Preignition

[A64Pilot]

I would be surprised to see an engine TCDS state, either 20 or 25 degrees, whichever you prefer.

I’ve not looked, does one state either or?

Or are you saying that at some time in the past it was 25, then later changed to 20? 

[PT20J]

SI 1325 Timing Change for IO-360 Series Engines.pdf

[N201MKTurbo]

You get different deposits in your cylinders when running ROP and LOP, When LOP you get a lot of Lead Bromide when ROP you get a lot of carbon. Preignition is often caused by a hot flake of deposit which ignites the fuel charge. I found if you switch it up periodically by doing a few trips ROP, your cylinders stay squeaky clean. ROP will reduce the lead bromide and LOP will oxidize the carbon.

[A64Pilot]

1 hour ago, PT20J said:

SI 1325 Timing Change for IO-360 Series Engines.pdf 470.94 kB · 0 downloads

Had a whole response typed up, then downloaded and read the SIL

‘It said pretty much exactly what I have been saying, that is that reducing the timing by 5 degrees will make the engine run cooler, last longer and give you more margin on detonation.

‘It didn’t say the decreased timing advance will decrease HP, but it will trust me. The reduced power is largely why it will run cooler, and last longer.

‘Now some of you will think this is it picking and that’s what aviation is, but it does require parts to be changed, and doesn’t say that you can take an engine that the SB has been complied with and return it to the pre SB configuration, and if your just cranking it up to 25 degrees leaving the SB parts in, that’s incorrect too and may cause damage if the engine kicks back during starting.

 

Question for those that are bumping the timing to 25 degrees, have you replaced the magneto parts and engine ID plate?

 

 

Edited March 20, 2021 by A64Pilot

[A64Pilot]

47 minutes ago, N201MKTurbo said:

You get different deposits in your cylinders when running ROP and LOP, When LOP you get a lot of Lead Bromide when ROP you get a lot of carbon. Preignition is often caused by a hot flake of deposit which ignites the fuel charge. I found if you switch it up periodically by doing a few trips ROP, your cylinders stay squeaky clean. ROP will reduce the lead bromide and LOP will oxidize the carbon.

Agreed, I climb at a very rich setting and high power, Plus once I get to patter altitude I’m rich again I believe that will help with cleaning it out.

[PT20J]

4 minutes ago, A64Pilot said:

It didn’t say the decreased timing advance will decrease HP, but it will trust me. The reduced power is largely why it will run cooler, and last longer.

Talking in generalities leads to confusion. No one said that changing timing wouldn't affect power. But what happens is that small changes have a greater effect on temperature than they do on power. Just look at the slope of the curves.

Power doesn't wear out engines. Power is simply the rate at which work is produced. Work comes cylinder pressure moving the piston through  its stroke. The pressure comes from combustion which produces heat. Heat is what damages engine components. Power is just a result of thermodynamic transfer of chemical energy to heat to mechanical energy.

Skip

[A64Pilot]

9 minutes ago, PT20J said:

Talking in generalities leads to confusion. No one said that changing timing wouldn't affect power. But what happens is that small changes have a greater effect on temperature than they do on power. Just look at the slope of the curves.

Power doesn't wear out engines. Power is simply the rate at which work is produced. Work comes cylinder pressure moving the piston through  its stroke. The pressure comes from combustion which produces heat. Heat is what damages engine components. Power is just a result of thermodynamic transfer of chemical energy to heat to mechanical energy.

Skip

Circular argument, heat is where the power comes from, even LOP, these are “heat” engines.

However power does wear out engines faster, HP is Tq x RPM, so higher power is higher RPM, plus higher power will result in higher cylinder pressures, and that forces the rings against the cylinder walls at a higher pressure and increases wear, plus it loads the main and rod bearings higher, which increases wear.

‘It all gets back to TANSTAAFL.

https://en.wikipedia.org/wiki/There_ain't_no_such_thing_as_a_free_lunch

 

On edit, it’s probably a pretty easy case to make that friction is what wears out engines 

Edited March 20, 2021 by A64Pilot

[EricJ]

9 minutes ago, A64Pilot said:

Circular argument, heat is where the power comes from, even LOP, these are “heat” engines.

