TSIO-360-MB detonation event?

[goncaloareia]

Dear all,

Yesterday, on a flight during the typical hot Portuguese summer (temperature was ISA + 15 degrees celsius), we were climbing our 252 to altitude (and fresh air) at the typical 32'' manifold and 2500 RPM, and while passing around 5500 feet, we had a quick CHT rise that was scary and very quick, with CHT on that cylinder nº 5 reaching 450ºF in less than a minute.

EGT remained stable and the differential values of EGT were normal (around 70º F).

After immediately reducing power to a mild 22'' MP the EGT and subsequent CHT drop was evident and the flight resumed normally, with no other abnormal symptoms.

After discussing this event and looking into the JPI EDM-700 data (excel data and graph that I'm sending attached) we are concluding that this was a detonation event on that cylinder, since we saw a quick and sharp rise of CHT on a cylinder with similar (if slightly lower) EGT.

Can someone give us some hints or different perspectives on this?

What should we do now? We are doing a borescope inspection to that cylinder, a compression check on the engine and also checking the plugs on that cylinder. Anything else we should check or do?

Thanks for the help and safe flights!

Goncalo

 

detonation.pdf

detonation2.pdf

[terbang]

Hi Goncalo,

CHT#5 rises sharply, indeed and I would also guess detonations are the culprit. However, other CHTs rise as well. Therefore I don't believe it's a broken insulator in one spark plug or some thing like that. I would have the magnetos checked, might be a timing problem.

Best Regards,

Gunter

[jackn]

Use more fuel. In climb at those settings, I'm burning 18 gph.

[kmyfm20s]

Good job on reducing the power quickly! I would also use a higher fuel flow on the climb.

[kortopates]

I've seen this happen due to oil leakage past the turbo on the induction side (as opposed to exhaust) and going into one of the 2 front cylinders - which are most susceptible since there induction tubes are the lowest. Oil reduces the octane and the detonation event didn't begin until leaning the mixture in cruise. For this, look for an oily induction tube or an oil puddle behind the turbo controller (another low spot).

Another possibility is a clogged fuel injector. Yet with this you should see an elevated CHT with any moderate or higher power setting - which didn't look like the case here.

Magneto timing would not affect a single cylinder.

Sent from my iPhone using Tapatalk

[terbang]

In fact all CHTs do rise, #5 only rises the steepest. However, the oil leak in the turbo is a good explenation.

[aaronk25]

Good for you for having good instrumentation and a great job of taking IMMEDIATE action.

Never heard the oil in the intake issue but I'd buy it.

Octane is a huge issue, makes the fuel more resistant to exploding before it's supposed to and in a air cool engine when the cylinder heads are 370+ on a slow turning (2700rpm) max and given the fuel sits in the cylinder for quite some time before the plug fires means the octave is necessary.

As a reference run 91 octave gas in a 380+ degree cylinder and your gonna have detonation. So if the oil does cause issues...well there you have it ......

Still thinking about this one...

[Bob - S50]

Use more fuel. In climb at those settings, I'm burning 18 gph.

I agree.  Our J burns about 18 or 19 GPH at full power at sea level.  I would not expect to see fuel flows down around 15 GPH (like you had) until I was above 6000' (normally aspired).  Since your engine is a turbo and produces full rated power to a much higher altitude, I would expect to see 18 or 19 GPH all the way until the wastegate is fully closed.  That is, run full rich until that point.  If full rich only provides 15 GPH you need to have your mechanic adjust it higher.

 

Here is a link to a John Deakin article.  If you don't want to read the whole thing, scroll down until you see the part about takeoff:

 

http://www.avweb.com/news/pelican/182179-1.html

 

And here is one on climb:

 

http://www.avweb.com/news/pelican/182176-1.html

 

Nice job of catching it before you lost the engine.

 

Bob

[PTK]

Gonzalo, I echo the fuel flow remarks.

"...Even half a gallon per hour can make a large difference in CHTs right after takeoff, and during climb..." John Deakin

Great job in reducing power immediately and saving the engine.

[aaronk25]

Not so sure it was detonation as egt didn't fall....normally egt falls around 100 or more degrees during detonation, since the burn starts eariler......maybe just lean???

[goncaloareia]

Thank you VERY MUCH to all of you for the precious inputs!

I forgot to mention that the lean mixture situation had already been identified and its clearly something that may have been a factor here.

We're seeing 20-21 GPH on takeoff according to the JPI fuel flow and the correct figure should be between 22 and 25.3 GPH. It's something that its being corrected now.

