aaronk25 Posted August 3, 2013 Report Posted August 3, 2013 My dentist out of Rochester MN, just traded his tks and TV screen ovation 2 for a 08 acclaim and I got to go for a ride with him and screw around with power settings! My impressions of the bird was it's alot like a ovation that doesn't run out of power as DA increases. We were at 7k 28" at 2400 and about 14.8gph at 177kts. He said its faster than his ovation at 7k but not by much. I asked him to do the Mike Busch cruise power setting and we lowered rpm to bottom of green 2200rpm and increased MP to 31ish and we set fuel flow to same vale as before at 14.8gph and no surprise the bird picked up 3kts! He didn't believe it at first but after a while I think he gave in as numbers don't like. Lower rpms higher mp is alot more efficient. Cht were 300ish! Now I'm sure if we went to fl180 the chts would come up but at almost any power setting that we used the CHTs were lower than his NA ovation! Continental did a great job with that engine! Awesome plane! 1
Marauder Posted August 4, 2013 Report Posted August 4, 2013 How long did it take for you to clean up the drool you left behind?
aviatoreb Posted August 4, 2013 Report Posted August 4, 2013 That is a VERY interesting observation. But for my thought. 31'' at 2200rpm sounds like a lot of internal cylinder pressures. Actually my mooney rocket includes both 26'' 2200rpm as 55% and 30'' at 2200rpm as 65% setting. But I have always been suspicious of running those higher pressures at lower rpms. And wasn't there a service bulliten warning of sudden stoppage incidents as being related to running low rpms and higher pressures? Anyway, generally I don't run lower than 2300rpm. So for example 2300, 26'' or 29''....and on up. But as per my poh rpm's go up with the even higher pressures - e.g., 2300 31'' or 2400 31'' but 2400 32''. Here is the service bulletin - and it covers the TSIO520NB in the rocket. So it contradicts the POH by advising against the <23000rpm settings that are in my POH (and on my sun-visor!). http://www.tcmlink.com/pdf2/CSB09-11.pdf Is the acclaim engine included?
aaronk25 Posted August 4, 2013 Author Report Posted August 4, 2013 Interesting, Mike Busch has about 4000 hours tsmoh on 310 turbo motors running 2100rpms which is lower than the 2200rpms we were running at, however the acclaim has 2 smaller turbos where the 310t had one big one, not sure if there is a difference, I'm guessing not. I think, my opinion only that high chts are way worse than low chts with higher cylinder pressure as its heat that weakens cylinders......4000 hours can't be wrong, right?
aviatoreb Posted August 4, 2013 Report Posted August 4, 2013 Interesting, Mike Busch has about 4000 hours tsmoh on 310 turbo motors running 2100rpms which is lower than the 2200rpms we were running at, however the acclaim has 2 smaller turbos where the 310t had one big one, not sure if there is a difference, I'm guessing not. I think, my opinion only that high chts are way worse than low chts with higher cylinder pressure as its heat that weakens cylinders......4000 hours can't be wrong, right? Mike Busch definitely knows a lot more about engines than I do - no doubt! I can say this though - one engine can do well doing something bad... n=1 we call it in statistics as sort of a joke about "studies" with one anecdotal indication. Sort of like a smoker who says he has been smoking his whole life and no problem so there must be nothing wrong with smoking. I did change my own operations following that continental SB, and I would love to be convinced to convert back to 2200. YMMV
Cruiser Posted August 4, 2013 Report Posted August 4, 2013 I guess statistics go both ways.. I wonder what data Continental used to validate the SB?
aaronk25 Posted August 4, 2013 Author Report Posted August 4, 2013 Very interesting....to maintain the same airspeed it required less mp and higher rpms and all the temps went up....yes that's right ....tit...Cht...egt all went up. That's why I'd like to seethe data for the SB. I'm guessing the data derives from hot CHT where detonation could play a part, however I saw Cht drop 20 degrees at the lower rpm.
triple8s Posted August 5, 2013 Report Posted August 5, 2013 I'm no aircraft expert that's for sure, but ponder on this. Diesel engines are low rpm high pressure engines. They have very substantial reciprocating components designed to handle very high cylinder pressures and vibrations (power stroke pulses) associated with low rpm applications. Aircraft engines aren't very meaty looking in the bottom end, I can tell you that. All that being said, I don't plan on using my engine as a test platform.
David Mazer Posted August 5, 2013 Report Posted August 5, 2013 Eric, I agree with you. Continental put out that SB because of a series of failures and the only similarity was the RPM below 2300. However, the SB doesn't cover Lycoming engines and I would go back to 30/2200 if I could. I've modified to 29/2300 as my usual cruise setting using a little more gas per hour still.
aaronk25 Posted August 5, 2013 Author Report Posted August 5, 2013 I find the sb a bit hard to believe as decreasing cylinder speed while maintaining same mp would pack some more air in the cylinder but I would think it would create a longer slower power stroke as the lower rpm gives the lean mixture more time to burn. I guess I'm not going to argue with the engine designer, just interesting mike bush engines lasted so long.....
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