No, heat is wasted energy.   If it was 100% thermodynamically and otherwise efficient all of the energy would be converted to work (propulsion, thrust, entropy, whatever), and none would turn into heat.   The heat is the energy that didn't get turned into work, which, over time, is power.

This is a small part of the differences between ROP and LOP, too.   If you can reduce the wasted heat the efficiency goes up, and done very carefully, the power isn't affected, or not very much.

 

[Shadrach]

On 3/19/2021 at 10:29 AM, A64Pilot said:

Perhaps the Biggest reason why LOP can reduce fuel consumption is the basic operating principle of how an internal combustion engine operates.

‘Engines do not develop power from the pressure from “explosions” as many think, they develop power from the rapid expansion of heating a gas (air)

Within reason of course if you reduce the ratio of air to fuel and still generate the heat, your increasing the amount of gas to expand when compared to the amount of fuel it takes to expand it.

Fuel enrichment at high power isn’t so much to do with being required to make the power, it’s required to make the power without overheating the engine

‘Those of you that are bumping the timing up are playing with fire, I disagree with the plus or minus 5 degrees of timing won’t make much difference, it will make big differences, increasing timing will certainly increase power, but your reducing your margin for detonation.

Who here had advocated “bumping the timing up”? 

[A64Pilot]

1 hour ago, EricJ said:

No, heat is wasted energy.   If it was 100% thermodynamically and otherwise efficient all of the energy would be converted to work (propulsion, thrust, entropy, whatever), and none would turn into heat.   The heat is the energy that didn't get turned into work, which, over time, is power.

This is a small part of the differences between ROP and LOP, too.   If you can reduce the wasted heat the efficiency goes up, and done very carefully, the power isn't affected, or not very much.

 

Yes heat is washed energy, but as you can’t effect BSFC very much, the way to more power, is more heat.

LOP only slightly increases BSFC, and yes the power is affected quite a bit, but that can also be argued, if your only at 55% power ROP, then yes you can run LOP without losing any power.

Try that at 75% or greater power, you might can at 75%, that’s pretty much about it, but higher than 75% LOP is playing with fire, and I mean actual power, not a manifold pressure that gives power ROP and thinking the same manifold pressure gives the same power LOP.

Do this set up a cruise at 75% power at best power mixture, record your airspeed, then go LOP and see if you can maintain airspeed.

I am not against LOP, I run LOP more often than not, but I don’t try to run high power LOP, I run a manifold pressure and RPM that will give me 65% power ROP, I run that LOP and accept the reduced power, gives me more margin, I would have to save a LOT of fuel to pay for a couple of cylinders.

You can get very efficient LOP, it comes from two things, slowing down is a large gain in efficiency, and there is some LOP too. If I slow down to 120 kts running pretty deep LOP I can actually burn less fuel per mile than my 85 HP Cessna 140 does at 90kts, and the little Cessna is about the most efficient of the little airplanes.

 

Edited March 20, 2021 by A64Pilot

[carusoam]

Hey...,

The weekend is here....
 

I’m thinking of changing the timing on my engine...

Thanks A64, I didn’t know I could skip the rules and make it so easy...

Now I see all I have to do is stamp the proper name plates and everything is good...

 

What I have noticed over the years...

When people write things... they can be interpreted differently very easily...

 

I have also noticed when you call somebody out for the way they wrote something... you don’t make a lot of friends...

 

If you choose a path that says everyone is wrong... and you know the right way...

How did that work for you on the sailing site?

 

Sometimes it is OK to let things go that you don’t understand...

Sometimes it is best we work together as a team...

I expect that you won’t understand what I am writing here...

PP observations only, not everyone here is a scofflaw...

Best regards,

-a-

 

 

[A64Pilot]

You can believe what you want, it’s more convenient that way. I’m not trying to make friends. When I see information that is incomplete and has people believing things are acceptable and legal when they aren’t. I speak up. They should hear the other side to make a decision.

‘But the FAR’s are pretty clear, the timing has to be set according to the data plate. 

‘Aircraft engines and systems are very often modified, and often these modifications are captured by changing a data plate  or an additional data plate, I’ve even developed a custom kit to change one aircraft into another, specifically the S2R-T34 into an S2R-T65HG, which of course when completed you installed an additional data plate beside the original aircraft data plate.

