Is this a scratch or a crack?

[FlyBoyM20J]

12 minutes ago, Shadrach said:

Take off is not notated in the graph but it looks to me like take off EGTs (mid to high 1100s) suggest excellent fuel delivery on take off. 

I think the reason folks asked about 25 squared is because it’s well understood that there’s no benefit to reducing throttle unless you’re trying to go down or slow down. The term is kind of a relic from when we had little to know engine instrumentation. 

I’ve broken in  one set of Cylinders LOP and will likely do any future cylinders the same way if operationally possible. Cool CHTS and high mean ICPs make for optimal results. It can be done on either side of the mixture spectrum but it’s cleaner and more efficient going lean.

Your cylinder is likely broken in by now. If you think about what is actually occurring during the process (sharp peaks from the hone process being blunted to a smooth, consistent surface with valleys to hold oil on the cylinder wall) it seems crazy that some claim tens of hours to achieve break in. I’d love to see some data on why/if that actually happens.

I posted the JPI graph in the other thread in which we see a 20F drop in C2 CHT while all other CHTs stay constant.  That was on the 2nd 1.5-hour break-in flight at 25 sq, 3500 MSL.  I think at that point, we can probably say the overhauled cylinder turned the corner. 

Interesting about breaking in LOP.  I had understood from reading Mike Busch that the goal of running hard at break-in was to maximize internal cylinder pressure (ICP), thereby forcing a situation that with mineral oil (no synthetic additives to smooth things over), we get metal-on-metal and the sharp peaks from the hone process blunt against the rings which also conform in the process, as you describe.

My understanding (based on reading) is that ICP is maximum at about 50F ROP when running at 75% power or above, which is why I did all the break-in in that region.

How would running LOP be better if what we want is maximum ICP?  I'm just learning and I find this fascinating, so thank you for your patience.

Also, what I'd like to know is, in the graphs above in this thread, why is C2's CHT higher than the others on climb-out, but so much lower when running LOP?  This is one reason I want to do another compression reading on C2.  Is it because it has higher compression than the older cylinders (all at almost 1500 hours now since rebuild), or because it has excessive blow-by and thus, is not really broken in?

Cliff

PS - here's the JPI chart from last week when you can see C2's CHT drop while the other CHTs stay constant. 

[Cyril Gibb]

40 minutes ago, FlyBoyM20J said:

How would running LOP be better if what we want is maximum ICP?  

You want a high ICP,  but you also want to keep CHTs under control and minimize excessive lead/carbon deposition during this period of high blowby.  LOP does that.  Everything is a compromise. 

[Shadrach]

5 hours ago, FlyBoyM20J said:

I posted the JPI graph in the other thread in which we see a 20F drop in C2 CHT while all other CHTs stay constant.  That was on the 2-nd 1.5-hour break-in flight at 25 sq, 3500 MSL.  I think at that point, we can probably say the overhauled cylinder turned the corner. 

Interesting about breaking in LOP.  I had understood from reading Mike Busch that the goal of running hard at break-in was to maximize internal cylinder pressure (ICP), thereby forcing a situation that with mineral oil (no synthetic additives to smooth things over), we get metal-on-metal and the sharp peaks from the hone process blunt against the rings which also conform in the process, as you describe.

My understanding (based on reading) is that ICP is maximum at about 50F ROP when running at 75% power or above, which is why I did all the break-in in that region.

How would running LOP be better if what we want is maximum ICP?  I'm just learning and I find this fascinating, so thank you for your patience.

Also, what I'd like to know is, in the graphs above in this thread, why is C2's CHT higher than the others on climb-out, but so much lower when running LOP?  This is one reason I want to do another compression reading on C2.  Is it because it has higher compression than the older cylinders (all at almost 1500 hours now since rebuild), or because it has excessive blow-by and thus, is not really broken in?

Cliff

PS - here's the JPI chart from last week when you can see C2's CHT drop while the other CHTs stay constant. 

A lot to unpack here and I should be working not killing time on MS.  I will address your ROP/LOP question.

