LOP MP at high altitude

[231LV]

Followup to the original problem.....well, I should have guessed the cause of the problem as a mechanic at the field where the plane is sitting guessed it right away before even opening the cowl...induction tube popped off. In thinking back through the sequence of events, it pointed to a sudden loss of induction air when the engine sagged across the board. No specific problem noted on the JPI and a lower than normal MP while at 17k ft. The induction system must have developed a leak during the previous trip causing me to see lower than normal MP and then failed with full power. I was fixated on a turbo failure or a low compression cylinder. Lesson learned...I need to think through the basics of what causes an engine to make its power before moving to the more esoteric stuff. I'm waiting for a repair estimate but included the pic the mechanic sent me.

[Warren]

That looks more like an exhaust system failure.  Isn't that where the exhaust crossover tube (not sure about terminology here) enters the exhaust on the co-pilot side?  It looks like the silicone hose from the cabin heating and the shroud around the exhaust.  It appears the bracket failed and you were dumping exhaust and losing the exhaust pressure that drives the turbo. 

 

[231LV]

3 minutes ago, Warren said:

That looks more like an exhaust system failure.  Isn't that where the exhaust crossover tube (not sure about terminology here) enters the exhaust on the co-pilot side?  It looks like the silicone hose from the cabin heating and the shroud around the exhaust.  It appears the bracket failed and you were dumping exhaust and losing the exhaust pressure that drives the turbo. 

 

It sure looks like you are right!......Either way, the compressed air wasn't getting to the cylinders....thanks for the sharp eye!

[carusoam]

+1 for looking like exhaust parts... heater shroud and hot air hose...

+1 for taking a look at where the heat has caused some fiberglass repairs to be made....

Turbo Mooneys require some extra care to not Accidently leak exhaust streams under the cowling...

Think cutting torch up front while flying....

Very important to have somebody technical review this with you...

M20Ks don’t have the usual muffler/exhaust system.

Mr. Gilliland brought us this knowledge.  PP thoughts only, not a mechanic....

Best regards,

-a-

[jlunseth]

There is a major difference between induction failure and exhaust failure.  Induction air is maybe 250 dF, and that would be high.  Exhaust temp is approx. 1600 dF or more, its a flamethrower.  You are very lucky to have survived.

[N231BN]

On 5/6/2018 at 5:18 PM, N201MKTurbo said:

I hate to nag, but you shouldn't have taken off if it wasn't working right. 

+1! Another reason to always check FF on takeoff with a TC Continental.

[231LV]

1 hour ago, N231BN said:

+1! Another reason to always check FF on takeoff with a TC Continental.

yea...pretty easy to think what "should have been done" ....between watching the runway , slowing increasing throttle, applying slight up elevator, I was airborne before I registered that the MP was abnormally low...FF was normal.....left turn to base and "boom" the power drops...request a return to landing with a rough engine.....turn to land and touchdown...total time elapsed.....maybe a minute or two max......the problem did not present itself it a way that was obvious or I obviously would have discontinued to takeoff roll.

[N231BN]

I'm sorry if I sounded like a jerk, it wasn't my intent. Glad you are back on the ground safe. If you were only getting 28" on takeoff there is no way the FF would have been normal on a Turbo Continental. Perhaps if an induction hose blew off down stream of the throttle body, the upper deck pressure would have still been there to drive the FF up. I just think this is a good example of why it is so important to verify takeoff power on a turbocharged engine. That exhaust leak was very close to the fuel pump and associated hoses.

[231LV]

11 minutes ago, N231BN said:

I'm sorry if I sounded like a jerk, it wasn't my intent. Glad you are back on the ground safe. If you were only getting 28" on takeoff there is no way the FF would have been normal on a Turbo Continental. Perhaps if an induction hose blew off down stream of the throttle body, the upper deck pressure would have still been there to drive the FF up. I just think this is a good example of why it is so important to verify takeoff power on a turbocharged engine. That exhaust leak was very close to the fuel pump and associated hoses.