But using that as an example, once it became an S2R-T65HG, there was no custom kit to turn it back into a -34

So what I’m saying and yes I do understand, but you don’t like what your hearing is yes, your fine at 25 timing, if your engine is identified as an engine that 25 is correct for, and of course has the correct parts.

‘But your not allowed to bump your timing to 25 degrees on an engine who’s data plate says 20 because you read on the internet that it was OK.

Now if you get an STC approved, or a field approval. then you can.

‘That’s not what your wanting to hear, but don’t believe me, I’m just another guy in the internet, call the FSDO and tell an inspector that you have an engine who’s data plate says timing is 20 degrees, but you have heard on the internet that since they used to be 25 degrees that it’s OK to set it to 25. You may want to mention that one magneto was modified to correct retard for staring at 20 degrees to.

‘Report back what your told.

Oh, and I was never a PP. assuming PP s private pilot?

Edited March 21, 2021 by A64Pilot

[jetdriven]

3 minutes ago, A64Pilot said:

You can believe what you want, it’s more convenient that way. I’m not trying to make friends. When I see information that is incomplete and has people believing things are acceptable and legal when they aren’t. I speak up. They should hear the other side to make a decision.

‘But the FAR’s are pretty clear, the timing has to be set according to the data plate. 

‘Aircraft engines and systems are very often modified, and often these modifications are captured by changing a data plate  or an additional data plate, I’ve even developed a custom kit to change one aircraft into another, specifically the S2R-T34 into an S2R-T65HG, which of course when completed you installed an additional data plate beside the original aircraft data plate.

But using that as an example, once it became an S2R-T65HG, there was no custom kit to turn it back into a -34

So what I’m saying and yes I do understand, but you don’t like what your hearing is yes, your fine at 25 timing, if your engine is identified as an engine that 25 is correct for, and of course has the correct parts.

‘But your not allowed to bump your timing to 25 degrees on an engine who’s data plate says 20 because you read on the internet that it was OK.

Now if you get an STC approved, or a field approval. then you can.

‘That’s not what your wanting to hear, but don’t believe me, I’m just another guy in the internet, call the FSDO and tell an inspector that you have an engine who’s data plate says timing is 20 degrees, but you have heard on the internet that since they used to be 25 degrees that it’s OK to set it to 25. You may want to mention that one magneto was modified to correct retard for staring at 20 degrees to.

‘Report back what your told.

You're advocating an STC for setting the engine to something that is on the type certificate?

You can call the FSDO inspector and ask him if you can set the timing to the TCDS, and forego the "optional 20 degrees". He'll probably tell you to refer to Lycoming.

[A64Pilot]

I’ll give you an example, it was discovered by the FAA that Maule way back in the 60’s hadn’t conducted load testing of the baggage compt correctly. so Maule issued a mandatory SB that had you replace the placards and change the POH to lower weight limits.

https://fdb41ebf-dcb9-418b-8328-810edcfc833e.filesusr.com/ugd/7377f0_1ffbc3bd15dc447291bd46f10c4c0def.pdf

Now an SB for part 91 aircraft isn’t mandatory, but the POH and placards are, so if complied with, this SB significantly reduced your useful load.

‘However once complied with, you can’t put the old pages back into the POH and put old placards into the baggage compt.

Why? because there is no FAA approved method for doing that, no SB, no Custom kit etc, or STC.

The Lycoming SIL is the same, you didn’t have to do it, but once it’s done you can’t decide you don’t like it anymore and remove it, not without something authorizing you to do so.

‘If you don’t understand how these are related, I can’t help you.

[A64Pilot]

20 minutes ago, jetdriven said:

You're advocating an STC for setting the engine to something that is on the type certificate?

You can call the FSDO inspector and ask him if you can set the timing to the TCDS, and forego the "optional 20 degrees". He'll probably tell you to refer to Lycoming.

No, it’s not the TCDS, besides placards and data plates are mandatory, if the SIl was complied with as evidenced by the data plate, the Type Certificate was changed.

‘But yes, I think calling Lycoming would be called for, just be sure to give them all the info, don’t leave out a small detail like the data plate says 20 degrees.