For folks near SL, high power, LOP operations are doable depending on the season.  In the Fall, Winter and and early Spring my 701' filed often has DAs well under SL.  I can pull over 80% power LOP on a cold day with CHTs in the low 300s.  Why would I do that rather than ROP?  Well, year and years ago, I was involved in a red board discussion with Walt Atkinson (of APS fame).  He made it pretty clear that for a given power setting LOP ops made power with higher mean ICP (closer to consistent pressure throughout the power stroke BMEP = Brake mean effective pressure) and that ROP ops made power with higher peak ICP...Think hammer blow versus a strong consistent push.  A good break in requires high ICPs because the pressure is needed on the back side of the rings to force the rings (see attached image)  One of the reasons engine manufactures tell you to vary RPMs during break in is that it varies where (degrees ATDC) the peak pressure occurs in the power stroke by changing the piston speed.  High power LOP ops still make plenty of pressure but it is more evenly distributed throughout the power stroke. In theory this means more consistent ring pressure against the cylinder wall through out the power stroke. The added benefit is that it transfers less heat to the cylinder (lower CHTs, lower risk of glazing) and burns less gas.  All of the above being said, getting a good break in ROP is the norm not the exception if factory procedures are followed. The guideline have been in place since these engines were introduced.  I went did my break in LOP because over the years I have become quite comfortable with low level, high power, LOP ops for local flights and to stay out of headwinds when westbound.  I would not recommend it to folks without a good understanding of combustion science or breaking in a factory engine where warranty is dependent on factory guidelines.

Many folks would balk at how I run down low until the see the cylinder temps =<330, CF closed and 152-156KIAS (which when corrected is somewhat less).  

Circling back to my conversation with Walt. I have never seen APS's  BMEP graphs but my own observation is that any IAS that I can attain while LOP has lower CHTs than that same IAS on the rich side of peak.  Stated simply for a given power output CHTs tend to be cooler on the lean side of the spectrum. This is consistent with what I took from my conversation with Walt. 

Edited May 28, 2019 by Shadrach

[FlyBoyM20J]

7 minutes ago, Cyril Gibb said:

You want a high ICP,  but you also want to keep CHTs under control and minimize excessive lead/carbon deposition during this period of high blowby.  LOP does that.  Everything is a compromise. 

Thanks!  I really want to run LOP but was afraid I was throwing away access to the high ICP zone once I went lean since, among other things, my fuel flow drops precipitously when LOP and that means I'm losing power very quickly.  But I assume if I'm just barely LOP, say, 20F lean, then I'll see the benefits you're describing.

What do you think, though, of how my C2 CHT is so elevated on climb-out but so low when LOP relative to all the other CHTs in the chart below?

Thanks again,

Cliff

[Shadrach]

30 minutes ago, FlyBoyM20J said:

Thanks!  I really want to run LOP but was afraid I was throwing away access to the high ICP zone once I went lean since, among other things, my fuel flow drops precipitously when LOP and that means I'm losing power very quickly.  But I assume if I'm just barely LOP, say, 20F lean, then I'll see the benefits you're describing.

What do you think, though, of how my C2 CHT is so elevated on climb-out but so low when LOP relative to all the other CHTs in the chart below?

Thanks again,

Cliff

RE cyl #2:

Cyl2 is likely your leanest cylinder (on my engine #3 is the leanest and #2  the richest). It looks as though you leaned a bit too aggressively in climb. This put number #2 closer to the highest peak pressure part of the mixture spectrum (hottest setting ~40-50ROP). When you went LOP that cylinder (being the leanest) is now the furthest from the hottest part of the mixture spectrum.  Cyl#2 is behaving just as I'd expect.  Did you determine which cylinder is richest and leanest and do you use them accordingly for ROP vs LOP ops?

For climb it's best to keep EGTs close to where they were on take off until MP falls off so much that CHTs start to drop.

Edited May 28, 2019 by Shadrach

[FlyBoyM20J]

1 minute ago, Shadrach said:

RE cyl #2:

Cyl2 is likely your leanest cylinder (it is on my engine and #3 is the richest). It looks as though you leaned a bit too aggressively in climb. This put number #2 closer to the highest peak pressure part of the mixture spectrum (hottest setting ~40-50ROP). When you went LOP that cylinder (being the leanest) is now the furthest from the hottest part of the mixture spectrum.  Cyl#2 is behaving just as I'd expect.  Did you determine which cylinder is richest and leanest and do you use them accordingly for ROP vs LOP ops?