All is good...no worries.....#5 cylinder....mechanic says a week or so, assuming the flange and failed area can be welded...otherwise, a new pipe....yea, definitely will revise my takeoff scan....

[DanM20C]

28 minutes ago, 231LV said:

All is good...no worries.....#5 cylinder....mechanic says a week or so, assuming the flange and failed area can be welded...otherwise, a new pipe....yea, definitely will revise my takeoff scan....

I'm glad it turned out how it did.  Like @N231BN stated above, Verifying MP and FF in the takeoff run is critical. Always be prepared to abort if not making one or the other.

Do you have a CO monitor?  A Sensorcon or similar may have shown some CO on the flight at 17K then the problem started.  Not long ago a 252 here on MS reported a #3 exhaust stud/gasket failure and his sensorcon didn't pick it up.  But I have had many others report elevated readings with exhaust leaks under the cowl.

Thanks for sharing.  I'm glad you made it down safely!

Cheers,

Dan

[231LV]

1 hour ago, DanM20C said:

I'm glad it turned out how it did.  Like @N231BN stated above, Verifying MP and FF in the takeoff run is critical. Always be prepared to abort if not making one or the other.

Do you have a CO monitor?  A Sensorcon or similar may have shown some CO on the flight at 17K then the problem started.  Not long ago a 252 here on MS reported a #3 exhaust stud/gasket failure and his sensorcon didn't pick it up.  But I have had many others report elevated readings with exhaust leaks under the cowl.

Thanks for sharing.  I'm glad you made it down safely!

Cheers,

Dan

Yes I do....nothing abnormal at 17k or for the entire trip...

[231LV]

4 minutes ago, Hyett6420 said:

i know it might cost more, but a new pipe would be my option.  You never know how good the weld is going to be.  

Glad you made it down safe.  i have to run in a new engine soon and I'm honestly bricking it.

Yea....discussed with the mechanic and since the plane is not at my home base and I am planning a replacement engine this year, I'm electing a quick fix to get it home with an anticipated exhaust overall when the engine comes off. The mechanic said he would recommend an entire overhaul just to be safe but felt a repair was good for 50 hours or so...

[231LV]

OK...just to close this thread off...or maybe not since I do have a question.....the plane came home yesterday and all ran well....the mechanic was satisfied with the weld AND replaced the clamps in the induction system plus "mucked" (his words, not mine) with the PRV on the induction system. All this brought the MP back to where it typically sits however, (and this is where I need to advice of the smart guys), on takeoff power, I found the JPI 800 showing 100%hp at 30 inches of MP....typically, I would see 100% hp on the JPI at about 37 inches (I have an intercooler on the engine so I have to limit the MP 1 inch per 10 degrees or 3 inches total)...I'm initially thinking I need to recalibrate the JPI hp constant which I will do today. If that doesn't work, then, thinking this through, I'm struggling with why I'm seeing 100%hp (on the JPI) so much earlier than I normally do? There is plenty of throttle and  the engine acts as if it is turbonormalized with me controlling the throttle as I climb and limiting the MP to 30 inches all the way up. By the time I hit 17.5k ft yesterday, I was showing a bit less than 24 inches with throttle fully in running 2500 rpm LOP...hottest cyl was 370 and 1610 EGT...10 gph....I was seeing 175 TKTS...with a GS of 185 kts

[kortopates]

6 hours ago, 231LV said:

OK...just to close this thread off...or maybe not since I do have a question.....the plane came home yesterday and all ran well....the mechanic was satisfied with the weld AND replaced the clamps in the induction system plus "mucked" (his words, not mine) with the PRV on the induction system. All this brought the MP back to where it typically sits however, (and this is where I need to advice of the smart guys), on takeoff power, I found the JPI 800 showing 100%hp at 30 inches of MP....typically, I would see 100% hp on the JPI at about 37 inches (I have an intercooler on the engine so I have to limit the MP 1 inch per 10 degrees or 3 inches total)...I'm initially thinking I need to recalibrate the JPI hp constant which I will do today. If that doesn't work, then, thinking this through, I'm struggling with why I'm seeing 100%hp (on the JPI) so much earlier than I normally do? There is plenty of throttle and  the engine acts as if it is turbonormalized with me controlling the throttle as I climb and limiting the MP to 30 inches all the way up. By the time I hit 17.5k ft yesterday, I was showing a bit less than 24 inches with throttle fully in running 2500 rpm LOP...hottest cyl was 370 and 1610 EGT...10 gph....I was seeing 175 TKTS...with a GS of 185 kts

