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Turbo69bird 06-07-2017 11:13 PM

Ground roll and climb out RPM?
What should my RPM be with a 0320 160, metal sensenich prop, need to look up size and pitch still

I'm only seeing 2260 on ground roll and climb out, placard on panel,says not to exceed 2600 but I'm reading numbers more like 2750 in other threads.

Just wondering where it should be. I've got to climb out of my 2100 ft runway pretty flat to achieve 90mph and getting cyl head temps at 400 to 410 before 1000 ft which I'd like to be cooler.

Top end is pretty good in my opinion at about 178 mph at low (3500) ft altitude (don't recall rpm ) though I really haven't pushed it much. To see if it'll run faster.

I just feel like the climb out is kind of anemic compared to the 180 hp archer I flew and my friends 7a with 195 hp constant speed prop climbs out like an animal.


Bicyclops 06-07-2017 11:50 PM

2600 is the limit!
We've got a 6A with O-320 and Sensenich. On the takeoff roll, I want to see close to 2300 RPM. 2260 wouldn't scare me. Solo, I climb at close to 1000fpm. Once I feel OK about safe altitude, I like to cruise climb at 130kt indicated and the rpm will rise to almost 2500. Better cooling and visibility, too. With the extra HP that I can make with more rpm it still climbs about 7-800fpm. I can usually get 155-160 kts true in level flight at 3.5K. At that altitude, I can pretty much leave the throttle full open but dropping the nose at all will overspeed the prop.

400* CHT at pattern altitude is too high. You should do something about that. Baffle sealing, correct timing, enough fuel flow.

Careful with the prop rpm. The 70CM series on the O-320 is limited to 2600. There is apparently a nasty harmonic at about 2650 that would fail the prop if you operated there very long. Calibrate your tach and stay under the limit.

Have fun,

Ed Holyoke

cajunwings 06-08-2017 05:24 AM

First step is to make sure the tach is accurate.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

Turbo69bird 06-08-2017 08:43 AM

Tach is an EI unit and just had it serviced to be sure it was accurate.

So the 2260 is not really way off then I expected higher rpm on take off. Sounds like top speed it's pretty similar too. This thing will climb fine after I reach 100 it's getting up over those first set of trees that's a little daunting and as it gets hotter I'm more concerned. This was with myself at 230 and pass at 150 at about 70 degrees. I've done the washer trick and baffling seems to be sealed pretty well. Don't know what else to do for CHTs to get them down. Once I level off it's fine but there's no way I could climb at 80mph in this I'd over heat it.
If I flatten it out to get 100 mph climb I just touch 400 cht by pattern altitude. But I can't always climb out at 100 and clear obstacles.

I'm thinking of wrapping the plane and that would add another 23 lbs can't even imagine climb performance at that point. 😳

I wil say I probably keep 40 lbs baggage at all point she in time with tools etc but I'd think I'd be fine with that. This was also at 75% fuel.

Kyle Boatright 06-08-2017 09:04 AM

Climb at whatever speed is necessary to clear the trees at the end of the field, but after that, accelerate to 110-120 knots. Your climb rate won't change much, but your CHT's will benefit substantially.

N941WR 06-08-2017 11:50 AM

Don't worry about 400F CHT's on climb out. Lycoming lists 500F as max CHT. They do suggest you stay below 400F for continuous operation.

It is not uncommon to see 425 in a Cessna or Piper on climb out.

Once you level out, your CHT's will come down.

Raymo 06-08-2017 01:42 PM

Do you have the landing gear fairings installed? My -7A does not yet have them and, according to the installation instructions, could cost 20-25 HP in drag.

I have similar numbers for my 180 HP fixed pitch 3 blade Catto but with full tanks and two passengers can still get 800 FPM climb at 105 knots. CHT is fine until I start to try leaning out above 3000 ft.

Watch your EGT on take-off and try to maintain that temp while climbing via mixture control. If your CHT is still high in that realm, you have cooling/baffling issues to solve.

MarkW 06-08-2017 01:59 PM

To answer your question, if I remember correctly my initial full throttle roll is about 2160. It very quickly starts to increase with ground/air speed.
I have a ECI I0-320 with a fix pitched Catto three blade. I can hit redline at low altitude and full throttle at about 50 rich of peak. I believe I am pitched about perfect.

titanhank 06-08-2017 05:45 PM

My -6 with 0-320 b2b, 160 hp, catto 3 blade gen 3 prop weighs 1044 lbs. i take off from a grass strip with half flaps with 2200rpm static and climb to 200 ft to clear the trees at 80mph and lower the nose. I can't see over the nose at this speed. When i have a positive airspeed trend, i retract the flaps and set a 500fpm climb until the the tach reads 2450rpms. I then climb at whatever this speed is. This gives me 1000-1200 fpm depending on weight and temperature with no tendency to overheat. At 8000ft DA, i turn 2650rpms for a four way gps avg tas of 182.5mph. I think i am about 2" overpitched, but when i add the dual pmags, i think i will turn 2750rpms or so. It sounds like with your prop, it is doing fine except for the overheating. Check your baffles and carb jet size for proper fuel flow on takeoff. You could be running excessively lean even with the mixture knob full forward.

Turbo69bird 06-09-2017 12:09 AM


Originally Posted by Kyle Boatright (Post 1179065)
Climb at whatever speed is necessary to clear the trees at the end of the field, but after that, accelerate to 110-120 knots. Your climb rate won't change much, but your CHT's will benefit substantially.

110 to 120 is a pretty shallow climb out and with noise abatement procedures in effect I don't know that that sallow of a climb out would be appreciated in my area to pattern altitude.

at a 90 mph climb I'm at the end of x wind by the time I reach pattern altitude.

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