Real world RPM

[ken6881]

zdz 210 on home mad cans
31X12 3blade carbon fiber.
5250 on the ground
32:1 lawnboy ashless(and tuned a little on the rich side)
motor has less than a gallon threw it.
However you can here the prop rip in flight at wide open throttle.
Its in a 43% carden 300 midwing 41.8lbs

[Alexzzz]

	Quote: Originally Posted by ken6881
	31X12 3blade carbon fiber.

Which one?

[ken6881]

mejzlik

[WrongWayRC]

	Quote: Originally Posted by pe reivers
	If the carb is tuned, rpm compare well regardless of altitude. The variables involved cancel each other out. The engine will make less power, but in the thinner air, the prop needs the same amount less power to spin at the same rpm.

Attached is photos out of a 1980 Cessna 152 (one I grabbed out of storage). This plane has a fixed pitch prop, much like our models and adjustable carburetor control so the chart is adjusted for optimal power.

At 8000 foot altitude maximum power at standard temperature is 75% but only 71% at 20 degrees above standard.

That 75/71% power is being attained at the same RPM as 100% power at sea level.

Also note that max rpm of 2550 is no longer in the chart starting at 10,000 foot (albeit only 50 rpm) so there is a point where percent of power will no longer turn the same rpm at higher altitude but I hope we don't have that many modelers flying much over those altitudes.

Also on another page landing (I chose landing performance cause it takes engine power out of the question and basically shows what is happening to the airframe) performance increases at altutude going from 475 foot landing roll at sea level and 15 Degrees C (standard temp) to 550 foot at 5,000 foot and 5 degrees C also standard temp for that altitude.

So a guy goes from sea level on a standard day to 5000 foot airstrip and he needs nearly 17% more room to land and when he goes to 8000 foot he needs nearly 28% more room to land all due to thinner air when temperatures are standardized. Same guy goes from sea level standard temp to 8000 foot and the 8k is 20 degrees over standard he needs like 37% more runway to land than at sea level.

That was fun.

[WrongWayRC]

Also good to note that you can reduce landing distance by 10% for each 9 knots of headwind but landing distances increases 10% for each 2 knots of tailwind......for those guys doing that 5 mph downwind landing they are looking at 25% more runway used on a short field landing.

[rcalbuquerque]

	Quote: Originally Posted by AHP
	A buddy of mine had a ZDZ 210 on standard mufflers that would rip the snot out of a ZM 34x14 prop. I don't remember the exact tach figures, but it was in the upper 5000 range. It was a monster -- it drug a 50lb 40% TOC Yak around like a foamie.

I also ran the ZM prop and could easily rip it at sea level turning 5600 on the ground. I switched to the 32-12 to reduce noise and have better pull on verticals.

[pe reivers]

Also good to know is how the GPH at 2400 reduces as altitude increases. Somewhere in that book must be carb setting corrections for altitude, since less power meand less fuel, and carb settings must be leaned out accordingly.

[WrongWayRC]

On the instrument panel there is a throttle control and next to that a mixture control. The book says to use full mixture below 3000 foot altitude on climbout and can lean above that. For cruise they recommend to lean for peak rpm and then richen for 25-50 rpm. [Edit manual further states that best economy with EGT is peak below 75% power, normal lean is 25 degrees rich of peak, peak EGT would give 8% greater range and a 4 knot airspeed loss}
On the bigger planes equipped with (EGT) exhaust gas temp gauges we would lean, if memory serves me, 150 deg. below peak for climb out, then 50-75 deg below (both on the rich side of peak) peak for high powered cruise (70-75% power) and my favorite on the Piper Navajo with the Lycoming TI0540J2B was to run I believe it was around 75-100 degrees on the lean side of peak at 60% power. This gave great fuel economy and a very small loss in indicated airspeed and [was within engine longevity parameters]. Of course not a good idea in model airplanes unless you are trying to set an endurance record.....

[pe reivers]

EGT is a great way to tune the engine, especially in 4-strokes. I have however no idea how to use it to the limits in two stroke engines with premix fuel, because leaning also means less oil.
T.O.M. surely knows.

[jamesrxx951]

tested a menz 27/10 with my DA100L and re2 tuned pipes. 6750, and the mejlik 26/12 still 6950. atleast on the ground run up the menz was abit louder. mezjlik 28/10 6810rpms.

[kickerfx4]

DLE 55 1 gallon of fuel 32:1 Pennz 22x10 MenzS 6900

[Super08]

DLE111 first tank of fuel Xoar C.F. 27x10 6600rpm

[skypilot_one]

MT70s Twin, 1 gallon Pennzoil 32:1, 300' asl, 60*F, 60% humidity, Xoar 23x8 laminated 6800 rpm

Weighs 2 oz more than DA50

[clivem]

.

[pe reivers]

MVVS152, int80 mvvs mufflers, mejzlik 32x10, 6050 rpm
Mets30x12, 6900 rpm (rips badly)