Alright, the Maule I own has been in the family since I was a teenager. I learned to fly it from my father and brother who are both competent pilots (brother has 10,000 and flies 1000 hp otter on floats)
I was taught to cruise this plane/engine at 2250 rpm and 22.5. I haven't seen anything in writing indicating this is the correct (or best) setting, it's just what I was taught.
I've now got an EI fuel flow meter so I'm gonna make up a graph to compare speed-fuel flow at various settings to try to determine the best setting once I get my plane finished up.
Is this 2250/22.5 setting what I should be running it at? If not, what should it be?

Thanks

If it's been running for years with no problems, then I wouldn't change anything. I'm of the opinion that all engines aren't the same and they will even become accustomed to a particular type of operation. I'd stick with what has worked for you in the past.

The PZL/Franklyn 220 engine that being sold (off and on) today is not the exact same engine I guess, but it's pretty darn close. Can you get an operating handbook from PZL or maybe that outfit in Colorado who's doing the 170 conversions? It shhould have some operating guidelines. It seems to me that that's a fairly high-revving engine (2800 redline maybe?), 22-1/2" / 2250 sounds kinda low to me. But if it works, don't fix it.

Eric

I read an article one time, and now I can't remember where... that the old rule of thumb of matching the manifold pressure to the rpm, known as "squaring" is not necessarily the best method of deriving cruise settings.

It's easy to remember, and gets you in the ballpark, and that's about it.

zero.one.victor wrote:The PZL/Franklyn 220 engine that being sold (off and on) today is not the exact same engine I guess, but it's pretty darn close. Can you get an operating handbook from PZL or maybe that outfit in Colorado who's doing the 170 conversions? It shhould have some operating guidelines. It seems to me that that's a fairly high-revving engine (2800 redline maybe?), 22-1/2" / 2250 sounds kinda low to me. But if it works, don't fix it.

Eric

Yeah, red line is 2800. I thought 22.5 squared sounded a bit low to me as well. It's not a PZL engine and has less than 200 hrs on it (my dad didn't fly much prior to selling to me). I was just wondering what numbers the other Franklin 220 drivers here were using. There's no point in me wallowing around the sky at 22.5/2250 if higher numbers are more appropriate.
That's a good idea about contacting that outfit in Colorado...I will see if I can find a web site for them and drop them an e-mail.

I'm curious, the Maule POH doesn't have a chart of operating ranges?

I generally like to cruise near the lowest allowable RPM for a given MP. Slightly more efficient (not to mention it saves tach revolutions for your engine log )

My PZL AFM supplement is not much help when selecting a cruise power setting. My 220 "feels" happiest at 23" and 2350 rpm. I get 8.5 gph leaned to 25 degrees cool of peak at 5000 MSL, and cruise at about 125 ktas.

I usually end up cruising at a much higher altitude, however, because I have to around here! At 10000 MSL I use full throttle (~20-21") and 2300 rpm for fuel economy. Leaned to peak EGT, I get about 7.7 gph and 120 ktas. Not too shabby for the ol' 170. I can get even better economy with lower RPM, but my Frankin doesn't "feel" as happy there.

I would consider the mission (speed or fuel economy) and use what "feels" good.

M

once&futr_alaskaflyer wrote:I'm curious, the Maule POH doesn't have a chart of operating ranges?

I generally like to cruise near the lowest allowable RPM for a given MP. Slightly more efficient (not to mention it saves tach revolutions for your engine log )

I have never been impressed with the Maule POH for my plane...maybe they're better for the newer ones but to answer your question...no, the POH doesn't talk about engine settings...just some limits on pressures and temperatures.

http://www.mauleairinc.com/flight_manua ... c_220t.pdf

Punkin170b:
Thats incredible performance, especially the fuel economy. My O300 burns more than that.
Capt. Kirk:
How much are you burning per Hour?

Va170b wrote:Punkin170b:
Thats incredible performance, especially the fuel economy. My O300 burns more than that.
Capt. Kirk:
How much are you burning per Hour?

Excellent question!
The answer is...I don't know exactly. It's been years since I've filled up with anything that had a meter on it. I have a new EI fuel flow meter installed and purchased an in-line meter for my fuel pump so I'm going to get my fuel management dialed right in (as soon as my plane is finished). For trips I approximate 11.5 gph and, to date, I haven't fallen out of the sky due to lack of fuel. I usually end up with a bit more in my tanks than expected...if I had to guess I'd say 10.5 to 11 gph.

The fuel economy was a pleasant surprise with this engine. Our endurance is about the same as it was with the O-300, but the range is better. The 220 Franklin definitely makes good use of the constant speed propeller in climb AND cruise.

We ran our O-300 pretty rich all the time; mostly because it was such a hot running engine. It wasn't very good at dissipating heat and the oil temp was always bumping the red line in climb during the summer. The Franklin runs so cool we don't have any worries with the oil temp, CHTs or EGTs. However, I do not think we could eek that economy out of it safely without the JPI EDM-700 engine analyzer. Paired with the FS450, the digital fuel management is pretty darn accurate... I still start the flight timer when we depart, though!

If you want to cruise fast (~130 ktas) with the Franklin, you can. But it is THIRSTY! It drinks about 12 gph at high cruise power settings (25", 2500 rpm). The fuel flows during initial climb (full rich, full throttle @ sea level, & 2800rpm) push 15 gph.

M

Our local Franklin 220 guru (has two 170B's with them - one on floats and one on wheels) had this to say when I asked his opinion:

It is not an exact science, run it where it feels smooth. For me, it is 2450 rpm and 22" (or 24" if I need speed at the cost of another GPH).

My M4 was re-engined by the previous owner with the PZL and I have heard that both the original Franklin and the PZL like the higher RPM settings and consequently I have always run 24 squared and plan 10 GPH. The Franklin was used in helicopters at full output (2800 rpm) for extended periods of operation with no ill effects.

I may reconsider the 24" of MP at lower elevations to entice a little better economy now that Punkin tells me what he can do at 23 and 2350 as I don't see 100LL coming down in cost anytime soon...

Mark

N6EA wrote:My M4 was re-engined by the previous owner with the PZL and I have heard that both the original Franklin and the PZL like the higher RPM settings and consequently I have always run 24 squared and plan 10 GPH. The Franklin was used in helicopters at full output (2800 rpm) for extended periods of operation with no ill effects.

I may reconsider the 24" of MP at lower elevations to entice a little better economy now that Punkin tells me what he can do at 23 and 2350 as I don't see 100LL coming down in cost anytime soon...

Mark

I read on a Franklin site yesterday the same thing...that the Franklins were used in helicopters however it said that they ran it at a higher rpm...something like 3200 or 3400 rpm and that the 2800 used airplanes is under-stressing the engines. I don't think I'll fly around all day at 2800 but I may see how things feel at 24 squared. I am looking forward to comparing fuel burn/speed to the various engine settings.

Here's the paragraph from the franklin site.

"These are NEW FAA certified aircraft engines, not a rebuild of high time engine that has been subjected to years of unknown treatment. Because these engines are also used in helicopters (6-cylinder versions), where they are turned at 3200 RPM, they are under stressed in fixed wing aircraft where they are operated at 2800 RPM."