All the flat CMI (was TCM) and flat Lycomings are very happy at 85% to 90% power LOP (LOP ONLY).
"OldAkro" Quote:JD. Including turbos?
Nice catch, THANK YOU!
Here's George's opinion:
No… the 350 Hp engines are not happy at 85% = ~ 305 BHp.
That includes the TCM TSIO-550C (350Hp at 2700) and the Lycoming TIO 540 J2xx series engines (350 BHp at 2575 RPM).
The 550C is reasonably happy at 260-265. The Lycomings -- we have less extended experience with - - but based on the test stand operation, those engines typically run at cruise in the 2100 to 2200 RPM range and about 28 to 32” MP and LOP and do OK. But that is much less than the full power 43” x 2575 standard day power.
About 260-265 BHp at 2500 RPM is about the range at which I think the 550 c.i. engines are comfortable
The TSIO-520NB (typical RAM twin Cessna) at 335 BHp is pushing the limit for max power for a 520, especially the way that RAM sets them up.
That 520 c.i. engine doesn’t do well at more than 75-80% power even LOP. It is often difficult to get them to run well LOP.
Part of the problem with those engines is managing the TIT values.
A typical C 340 running at higher power and LOP will end up with a TIT at the 1630- 1640 range. While that is not a specific issue for the turbocharger - - the rest of the exhaust system can be challenged with continuous operation like that in the twin Cessna exhaust configuration. If you try to push up the BHP you end up butting heads with the TIT and exhaust operational considerations.
George