deaths of paying passengers, read here;
http://www.airsafety.com.au/pelp0057.html
http://www.avweb.com/news/pelican/182153-1.html
You will want an engine monitor, and the knowledge on how to use and understand what its telling you.......yes...APS seminar!
Nitey nite!