Wow, this makes so much sense!  C2 was never an outlier like this before the overhaul so this is a new characteristic that I'm trying to understand.

I haven't yet done a GAMI spread on this plane because my FF computer is an old Shadin system that is flaky, to put it mildly.  I can't yet tell if the Shadin computer is dying or if the FF sensor is bad, but either way, I'm planning on removing the EDM 700 and sending it back to JPI to add the FF option so I can start dialing all this in tighter.

Thank you so much for taking the time to comment on this stuff.

Cliff

[Shadrach]

5 minutes ago, FlyBoyM20J said:

Wow, this makes so much sense!  C2 was never an outlier like this before the overhaul so this is a new characteristic that I'm trying to understand.

I haven't yet done a GAMI spread on this plane because my FF computer is an old Shadin system that is flaky, to put it mildly.  I can't yet tell if the Shadin computer is dying or if the FF sensor is bad, but either way, I'm planning on removing the EDM 700 and sending it back to JPI to add the FF option so I can start dialing all this in tighter.

Thank you so much for taking the time to comment on this stuff.

Cliff

You don't need FF to determine richest and leanest cylinder.  Take a moment to do it.  Your engine clearly runs LOP.  Once satisfied with the break in, it would prudent to pull to lean of peak and then slowly enriches to see which cylinder peaks first and  which peaks last.  First to peak is your richest and that should be used for all LOP ops. Last to peak is your leanest and should be used for all ROP ops.  This ensures the when setting power, the other three cylinders are at a setting that is equal to or more conservative then the cylinder being used as a reference. 

[Shadrach]

16 minutes ago, FlyBoyM20J said:

Wow, this makes so much sense!  C2 was never an outlier like this before the overhaul so this is a new characteristic that I'm trying to understand.

I haven't yet done a GAMI spread on this plane because my FF computer is an old Shadin system that is flaky, to put it mildly.  I can't yet tell if the Shadin computer is dying or if the FF sensor is bad, but either way, I'm planning on removing the EDM 700 and sending it back to JPI to add the FF option so I can start dialing all this in tighter.

Thank you so much for taking the time to comment on this stuff.

Cliff

I actually misspoke in my previous post and edited it.  On my engine #3 is leanest (used for ROP ops) and #2 is richest (used for LOP ops).  As I stated above, you should know the same about your engine. It's important to know not only operationally but if it changes it's a sign that something should be investigated.

[FlyBoyM20J]

Just now, Shadrach said:

I actually misspoke in my previous post and edited it.  On my engine #3 is leanest (used for ROP ops) and #2 is richest (used for LOP ops).  As I stated above, you should know the same about your engine. It's important to know not only operationally but if it changes it's a sign that something should be investigated.

On mine, I guess we can predict from this LOP section of the annotated JPI graph that C3 will be richest and C2 leanest.

[Shadrach]

58 minutes ago, FlyBoyM20J said:

On mine, I guess we can predict from this LOP section of the annotated JPI graph that C3 will be richest and C2 leanest.

Maybe... It appearers you're moving the mixture pretty quickly (nothing wrong with that if you know where you want to be).  Let's not forget in this scenario that raw EGT numbers don't determine richest and leanest. The lowest number does not mean it's the leanest while LOP anymore than the lowest number means it's the richest while rich of peak. It might work out that way but then again, it might not.  I've pointed out below why that line of thinking can be wrong.  IT looks like you did a fast pull to LOP and then enrichened to your desired power setting.  Look at what happened while you were enrichening to your desired setting.  It appears that Cyl 3&4 peaked again before 2 or 4.  In reality, it doesn't mean anything because I am betting that several of the cylinders never actually saw peak EGT (it takes a little time to find true peak EGT (5-10 sec) on any cylinder. If you pull the mixture through and past a cylinder's particular peak EGT fuel flow you can not count on the position of peak depicted in the graph. A gross exaggeration of this would be quickly going from full rich to slightly rough lean.  Your graph would indeed show EGT peaks, but they would not be representative of actual EGT peaks and the data would be meaningless.  This is why you need to take a little time to determine richest and leanest.

