Shock cooling on descent

[KSMooniac]

I asked TAT about a 4-cyl Mooney kit last year at OSH and they indicated that it would be unlikely.  Their price is unfortunately as unrealistic as the M20 kit anyway, so I'm not sure they'd get many takers even if they brought it to market.

[Kwixdraw]

A thing to think about in all of this is how it fits with the FAA and certification. All manufacturers these days are spending huge sums to try to be ahead of the product liability situation. Back in '82 Harley-Davidson claimed it was about 60% of their R&D budget. I'm sure it's no different for Lycoming and probably a large part of why TCM sold to the Chinese. GAMI can do their thing and not be as big a target for suit as Lycoming because Lycoming is the deeper pocket. Lycoming will always be more cautious than an aftermarket supplier because of this situation. I'm as interested in better performance as anyone but it does amaze me that we have so many test pilots out here. Over on the experimental side of things Vans has some great articles on why you shouldn't cram a bigger or turboed engine into your aircraft without looking at the bigger engineering picture. He explains TAS related to flutter speeds and safety margins. Not saying any of you are right or wrong but there is a lot to know about all this before we do much modification to our aircraft. Personally I think aviation would be in a way better situation if the certification process granted some level of protection from product liability suits, otherwise why should anyone bother with the process. No new product coming along except LSAs so I guess thats the answer. LSAs are so pitiful they can only barely kill you.

[KSMooniac]

One more thought on shock cooling since that was the original topic....

If you could hurt an engine by cooling it quickly, wouldn't the converse be true as well?  ie when you start it at room temperature and quickly heat it up to 300+ degrees over the course of a couple minutes at idle?  How about when you fly through rain?  That has the capacity to cool it much quicker than pulling the throttle back, yet we are not prohibited from flying in the rain.

[John Pleisse]

Quote: KSMooniac

I asked TAT about a 4-cyl Mooney kit last year at OSH and they indicated that it would be unlikely.  Their price is unfortunately as unrealistic as the M20 kit anyway, so I'm not sure they'd get many takers even if they brought it to market.

[KSMooniac]

It used to not be that expensive, and since he passed on the widow raised the price up to $34k + installation, which requires close to 80 hours of labor vs. the advertised 40 when the creator was running the business.  I understand the parts just don't fit together correctly anymore, and require a lot of fiddling and rework...  they won't sell any at that price when the majority of their market is only worth $50-100k.

[jetdriven]

Quote: DaV8or

If shock cooling is such an OWT, then why are there so many cracked engines out there? Why are there companies specializing in welding up cracked engines? What causes these cracks? Just bad luck?

[KSMooniac]

Not to mention engines that get welded-up are the cases, not the cylinders.  Case cracking is due to a variety of causes not related to potential shock cooling...  Cracked cylinders go in the trash or get turned into ornaments.

[danb35]

Quote: allsmiles

Your wannabes you so very passionatly carry water for, have they come up with a better engine??  What do they do?  they talk about lop rop etc etc as if it's a new concept!  Lindbergh did this when he crossed the Atlantic Ross!!

[sleepingsquirrel]

Whoa! Did I miss something? Just put my planes in the hangar for the front to move through. 52 MPH sustained gusts. Mooney is safe , 150 safe , I hope the rapid temperature change after the front passed doesn't shock cool my engines.

Back to my favorite pass time, squirrel dreams.

[Parker_Woodruff]

Quote: KSMooniac

I asked TAT about a 4-cyl Mooney kit last year at OSH and they indicated that it would be unlikely.  Their price is unfortunately as unrealistic as the M20 kit anyway, so I'm not sure they'd get many takers even if they brought it to market.

[Shadrach]

Quote: trey2398

Ha...  So the answer is 50 degrees/minute.  Got it...thnx.  Sorry for starting all this...

[DaV8or]

Quote: jetdriven

there arew plenty of cylinders that crack, I think its bad castings or flaws in the metal.

[DaV8or]

Quote: KSMooniac

Not to mention engines that get welded-up are the cases, not the cylinders.  Case cracking is due to a variety of causes not related to potential shock cooling...

