252 peak EGT spread-what's yours? And: too much engine roughness?

[Z W]

How is our turbo configuration "unusual"?

 

 

I have not.  One of the things I've been frustrated with is the lack of "small block" information (Zane seems to agree--don't meant to put words in his mouth, though).  The TSIO-360-M/SBx in particular seems to be a real "asterisk" engine with GAMI anyway, perhaps because of the tuned induction (?).  Correct me if I'm mistaken, but I thought the TSIO-360 didn't even have GAMIjectors available for it until fairly recently.

 

Zane, do you open the cowl flap when cruising at the 28"/2500 RPM/11.5 (Peak TIT) power setting?  From memory, I think that's a pretty high power setting (>70%), and if I did that, my hottest (#5 up front--which has always seemed weird to me) would definitely be 400+ without opening cowl flaps at least 1/4.

 

The "unusual" comment comes from what my A&P told me, so take it with a grain of salt.  We have a factory intercooler setup that was pretty much unheard-of at the time it came out in the 80's.  It's one of the most modern turbo designs available in the older fleet.  We also have the automatic wastegate, and a turbo controller that regulates MP separately from the wastegate.  Basically it's a very complicated system that makes it to where you just push the black throttle knob all the way in and get the power you want without overboosting, up to wherever our critical altitude is in the 20's.  I know because our turbo controller went bad and we replaced most of the rest of the system before we figured out what was causing the problem, which was MP fluctuations at any power setting that used the turbo for boost.

 

I've also been told by two A&P's that the fuel delivery system on our engine is unusual.  It's a very complicated spider.  It's supposed to be very efficient at keeping fuel flow balanced, even without GAMI's.

 

I do agree about the lack of small block information.

 

I do have to crack the cowl flaps about 1/4 or 1/3 in cruise at 2500/28"/11.5 GPH.  Sometimes as much as 1/2 on hot days down low.  That puts them in the middle of where they're marked "cruise" on the indicator.  I just crack them enough to keep my highest CHT under 380.  I do not notice a significant speed loss from doing that, although I'm probably losing 1-2 knots.  You are correct, it's a 75% power setting.

 

I can keep the cowl flaps closed all the way (where it says "descent" on the indicator) running 20 degrees LOP, and still have CHT's under 350 usually.  But I get the roughness.

 

I'll have to look into Tempest Fine Wires. 

[Earl]

Scott,

No offense intended. Seriously. But some version of your post appears in every LOP/ROP thread on the internet. It adds zero useful information to the discussion, beyond the fact that there is a really good live course available. It's one of the things that I find frustrating about trying to find good information.

If you attended the course, can you tell us why a lot of our engines are rough at 20-30 degrees LOP TIT? My EGTs all peak at almost exactly the same time. My engine has GAMI's. Can you tell us how many hours we can expect to lose on TBO, on average, if we run our engines at peak TIT, instead of 100+ ROP? Or how many hours we can expect to lose between overhaul/replacement of cylinders? Or how many hours we lose, on average, between catastrophic in-flight engine failures?

Can you tell us, for certain, if we should base our ROP/LOP measurement off of peak TIT, or the last EGT to peak?

I submit that's the kind of information we need to be able to make an informed decision about where to set the red knob.

I don't mean to bash the APS course. I have not been able to attend it, and I would like to. I've read posts by the guys that put it on, and they seem knowledgeable. When life slows down a bit (ha ha) I plan to do it. Right after I've gotten my tailwheel endorsement, seaplane rating, glider rating, aerobatic course, etc. done...

For now, I have to settle for what some people will post on internet forums.

Zane. I think the problem with those of us that have taken the course and posting useful information is that there is too much to post, many of which are graphs from tests they conducted, etc. What I can tell you from the data they developed is that if you are running a big block Continental at 65% power and 50 degF ROP using EGT you are at the highest ICP. I am 100% convinced of that unless the AP guys somehow rigged their test (they run the engine and show you the gauges live). You ask a good question about whether this also applies to small block Continentals and I plan to ask the guys at AP. As I said in my reply to your post if you are getting to TBO without having to replace cylinders running your engine the way you do that is all the data you need.

[KSMooniac]

Scott,

 

No offense intended.  Seriously.  But some version of your post appears in every LOP/ROP thread on the internet.  It adds zero useful information to the discussion, beyond the fact that there is a really good live course available.  It's one of the things that I find frustrating about trying to find good information.  

 

If you attended the course, can you tell us why a lot of our engines are rough at 20-30 degrees LOP TIT?  My EGTs all peak at almost exactly the same time.  My engine has GAMI's.  Can you tell us how many hours we can expect to lose on TBO, on average, if we run our engines at peak TIT, instead of 100+ ROP?  Or how many hours we can expect to lose between overhaul/replacement of cylinders?  Or how many hours we lose, on average, between catastrophic in-flight engine failures?

 

Can you tell us, for certain, if we should base our ROP/LOP measurement off of peak TIT, or the last EGT to peak?  

 

I submit that's the kind of information we need to be able to make an informed decision about where to set the red knob.

 

I don't mean to bash the APS course. I have not been able to attend it, and I would like to.  I've read posts by the guys that put it on, and they seem knowledgeable.  When life slows down a bit (ha ha) I plan to do it.  Right after I've gotten my tailwheel endorsement, seaplane rating, glider rating, aerobatic course, etc. done...