 

[FlyBoyM20J]

8 minutes ago, Shadrach said:

Maybe... It appearers you're moving the mixture pretty quickly (nothing wrong with that if you know where you want to be).  Let's not forget in this scenario that raw EGT numbers don't determine richest and leanest. The lowest number does not mean it's the leanest while LOP anymore than the lowest number means it's the richest while rich of peak. It might work out that way but then again, it might not.  I've pointed out below why that line of thinking can be wrong.  IT looks like you did a fast pull to LOP and then enrichened to your desired power setting.  Look at what happened while you were enrichening to your desired setting.  It appears that Cyl 3&4 peaked again before 2 or 4.  In reality, it doesn't mean anything because I am betting that several of the cylinders never actually saw peak EGT (it takes a little time to find true peak EGT (5-10 sec) on any cylinder. If you pull the mixture through and past a cylinder's particular peak EGT fuel flow you can not count on the position of peak depicted in the graph. A gross exaggeration of this would be quickly going from full rich to slightly rough lean.  Your graph would indeed show EGT peaks, but they would not be representative of actual EGT peaks and the data would be meaningless.  This is why you need to take a little time to determine richest and leanest.

 

Yes, I generally just let the engine stabilize for a few minutes ROP after a climb, then I do a smooth pull past peak well into LOP territory, then enrich until things run smoothly.  It all takes about 15 seconds.

Prior to the C2 overhaul and the installation of GAMI injectors (all done in the last 2 weeks), I would find that this pull-lean-then-enrich method left me about 30F LOP as measured by going back ROP, letting it stabilize, then using the LOP lean-find method on the EDM-700 (for longer flights, I'd sometimes go through this exercise just to verify my LOP position relative to the peak).

I'm wondering now if I ever needed GAMI injectors and it certainly doesn't help the situation now that I both over hauled C2 and changed injectors, so there are more variables at play than one could wish for.  But now that I have GAMIs, I can really fine-tune things, I suppose.

All that said, I hear you about raw EGT numbers and I was just re-reading the EDM-700 manual where it says that the hottest cylinder does not necessarily peak first.

 

[Shadrach]

5 minutes ago, FlyBoyM20J said:

Yes, I generally just let the engine stabilize for a few minutes ROP after a climb, then I do a smooth pull past peak well into LOP territory, then enrich until things run smoothly.  It all takes about 15 seconds.

Prior to the C2 overhaul and the installation of GAMI injectors (all done in the last 2 weeks), I would find that this pull-lean-then-enrich method left me about 30F LOP as measured by going back ROP, letting it stabilize, then using the LOP lean-find method on the EDM-700 (for longer flights, I'd sometimes go through this exercise just to verify my LOP position relative to the peak).

I'm wondering now if I ever needed GAMI injectors and it certainly doesn't help the situation now that I both over hauled C2 and changed injectors, so there are more variables at play than one could wish for.  But now that I have GAMIs, I can really fine-tune things, I suppose.

All that said, I hear you about raw EGT numbers and I was just re-reading the EDM-700 manual where it says that the hottest cylinder does not necessarily peak first.

 

As a data point, I have run a number of angle valve IO360s on the lean side of peak.  I have never flown behind one with GAMIs.  They generally have excellent F/A distribution between cylinders in stock format.  Jean Paul is typically very up front about the need for GAMIs or lack-thereof.  If he sees a well conforming engine he is going to tell you that he can't do measurably better than stock.  Are you theorizing that your previous cylinder problems caused you to believe you needed GAMIs?  Did you use old EGT data from the engine with a sticking valve to determine how to set up the GAMIs?

[FlyBoyM20J]

On 5/28/2019 at 12:57 PM, Shadrach said:

As a data point, I have run a number of angle valve IO360s on the lean side of peak.  I have never flown behind one with GAMIs.  They generally have excellent F/A distribution between cylinders in stock format.  Jean Paul is typically very up front about the need for GAMIs or lack-thereof.  If he sees a well conforming engine he is going to tell you that he can't do measurably better than stock.  Are you theorizing that your previous cylinder problems caused you to believe you needed GAMIs?  Did you use old EGT data from the engine with a sticking valve to determine how to set up the GAMIs?