Until you go through the calibration procedure for adjusting the HP Constant you can't rely on the %power parameter on your EDM - right now its probably garbage in and garbage out. (Defaults on the JPI would be based on normally aspirated engine making full power at 30", as well which is probably why you are seeing what you are. ) You will also have to verify the Engine HP field is set to 210 for your engine, and if your unit has a Engine Constant you'll want that set to 13.7 (this is for LOP calc's, but it may only be on the TSO'd for primary units e.g. EDM-9xx). Also I suggest you verify or go through the MAP calibration procedure to make sure that is as accurate as you can get it.

Personally I don't pay any attention to the calculated %power field but it can be helpful in cruise to know the approx % power you are at. Its actually intended to read cruise power most accurate - not takeoff, but I suggest you calibrate to your max cruise power setting - whatever it is you use. But at takeoff you should be scanning for MAP, RPM and TIT and abort if TIT is going north of 1500+  Properly set up, TIT should be well under 1450F. TIT will go high from lack of FF as well as vapor lock so I prefer it over FF when you can't see both.

With your manual wastegate and intercooler you should targetting about 37.5" as your redline MAP. 

BTW, the weld that broke off to hold the bracket to secure the cross over pipe is a common  problem on these engines and easily fixed with a weld to be as good as new. The problem is that the #5 exhaust tube needs to come off to properly welded and sometimes that could mean taking off #3 as well in order to get #5 off if the exhaust tubes are stuck together. There would be no point in replacing the #5 tube just to fix that, spend the savings on getting the entire exhaust overhauled where necessary and you'll be much much better off!

Edited May 24, 2018 by kortopates

[N231BN]

...There is plenty of throttle and  the engine acts as if it is turbonormalized with me controlling the throttle as I climb and limiting the MP to 30 inches all the way up...

Can you clarify this, are you only able to maintain 30" in the climb?

[Warren]

10 hours ago, 231LV said:

OK...just to close this thread off...or maybe not since I do have a question.....the plane came home yesterday and all ran well....the mechanic was satisfied with the weld AND replaced the clamps in the induction system plus "mucked" (his words, not mine) with the PRV on the induction system. All this brought the MP back to where it typically sits however, (and this is where I need to advice of the smart guys), on takeoff power, I found the JPI 800 showing 100%hp at 30 inches of MP....typically, I would see 100% hp on the JPI at about 37 inches (I have an intercooler on the engine so I have to limit the MP 1 inch per 10 degrees or 3 inches total)...I'm initially thinking I need to recalibrate the JPI hp constant which I will do today. If that doesn't work, then, thinking this through, I'm struggling with why I'm seeing 100%hp (on the JPI) so much earlier than I normally do? There is plenty of throttle and  the engine acts as if it is turbonormalized with me controlling the throttle as I climb and limiting the MP to 30 inches all the way up. By the time I hit 17.5k ft yesterday, I was showing a bit less than 24 inches with throttle fully in running 2500 rpm LOP...hottest cyl was 370 and 1610 EGT...10 gph....I was seeing 175 TKTS...with a GS of 185 kts

Those numbers seem way low for MP.  I can easily maintain 36" past FL200 (intercooled with Merlin upper deck pressure controller).  Even a base -GB engine doesn't reach critical altitude until 14.5k.  You should be able to keep a much higher MP.  LOP 11.3-11.5 gph is 75% power (I usually run at approx. 33" MP).  At 75% and 17.5k I see 175-180 knots.  Is there a chance your MP pressure is reading incorrectly and/or fuel flow.  It is hard to imagine with 10 gph you would see these speeds (10 gph x 13.7=137hp --- 65% power if LOP).   Your temperatures look reasonable but with 370 CHT you may be a close to peak EGT instead of LOP.