Unfortunately this low mixture situation only become visible after installing the fuel flow add-on (and its transducer) to the JPI-EDM 700 that we already had. We were trusting the old Hoskins FT-101 (and its original transducer) that came original with the Mooney, and this old transducer is giving us 1-1.5 GPH more than the correct fuel flow...

So to all of you that still have these FT-101 instruments installed or similar ones, DO FOLLOW the recommendation to exchange the transducer after 1500hours or some years of use, like the manual says.

I'll give further news on the outcome of this situation after the checks being made to the engine and some further flights.

Thanks and kind regards to all.

Gonçalo

[pinerunner]

Were you using 91 octane fuel? That may have been part of the scenario that put it over the edge. I'm glad you have the improved fuel flow measurement; that will be a big help in staying on top of the situation. For maximum power situations like take-off and a high performance climb ROP is clearly indicated. I've heard/read either Deakins or Busch recommend you insist you get your mechanic to set the take off mixture even higher than many of them do, even fight with them over it. This advice coming from the guru's (hated in some circles) of LOP makes it clear to me that ROP has its place. Your experience appears to back that up. Excellent thread on an important subject.

[pinerunner]

Not so sure it was detonation as egt didn't fall....normally egt falls around 100 or more degrees during detonation, since the burn starts eariler......maybe just lean???

Could you be describing preignition? The burn for detonation starts with the spark. Then you get detonation events ahead of the flame front. I'd bet there was at least light to moderate detonation going on. Just saying.

[aaronk25]

Could you be describing preignition? The burn for detonation starts with the spark. Then you get detonation events ahead of the flame front. I'd bet there was at least light to moderate detonation going on. Just saying.

You are correct pre-ignition......

[jackn]

Actually Gonçalo, As per TCM SID97-3F, which was revised on 5/10/2013 the TSIO360-MB should be set from 21.3 to 23 gph. On page 6 #16, it states that if you want to climb partial power(32" 2500rpm) you need to adjust 5% higher. If it were me I'd set it to 24.5 gph. You're right, reliable engine instruments are critical, I replaced all mine with the jpi-930.

Good Luck

[aaronk25]

Why is there no decimal point in his fuel flow numbers? My 830 shows fuel 17.7 ect.....?

[Marauder]

Could it be he is using pounds instead of gallons? 154 lbs/hr is roughly 25 GPH. The JPI manual does allow for pounds to be used.

[Dave Marten]

Actually Gonçalo, As per TCM SID97-3F, which was revised on 5/10/2013 the TSIO360-MB should be set from 21.3 to 23 gph. On page 6 #16, it states that if you want to climb partial power(32" 2500rpm) you need to adjust 5% higher. If it were me I'd set it to 24.5 gph. You're right, reliable engine instruments are critical, I replaced all mine with the jpi-930.

Good Luck

Just to be clear: 21.3-23.0 gph is for 36" MAP and 2700RPM.

 

Also, in the climb leave her throttled up at 36" MAP and 2700 RPM and set 120 KIAS for your climb to cruise altitude. I do not advocate partial power climbs, especially in turbos, you're not flying the airplane efficiently and you are likely encounter insufficient cooling. 

 

I suspect your issue was due to a combination of climbing at reduced power, low IAS (lack of sufficient cooling air), hot ambient temp, and low fuel flow. Most likely if your engine is acheieving the correct takeoff power settings (36"/2700RPM/21-23gph/1450-1500 TIT) then you should be dialed in.

 

BL: Cruise at 2500RPM, but don't climb to altitude at 2500RPM. Climb Full throttle 36", 2700 RPM, target 1450 TIT (about 23 GPH), cowl flaps full open and 120 KIAS all the way up to the FLs. You'll run cool and optimize your performance.

[goncaloareia]

Hi again,

We were using 100LL avgas (i sure hope so)!!

The fuel flow numbers are gph although the data numbers are missing the decimal point.

I totally agree that something in the vicinity of 24.5 gph is the correct number for fuel flow.

Finally, i've tried the 36-2700 rpm climb sometimes in the past and the more i try it the more i'm convinced that the partial power climb to FL with 32-2500 makes no sense. I agree that 36-2700 with 1450 tit and 23-24 gph at 120 kias are the golden numbers for an efficient climb in the 252!!

Rich of peak and full mixture are for me the safest and more efficient way of climbing (not cruising). The mixture big pull at such high power on a turbo engine look dangerous to me.

I've flown a piper arrow for almost 10 years before the mooney and the big difference of this continental tsio-360 for the lycoming io-360 of the arrow is the huge temperature amplitude that we must manage, and therefore the caution needed in operating the engine. In the piper you have bigger margins for error in engine management.

I can only try to guess how tricky it is to operate a mooney 231, specially with the LB engine!!

Thank you all!

Goncalo