Good afternoon,

I'm operating Cessna 206s/207s out of Southern Africa, where temps will reach almost 50C during the summer. Very sandy and dusty. The aircraft are equipped with IO520/IO550s, just curious about what cruise power settings you use. 23MP/2300, 21MP/2300, 24 squared, etc? 25 rich of peak? 50 rich? 100 rich? Oil and air filter change at 50 hours? We usually have to perform top-end overhauls anywhere from 550-800 hours. Just wondering what would work best out here with the heat/dust/sand for engine longevity. Also, has anyone installed the remote oil cooler from Atlantic Aero? Thanks.


Cheers,

A2A

First of all, make sure your fuel flow on take off is set for a 550 and not a 520. If I remember correctly fuel flow for a 520 is 28.5 GPH, if the 550 is set at 28.5 on take off it will be way too lean and cause hot cylinders and hi egt. There was a problem long ago when everyone was converting their 185 and 206's to 550's, some mechanics were not increasing the fuel flow higher for take off power which resulted in a lot of cooked cylinders.

Second, if you are going to run rich of peak make sure you are at least 125 degrees rich of peak or a bit more(richer), stay away from peak or 50 degrees rich of peak, this is too hot at higher power settings. Running lean of peak is ok if you have GAMI injectors and a full engine analyzer and are well versed in LOP operation. For now, I would fly 125-150 degrees rich of peak, this is also the "best power" setting.

Just my 2 cents worth.

G44

206 seems to run hot with -520's anyway. Most guys here that use them run 24/24 and 16 - 16.5 gph in cruise. On warmer days cowl flaps stay open. In the hot country one really has to watch the temps on climb out, maybe even limiting it to 500 fpm where practical. I agree with G44, make sure takeoff fuel flow is set correctly or maybe even a bit higher fuel flow than spec.

A couple of points:

As G 44 noted, fuel flows for the IO 550 need to be set well over 30 gph at takeoff power. Basically, you'll want to see the fuel flows on the standard fuel flow gauge (which is actually a pressure gauge, not a flow instrument, but calibrated in flow) go well past the max indication on that gauge.

Secondly, you CANNOT run a 550 like you do a 520. It appears from your post that you are running BOTH 520s AND 550's??? If so, you need to understand the differences in percentage of power. Continental prohibits leaning of any of their big engines at power settings over 70 % or 75 %, depending on the engine. Bear in mind that a 520 is NOT a continuous rated 300 hp engine, whereas the 550 IS continuous rated at either 300 hp or 310 hp, depending on the model of engine you have. So, you can't use the same combinations of MP/RPM for the two engines. 24 squared works fine in a 520, and you can lean that engine pretty much as you please at that power setting, but 24 squared in a 550 produces more than 75 % power under most conditions. Run that 550 at 24 squared, like the 520, and you WILL fry cylinders.

You need to get a power chart for the engines....the 520 power charts should be in the POH for the airplane. The 550 is a modification, but a power chart of some sort should have been provided with the conversion.....READ it! Frankly, some of the power charts I've seen for these engine conversions were really difficult to interpret. The best I've found was from Atlantic Aero. I just looked at their website (https://www.atlantic-aero.com/main/docs ... ochure.pdf), but I don't see their power charts, which used to be there. But, in any case, find the data for YOUR engine conversion, and then study the power settings, and READ the recommendations and limitations. You'll find the prohibition on high power leaning in there somewhere.

I ran IO 550 D model engines in 206s and ran around 2300 rpm and 20 to 21 inches of MP commonly. That is about 70 % power at sea level on a standard day, as I recall.

Finally, Wipaire manufactures cowl flap extensions that are required on the 206 for operation on their big floats. These are simply rod extensions that open the cowl flaps further than they normally open, and when the cowl flap control is completely closed, the flaps themselves remain partially open....providing additional cooling. This is a very simple modification.....legal in South Africa????? I don't know. There is a saying about such things, however...."Don't ask, don't tell". I'd buy a set and see if they help.

Big thing is setting proper power and LOTS of fuel flow at max power, though.

MTV

A2A,

I have no experience with the 550, but am running a IO520D in my 185. Our Texas summers get hot although more like 40C.

For me running Lean Of Peak (LOP) is by far the best, quickest, and coolest way to run the IO520. As has been said it requires GAMIjectors and something like the EDM 711.
http://www.gami.com/
https://www.jpinstruments.com/shop/edm-700/

At 23 squared I burn 9 gph. At 25 squared 12 gph. These numbers vary slightly at different altitudes, but not worth reporting. When flying with my slower friends at 100mph, with 10 degrees flaps I can lean it to where the needle is bottomed, 4 gph. Engine running absolutely smooth and cool.

On a cruise climb I'll be somewhere LOP, anything more aggressive and I'm Rich Of Peak (ROP) until I'm done climbing. Watching the CHT's in both instances.

Flying LOP is much less complicated then it seems. I went thru the Lean Find process the first time, since then I go straight from ROP to either 10 gph (23 squared) or 12 gph (25 squared). Then I just watch the CHT's and lean or richen as needed or desired.

LOP you see the engine oil stay much cleaner between changes, and the inside of the pistons very clean and mostly void of deposits. I have no scientific proof but this has to extend engine life.

Hope this helps.

Cheers

OK - I'm confused... For Takeoff, I run the IO-520-BA in my Bo about three turns ROP. My cylinders (EGT's and CHT's) seem fine. When I advance to full throttle for TO, my fuel-flow sensor goes all the way to max (I realize that it is more a pressure sensor than actual fuel-flow). My temps seem to stay in the green. I'm departing from a 5,500 MSL strip here in Denver and if I were to take off with the mixture all the way in, it would run very rough (It runs much smoother leaned on the ground).

I flew from Ottumwa, IA to Denver yesterday and climbed from 850 foot MSL to 10,500 and leaned it all the way up (because it was running rough as I gained altitude). Then I flew it all the way home (to Denver) at 20" MP and 2300 rpm, 11GPH.

EGT's and CHT's were fine...

Am I doing something wrong here?

Apples and oranges folks. An IO-550 is NOT an IO-520, and as MTV said so well, you can't run them the same without cooking jugs.

I gots lots of 520 time, mostly 23/23 or 24/24 full rich, burning about 16 gph. That's at sea level never getting above 2,000 AGL in a 1,400 hour flying year. Can't do that in a 550.

Have your mechanic check fuel flow, and for fuel leaks in the injection system, and fly it by the book settings.

Gump

jaudette wrote:OK - I'm confused... For Takeoff, I run the IO-520-BA in my Bo about three turns ROP. My cylinders (EGT's and CHT's) seem fine. When I advance to full throttle for TO, my fuel-flow sensor goes all the way to max (I realize that it is more a pressure sensor than actual fuel-flow). My temps seem to stay in the green. I'm departing from a 5,500 MSL strip here in Denver and if I were to take off with the mixture all the way in, it would run very rough (It runs much smoother leaned on the ground).

I flew from Ottumwa, IA to Denver yesterday and climbed from 850 foot MSL to 10,500 and leaned it all the way up (because it was running rough as I gained altitude). Then I flew it all the way home (to Denver) at 20" MP and 2300 rpm, 11GPH.

EGT's and CHT's were fine...

Am I doing something wrong here?

Nope. Just the altitude richening the mixture on you.