It seems like your MP  is reading incorrectly (easy to check on the ground without the engine started) or you still have a boost problem.  This could be an exhaust leak or potential damage to the turbocharger.  It seems based on your experience that the exhaust leak was the obvious problem and that should now be fixed.  It wouldn't hurt to look for exhaust residue as as leak that limits you to 30"MP is a huge leak.  "mucked" with the PRV also is a little concerning.  Any chance this got adjusted incorrectly?  However, if set to relieve at 30" it doesn't explain why you can only get 24" at higher altitude.

If all the inspections look good and it is safe to fly you can go out and get a little more data..On takeoff can you achieve full power?  36" MP and approx. 23gph fuel.  Ignore the JPI % reading and go with the POH full power recommendations (plus intercooler MP reduction).  Climb to see where your critical altitude is for a rough reference to validate the health of your turbocharger system.

100% hp reading seems crazy on the JPI.  It almost seems like it was setup for an non-turbo engine.  Either way, first challenge is to figure out why you are not getting the correct MP then the JPI can be adjusted later.

[231LV]

Thanks guys....it is definitely NOT putting out the power I have seen in the past. I flew today and had full throttle at 9500 so clearly, I am losing pressure somewhere. The CA mechanic stated that he checked the turbo and it looked fine. I'm betting the PRV is opening prematurely (which is what the CA mechanic saw when he ran the engine up on the ground). It also looks like the exhaust residue is quite dark...almost black which would lead me to believe its running really rich.....the ff is way high with full power...over 25 gph......

[N231BN]

Thanks guys....it is definitely NOT putting out the power I have seen in the past. I flew today and had full throttle at 9500 so clearly, I am losing pressure somewhere. The CA mechanic stated that he checked the turbo and it looked fine. I'm betting the PRV is opening prematurely (which is what the CA mechanic saw when he ran the engine up on the ground). It also looks like the exhaust residue is quite dark...almost black which would lead me to believe its running really rich.....the ff is way high with full power...over 25 gph......

That makes sense, the HP function on the JPI is driven by FF. The fuel pump uses upper deck pressure for regulating FF so your turbo is working. You probably have an induction leak, a big one. Does the MP on your JPI agree with the gauge?

 

[jlunseth]

First, on the JPI displayed horsepower, Paul is absolutely right.  It is important to understand that the JPI does not measure horsepower, it calculates horsepower.  In other words it is just an algorithm, and if the constants are not set correctly, then the reading will be wrong.  JPI does not publish the algorithm, but from long use of my JPI 930 it appears to work the same way we pilots would manually calculate HP.  MP and RPM drive HP when ROP, and fuel flow when LOP.  The important point from that is that if your MP was 30” and the JPI was saying 100% HP, then the JPI was just wrong.

The other issue though is the MPs you are reporting. Either your MP is not being read correctly or you still have a problem with your turbo/induction system.  You should be able to make 36” on takeoff, actually you should be able to make quite a bit more than that, but you don’t want to overboost the engine.  The rest of the throttle stem is for keeping power up (by the pilot adjusting the black knob) on your way to the flight levels.  If I recall correctly you have the intercooler, but the GB engine and no Merlyn.  I would expect your critical altitude to top out right about where you are reporting it, somewhere in the 17k range.  The nonintercooled engine is about 15k, you would get a little more, the Merlyn would give you quite a bit more (it allows the wastegate to fully close).