Yes, I didn't research my need for GAMIs well enough.  I thought that I had a healthy engine that wouldn't run stably past 30F LOP and was sure that installing GAMIs would give me better balance.

Sequence was like this:

1) Bought plane April 2018

2) Worked out how to do LOP flying September 2018

3) Determined that engine ran well (without doing inflight LOP mag test, since I didn't know about it at the time), but that LOP was stable usually to 20F and never past 30F LOP.

4) Decided GAMIs were the answer.  Put them on the list for stuff to buy soon.

5) C2 EV stuck hard 29 APR 2019, bent push rod, C2 sent to Jewell for overhaul

6) Ordered GAMIs since engine was taken apart and this looked like the time to install

7) Re-installed C2, did break-in for 10 hours

8) Installed GAMIs at 10-hour oil change.

Once I installed the GAMIs, I saw very similar ROP behavior to what I saw with stock injectors for ROP, even with the recently overhauled C2.  Visually, the graphs on the EDM-700 look more uniform with GAMIs than with stock injectors, but the downloaded data looks about the same for ROP.  I never ran LOP for the initial 10 hours of break-in.

So, I have lots of JPI data for stock injectors ROP and LOP, but only 3 break-in flights of data for stock injectors and the overhauled C2 prior to installing GAMIs, and all of those break-in hours were ROP.

The annotated JPI graph is from post-GAMI flights in which I started to go LOP and do the LOP mag test.

I suppose the good news about GAMIs, though, is that I can work with GAMI to get a good balance with the new C2.

[Shadrach]

3 minutes ago, FlyBoyM20J said:

Yes, I didn't research my need for GAMIs well enough.  I thought that I had a healthy engine that wouldn't run stably past 30F LOP and was sure that installing GAMIs would give me better balance.

Sequence was like this:

1) Bought plane April 2018

2) Worked out how to do LOP flying September 2018

3) Determined that engine ran well (without doing inflight LOP mag test, since I didn't know about it at the time), but that LOP was stable usually to 20F and never past 30F LOP.

4) Decided GAMIs were the answer.  Put them on the list for stuff to buy soon.

5) C2 EV stuck hard 29 APR 2019, bent push rod, C2 send to Jewell for overhaul

6) Ordered GAMIs since engine was taken apart and this looked like the time to install

7) Re-installed C2, did break-in for 10 hours

8) Installed GAMIs at 10-hour oil change.

Once I installed the GAMIs, I saw very similar ROP behavior to what I saw with stock injectors for ROP, even with the recently overhauled C2.  Visually, the graphs on the EDM-700 look more uniform with GAMIs than with stock injectors, but the graph data looks about the same for ROP.  I never ran LOP for the initially 10 hours of break-in.

So, I have lots of JPI data for stock injectors ROP and LOP, but only 3 break-in flights of data for stock injectors and the overhauled C2 prior to installing GAMIs, and all of those break-in hours were ROP.

The annotated JPI graph is from post-GAMI flights in which I started to go LOP and to the LOP mag test.

I suppose the good news about GAMIs, though, is that I can work with GAMI to get a good balance with the new C2.

John Paul will certainly work with you if you have a balance issue.  As an anecdotal data point, my stock IO360A1A will run smoothly in excess 100LOP at high power settings.  

[FlyBoyM20J]

1 minute ago, Shadrach said:

John Paul will certainly work with you if you have a balance issue.  As an anecdotal data point, my stock IO360A1A will run smoothly in excess 100LOP at high power settings.  

That's good to know.  I've heard only great things about working with GAMI and I look forward to this process.

I should mention that my brief excursions into 65% LOP cruise in the last couple of post break-in flights have shown greater stability farther from peak than I could run prior to GAMIs or the C2 overhaul.  I believe I now run 50F to 80F LOP stably at 2400 RPM at 6-7k MSL.  That could be GAMIs or could be that C2 no longer has a sticking EV.  Or both.

 

[Shadrach]

7 minutes ago, FlyBoyM20J said:

That's good to know.  I've heard only great things about working with GAMI and I look forward to this process.

