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Old 12th Apr 2018, 09:05
  #261 (permalink)  
 
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Originally Posted by A Squared
Unless it's a turbonormalized IO-550, then it's not really a TIO-550.


Nice try - link me the 550 engine in question.
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Old 12th Apr 2018, 09:16
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Originally Posted by A Squared
OK, going back and reading a few earlier posts I'd skipped over previously:




Not sure what your point is here. You seem to be trying to suggest that all those tolerances can stack up to throw your timing off even more. Not true. The internal timing of the magneto (e-gap or point gap) only determines where the spark fires at the optimum time in the field rotation, it has nothing to do with where that happens relative to the crankshaft rotation. That is determined solely by the magento-to-engine timing. (ie: rotating the magneto on the accessory case so that point opening happens at a certain crankshaft angle) If your magneto is timed so that the points open at 22 deg. BTDC, it really doesn't matter whether your e-gap is set at 13 degrees or 17 degrees, the spark still fires at 22 Deg. BTDC. The e-gap setting only determines the efficiency of the spark generation. (that's what the "e" in e-gap stands for; efficiency)



Jeeeez dude. Are you not reading anything? He told you how he knew. He Noted higher than normal CHT's on climbout, did an airborne mag check, noted a difference from one mag to the other, then when on the ground, checked the timing (as we later were told, using a Mag-rite electronic protractor set-up) and found one of his mags to have been set to 25 degrees BTDC.

Mate,


A) there is the mag to engine timing tolerance of +/- 1 degree (it was my first point in that list) but within this rage will give indication changes.

But not timing incorrectly!


B) all other variable parameters listed will change the actual spark and its intensity.


A wider spark plug gap will slightly delay the spark (greater gap more resistance - more spark power needed)


You also will find plugs make a big difference to engine ops - spend the bucks on some fine wires and compare them to the massive electrodes.
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Old 12th Apr 2018, 09:21
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http://www.continentalmotors.aero/up...ies_032012.pdf
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Old 12th Apr 2018, 09:38
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Originally Posted by Bend alot
An IO550 will not have a "Density Controller" that is a component fitted to a "T" engine.


Some may be all IO-550 engines have altitude compensating bellows.
Well excuse me, I left of the T for turbo.
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Old 12th Apr 2018, 10:03
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Originally Posted by Eddie Dean
Well excuse me, I left of the T for turbo.


A "T" engine maintains a pressure of intake air to the cylinder.


It can be at a pressure to that at sea level - or more or less at 16,000 feet.


But it is not flying at sea level or at sea level conditions at 16,000 - only the intake pressure of 29.92 inches.
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Old 12th Apr 2018, 10:35
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Bend, are you being purposely obtuse?
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Old 12th Apr 2018, 11:53
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Andrewr
Loved the cartoon. It shows the very reason I'm often tardy with replies. All wives must be tarred with the same brush. They fail to realize what's REALLY important.

The reason IO520s with equal sized injector nozzles have such a disparity in mixture strengths between the 6 cylinders is partly due to the type of injector system used and even more due to the built in induction design fault.

At rich mixture settings uneven mixtures are not much of a problem IF each cylinder is receiving pretty equal quantities of air. When the oxygen is burnt in each cylinder it takes the fuel it needs and the unburnt surplus is wasted down the exhaust.

The power produced from each cylinder will be pretty even because the amount of fuel and oxygen burnt in each cylinder is equal. The engine doesn't care if unburnt fuel goes down the exhaust. This is only true if the air to each cylinder is equal.

If an engine has uneven mixtures it causes uneven power when leaning brings the cylinder with the weakest mixture to the point where there is an excess of oxygen. Power from there on is governed by mixture.

As leaning is continued that cylinder puts out less and less power. As the other cylinders reach peak EGT they too put out less power as the leaning continues. If there is a big gap between when the first cylinder peaks and the last one it is readily obvious the engine will be running pretty roughly with all the cylinders putting out different horse powers unlike the situation with uneven rich mixtures with cylinders having equal air supply.

