Can the heat cause a bad engine run?

[Paul Taylor]

I tried to get out early this morning before the temp hit triple digits. It was into the 90's (with the heat index I bet it was close to 100) by about 10:30am. I put up two flights and called it quits. I could not see from the sweat running in my eyes.
Any way I am running a LA 40 on 10/22 fuel. I launched at 9700 rpm. After about the first lap the engine sagged and there I was with a gutless run.
I figured that the heat was the cause of the bad engine run.

Any thoughts?

Whew! I am tired of this heat!!! It sure zaps me.

[Bob Whitely]

Short answer. Yes.  You need to use 20-25 percent nitro, lower the compression and back down the rpm and everything will be fine.  You tried to run the engine beyond the torque curve by leaning it out too much which makes it run hot and then it sags and then quits.  RJ

[peabody]

I imagine that your LA is stock....

Randy and others rework engines to combat this type of behavior....stock engines (LA/FP, etc) all seem to run okay in cool temps...but we fly in warm weather.....

Another thought is that it is "over propped".....too much pitch, and this is evidenced in the heat....A stock LA runs pretty well on a 10 1/2 X 4 1/2 APC.....far to many try 11 X 5's or such.

I've never poured more nitro as the heat here in New Jersey is not nearly as awful as where Bob is, but I wager that he is right....

[Matt Colan]

Yes, heat can cause a bad engine run.  You need to add more nitro and lower the RPMs to keep the motor running where it is supposed to be run (in hot temperatures). 

[Norm Faith Jr.]

Hi Paul..."AB-O-SO-LUTE-LEE." Ran my LA.46 on 5% with a 12X4 Pro Zinger prop and my usual RPM's, at the Summer Heat contest in Dallas this past June..."Burned-er-up." 
Norm

[Martin Quartim]

The hoter the day the less power your engine will develop. To compensate for this loss you can use higher nitro and/or use a larger venturi.

In the hot days I also like to use higher pitch props in addition to more nitro and/or larger venturi.

Martin

[Brett Buck]

The hoter the day the less power your engine will develop. To compensate for this loss you can use higher nitro and/or use a larger venturi.

In the hot days I also like to use higher pitch props in addition to more nitro and/or larger venturi.

  Nitro and pitch, I like, but I would go easy on the larger venturi part. It gets you more power but also reduces the fuel draw, which makes the needle touchier and makes it more likely to run away (since it leans out more in the maneuvers, heating it up, and maybe never coming back, particularly when its hot outside). There's a very real limit to how far you can go.
 
    Brett

[Jim Thomerson]

Now that you have heard from the experts, here is what I think.  Do not touch the needle!   OK, the engine ran fine earlier in the day at 78 degrees.  With the heating up of the air, the 78 degree setting is a little rich, and maybe down a couple hundred RPM's.  First, you should have enough power that a couple of hundred RPM's is not a big deal one way or the other.  If you had left the needle alone, the engine would have run adequately cool and no problem.   You leaned the engine out, giving it less cooling and less lubrication, to get the tach figure you thought you needed, and fried your engine.     

[Randy Powell]

I would also note that it helps to increase oil content along with nitro when it heats up. I have a can of hot weather fuel that is 15% nitro and 24% oil that I use when the temp climbs into double digits. Works pretty well.

[Norm Faith Jr.]

Hi Jim, if you were refering to me...YEP! That is what I did...Good engine run in the morning practice...Come the afternoon...Set those RPMs...The run started out great, got to the squares and the rest was history. One each .46LA 
Norm

Now that you have heard from the experts, here is what I think.  Do not touch the needle!   OK, the engine ran fine earlier in the day at 78 degrees.  With the heating up of the air, the 78 degree setting is a little rich, and maybe down a couple hundred RPM's.  First, you should have enough power that a couple of hundred RPM's is not a big deal one way or the other.  If you had left the needle alone, the engine would have run adequately cool and no problem.   You leaned the engine out, giving it less cooling and less lubrication, to get the tach figure you thought you needed, and fried your engine.     

[Wynn Robins]

dont have that problem with eletrics Paul...

mind you - it NEVER gets that hot in New Zealand anyways  - HA HA

[Neal Beekman]

Yes ,on the LA 40/46 heat will do it with the plastic backplate , change it with the one from Curtis Shipp.

[dennis lipsett]

I have used 30/24 heli fuel at 100 degrees. It works and is an interesting flight.
Dennis

[Grady Widener]

"I would also note that it helps to increase oil content along with nitro when it heats up. I have a can of hot weather fuel that is 15% nitro and 24% oil that I use when the temp climbs into double digits. Works pretty well."

Typically temps in single digits up north left?
Usually triple in Phoenix June, July, August & September then mostly double the rest of the time.

Echo oily, nitro laden fuel package and up pitch prop = happier lathered up good with tons of sun block pilot.