‘You guys seem to also ignore that the magneto retard was also changed, just ignore that?

Do you understand why timing is retarded for starting?

Edited March 21, 2021 by A64Pilot

[jetdriven]

2 minutes ago, A64Pilot said:

Why? because there is no FAA approved method for doing that, no SB, no Custom kit etc, or STC.

isnt the reverse of removal an approved method?   Where does it state you need some approved method otherwise? What about someone who removes their Century IIB autopilot?  Youre returning it to a factory-like state. 

You can't help me becuase your help seems a bit nonsensical.

[A64Pilot]

OK, another example, the same engine is also Type Certificated as a 160 HP engine, a person who has an aircraft with a 160 HP engine isn’t allowed to turn the prop RPM up to 2700 RPM and operate at 200 HP. But why not the TCDS says he can right?

[jetdriven]

Just now, A64Pilot said:

No, it’s not the TCDS, besides placards and data plates are mandatory, if the SIl was complied with as evidenced by the data plate, the Type Certificate was changed.

‘But yes, I think calling Lycoming would be called for, just be sure to give them all the info, don’t leave out a small detail like the data plate says 20 degrees.

‘You guys seem to also ignore that the magneto retard was also changed, just ignore that?

Do you understand why timing is retarded for starting?

I understand a lot of things. I actually own an aircraft repair shop, do you? Undo the optional SI. Replace the magneto for the one in the parts catalog, correct lag angle for 25 degrees timing. Set the timing. Restamp the data plate or get a new one. Make log entry.

 

[A64Pilot]

Just now, jetdriven said:

isnt the reverse of removal an approved method?   Where does it state you need some approved method otherwise? What about someone who removes their Century IIB autopilot?  Youre returning it to a factory-like state. 

You can't help me becuase your help seems a bit nonsensical.

You don’t want to understand, besides are you guys really having your Magnetos rebuilt to old specs and changing data plates?

 

[jetdriven]

Just now, A64Pilot said:

OK, another example, the same engine is also Type Certificated as a 160 HP engine, a person who has an aircraft with a 160 HP engine isn’t allowed to turn the prop RPM up to 2700 RPM and operate at 200 HP. But why not the TCDS says he can right?

What does the TCDS say for that exact model engine?  And then what does the POH limitations say, if there is anything more limiting? Its not cut and dried across all models, but the M20JIO360 A3B6  is pretty simple.

[A64Pilot]

Just now, jetdriven said:

I understand a lot of things. I actually own an aircraft repair shop, do you? Undo the optional SI. Replace the magneto for the one in the parts catalog, correct lag angle for 25 degrees timing. Set the timing. Restamp the data plate or get a new one. Make log entry.

 

No, I don’t own a repair shop, I ran an aircraft manufacturing plant and was accountable manager for the repair station for 15 years 

[A64Pilot]

7 minutes ago, jetdriven said:

Replace the magneto for the one in the parts catalog, correct lag angle for 25 degrees timing. Set the timing. Restamp the data plate or get a new one. Make log entry.

 

If that’s what’s happening, then your likely fine, but that’s not what I’ve read here.

‘I think some may have done as you say, but I believe some have just retimed the mags to 25 degrees, and those people need to know what that may cause

Edited March 21, 2021 by A64Pilot

[jetdriven]

3 minutes ago, A64Pilot said:

If that’s what’s happening, then your likely fine, but that’s not what I’ve read here.

‘I think some may have done as you say, but I believe some have just retimed the mags to 25 degrees, and those people need to know what that may cause

We are in agreement on that.  If you choose to undo the SI, then undo it precisely.

[PT20J]

1 hour ago, jetdriven said:

Replace the magneto for the one in the parts catalog, correct lag angle for 25 degrees timing. Set the timing. Restamp the data plate or get a new one. Make log entry.

 

I actually did contact lycoming when I purchased my IO-360-A3B6 and this is precisely what they told me I should do if I wanted to change the timing.

Skip

[Andy95W]

2 hours ago, A64Pilot said:

 I’m not trying to make friends. 

Well, that’s obvious.

We’re not as ignorant as you assume.  Some of the folks you’re lecturing to here are as experienced and knowledgeable as you.  Some more.