Back to theIO520. It's injector system is known as constant flow system.

The best description I've heard for it that it has 6 hoses all the same size coming from a central distribution point . These hoses have a nozzles on the end and each nozzle, inside the inlet manifold, sprays fuel in the general direction of the inlet valve. It sprays at a constant rate (controlled elsewhere by the quantity of air flow) whether the cylinder head inlet valve is open or not. When the valve does open fuel and air are sucked into the cylinder, the valve closes and the fuel air build up continues.

What could go wrong?

Well it's this. There is a manifold tube down each side of the engine. Each one feeds air to 3 cylinders. The air makes it way from the air filter down this tube to the three cylinders . Each cylinder has a fuel hose making a fuel puddle or more likely a mini fuel and air vapor storm outside the inlet valve that spends most of it's time shut.

If the injector nozzles are all equal size and we assume the mixture is correct at the cylinder nearest air filter then the 2nd one from the filter will be richer and the third one richer again. The air rushing past the first cylinder steals a bit of fuel vapor as it goes past. So the second cylinder gets not just air but a bit of stolen fuel as well. It is even worse at the third cylinder because it has stolen fuel from both cylinders before it.

That's why GAMI has progressively smaller injector nozzles on the cylinders as they get further from the air filter. Who needs big nozzles if you can steal from somewhere else.

Without GAMI or similar balanced injectors IO520s are rough running LOP.

I hope Continental have lifted their game. 5 years ago I bought a factory exchange IO520 engine for the 210 They assured me that it had balanced injectors installed. It didn't. I now have GAMIs and it runs beautifully to way below peak EGT if I want it to.
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Old 12th Apr 2018, 14:16
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Originally Posted by Lead Balloon
So for the aircraft that don’t have EDMs, how do you know where on the lean curve each cylinder happens to be when leaning is by reference to a single probe? If we assume that LOP operations are not only “not approved” but “unsafe”, how do you know that each cylinder is peak or rich of peak far enough? Do the laws of physics and safety only apply to the cylinder with the probe?

You say that the mixture with the smallest detonation margins at any given power setting is peak EGT. Are you sure about that?
You don’t know precisely where each cylinder is. The assumption is that the leanest cylinder is within 25F of the indicated EGT when using the thermocouple on the collecter. The recommended best power setting for the engine is 50ROP so that is where our minimum 75ROP comes from.

Even the aircraft in our fleet with EDMs cannot be relied upon because the environment is too harsh, hot and high, dusty and corrosive. These aircraft are doing 100 hours a month, 10 or 12 starts a day and it isn’t long before one or other probe plays up. One day it is an aircraft with an EDM, the next it is an unreliable EDM, the next it’s no EDM. We cannot afford our aircraft to go in for a 50hour check and get stuck for a week waiting for a thermocouple or harness. We have to have them back online. There are enough other snags to sort out such as the brakes, starter motors, alternators and radios. However, the alcor type EGT installation is robust so our SOP is based on it. That is the real world for us.

Yes, I am sure that the minimum detonation margin for a given power is at peak EGT or at least very close. I am sure because the extensive research published on detonation says so.
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Old 12th Apr 2018, 18:09
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Rich and lean are relative concepts, not absolute. You can pick your reference point. It could be:
rich/lean of stoich
rich/lean of best power
rich/lean of peak egt
or simply rich/lean of the intended mixture.
Certainly rich and lean are relative but the only “reference point” in that list that isn’t arbitrary is stoichiometric. That is because stoichiometric is the mixture where there is physically neither an excess of fuel nor an excess of air. It is an equivalence ratio of 1.

