Searching for more RPMs

[jwd3ca]

Greetings... I would like to hear from Sonex/AeroVee drivers that use a Prince P-Tip prop, 54/44. With 12 hours on my engine, I'm only seeing 2900-3000 static, less (2750-2780) during climbout. Resulting in doggy rate-of-climb. What sort of numbers are you Prince prop flyers seeing? I'm trying to borrow a Sensenich 54/44 to compare, but I would like to know if the P-Tip is actually capable of spinning your engine up to say, 32-3400 static, Thanks!

[MichaelFarley56]

Just out of curiosity, what rpm do you see at full throttle in level flight? What climb rate are you seeing and at what airspeed?

Before I installed the turbo on my engine, I had a P-Tip 54 X 44 and would normally see 3150 rpm on climb out around 90 mph, and a full throttle maximum rpm of 3450-3500.

[mike.smith]

Just out of curiosity, what rpm do you see at full throttle in level flight? What climb rate are you seeing and at what airspeed?

Before I installed the turbo on my engine, I had a P-Tip 54 X 44 and would normally see 3150 rpm on climb out around 90 mph, and a full throttle maximum rpm of 3450-3500.

Sorry, I do KTS and not MPH, so you'll have to convert...

And I've never seen numbers like those with my AeroVee. Sensenich prop, 2950-3000 on initial climb out. In cold weather, 700 fpm. In warm weather at full gross, 200 fpm. 3250 max level flight, but that burns close to 7 gph. Normal cruise is 95 kts, 2,950 rpm at 4.5 gph. 100 kts will put me just over 3100 rpm and about 5 gph. To get 900+ miles to OSH from BOSton is about 10 hours for me, and I average very close to 4.5 gph all the way. 300 mile legs with at least a 45 minute reserve.

My best climb outs over the hill and trees at one end of my runway are at 55-60 kts. Yup, 55 kts. That's still more than 20 kts above my indicated stall speed. If I don't have obstacles to contend with then 65 kts. Once I've got some altitude, climbs are generally at 70 kts.

But things to remember about fixed pitch props (analogy given to me by Sensenich engineer): they are like gears on a bicycle. If you want to go up a steep hill you shift into low gear so your pedals are turning faster. That's a climb prop. If you want to cruise on level terrain you shift into a higher gear with your pedals turning slower. That's a cruise prop. If you get great climb performance, then by definition you will lose cruise performance. If you have great cruise performance then your climb rate will suffer. So if you have a good cruise prop, then your RPMs and FPM on climb out will be lower. There's no free lunch. There's middle ground, but then you might not be happy with either.

Oh, and on the ground I've never seen much over 3,000 rpm static. Certainly nothing even remotely like 3200+. If you see 3400 static on an AeroVee, I'd say your prop is too finely pitched. You might climb, but you're not going to cruise (bicycle analogy).

I'd love to try a Prince prop someday. It would be fun to check the numbers using the same engine.

[Fastcapy]

I was seeing the same rpm numbers as the original poster with a couple different props. After my mods to my Aerovee I am now seeing better numbers.

I now see about 3100 static, 3050 climbing at 70-75mph (60-65kts) and wot I see about 3300 and a touch over 130mph (112kts). I set cruise around 3000 and see about 120-125mph (105kts).

Last X/C I did I averaged 122mph and 4.2gph at 4500ft and 5500ft msl.

I know of some guys in the racing world who have cut the curled P-tips off their Prince P-tip props and have seen an awesome jump in performance. I am not quite that brave yet to hack up this prop.

[jwd3ca]

What mods, Fastcapy?

[Fastcapy]

Rotec TBI, Air straightener, K&N filter, aftermarket plug wires on both ignition systems, NGK plugs (Had a bunch of bad autolite plugs from various sources), different intake elbows, slightly modified intake ports.