Niko182 Posted November 30, 2018 Report Share Posted November 30, 2018 The 310HP STC was currently done on the Eagle I've been putting around in, and I cant help but notice I have really low CHT's. When I say low CHT's I mean during takeoff they don't seem to break 350, and in cruise all of them are below 300. When I was flying the 244hp 2 blade version, the CHT's would be higher around 310 to 330, and takeoff would show around 380 , but now unless I lean it out to the point where EGT's can be above 1500, I cant seem to get CHT's above 300. The only issue I have so far with the STC, is that the Fuel Flow needs to be increased to the max of 27.3. Its at 26.3 and EGTs are all around 1450 on takeoff which is a bit high. even with the EGT's this high, they still dont break 350. During descent they are around 260 to 280 degrees with 18 to 20 inches and 2400rpm. Don't get me wrong I love this STC. The way better Takeoff performance, plus the 1140 pound useful load (my goal is 1200Lbs) is absolutely amazing, but it just seems weird to me that the CHT's are so low. Better cool than hot I guess but let me know what you guys think. Thanks Nik Quote Link to comment Share on other sites More sharing options...
carusoam Posted November 30, 2018 Report Share Posted November 30, 2018 Sorry.... I can’t hear ya. Speak up? Dang 2700 rpm is getting too noisy..... Nick, What’s your OAT? When do you pull back the throttle? Look at this way... If you take off using full throttle, max rpm, the CHTs are going to rise... the initial climb rate is going to be near 2k’pm to keep the CHTs in order, add more FF... people report 29 or 30gph as a useable setting... The 310 STC allows for a cruise setting 2550 great for speed... 27.2 (?)gph is the top end of the stc’s range... anything less is probably the middle of the given range... Speaking with the STC’s author is worthwhile. He is a fountain of knowledge regarding the capabilities of the IO550... Next best, and MSer... is @StevenL757 Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Niko182 Posted November 30, 2018 Author Report Share Posted November 30, 2018 OAT was ranging from 2 to 10 degrees C. Takeoff is full power, and the moment the gear and the flaps go up, I pull the RPM back to 2400RPM. Climb is WOT at 2400rpm. I'm not farmiliar with power settings yet, but I run the iddenticale EGT's I used to see with the 244HP rated engine, so I would guess the CHT's would be around the same. Even with the lower than usual flowflow on takeoff, I still dont see temps of the CHT's passing 350. Is it bad that the cylinders stay cool, or is this just me over thinking. FYI, I also run ROP. I'm not ready to risk destroying my engine yet. thatll come when the EDM 900 comes in to play. Quote Link to comment Share on other sites More sharing options...
MIm20c Posted November 30, 2018 Report Share Posted November 30, 2018 Many pilots do not recommend pulling the prop right after the plane is cleaned up. Thought is that most engine failures occur when making large power changes. Higher FF is needed if you want to climb at 300hp vs 200 on warmer days. I’d leave it alone if you’re just using it to get off the ground. OAT are cold right now which is why the engine temps are staying so low and different vs the 2 blade on warmer days. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 30, 2018 Report Share Posted November 30, 2018 So is this the same engine with a prop change and governor change? I would say that colder CHTs at 2700rpm over 2400rpm at WOT and full rich should not be surprising. The inverse of that being that if I adjusted my prop control for 2400rpm on take off, I would expect higher CHTs. The reason for this is due to the internal cylinder pressure being higher at the lower RPM (All other things being equal). What has changed significantly going from 2400 to 2700? The answer is piston speed. Mixture and ignition timing remain the same, meaning the speed and starting point of the combustion event are theoretically the same. The result is more power strokes per minute, but lower internal cylinder pressure per stroke because the piston is moving through the combustion stroke faster. Quote Link to comment Share on other sites More sharing options...
ArtVandelay Posted November 30, 2018 Report Share Posted November 30, 2018 What has changed significantly going from 2400 to 2700? The result is more power strokes per minute, but lower internal cylinder pressure per stroke because the piston is moving through the combustion stroke faster. If everything remains the same (fuel burn, horsepower), then isn’t the increase cylinder pressure simply because you are burning more fuel per piston stroke?I don’t see how a faster moving piston changes the pressures. Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 30, 2018 Report Share Posted November 30, 2018 (edited) 11 minutes ago, teejayevans said: If everything remains the same (fuel burn, horsepower), then isn’t the increase cylinder pressure simply because you are burning more fuel per piston stroke? I don’t see how a faster moving piston changes the pressures. So piston speed effects how fast the combustion chamber expands (TDC to BDC). The speed/expansion and timing of the combustion event remains the same (volume, mixture and ignition point). At lower RPM the combustion event is expanding more rapidly than the the combustion chamber is expanding relative to the higher RPM. In both cases the CE expands faster than the combustion chamber, however that difference increases as RPM decreases. This is why a car engine detonates if left in too high a gear when climbing a hill. Edited November 30, 2018 by Shadrach Quote Link to comment Share on other sites More sharing options...
Shadrach Posted November 30, 2018 Report Share Posted November 30, 2018 (edited) 1 hour ago, teejayevans said: If everything remains the same (fuel burn, horsepower), then isn’t the increase cylinder pressure simply because you are burning more fuel per piston stroke? I don’t see how a faster moving piston changes the pressures. I think the key thing you're misunderstanding is that FF in GPH does not remain the same. Same mixture per combustion event but more combustion events per minute equals greater fuel flow in GPH. Edited November 30, 2018 by Shadrach Quote Link to comment Share on other sites More sharing options...
carusoam Posted November 30, 2018 Report Share Posted November 30, 2018 Nik, Is anything new regarding the engine? As in, any break-in required? I would be thinking an engine running 2400 rpm for 1k hours, now running 2700 rpm might want to have some cylinder work, before this occurs? Aside from break-in, some Transition Training or instruction of some form is a pretty good idea... You have gone from a low power IO550 to a medium power IO550... High power IO550s are over 500hp... So blowing up your engine at medium power is probably not on the menu... but following good guidance probably is... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Niko182 Posted November 30, 2018 Author Report Share Posted November 30, 2018 Lately other than takeoff i try not to run the engine high powered yet. Im stoll running around 21 inches and 2400rpm in cruise which gives me about 175 ish knots. Ill start running it fast when i can catch up with the aircraft. Not saying im behind, just saying things happen alot faster at 310hp, including the takeoff, climb, descent, and landing, and i have no need to firewall the power as of now. Quote Link to comment Share on other sites More sharing options...
carusoam Posted November 30, 2018 Report Share Posted November 30, 2018 Proper break-in should be considered... as the arc of pistons is sometimes known to be different at 2700 rpm and full power vs. previous operational window... The break-in of a factory reman includes running max MP and varying RPM on a 15 minute schedule... Running a 310hp engine like a 244hp engine doesn’t sound like a fully fleshed out idea... to me? Got any procedures to follow from your engine builder? Get some experience from a Mooney CFI with 310hp experience. Things are going to happen twice as fast or half the distance when going full power... Learning this on your own is going to be less than optimal, no? PP thoughts only, not a CFI, I rented a couple Mooney specific CFIIs for break-in flights... and took Byron along for a flight after that... Best regards, -a- Quote Link to comment Share on other sites More sharing options...
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