 

For now, I have to settle for what some people will post on internet forums.

 

Ditto to what Earl just posted.  The information is known, but learning it is a challenge.  It is highly technical, and doesn't lend itself AT ALL to casual internet posts.  It is doubly-complicated by all of the old wives tales out there, or people that don't know what is really going on telling you to do this or that (especially mis-informed mechanics or shops!).  Not to mention how do you know to listen to me vs. anyone else you've never met?  

 

You go to college to learn engineering, or medicine, for example, because you cannot effectively teach it to yourself at home by reading an internet forum now and then.  The learning takes place most effectively in person with excellent instructors and presentation material, and is reinforced by actually seeing the concepts in action with your own eyes.  I'm sorry there isn't any better way to do it.  I learned a TON in Ada in 2.5 days, and I'll continue to preach the virtues of their course every time this topic comes up because it is without question the most effective way to learn.  The Q&A sessions and test stand sessions are especially valuable, and missing from the online version.  I'm a degreed engineer and learned more there in that weekend than I did in some semester-long courses.  It is *that* good.  I'm sorry my education can be shared more effectively in this virtual world.

 

Regarding your questions in particular, I lean on the LOP side based on last to peak, and stay below the limits of TIT where appropriate.  Your question about life reduction at peak vs. 100 ROP...well that depends on your power setting.  Lean to peak at 60% or maybe 65% all you want... at 70 or 75%, you're adding a lot of unnecessary stress to your engine.  Your roughness at 20-30 LOP could very well be due to a weak ignition system...mags, wires, or plugs.  I'd start at plugs.  And there are too many variables with cylinder life (especially) and the engine in general to say you'll lose XX% by running it hard in a fashion that is sub-optimal.  Your valves might have been installed poorly from the factory, and that will cause a premature failure long before your mixture management can influence a failure.  But if you have valves done well, it is entirely possible to run 2500 or 3000 hours or more without failure.  Maybe.    I know I just overhauled my first-run cylinders because they checked out great, and that saved me 4+ AMU vs. new and unknown factory jugs.

 

Regarding priorities for spending your aviation budget, I recommend putting the APS course at #1, and engine monitor installation (if not equipped) at #2.  Those two will end up saving you money, and possibly your backside, by teaching what really happens with our engines, how to maximize efficiency, and how to interpret an engine monitor and take appropriate action before it is too late.  The knowledge also helps you diagnose engine maladies and save on troubleshooting time with a mechanic.  The fuel savings over 1000 or 2000 hours add up to staggering amounts.  It is all of the "stuff" we should be taught in primary training, but sadly much of what is taught is incorrect at best.  It is also the stuff that would be included in Aircraft Ownership 101, if there was such a course, to help you make better decisions.

 

APS offers a money-back guarantee as well... and thus far not a single customer has asked for it.  It is that good, and every owner-pilot will benefit.

[Z W]

Good points.  I do understand it's hard to tell whether I should listen to you vs. some other random stranger on the internet.  I've seen enough of your posts around that I actually give them great credit.

 

However, I disagree that anything can't be learned in a forum, or that you have to attend a formal, structured educational course to learn these things.  Data speaks for itself.  The source is not important.  Some people require a structured environment to learn, but not everyone.  Again, not knocking the course here.  Would like to take it someday, etc...

 

I can understand the theory that high ICPs leads to increased failure rates, and that ICP's are highest at peak to 50 ROP.  I remain unconvinced that higher ICPs actually result in a statistically measurable increase in failure rates.  I don't care what my ICPs are, unless they result in the big fan going quiet in fewer hours than if I had lower ICPs.

 

I am with you on believing that data is not available because there are too many other factors with cylinder and engine life.  If you want to be realistic about these things, I bet gear-ups, A&P screw-ups, and zero-fuel off-airport landings destroy far more engines, statistically, than any mixture setting.

[KSMooniac]

My view on the ICP issue is from a long-term fatigue standpoint.  There is a practical limit on cylinders...but who is to say whether it is 2000 hours (as in typically replaced with new at overhaul) or 8000 or 10000 hours?  Fatigue life in metal is a function of stress (ie ICP) and temperature (ie CHT).  The higher either of them are, the shorter the fatigue life...and that's the way it is for any engine.  Minimize both while making the power you want, and the longer they'll live.  (ditto for the case/crank/rods/bearings/etc.)  You can make 75% power with very high ICPs and CHTs, or much, much lower, and especially with a turbo you have a wide range of options.  The test cell in Ada showed in action the fact that you can run an engine at 87% power with lower ICP and CHT than a POH setting at 75% power.  Truly eye-opening.

 

I'm interested in getting 3000 hours out of an engine.  Who knows if I'll make it on the one I'm building now, but I'm damn sure gonna try.    I may not own it that long, but maybe the next owner will get there.  Running an engine to 3000 hours, and/or preserving your known-good cylinders for overhaul make a noticeable difference on operating costs, and since we're all Mooney pilots we're by definition frugal and that should be important.  It is quite possible to run it by the book and just open the checkbook up at every opportunity if you wish, but I choose to understand it fully and make the optimal choices for my checkbook.

[Greg_D]

I'm having this same discussion with a friend who is trying to learn how to run LOP through internet forums.  He's been trying for over a year now and still doesn't grasp the concept fully.  If a picture is worth a thousand words, seeing a heavily instrumented engine run on a test stand, like the one in Ada, must be worth a million.