Lean Mixtures

dmccormack said:
It's disconcerting that a phenomenon that can cause such damage is not clearly indicated...
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Crazy people don't carry warning labels either. The best route for both issues is to stay away from the areas where they can be found. Read Deakin's articles about the "Red Box" and don't fly there.
 
airguy said:
Crazy people don't carry warning labels either. The best route for both issues is to stay away from the areas where they can be found. Read Deakin's articles about the "Red Box" and don't fly there.
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Where do you believe that Deakin got his information and beliefs?
 
Ted DuPuis said:
...and your engine rated at 2700 RPM won't get you off the ground very well if all you get out of it on the ground is 2000 RPM.

That would be a bigger factor, especially on any engine that has a fixed pitch prop that I've tested.
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That's one of the reasons, the engine will not develop proper horse power, it will also be running at a low RPM at WOT. in the red zone and probably detonating.
 
flyingcheesehead said:
OK.

It's mixture-related - And may just be slightly unbalanced fuel flows. :dunno: But it doesn't run "rough" by my definition. It's noticeable only if you're really paying attention.
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Engines with a carb, and fixed pitch props will be designed in a manor that will not allow the pilot to get in to the detonation areas. The cruse jet in the carb controls full rich mixture, and the idle jet controls the mixture when the throttle is closed. even when the pilot leans at WOT the prop can not load the engine heavy enough to cause the RPM to drop to the point of detonation.

If your engine runs rough at all settings I'd be looking for a discrepancy. such as an induction air leak. you may have 1 cylinder simply starving for fuel. (that would be a mixture related)
 
dmccormack said:
Is it incorrect?
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No, but he was taught by an old narly pilot way back in his career. Deakin got most of his experience as a Air America pilot in VN. flying Buck 18's, running P&W 2800s.

We saw those guys in the club but we never associated with those pukes, :)

No I did not know him. but I have read his books.
 
"Internal Combustion Engine Fundamentals" John B. Heywood (Who somehow reminds me of Bob Hoover in appearance)

"As yet, there is no complete fundamental explanation of the knock phenomenon over the full range of engine conditions at which it occurs" Pg. 457



 

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Capt. Geoffrey Thorpe said:
"Internal Combustion Engine Fundamentals" John B. Heywood (Who somehow reminds me of Bob Hoover in appearance)

"As yet, there is no complete fundamental explanation of the knock phenomenon over the full range of engine conditions at which it occurs" Pg. 457
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Your man should have reads the Curtis Wright engine operators manual.
 
Capt. Geoffrey Thorpe said:
"Internal Combustion Engine Fundamentals" John B. Heywood
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Reading your reference, it occurred to me that this guy is talking about a Model "T" or model A ford engine, we can't adjust timing in any of the engine we commonly fly today.
 
Tom-D said:
Your man should have reads the Curtis Wright engine operators manual.
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Wouldn't surprise me if he had.

Heywood's work at MIT follows C.F.Taylor (Professor of Automitive Engineering, M.I.T.) and E.S.Taylor (Professor of Flight Propulsion, M.I.T). Their book "The Internal - Combustion Engine" has quite a bit of data from aircraft engine companies. If I wasn't lazy, I would look up a couple examples...

Chances are, anyone who is designing internal combustion engines today has read one or the other of those books (I have both).

Hmmm. C.F. may have even written said Curtis Wright manual...

From 1920 to 1923, Taylor was the engineer in charge of the U.S. Army's Air Service Laboratory in Dayton, Ohio, where he supervised engine endurance tests, aircraft flight tests and fuel anti-knock tests. It was there that he met Orville Wright. From 1923 to 1926 he was in charge of airplane engine design and development at the Wright Aeronautical Corporation; he was involved in developing the air-cooled "Whirlwind" engine used on the historic flights of Lindbergh and Byrd.
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web.mit.edu/hmtl/www/taylor.pdf
 
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Tom-D said:
Reading your reference, it occurred to me that this guy is talking about a Model "T" or model A ford engine, we can't adjust timing in any of the engine we commonly fly today.
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And?

I can't adjust the timing on my Ford Focus as I drive either.

That doesn't change the physics behind the phenomena...
 
Capt. Geoffrey Thorpe said:
And?

I can't adjust the timing on my Ford Focus as I drive either.

That doesn't change the physics behind the phenomena...
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Your Ford Focus does it all by its self.. your aircraft has set timing by mag. does any car later than 1930?
 
Mixture effect on knock / detonation - From Taylor and Taylor.

The graph that would make the most sense to a pilot would be the upper left. The Y axis is the maximum manifold pressure without knock. The X axis is normalized fuel air ratio where 1.0 would be close to peak, larger numbers are richer.

Lower left graph shows knock limited IMEP (Indicated Mean Effective Pressure) - essentially the work done on the piston by the combustion process - as a function of the fuel air ratio

It doesn't say exactly what engine was used, but considering the source (A NACA report) and the fuel used, I would assume it was an aircraft engine.


Lower right is the result from a variable compression ratio engine that shows the knock limited compression ratio.

(You will have to rotate / zoom to really read the graphs - sorry)
 

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Tom-D said:
Your Ford Focus does it all by its self.. your aircraft has set timing by mag. does any car later than 1930?
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Dad's 1959 Rambler American had a Continental industrial engine with a magneto in it. Really. One of the reasons American Motors struggled so.

