Max Power at high altitude

[crxcte]

I flew to a 7K' altitude airport and when used the max power method on take off by pulling the mixture.  The mixture was leaned out on rollout with full power until it coughed then a couple of turns to rich until it sounded smooth.  After leaving the runway then up to about 1K' for a minute of two I noticed I my cylinder temp was about 475-500 degrees.  Normally it would be 435-450 degrees.  I stopped climbing and checked to make sure the cowl flaps were open (they were), and built up some airspeed to cool.  After a minute or two no big reduction in cyl temp so I set the mixture to more rich.  The cyl temp then came down.  Anyone used this max power mixture setting and experienced high cyl temps? 

[jetdriven]

Wow, even 435 is a critically hot temperature.  At 475-500 the cylinder barrels turn blue. You should lean to the EGT value you use as a target, usually this is the EGT value you see at sea level on a standard day, at full power-ful rich.  For us it is straight up on the alcor gauge, and the number is 1385.  Further, the air is thinner so after liftoff, go to a higher airspeed for climb to keep it cool.  Watch that CHT like a hawk, if it starts to move up, go richer and / or add more airspeed immediately.

[crxcte]

Thats pretty much what I did, higher airspeed and richer mixture after takeoff.  Really didn't notice the EGT setting on takeoff and wonder if it was straight up as you mentioned. Outside temp was about 7 C.  My 20F always runs in the upper green on cyl temp.  I had about 6.5 qts of oil.  I think next time I will make sure the oil level is at least 7 to 8 qts.  I'm wanting to get a better method in order to land at an 8400' airport elevation.

[Parker_Woodruff]

That is way too hot, but the factory gauges aren't terribly linear in their presentation, either.

What is your fuel flow, full rich, at approximately sea level (where you take off in oklahoma)?  Are your CHTs in the 400s then?

[crxcte]

Home is near the Norman, OK area.  Elevation is about 1200'.  I wondered about on the accuracy of the gauges.  They are all OEM.  I can get the chts at 400 at level flight with the cowl flaps slightly open.  Don't have a fuel flow monitor.

[Parker_Woodruff]

Quote: crxcte

Home is near the Norman, OK area.  Elevation is about 1200'.  I wondered about on the accuracy of the gauges.  They are all OEM.  I can get the chts at 400 at level flight with the cowl flaps slightly open.  Don't have a fuel flow monitor.

[crxcte]

The procedure I use to set the mixture was from taking a mountain flying course that mooney setup in Col Springs several years ago.  To set the mixture was just to pull until it coughed then a couple of turns in until it ran smoothly.  That was considered as max power.

[jetdriven]

A fuel injected Lycoming may not "cough or sputter" until 150 LOP, so then a couple turns in is right at peak, which is the mixture setting that will cause detonation and 500 degree CHTs.   Establish a reference EGT that is safe but not wasteful, some value that gives you 330-350 CHT on climb out, and always climb out with that value set.

 

For reference peak power is 150 ROP, and even that might not be sustainable at a lower altitude.

[stevesm20b]

Leaning for max power on take off will always result in elevated CHT's. Filling the crankcase with 8 qts of oil is not going to lower CHT's a significant amount on take off leaned for full power. I think I would go with the advice given by jetdriven. The simple solution, if your concerned with your clime performance at high altitude airports is to take off with less weight.

[John Pleisse]

I flew to a 3772 field last week, density alt was 6700 on t/o. I did not do this procedure and had no issues running rich. I also found cruise climb at 105 KIAS netted the best climb performance (600fpm) and cooling. It was 92 degrees and I didn't have a CHT above 400.

[DaV8or]

Chris-

Your engine seems to run really hot. Aside from checking the instruments to see if they are accurate, have you checked your baffling? Also, maybe consider the oil cooler relocation mod. Maybe your oil cooler needs a looking at. I would think you should be able to keep your CHTs well under 400.

[DaV8or]

Quote: N4352H

I flew to a 3772 field last week, density alt was 6700 on t/o. I did not do this procedure and had no issues running rich. I also found cruise climb at 105 KIAS netted the best climb performance (600fpm) and cooling. It was 92 degrees and I didn't have a CHT above 400.

