May 24, 2012, 2:20 PM
Post #1 of 9
Cessna IO-550 engine questions
I am looking for some information from those that may know about cylinder temps on an upgraded IO-550. PM me if you wish instead of being scrutinized here :)
Just recently upgraded our Cessna 206 from a IO-520 to a IO-550 (two blade up to a 3 blade as well) and are still in the break in period for the engine. There were no modifications done for the cowling, just take the old one out and Lego block plunk the new one in .... if it were only that easy.
The issue we are having is that #6 gets warm like right now. Simply taxing to the end of the runway it is very warm. #1 stays very, very cool on descent. To the point that the pilots are backing off on their descent rate. All monitored through the new electronic temp gauge that can select each cylinder head temp individually.
PRM and mechanics have checked everything out and it seems fine. Temp probes test good. #1 reads lower because it is different from the rest. Its just a washer under the factory installed probe. Fuel pressures tested normal.
The backward rules for aircraft are that you need to have functioning original gauges in the plane then you can have the fancy new electronic gauges as extras if you wish. If when the aircraft was certified back in 1965 it had a spindle mounted hamster driven gauge, that is what must be working and installed before you can add whatever else you want. Have (x5) fuel gauges if you wish but at least one of them must be the original working format even though the new 2012 electronic system is much more reliable. This is why #1 cyl temp system is a washer with a probe attached to it to sense the temperature instead of replacing it with 2012 technology that is not only more reliable but dead on accurate.
My question is, what can be done to make the new engine perform like it should without making things go "boom"? Pilots are backing off because of hot/cold temperatures and the only real issues with the engine is #6 being hot while #1 is really cool.
P.S. yes we know #1 is at the front that gets all the air first and #6 is at the back by the firewall but the old IO-520 flew awesome without this great temperature differential. Fly so #1 doesn't get shock cooled and #6 will take care of it's self.
(This post was edited by goobersnuftda on May 24, 2012, 2:24 PM)
Can't make it perform like it should if you don't have the instrumentation to know what its doing. If you don't know EGT, CHT and fuel flow you can only guess. Even without fuel flow you could see any problems due to a blocked injector, induction leak,sticking valve or a fouled plug. Leave the old cht installed and get an engine analyzer, it will help protect your investment and let you know whats really going on.
After a quality graphic engine monitor. Lean of peak check. Some cylinders may be on the rich side of peak but near best power = hot , # 1 may be on the lean side of peak but indicating nearly the same numbers (egt cht) as a best power but not producing as much power = colder. As the throttle is pulled back that cyl goes leaner and colder. Many things can cause an imbalance of air fuel mixture. partially blocked fuel injector, induction air leak, exhaust backpressure. Air/ fuel is your primary temp control, next oil, then cooling airflow. A quality graphic engine monitor and a pilot that understands it is the best insurance for that tightly wrapped big bore. When you have a pilot that can control the mixture knob and that engine dialed in it makes good power.