Dan
 
Tom-D said:
Engines with a carb, and fixed pitch props will be designed in a manor that will not allow the pilot to get in to the detonation areas. The cruse jet in the carb controls full rich mixture, and the idle jet controls the mixture when the throttle is closed. even when the pilot leans at WOT the prop can not load the engine heavy enough to cause the RPM to drop to the point of detonation.

If your engine runs rough at all settings I'd be looking for a discrepancy. such as an induction air leak. you may have 1 cylinder simply starving for fuel. (that would be a mixture related)
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Well, this is an injected engine with a constant speed prop that runs nice and smooth ROP but has this *tiny* (and I mean it, I've flown with other pilots that can't tell it's there even after I point it out) "tick" when you get LOP. It's not rough at all, and the CHT's and EGT's still look good.

By "mixture related" I mean that it goes away when I push the red knob in, and comes back when I pull it out.
 
flyingcheesehead said:
Well, this is an injected engine with a constant speed prop that runs nice and smooth ROP but has this *tiny* (and I mean it, I've flown with other pilots that can't tell it's there even after I point it out) "tick" when you get LOP. It's not rough at all, and the CHT's and EGT's still look good.

By "mixture related" I mean that it goes away when I push the red knob in, and comes back when I pull it out.
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Do you have Gammies ?:)
 
dmccormack said:
Didn't Corvairs have a Lycoming?
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No. Corvairs had an engine designed and built by GM for that car. A long ways from Lycoming's robust design. There are some Corvairs flying in homebuilts.

GM was trying to horn in on the VW market with a rear-mounted, air-cooled engine. Didn't work so well.

Lycoming built auto engines before they built aircraft engines. The Cord company used them in their cars.

Dan
 
Dan Thomas said:
No. Corvairs had an engine designed and built by GM for that car. A long ways from Lycoming's robust design. There are some Corvairs flying in homebuilts.

GM was trying to horn in on the VW market with a rear-mounted, air-cooled engine. Didn't work so well.

Lycoming built auto engines before they built aircraft engines. The Cord company used them in their cars.

Dan
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Actually it was a Franklin design. and took many of the Franklin 150 horse power lower end parts. Case, crank, and bearings, the cylinders were different, as was the head design. 3 in 1 rather than each cylinder have its own.

many old Franklin 150s got over hauled by the Franklin engine club using the corvair parts, see the AD.
 
Tom-D said:
No, but he was taught by an old narly pilot way back in his career. Deakin got most of his experience as a Air America pilot in VN. flying Buck 18's, running P&W 2800s.

We saw those guys in the club but we never associated with those pukes, :)

No I did not know him. but I have read his books.
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That's where he got his experience with piston engined airplanes but after that he flew jets for JAL. Now he flies a TN Bonanza.
 
Tom-D said:
No, but he was taught by an old narly pilot way back in his career. Deakin got most of his experience as a Air America pilot in VN. flying Buck 18's, running P&W 2800s.

We saw those guys in the club but we never associated with those pukes, :)

No I did not know him. but I have read his books.
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And while you watched the detonation sensors go crazy on the Connies as a flight engineer, it's worth pointing out that each engine has different "red boxes."

For example, I've tested several naturally aspirated engines which have lower detonation propensities at lower RPM than higher RPM. That's why I say there's more to it than any one factor.
 
Ted DuPuis said:
And while you watched the detonation sensors go crazy on the Connies as a flight engineer, it's worth pointing out that each engine has different "red boxes."
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We didn't have detonation sensors per say, we had a BMEP gauge and a torque meter, both readings would drop when detonation occurred, we had very specific guidelines as to what power settings we could use. that varied with HQ, temp. and a bunch of other parameters.

we also had ADI, with charts to tell us when and how much.
 
Tom-D said:
We didn't have detonation sensors per say, we had a BMEP gauge and a torque meter, both readings would drop when detonation occurred, we had very specific guidelines as to what power settings we could use. that varied with HQ, temp. and a bunch of other parameters.

we also had ADI, with charts to tell us when and how much.
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I'm curious about the BMEP gauge. I was under the impression that this was actually based on torque (measured in the reduction gearing) not a direct measurement of cylinder pressure. If that's true it sounds redundant to a separate torque meter. Do you know how the BMEP gauge worked?
 
gismo said:
I'm curious about the BMEP gauge. I was under the impression that this was actually based on torque (measured in the reduction gearing) not a direct measurement of cylinder pressure. If that's true it sounds redundant to a separate torque meter. Do you know how the BMEP gauge worked?
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Ours was a direct reading pressure gauge. tapped into the cylinder head.

the torque meter was a variable orifice in the gear box that measured oil pressure, and changed when the ring gear moved under load.
 
Ted DuPuis said:
Which my car doesn't do now, but my '68 Cadillac did.

A visual understanding of what the pressure trace looks like helps to understand the sound you hear in your car:

crank.gif
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You had a '68 Caddy? Which one - de Ville, Calais or Eldorado?

The 472 is a righteous motor.
 
SCCutler said:
You had a '68 Caddy? Which one - de Ville, Calais or Eldorado?

The 472 is a righteous motor.
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I made a slight typo. It was a '69 Cadillac Fleetwood Series 75. We called it "Moby" - the white whale. It wasn't uncommon to put 12 people in it.

472 and a TH400. Best car I've ever had in the snow. Got 12 mpg highway.
 
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