John Deaking said... what exactly?

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slavinger

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I take it most of you folks have heard of Mike Busch & John Deakin. I watched/read pretty much all of Mike Busch's videos up on EAA video site and his columns on AvWeb, and same for John Deakin. Most of what they say makes perfect sense. I have two questions, though:

1) Carb heat to help with mixture distribution in carbureted engines trying to get to LOP. Why does enriching the mixture with partial carb heat in cruise help mixture distribution? Or is there something to this besides just richer mixture?

2) In Pelican Perch #18 "Mixture Magic", J.D. talks about climbing all the way up to altitude with full throttle, and also talks about the dangers of pulling back on RPM with engine at high power due to max pressure occurring closer to TDC, detonation potential, higher stresses and CHTs. Does that mean he climbs thousands of feet with max RPM, until the naturally aspirated engine lost enough power to pull back on RPM? Even smaller engines don't drop below 75% power at full throttle 'til like 7,000'. He says don't run 25 squared but also doesn't say what RPM to run in climb, unless I missed something. Mike Busch says he climbs full throttle and pulls back on RPM after take-off in his 310T, but doesn't provide any guidance.

Thanks.
 
Regarding (2):

I follow what's in the poh and my engine manual. Full power is only allowed for like 2 minutes. And then it's back to 75%. I usually get 1000ft AGL and then come back to 75% which is still plenty to then continue to cruise climb at Carson speed.
 
What if there's no POH time limitation on full power?
 
John Deakin says a lot of things about engines. Some of them are right, some of them aren't. I climb at 25 squared and the engine's happy.

As for MP and RPM, it depends completely on the engine/prop combination. Some engines and prop combinations do allow even full throttle with less than rated RPM. Check your POH/owner's manual for guidance. The people who certified your engine went to a lot of effort to determine appropriate manifold pressure and RPM combinations.

He's also not necessarily correct about increased detonation risk with lower RPM. Yes, there are some aspects of lower RPM that make an engine more prone to detonation, but also the engine is making less power (and thus less heat) which reduces the risk of detonation. When I've done detonation testing on our engines, I pretty consistently found that higher RPM had increased risk of detonation because of higher power.
 
slavinger said:
1) Carb heat to help with mixture distribution in carbureted engines trying to get to LOP. Why does enriching the mixture with partial carb heat in cruise help mixture distribution? Or is there something to this besides just richer mixture?
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Something else. The theory is that warming the air coming in improves atomization of the fuel, and that helps even the fuel/air mix throughout the engine. You then have to lean the mixture to compensate for the enrichment due to reduced density of the heated air.
 
As Ron said:
Ron Levy said:
The theory is that warming the air coming in improves atomization of the fuel, and that helps even the fuel/air mix throughout the engine.
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And I used to drink the "carb heat during cruise" tea. But back when I was flying a lot of cross country trips, I did a lot of experimenting and determined that the method cost way too much power and speed for my liking. The reduction in speed was proportionate, or more so, than the reduction in fuel burn. IIRC the target carb temp was 60*F but my memory is a bit foggy since it's been quite some time since I drank that tea.

O-470-L here.

Oh...and I can regularly attain less than a 50*F spread w/o carb heat and on many days less than 25*F
 
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slavinger said:
2) In Pelican Perch #18 "Mixture Magic", J.D. talks about climbing all the way up to altitude with full throttle, and also talks about the dangers of pulling back on RPM with engine at high power due to max pressure occurring closer to TDC, detonation potential, higher stresses and CHTs. Does that mean he climbs thousands of feet with max RPM, until the naturally aspirated engine lost enough power to pull back on RPM? Even smaller engines don't drop below 75% power at full throttle 'til like 7,000'. He says don't run 25 squared but also doesn't say what RPM to run in climb, unless I missed something. Mike Busch says he climbs full throttle and pulls back on RPM after take-off in his 310T, but doesn't provide any guidance.
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Probably because it depends on the engine what a safe setting is. Like Ted said, the manufacturers have done lots of testing - See what they'll allow. With respect to RPM, what Mike Busch does in his 310 is irrelevant to what I should do in a Mooney or you should do in an Arrow.