The point is, there are rich and lean mixtures. it is incorrect to say “all mixtures are lean”, which was what I was responding to.
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Old 12th Apr 2018, 18:37
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Originally Posted by LeadSled
Folks,
At the risk of being flamed by Rod the Con(and recognizing, as at least some of you do, that any measurement has an error) finding top dead center by any measures that rely on the height of the piston at TDC, results can vary quite markedly.
Perhaps some of you should acquaint yourselves with common practice on high performance auto racing engines from the era before all timing being determined by precision electronics.
In short, you determine a crank position for a chosen distance of the piston from approx. TDC, say 1", you measure this distance with the piston rising from both sides of TDC, ie: Normal and reverse rotation. Then you halve that on your protractor fixed to the crank, that is the most accurate TDC I know how to measure, and far less prone to error than trying to pick the piston at the top of the stroke. If you have a nice big protractor (mine is an aluminium disk, suitably engraved, about 15" diameter) that should get you TDC +/- 1 degree.
Tootle pip!!
Oh well the bus driver has almost got it right. You use the dial indicator to provide the start of the most upward stroke of the pistion on both sides of the crank. This is the only way you can actually acquire the ture tdc. Then with both drgrees known half the difference.
And as the aps team carry on about timing as much as they do they never said to use this method. Old jaba jaba was so impressed with a digital vervions he was going to buy his engineer on. A stardard protactor will acquire the degress as well if not better than a digital. And before you ask any one that uses a digital watch as opposed to a dial watch will tell you one you have to read one you dont.

So mr bus driver you almost got it right but the main thing of finding top of stoke you missed on both sides you missed.
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Old 12th Apr 2018, 18:42
  #271 (permalink)  
 
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Originally Posted by Bend alot
Nice try - link me the 550 engine in question.
Don't know, only Eddie Dean knows for sure.

Regardless, your entire tangent about whether an engine is at sea level, is just that; a tangent and not a particularly relevant one.

LB asked you which would make more power; an IO-520 with all the knobs forward and the timing advance set to 20 degrees BTDC or the same engine under the same conditions with the advance set to 22 BTDC.

There was a point to the question, but instead of answering the question you started this completely irrelevant tangent about his use of "sea level" (Apparently you didn't know that "Sea level" is the standard reference for engine power output. )

Originally Posted by Eddie Dean
Bend, are you being purposely obtuse?
The most charitable assumption would be that he is.
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Old 12th Apr 2018, 18:52
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Originally Posted by rutan around
Andrewr
Loved the cartoon. It shows the very reason I'm often tardy with replies. All wives must be tarred with the same brush. They fail to realize what's REALLY important.

The reason IO520s with equal sized injector nozzles have such a disparity in mixture strengths between the 6 cylinders is partly due to the type of injector system used and even more due to the built in induction design fault.

At rich mixture settings uneven mixtures are not much of a problem IF each cylinder is receiving pretty equal quantities of air. When the oxygen is burnt in each cylinder it takes the fuel it needs and the unburnt surplus is wasted down the exhaust.

The power produced from each cylinder will be pretty even because the amount of fuel and oxygen burnt in each cylinder is equal. The engine doesn't care if unburnt fuel goes down the exhaust. This is only true if the air to each cylinder is equal.

If an engine has uneven mixtures it causes uneven power when leaning brings the cylinder with the weakest mixture to the point where there is an excess of oxygen. Power from there on is governed by mixture.

As leaning is continued that cylinder puts out less and less power. As the other cylinders reach peak EGT they too put out less power as the leaning continues. If there is a big gap between when the first cylinder peaks and the last one it is readily obvious the engine will be running pretty roughly with all the cylinders putting out different horse powers unlike the situation with uneven rich mixtures with cylinders having equal air supply.

Back to theIO520. It's injector system is known as constant flow system.

The best description I've heard for it that it has 6 hoses all the same size coming from a central distribution point . These hoses have a nozzles on the end and each nozzle, inside the inlet manifold, sprays fuel in the general direction of the inlet valve. It sprays at a constant rate (controlled elsewhere by the quantity of air flow) whether the cylinder head inlet valve is open or not. When the valve does open fuel and air are sucked into the cylinder, the valve closes and the fuel air build up continues.