[jetdriven]

Quote: DaV8or

there arew plenty of cylinders that crack, I think its bad castings or flaws in the metal.

[Shadrach]

Quote: DaV8or

there arew plenty of cylinders that crack, I think its bad castings or flaws in the metal.

[Shadrach]

How do you know this? Maybe it is related.

[Kwixdraw]

All of the problems Jetdriven mentions can come from a variety of reasons, this is why you get service letters, recalls and ADs on parts from time to time. If you want to read a lot about this subject get a copy of John Schwaners "Sacramento Sky Ranch Engineering Manual"  Its not light reading but you will understand a lot more about fatigue failures and crack propagation and other engineering problems of Lycoming and TCM. He mentions a series of cylinders that were prone to crack because a dull cutter was used in machining the fins and this caused a stress riser to start the failure at that location. These things happen.

[jetdriven]

We just changed to fine wire plugs and cleaned the injectors.  All 4 peak at the exact same fuel flow and get this, it will run smoothly to 70 degrees LOP and will cruise at 25"-2500 RPM, 50 LOP at 145 knots TAS and 8.5-8.8 GPH at 4500 feet.   CHTs are in the 330 range.  At 50 ROP they are 380..  I am sold.

[KSMooniac]

FYI, jetdriven, you don't have to go that far LOP if you're in the <9 GPH range.  That translates to 67% power so you can fly at peak or 10-20 LOP if you prefer.  No need to give up additional power!  Also keep the throttle wide open if you're not doing that already.  At altitude (typically 7000'+) I typically try to set the mixture at peak or 5 LOP and see where my CHT ends up...if it gets above 380 then I lean a little more and watch them come down.  It works great!

[Magnum]

Quote: KSMooniac

FYI, jetdriven, you don't have to go that far LOP if you're in the <9 GPH range.  That translates to 67% power so you can fly at peak or 10-20 LOP if you prefer.  No need to give up additional power!  Also keep the throttle wide open if you're not doing that already.  At altitude (typically 7000'+) I typically try to set the mixture at peak or 5 LOP and see where my CHT ends up...if it gets above 380 then I lean a little more and watch them come down.  It works great!

[jetdriven]

We are figuring this out on our own because it is not written anywhere for Lycoming IO-360s.   It seems 30-50 LOP has the best BSFC.  It loses SHP and airspeed at a frightening rate anything less than 50 LOP.  Also, logic says 50 LOP is the exact same as 50 ROP so I do not know why the flame tubes are burned away in your muffler, EGT is EGT.  ROP or LOP.  THe airplane, even at 75% power, likes LOP, it has about 3 MPH less TAS, 2 GPS less. and cooler temps.  for the 12$ saving an hour, and 150 houts of flying, the 1800$ saved can buy me 4 mufflers, or a complete powerflow system.  I got the money for that easily in this case.

[jetdriven]

Quote: KSMooniac

FYI, jetdriven, you don't have to go that far LOP if you're in the <9 GPH range.  That translates to 67% power so you can fly at peak or 10-20 LOP if you prefer.  No need to give up additional power!  Also keep the throttle wide open if you're not doing that already.  At altitude (typically 7000'+) I typically try to set the mixture at peak or 5 LOP and see where my CHT ends up...if it gets above 380 then I lean a little more and watch them come down.  It works great!

[jetdriven]

Quote: jetdriven

yeah i hear you. Set POP with fuel flow.  Just like in turbines, really.  We were at 4500 feet and that was a little to low to run WOTLOP.  Almost, though.

[Shadrach]

Quote: jetdriven

yeah i hear you. Set POP with fuel flow.  Just like in turbines, really.  We were at 4500 feet and that was a little to low to run WOTLOP.  Almost, though.

[Skywarrior]

Quote: Magnum

Don't fly at peak, even with 65% or below. I burned my exhaust system within 150hrs flying at peak (the flame tubes in the muffler were gone).

Quote: jetdriven

Also, logic says 50 LOP is the exact same as 50 ROP so I do not know why the flame tubes are burned away in your muffler, EGT is EGT.  ROP or LOP.

 

He wrote PEAK, not 50 LOP.

 

Chuck M.