Edited May 25, 2018 by jlunseth

[231LV]

Yes, I understand what everyone is saying.....what threw me is I don't believe the mechanic in CA touched the JPI so why is it so far out of whack? Why is FF so much higher now than when I flew to CA as he didn't say anything about adjusting FF? I will run out to the airport and do a full power takeoff and ignore the JPI and follow MP only.....my intercooler engine should easily make 40 inches MP at full power (although I limit it to 37). I don't think the turbo is the problem as it was checked and pronounced OK. The weld should have fixed the exhaust problem and the new clamps should have solved the multitude of induction leaks which were found. That really leaves the PRV which the CA mechanic did not repair or replace but simply "mucked with". He said he saw it opening prematurely and when he held it closed on a full power run up(not very fun, he said), and he was able to get full MP and 2 inches beyond or 42 inches....BUT, he told me he wasn't sure it would hold although it held during a couple of subsequent runups.........I spoke with my local mechanic and we are trying to decide whether it's worth simply replacing it now...even though I plan to "down" the engine for an overhaul in the next few weeks...as he said, we can always take the new one off when he sends the old engine out for OH and put it back on when the OH engine comes back....assuming the OH engine doesn't get a new or OH PRV....waiting to hear from the engine overhauler on that question...

[N231BN]

Your FF went up after fixing the exhaust leak because the upper deck(pressure before the throttle body) is higher now that the turbo is working. The fuel pump senses that UDP, not manifold pressure, and regulates accordingly. It's possible that you have had exhaust leaks for a while and the fuel pump was adjusted to compensate. Something is still very wrong though, have you verified the accuracy of your MP gauge? You may need to leak check the line going to the gauge as well.

[231LV]

8 minutes ago, N231BN said:

Your FF went up after fixing the exhaust leak because the upper deck(pressure before the throttle body) is higher now that the turbo is working. The fuel pump senses that UDP, not manifold pressure, and regulates accordingly. It's possible that you have had exhaust leaks for a while and the fuel pump was adjusted to compensate. Something is still very wrong though, have you verified the accuracy of your MP gauge? You may need to leak check the line going to the gauge as well.

excellent suggestion!

[231LV]

For those interested, I took the plane up this am for a quick turn in the pattern. The airport is at 4500 ft ....DA was the same since the air was still pretty cool. I used full throttle on takeoff roll ignoring the JPI (which claimed 136%hp). Normally, I am unable to use full throttle due to overboosting so I self limit to 37 inches MP....best I could get with full throttle was 37 inches so yes, there must still be a leak somewhere. Also, FF looks to be around 36 gph! Wow! I'm getting ready to send the engine off for overhaul at Ly-Con in CA; the exhaust system is going to WI for overhaul at Dawley, I'm purchasing a Merlyn waste gate plus having hoses, engine mount, intercooler serviced or replaced plus the accessories (vacuum pump) overhauled...alternator is relatively new as is the starter....3 to 4 months is the estimated down time from Ly-Con. When it all comes back, this should all become a distant memory!

[N231BN]

That's good you are getting it all fixed. I would love to see a Savvy link for that flight if you have the capability.

[kortopates]

1 hour ago, 231LV said:

For those interested, I took the plane up this am for a quick turn in the pattern. The airport is at 4500 ft ....DA was the same since the air was still pretty cool. I used full throttle on takeoff roll ignoring the JPI (which claimed 136%hp). Normally, I am unable to use full throttle due to overboosting so I self limit to 37 inches MP....best I could get with full throttle was 37 inches so yes, there must still be a leak somewhere. Also, FF looks to be around 36 gph! Wow! I'm getting ready to send the engine off for overhaul at Ly-Con in CA; the exhaust system is going to WI for overhaul at Dawley, I'm purchasing a Merlyn waste gate plus having hoses, engine mount, intercooler serviced or replaced plus the accessories (vacuum pump) overhauled...alternator is relatively new as is the starter....3 to 4 months is the estimated down time from Ly-Con. When it all comes back, this should all become a distant memory!

I am surprised the aircraft even climbed at 10 GPH at over spec max FF! But maybe your FF isn't calibrated either. I've seen many aircraft not make power because of excessive mixture. Do you recall your TIT at full power? Glad this was your last flight with this engine, your test pilot luck could be running out! Be careful with the new engine doing ground runs and high speed taxi runs to check things out thoroughly before you commit to taking off.