What could go wrong?

Well it's this. There is a manifold tube down each side of the engine. Each one feeds air to 3 cylinders. The air makes it way from the air filter down this tube to the three cylinders . Each cylinder has a fuel hose making a fuel puddle or more likely a mini fuel and air vapor storm outside the inlet valve that spends most of it's time shut.

If the injector nozzles are all equal size and we assume the mixture is correct at the cylinder nearest air filter then the 2nd one from the filter will be richer and the third one richer again. The air rushing past the first cylinder steals a bit of fuel vapor as it goes past. So the second cylinder gets not just air but a bit of stolen fuel as well. It is even worse at the third cylinder because it has stolen fuel from both cylinders before it.

That's why GAMI has progressively smaller injector nozzles on the cylinders as they get further from the air filter. Who needs big nozzles if you can steal from somewhere else.

Without GAMI or similar balanced injectors IO520s are rough running LOP.

I hope Continental have lifted their game. 5 years ago I bought a factory exchange IO520 engine for the 210 They assured me that it had balanced injectors installed. It didn't. I now have GAMIs and it runs beautifully to way below peak EGT if I want it to.

True however not the whole of what is happening.
Given an io550 with top mounted induction stuffers the same problems. You you ever noted on a modern car induction there most often a separate part that is like a little apendix. This is to help stop the back px pluse from the inlet vavle closing. Induction is extremely complex the higher the rpm. On low rev engines its not as important. So even like i said top mounted induction suffers from uneven flow. So with everythin a constant ie cylinders are all the same and you will note that even the fuel nozzle lines are the same lenghts that why the centre has a loop in it. Crank angle is the main problem. This is the results in uneven charge flow into the chambers.
If this wasnt the case the io550 wouldnt need matched nozzles that they run.
Hi rpm short intake runners
Low rpm longer runners higher tq.
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Old 12th Apr 2018, 19:07
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Originally Posted by oggers
You don’t know precisely where each cylinder is. The assumption is that the leanest cylinder is within 25F of the indicated EGT when using the thermocouple on the collecter. The recommended best power setting for the engine is 50ROP so that is where our minimum 75ROP comes from.

Even the aircraft in our fleet with EDMs cannot be relied upon because the environment is too harsh, hot and high, dusty and corrosive. These aircraft are doing 100 hours a month, 10 or 12 starts a day and it isn’t long before one or other probe plays up. One day it is an aircraft with an EDM, the next it is an unreliable EDM, the next it’s no EDM. We cannot afford our aircraft to go in for a 50hour check and get stuck for a week waiting for a thermocouple or harness. We have to have them back online. There are enough other snags to sort out such as the brakes, starter motors, alternators and radios. However, the alcor type EGT installation is robust so our SOP is based on it. That is the real world for us.

Yes, I am sure that the minimum detonation margin for a given power is at peak EGT or at least very close. I am sure because the extensive research published on detonation says so.

So as you run your aircraft in the real world and run 75 rop, which is really what everyone runs to not 25 rop. What if any engine damage do you stuffer from.
Given that the aps heads state if you run rop you will damage your engine but if you run lop you will not. That was a quote from aps team hq in these pages.
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Old 12th Apr 2018, 19:11
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Originally Posted by Connedrod
You use the dial indicator to provide the start of the most upward stroke of the pistion on both sides of the crank. This is the only way you can actually acquire the ture tdc. Then with both drgrees known half the difference.
I'm not following your description there, can you try again? I'm always willing to learn something new, but to be honest, I can't figure out what you're trying to say here.





Originally Posted by Connedrod
A stardard protactor will acquire the degress as well if not better than a digital.
Possibly. Certainly a good quality protractor will measure the angle well enough for the accuracy required ( +/- 1 degree) a cheaper protractor can have a scale that hard to read accurately, and if it rubs anywhere the friction may prevent the pointer from being perfectly vertical.
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Old 12th Apr 2018, 19:13
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Originally Posted by Bend alot
A "T" engine maintains a pressure of intake air to the cylinder.


