Faster in Winter

[Hank]

Just now, PMcClure said:

Sounds like Dr. Dyer! But, I think the physics is different for IC engines. Higher delta T should mean higher efficiency. Also, fuel is more dense in addition to the denser air = more horsepower, in theory. 

Maples or Dyer, I had the pleasure of both . . . And you're right, I missed the denser fuel, which will pack more energy per unit volume to burn with the more oxygen per unit volume. Our fuel flow meters are volumetric, not mass based, so this would not be obvious.

[ArtVandelay]

Just now, PMcClure said:

Sounds like Dr. Dyer! But, I think the physics is different for IC engines. Higher delta T should mean higher efficiency. Also, fuel is more dense in addition to the denser air = more horsepower, in theory. 

As long as its warm enough to vaporize the fuel, the ignition point for gasoline is only 500F, the difference in heat energy of the intake air will be negligible compared with heat from combustion and compression.

[aviatoreb]

29 minutes ago, Hank said:

Engine efficiency should be reduced at low outside temps, as the air at the intake requires a larger ΔT  to reach combustion temperature. One if my Thermo profs in college worked as a consultant and helped companies increase their boiler efficiency, sometimes as simple as running the air intake up near the ceiling to get warmer air.

So in cold weather, our combustion efficiency is reduced but power output is increased.

Huh!  Well I got that upside down!

I was thinking in terms of a car engine with a cooling fan that turns on and off as the engine gets hot.  If it is not too hot then the fan does not need to turn on.

I know that is just an accessory and anyway airplane engines are air cooled only.

[carusoam]

With all the fun things we can do 

1) Somebody tried the 10:1 compression ratio for the IO360 based on the helicopter engine.  Not good results...

2) many have changed/preserved the ignition timing from 20 to 25° BTDC.  Good results with increased CHT as part of the cost...

3) improved intake and exhaust flow to maximize MP and minimize exhaust back pressure...

4) Add the TN.  There is one for sale on MS...!

5) add an extra pair of cylinders, theoretically speaking...

6) GO TSIO520 or IO550....   Rocket and Missile.

Side note: Continental lists the timing for the IO520 as 22° BTDC...

PP ideas I read about around here....

Best regards,

-a-

[bonal]

Lots of reasons that all make sense I definitely know Snoopy flys better and faster in winter cold. Of course our winter is pretty mild compared to most.

[Hank]

9 minutes ago, bonal said:

Lots of reasons that all make sense I definitely know Snoopy flys better and faster in winter cold. Of course our winter is pretty mild compared to most.

I've really noticed the summer effect since moving back to the South! At first I thought my engine was losing power . . . but now I realize it's not, which just confirmed my earlier thoughts about high temp, high humidity effects on DA.