I should mention that my brief excursions into 65% LOP cruise in the last couple of post break-in flights have shown greater stability farther from peak than I could run prior to GAMIs or the C2 overhaul.  I believe I now run 50F to 80F LOP stably at 2400 RPM at 6-7k MSL.  That could be GAMIs or could be that C2 no longer has a sticking EV.  Or both.

 

Remember that as you reduce RPM the lean limit at which the engine will run smooth gets closer to peak. The higher the RPM the further you can lean...(not that it's practical to do so).

[flyboy0681]

On 5/26/2019 at 1:09 PM, FlyBoyM20J said:

Here's the end of the scope.  I'm now assuming that I scratched it when I pulled the control to articulate the probe tip back to look around in there since when I look at the earlier pictures there are fewer scratches.  Looks like I must have scratched it when I first looked at it (new meaning to changing things by observation), then was alarmed, scoped all the other cylinders (without scratching anything), then came back and somehow managed to scratch this first EV again.

 

Any proctologist's out there who could weigh-in on this?

[MARZ]

I'm thinking that you drug the tip of the scope across the valve and it left a "pencil mark" on the face - the other valves had too much carbon build up to leave the same mark 

[Shadrach]

1 hour ago, flyboy0681 said:

Any proctologist's out there who could weigh-in on this?

None of those cylinders look like they’ve had the prescribed gallon of GI prep.

[PT20J]

On 5/28/2019 at 7:30 AM, Shadrach said:

A lot to unpack here and I should be working not killing time on MS.  I will address your ROP/LOP question.

For folks near SL, high power, LOP operations are doable depending on the season.  In the Fall, Winter and and early Spring my 701' filed often has DAs well under SL.  I can pull over 80% power LOP on a cold day with CHTs in the low 300s.  Why would I do that rather than ROP?  Well, year and years ago, I was involved in a red board discussion with Walt Atkinson (of APS fame).  He made it pretty clear that for a given power setting LOP ops made power with higher mean ICP (closer to consistent pressure throughout the power stroke BMEP = Brake mean effective pressure) and that ROP ops made power with higher peak ICP...Think hammer blow versus a strong consistent push.  A good break in requires high ICPs because the pressure is needed on the back side of the rings to force the rings (see attached image)  One of the reasons engine manufactures tell you to vary RPMs during break in is that it varies where (degrees ATDC) the peak pressure occurs in the power stroke by changing the piston speed.  High power LOP ops still make plenty of pressure but it is more evenly distributed throughout the power stroke. In theory this means more consistent ring pressure against the cylinder wall through out the power stroke. The added benefit is that it transfers less heat to the cylinder (lower CHTs, lower risk of glazing) and burns less gas.  All of the above being said, getting a good break in ROP is the norm not the exception if factory procedures are followed. The guideline have been in place since these engines were introduced.  I went did my break in LOP because over the years I have become quite comfortable with low level, high power, LOP ops for local flights and to stay out of headwinds when westbound.  I would not recommend it to folks without a good understanding of combustion science or breaking in a factory engine where warranty is dependent on factory guidelines.

Many folks would balk at how I run down low until the see the cylinder temps =<330, CF closed and 152-156KIAS (which when corrected is somewhat less).  

Circling back to my conversation with Walt. I have never seen APS's  BMEP graphs but my own observation is that any IAS that I can attain while LOP has lower CHTs than that same IAS on the rich side of peak.  Stated simply for a given power output CHTs tend to be cooler on the lean side of the spectrum. This is consistent with what I took from my conversation with Walt. 

Great summary. 

Here's some actual APS data for one operating condition for one (unspecified) engine. It's a little hard to read, but the original wasn't all that good. The graphs are internal cylinder pressure curves for the same engine at the same power output with the only difference being mixture.

Left graph: 27.2"/2500 rpm / 75F ROP / 390F CHT / 18.3 gph / 244 bhp / 140.5 BMEP / ICP_max= 825 psi

Right graph: 29.9"/2500 rpm / 50F LOP / 365F CHT / 16.4 gph / 244 bhp / 140.5 BMEP / ICP_max= 740 psi

Note that BMEP is not a "real pressure", but an average. It is equivalent to torque times a constant. As shown below, you can achieve the same BMEP with different shaped curves. 