It can be at a pressure to that at sea level - or more or less at 16,000 feet.


But it is not flying at sea level or at sea level conditions at 16,000 - only the intake pressure of 29.92 inches.

I think poeple are reading to much into what he said,
He said he was flying at 16000 feet and 84%rop at sl intake px .
Stanard answer really.
Just means the engine is not a n/a and has some sort of forced indiction.
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Old 12th Apr 2018, 19:32
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Originally Posted by Connedrod
Given that the aps heads state if you run rop you will damage your engine ....
No, they do not state that. They do claim that you are less likely to damage your engine operating it well LOP than you are running it slightly ROP, but they have never stated that you will damage your engine running it anyplace in the ROP range.


Originally Posted by Connedrod
That was a quote from aps team hq in these pages.
No, it's not. Find that quote anywhere on their site or in their material. Provide a link. You can't do it.
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Old 12th Apr 2018, 19:33
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Originally Posted by A Squared
I'm not following your description there, can you try again? I'm always willing to learn something new, but to be honest, I can't figure out what you're trying to say here.







Possibly. Certainly a good quality protractor will measure the angle well enough for the accuracy required ( +/- 1 degree) a cheaper protractor can have a scale that hard to read accurately, and if it rubs anywhere the friction may prevent the pointer from being perfectly vertical.
In real world you dont use this method.

As the piston moves upward it will come to a point were the piston will no longer move. Will call this X. The crank will still move in the same diection with no movement of the piston.
To be completely accurate that position needs to be set with a dial indicator. Normally any probe you can feel it.
Set your zero on both indication devices

Continue the movement till the piston moves downward.

Now reverse the the diection of the crank.
Now note where the the same in reverse as above. Call this X2

Half the difference X-X2

You have X1

This is tdc



Like i said normally just a probe in the plug hole as vertical as you can get it to the plug hole. But as these aps clowns go you should use a dail indicator.
Then you can charge them extra for the time to set up.

I also note they havent said how often you should get your edm calibration done as they running so close to the wind and expect complete accuracy with every thing maintenance dose.



Possibly. Certainly a good quality protractor will measure the angle well enough for the accuracy required ( +/- 1 degree) a cheaper protractor can have a scale that hard to read accurately, and if it rubs anywhere the friction may prevent the pointer from being perfectly vertical.[/QUOTE]
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Old 12th Apr 2018, 19:41
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Originally Posted by Connedrod
In real world you dont use this method.

As the piston moves upward it will come to a point were the piston will no longer move. Will call this X. The crank will still move in the same diection with no movement of the piston.
To be completely accurate that position needs to be set with a dial indicator. Normally any probe you can feel it.
Set your zero on both indication devices

Continue the movement till the piston moves downward.

Now reverse the the diection of the crank.
Now note where the the same in reverse as above. Call this X2

Half the difference X-X2

You have X1

This is tdc

OK, so the last detectable upward motion rotating forward, and the last detectable upward motion rotating backward, then split the difference. thanks, I just couldn't get what you were trying to describe the first time.
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Old 12th Apr 2018, 20:53
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Originally Posted by A Squared
No, they do not state that. They do claim that you are less likely to damage your engine operating it well LOP than you are running it slightly ROP, but they have never stated that you will damage your engine running it anyplace in the ROP range.




No, it's not. Find that quote anywhere on their site or in their material. Provide a link. You can't do it.
No. They stated in tnis forum that you Will damage ypur engine running rop but YOU WILL NOT RUNNING LOP.
Please remember that these people stated that running lean the mixture burns faster than burning rop. This ic completely flase and incorrect. To cover their tracts after i proved them wrong they removed a complete thread. They didnt even know the basic principles.
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Old 12th Apr 2018, 21:15
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Im sure it was john deakin that stated that in the pahes of this forum.
I tried to do a screach but it seams all his post have been deleted.
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