Glad to see the resident experts are still providing all of their superior knowledge...
Apparently it is now "Bad" to run over square.. Experts I tell ya..
the "other"forum
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Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
Does no one learn from the lessons of history?
[quote]Lindbergh returned with more fuel than the other pilots.
He explained to the skeptical youngsters that by [b]setting the RPMs low and the manifold pressure high, the engine would consume less fuel[/b].
In the huge Pacific theater, extending the range of the P-38 would be a significant extension of American airpower.
He flew 25 missions by early July, before he was summoned to General Douglas MacArthur's headquarters, to meet with MacArthur and General Richard Sutherland.
On learning of his methods for improving the Lightning's fuel economy and range, they asked him to spread the word throughout the Fifth Air Force.[/quote]
It's too bad that the ignorant, snot-nosed children over
on AvCan don't understand that there is no way in hell
that Alex's BMEP is going to cause detonation with 100LL
in a low-compression, naturally aspirated engine.
As long as he doesn't have a torsional resonance, he's fine.
Queen's University at Kingston, Faculty Of Applied Science, Class of 1986.
[quote]Lindbergh returned with more fuel than the other pilots.
He explained to the skeptical youngsters that by [b]setting the RPMs low and the manifold pressure high, the engine would consume less fuel[/b].
In the huge Pacific theater, extending the range of the P-38 would be a significant extension of American airpower.
He flew 25 missions by early July, before he was summoned to General Douglas MacArthur's headquarters, to meet with MacArthur and General Richard Sutherland.
On learning of his methods for improving the Lightning's fuel economy and range, they asked him to spread the word throughout the Fifth Air Force.[/quote]
It's too bad that the ignorant, snot-nosed children over
on AvCan don't understand that there is no way in hell
that Alex's BMEP is going to cause detonation with 100LL
in a low-compression, naturally aspirated engine.
As long as he doesn't have a torsional resonance, he's fine.
Queen's University at Kingston, Faculty Of Applied Science, Class of 1986.
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Slick Goodlin
- Posts: 721
- Joined: Thu Jun 11, 2015 6:46 pm
I get that not running over square is silly because those numbers are in somewhat arbitrary units that happen to put the values close to one another. Switch your manifold pressure gauge to PSI or feet of water or millibars and suddenly nobody would take issue with the power settings.
Anyways, high MP at low RPM seems to me like you would be getting closer to lugging the engine. Combustion is punching the piston as hard as it can but the prop is set coarse enough that it's pushing back pretty hard the other way. Should there be any concerns about that sort of thing if you ran wide open at, say, minimum prop RPM? Is torsional resonance the only real possible issue? I mean this seriously, I honestly don't know.
Anyways, high MP at low RPM seems to me like you would be getting closer to lugging the engine. Combustion is punching the piston as hard as it can but the prop is set coarse enough that it's pushing back pretty hard the other way. Should there be any concerns about that sort of thing if you ran wide open at, say, minimum prop RPM? Is torsional resonance the only real possible issue? I mean this seriously, I honestly don't know.
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Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
Any radial engine guys will know that the
"evil oversquare" rule is an unfounded myth.
The Wasp Jr ran fine at 30 inches and 20 turns.
A fine engine.
Hell, the Lycoming Operator's Manual for the
little normally aspirated engines recommends
5 inches higher than RPM.
"evil oversquare" rule is an unfounded myth.
The Wasp Jr ran fine at 30 inches and 20 turns.
A fine engine.
Hell, the Lycoming Operator's Manual for the
little normally aspirated engines recommends
5 inches higher than RPM.
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Liquid Charlie
- Posts: 524
- Joined: Sun Aug 23, 2015 1:34 pm
Ah all the shit that is lost in history and reinvented by the next generations. When I started flying we always ran boost over RPM on everything from 180's to Beech 18 on the small engines and normally aspirated engines.
We were all young once but it seems that now the standard is turning out anal retentive, brainwashed snots who can't think for themselves and have google permanently attached to one of there hands. It amazes me (and I consider myself fairly tech [color=rgb(42, 42, 42)][font=Merriweather][size=16px]knowledgeable and certainly use a smart phone) that when you walk into a room 9 out of 10 people have a death grip on there phones and are thumbing them to death, I'm a swipe guy -- lol - bottom line things do change but sometimes it's just painfully stupid. Pass the organic rum. [/size][/font][/color]
We were all young once but it seems that now the standard is turning out anal retentive, brainwashed snots who can't think for themselves and have google permanently attached to one of there hands. It amazes me (and I consider myself fairly tech [color=rgb(42, 42, 42)][font=Merriweather][size=16px]knowledgeable and certainly use a smart phone) that when you walk into a room 9 out of 10 people have a death grip on there phones and are thumbing them to death, I'm a swipe guy -- lol - bottom line things do change but sometimes it's just painfully stupid. Pass the organic rum. [/size][/font][/color]
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Colonel
- Posts: 3450
- Joined: Wed Apr 29, 2015 10:31 am
Take a vanilla 172. With a fixed pitch prop and
2300 RPM at takeoff with full throttle, it's probably
around 28 inches of manifold pressure, down slightly
from ambient 29-30 inches on the barometer due to
restrictions in the intake.
So, the guy who's made every takeoff of his life with
28/23 is now lecturing how bad oversquare is, because
he doesn't know what a manifold pressure gauge is.
Like Charlie, I need to get drunk.
2300 RPM at takeoff with full throttle, it's probably
around 28 inches of manifold pressure, down slightly
from ambient 29-30 inches on the barometer due to
restrictions in the intake.
So, the guy who's made every takeoff of his life with
28/23 is now lecturing how bad oversquare is, because
he doesn't know what a manifold pressure gauge is.
Like Charlie, I need to get drunk.
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Chuck Ellsworth
Lets see...
The DC3 with the R1830-94 take off power setting was 2800 RPM and 52 inches of M.P[font=verdana].[/font]
[font=verdana, arial, helvetica, sans-serif]I never had one come apart using those numbers.[/font]
The DC3 with the R1830-94 take off power setting was 2800 RPM and 52 inches of M.P[font=verdana].[/font]
[font=verdana, arial, helvetica, sans-serif]I never had one come apart using those numbers.[/font]
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Liquid Charlie
- Posts: 524
- Joined: Sun Aug 23, 2015 1:34 pm
CB16 power on the R2800 was 59.5 and 2800 rpm wet and (searching memory) 52 in and 2700 dry and ironically nothing came apart from adding power it was always from ham fisted power reductions and pulling the power off too far.