dans2992 said:
What if there's no POH time limitation on full power?
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My preferred method, should it be allowable for the engine, is to stay at full throttle for the climb but reduce RPM from 2700 to 2500 or so shortly after takeoff, as that makes quite a difference in the amount of noise the airport neighbors have to endure. Hopefully, that means the airport will stay open longer...

bartmc said:
2 people trying to sell GAMIs.
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And here's one person trying to sell 100LL! :D
 
flyingcheesehead said:
Probably because it depends on the engine what a safe setting is. Like Ted said, the manufacturers have done lots of testing - See what they'll allow. With respect to RPM, what Mike Busch does in his 310 is irrelevant to what I should do in a Mooney or you should do in an Arrow.



My preferred method, should it be allowable for the engine, is to stay at full throttle for the climb but reduce RPM from 2700 to 2500 or so shortly after takeoff, as that makes quite a difference in the amount of noise the airport neighbors have to endure. Hopefully, that means the airport will stay open longer...



And here's one person trying to sell 100LL! :D
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I don't think they're dumb guys, though I do think Deakin has moved over to the Evangelical side of the aisle. I asked a fairly simple question, his reply was to tell me that everything I was doing was wrong and then invited me to attend a seminar halfway across the country for a grand or two to find out why. pffffffffffftttt. Running an IO-470 ain't rocket surgery. The design is pressing 70 years old, there's not a lot of secrets left. The guy that taught me how to run em TBOs about 2 every year in his 135 fleet. I've seen results first hand and didn't have to pay 4 figures to attend a seminar to find out what I need to buy.
 
Full throttle is not full power. Full power isn't even possible in non-turbo'd engines after the first few thousand feet. I was always taught to climb with the knob all the way in. There are a few different reasons for that but it holds true for just about all engines. I come back to 2500 RPM however as soon as I'm clear of the obstacles to restrict power at sea level on the io550 (followed by rough setting the fuel flow to the marked position on the guage). The old gopher engine was only good for 3400 RPM for five minutes or so, so I tried not to exceed that.
 
I am curious if my NA IO-540 will run cooler CHTs at 2700 or 2500.

Coming back to 2500 helps with the noise, but reducing the RPM increases the peak pressure because peak pressure then occurs closer to TDC.

I need to do some testing, but could it be possible that CHTs run cooler at 2700 than 2500? Maybe it's a wash since there are more combustion events per minute at 2700.
 
dans2992 said:
I am curious if my NA IO-540 will run cooler CHTs at 2700 or 2500.

Coming back to 2500 helps with the noise, but reducing the RPM increases the peak pressure because peak pressure then occurs closer to TDC.

I need to do some testing, but could it be possible that CHTs run cooler at 2700 than 2500? Maybe it's a wash since there are more combustion events per minute at 2700.
Click to expand...

Lots of factors at play. Try and see. :)
 
flyingron said:
Full throttle is not full power. Full power isn't even possible in non-turbo'd engines after the first few thousand feet. I was always taught to climb with the knob all the way in. There are a few different reasons for that but it holds true for just about all engines. I come back to 2500 RPM however as soon as I'm clear of the obstacles to restrict power at sea level on the io550 (followed by rough setting the fuel flow to the marked position on the guage). The old gopher engine was only good for 3400 RPM for five minutes or so, so I tried not to exceed that.
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So you have never taken off from an airport with a -3000 ft density altitude?
 
Clip4 said:
So you have never taken off from an airport with a -3000 ft density altitude?
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Interesting point. But that would require an outside temperature below 15 Fahrenheit, at sea level. Even colder at higher elevations. I'd rather stay inside where it's nice and warm.
 
NoHeat said:
Interesting point. But that would require an outside temperature below 15 Fahrenheit, at sea level. Even colder at higher elevations. I'd rather stay inside where it's nice and warm.
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I took off once in -20F. I thought the 310 grew a couple of turbines!
 
LDJones said:
I headed to Vegas one time in my 180hp Mooney at -40F! Ran great, but a bit nippy inside.
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You just reminded me of a very cold day flying the Mooney, too. Sure flew nice! :)
 
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