[jetdriven]

I think his may have the dog house, but isnt there still some baffling?  anything over 400 is cause for investigation and repairs.

[Lood]

My farm sits at 4000' and the DA is almost always at 6k ft or even more. During run-up, at 1700 rpm, I lean slowly untill the rpm starts to drop. I then push the mixture back in about an inch. As soon as I have full power on roll out, among others, I check that I have around 14 - 15 gal on the fuel flow and not more than 1250 deg on the hottest EGT. Never had a problem.

I agree that leaning until the engine coughs is too lean and I wouldn't do the primary lean during the roll-out. From the moment that you've actually taken full power untill you reach rotation speed doesn't really amount to a lot of spare time - specially if you're below MAUW. I'd have my engine checked after the temps that you've encountered.

[jetdriven]

Everywhere I have read says peak horsepower comes at 150 ROP.   I could be wrong.  Here is some discussion.    http://www.vansairforce.com/community/showthread.php?t=63319

250 ROP is set up for fuel cooling. At altitude, you can get away with something in between, over 8-9000' you can almost run at peak in the climb

Quote: JimR

Where'd you get that information, Byron?  Everything that I have seen indicates that max power is to be found somewhere around 80 dF ROP.  This is not to suggest that one should run there at high power settings if long engine life is one's goal, but that is where maximum power is to be found. 

I think what you are trying to say is that the OP should stay at least 150 dF ROP in the climb, and maybe moreso if CHTs get too high, which is most likely to happen down low where more power can be produced.  Is that right?  

Jim

 

[crxcte]

My t/o was 300lb below max useful load.  I have no plenum (doghouse), baffling is original but not in bad condition.  Do have an oil cooler mod and really haven't seen a big improvement since installed.  If 8 qts would not reduce chts, as stated above, then neither would the oil cooler location.  Higher mixture provided the best bang for the buck.  As soon as I increase the mixture to more rich the chts came down.  I have never had chts below 400 with the cowl flaps closed.

[jetdriven]

Take another hard look at baffling. We replaced our rubber baffling with a Gee Bee kit, it lowered the CHTs 20-30 degrees all else equal.

[Shadrach]

Quote: crxcte

The mixture was leaned out on rollout with full power until it coughed then a couple of turns to rich until it sounded smooth.

[Shadrach]

Quote: N4352H

I flew to a 3772 field last week, density alt was 6700 on t/o. I did not do this procedure and had no issues running rich. I also found cruise climb at 105 KIAS netted the best climb performance (600fpm) and cooling. It was 92 degrees and I didn't have a CHT above 400.

[crxcte]

Quote: Shadrach

[Shadrach]

You don need no stinkin' Gamis mane.  Lyc 4s are typically pretty well balanced out of the box...  If I were going to lean for take off in your situation, I would just twist until I felt the slight bump in power. 

first and foremost though - you should have your guages checked out. 500CHT is no joke...running 400s while in cruise is not good either and should be completely avoidable in your F model.

[crxcte]

Attached is my cht temp gauge, the upper side of the green is 450 degrees. Red line from 450 to 500 degrees. 

[Swingin]

To the OP: This sounds 'caveman', but it's how I lean for takeoff from high DA airports regularly - DAs approaching 10K.

Taxi very lean, then go full rich as I'm taking the active, then slowly advance the throttle to full.  Pull (not twist) the mixture back from the firewall slowly.  You'll feel a surge of power as you get it leaned enough.  You'll have about another 1/2" of mixture travel behind that, with which the power will stay high like that, before you feel it fall off again.  I suspect you're operating back there.  Just pull slowly until you feel the power rise, that should be on the ROP side of max power.

This is my technique even though I have fuel-flow, and full digital CHT and EGT for each cyliner.  Works like a champ.  If I see CHTs or EGTs higher than I like on climbout, and I'm at 120MIAS, I enrich with a couple twists.

[crxcte]

Thanks Swingin, I definitely did not have the mixture set right from the get go.  My high cht was near instantaneous do to excessive leaning.   I don't get to high DA very often but will add your procedure to a check list in the future and give it a try. 

[MikeinFL]