2100 RPM cruise
Anyone know if it is bad for a continental engine I-470-R in a Cessna 182 to operate with the 2100 rpm cruise settings for cruise in the POH. When sight seeing and traveling short distances it really saves gas but mechanic at a show mentioned it may be bad for engine.
Comments
Hi Tom,
If the performance figures in the poh give numbers for that RPM then technically and legally you're in good shape. I'm not quite sure 2100 is a cruising RPM it's more like a loiter.
That being said since we are certainly not familiar with your engine and aircraft the mechanic advice warrants some thought. If you consider the fact that combustion pressure or bmep is what seats your piston rings against the cylinder wall you can draw some conclusions on the effect that the lower RPM may have on piston ring sealing. Of course that can affect blow by in the long run with corrosive and dirty oil doing its thing down the road.. my take if that's what the mechanic at the show was most likely thinking. I would tend to say the same thing to anybody that wanted to do this. It's just something to be aware of. Is it bad for the engine? Kind of a crap shoot. Also keep in mind that the Continental 470 is not exactly a good breathing engine as far as balance so lower volume metric efficiency is going to be a side effect of running at lower RPM.. short-term ops I don't think will have much effect.
Carl
IA 47yr A&P DAL A/C Inspector 172n
The POH shows that 2,000 rpm is the 'maximum range' setting, and MP as low as 17 inches , 35% power.
But as Carl mentions this puts minimal pressure in the rings, and may not be ok for extended time.