Skip

[Shadrach]

43 minutes ago, PT20J said:

Great summary. 

Here's some actual APS data for one operating condition for one (unspecified) engine. It's a little hard to read, but the original wasn't all that good. The graphs are internal cylinder pressure curves for the same engine at the same power output with the only difference being mixture.

Left graph: 27.2"/2500 rpm / 75F ROP / 390F CHT / 18.3 gph / 244 bhp / 140.5 BMEP / ICP_max= 825 psi

Right graph: 29.9"/2500 rpm / 50F LOP / 365F CHT / 16.4 gph / 244 bhp / 140.5 BMEP / ICP_max= 740 psi

Note that BMEP is not a "real pressure", but an average. It is equivalent to torque times a constant. As shown below, you can achieve the same BMEP with different shaped curves. 

Skip

Thanks Skip! This is the first time I’ve ever seen actual data. Was this pulled off the net or did you have it lying around? I’ve gotten the sense that you might be friendly with a few of the gents in Ada.  

In any case, thank you for posting this. It confirms what I thought I was seeing in my observations of the crude but consistent data to which I have access.

Edited May 29, 2019 by Shadrach

[PT20J]

2 hours ago, Shadrach said:

Thanks Skip! This is the first time I’ve ever seen actual data. Was this pulled off the net or did you have it lying around? I’ve gotten the sense that you might be friendly with a few of the gents in Ada.  

In any case, thank you for posting this. It confirms what I thought I was seeing in my observations of the crude but consistent data to which I have access.

Ross, I pulled this from the seminar handout I got when I attended the APS seminar in Ada back in 2007. Someone who has taken the online version might have more recent info. Since the seminar, I've had a couple of email exchanges with Walter Atkinson and quite a few with John Deakin, mostly regarding radial engine operation, but I wouldn't say I have any special connection. The APS team does a really good job of simplifying some complex ideas. But, as I have certainly learned by humbling experience here and elsewhere, simplifying complex issues has its pitfalls. It's great when people take the time to really understand what APS is trying to teach. It's not so good when people take concepts like the red box, without fully understanding the underlying principles, and loudly proclaim that running at peak (or 50F ROP, or take your pick) EGT will destroy your engine. It's not that simple.

I think it's been clearly shown that running LOP has certain benefits perhaps including improved cylinder longevity. But, much of the LOP operational experience has been at lower powers: Normally aspirated engines can't cruise very high and put out more than about 65% power LOP; the airlines ran the big radials LOP at about 55% power; I think I remember Mike Busch saying he runs his 310 LOP at 65% or less. So, I'm really curious to know if engines continue to show longevity improvement when run LOP at high powers. I believe John Deakin was running his turbo-normalized Bonanza at 80+% deeply LOP before he quit flying and claimed no ill effects, but I don't know how long he did that and it's still only one engine. Maybe over time we will get more data on this.

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Edited May 29, 2019 by PT20J

[carusoam]

Expect that the data is coming from the Continental IO550 at APS...

based on the engine timing of 22°BTDC, the FFs, and the only instrumented cylinders for internal cylinder pressure on the planet...

Seeing the lab and meeting the people is a long time goal...aka taking the seminar.  

Best regards,

-a-

[Shadrach]

9 hours ago, carusoam said:

Expect that the data is coming from the Continental IO550 at APS...

based on the engine timing of 22°BTDC, the FFs, and the only instrumented cylinders for internal cylinder pressure on the planet...

Seeing the lab and meeting the people is a long time goal...aka taking the seminar.  

Best regards,

-a-

Likely a TN’d engine given the MP for the LOP setting. There are certainly days when an NA engine will see 29.9” of MP but they are the exception, not the rule. Neither power setting would be attainable at most cruise altitudes for an NA engine.

Edited May 30, 2019 by Shadrach

[FlyBoyM20J]

Update.  I went in again (carefully) with the bore scope and the scratches are gone!  The cylinder has had 8.75 hours since the last time I scoped it, when I scratched the deposits with the brass end of the bore scope.

Total time on this cylinder is now about 18 hours.