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Climb rates? O-320 vs O-360?

D

Dmadd

Well Known Member
Just a lazy Sunday question for the Nine crews. What are the real world numbers for climb rates with the extra 20 HP? I know it's not exactly apples to apples because everyone's installation it a little different. I'm just trying to figure out if a light O-320 can match the "all the bells and whistles" O-360...
This has been batted around before, but can't we do it again?... :)
Dennis
 
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Dmadd said:
Just a lazy Sunday question for the Nine crews. What are the real world numbers for climb rates with the extra 20 HP? I know it's not exactly apples to apples because everyone's installation it a little different. I'm just trying to figure out if a light O-320 can match the "all the bells and whistles" O-360...
This has been batted around before, but can't we do it again?... :)
Dennis
Click to expand...

My plane started life with a 135 HP O-290D2 and I swapped it out for a 180+ HP O-360 from ECI a few years back.

Knowing I was going to be a bit over powered, I had Craig Catto cut me an "Uber Cruiser" prop, whereas the O-290D2 had a climb prop on it.

So, there is no such thing as an "apples to apples" comparison.

With the O-290 it could climb at 1600 FPM but was limited to 165 MPH (140 Kts). The O-360 can climb in excess of 2000 FPM (2200 Solo) and cruise right at 200 mph (170 kts).

There other important factor is weight. My -9 came in right at 1068 lbs empty but was 990 lbs when it lived with the O-290. The added weight is leather Classic Aero interior, auto pilot, paint, bigger engine, and a few other items. Not exactly a "bells and whistles" airplane as I have worked to keep it light.
 
The difference can be calculated. Climb rate is a direct function of available horsepower over and above what is required for straight and level flight at minimum airspeed.

One can back calculate this climb HP by using your own planes best climb rate and weight.

For instance, Take a 1600 lb plane that climbs at 1600 ft/min. Multiply to get 2560000 ft-lb/min. Divide by 33000 ft-lb/min(1 Hp) to get 78 hp. Adding 20hp to that figure (to go from a 320 to a 360) gives 98 available hp. You can ratio the HPs (98/78 = 1.25) or run the first calc backwards to give the climb rate. 98 x 33000/1600 lbs = 2021 Fpm

This ignores prop efficiency so the increase will be a bit less because you don't get the full 20hp you paid for. More like 17 @ 85% prop eff.

AS EXTRA CREDIT:
Think about what I just said and then think about your answer to a sailplane pilot that invites you to join in winch launch glider flights. (common winch power is about 300hp)......... available power minus minimum power = climb......:eek::eek:
 
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the real question, how much power?

I'd love to have a 180 hp on my -9a. No such thing as too much power for takeoff.
...but, would it make some sense to say 'HOW can I get another 20 hp?"

My 0-320, FP prop, spins about 2200 rpm at takeoff, generating about 110 hp or so ( depending on a bunch of other factors of course, so don't jump on my number just yet).
I can probably get another 20 hp by using a CS prop, letting the engine produce closer to it's full rated power, by virture of rpm......right? :) Likewise, I assume the CS will be able to hit the optimum rpm for max power at any given altitude, load etc.
 
flyboy1963 said:
I'd love to have a 180 hp on my -9a. No such thing as too much power for takeoff.
...but, would it make some sense to say 'HOW can I get another 20 hp?"

My 0-320, FP prop, spins about 2200 rpm at takeoff, generating about 110 hp or so ( depending on a bunch of other factors of course, so don't jump on my number just yet).
I can probably get another 20 hp by using a CS prop, letting the engine produce closer to it's full rated power, by virture of rpm......right? :) Likewise, I assume the CS will be able to hit the optimum rpm for max power at any given altitude, load etc.
Click to expand...

That's the advantage of the constant-speed prop, yes. The downside is the effect it has on your wallet on initial purchase. As we often do in aviation, it's trading dollars for knots. How fast ya wanna go?
 
airguy said:
The downside is the effect it has on your wallet on initial purchase.
Click to expand...

Downside? Rubbish! If you're looking for a better climb rate, the CS prop helps even more by making your wallet far lighter: less weight = better rate of climb.

;)
 
Dmadd said:
No body out there with O-320 AND constant speed?
Click to expand...

I have that combination.

Started out with Ed Sterba fixed pitch wood.
Moved to MT composite.
Moved to Catto 3-blade.
Moved to Hartzell constant speed.

Summary:
Better w&b for me.
Ability to fly aggressive formation (as in with Team AeroDynamix)
Better acceleration.
Shorter takeoff distances.
Better climb.
Top speed similar.
Not sure about fuel consumption differences.
NOT as smooth as the composites.

Don't have the climb improvement numbers but it was worth it.

I do wish though that I had the extra horses. Lots of side by side travels with buddy from next hangar and he has 180 horses in similar plane. He outclimbs me and gets better fuel mileage.

James
 
pirep on the composites? Wood?

jclark said:
I have that combination.

Started out with Ed Sterba fixed pitch wood.
Moved to MT composite.
Moved to Catto 3-blade.
Moved to Hartzell constant speed.

Top speed similar.
Not sure about fuel consumption differences.
NOT as smooth as the composites.

James
Click to expand...

So James.....did you have the MT 2 blade? how does it compare to the Catto? any maintenance issues? ( nickel leading edge etc.)

...about the only think I 'like' about my Sens FP aluminum club is the durability.
 
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