Turbo Issue?

[AH-1 Cobra Pilot]

Although this is not on a Mooney, please indulge me.

I fly a T-210 with a TIO-520.  It worked well until a flight a few days ago.  On takeoff, I was not getting the usual 35-40-ish" manifold pressure I had come to expect, so I landed.  I scoped the turbo and could not find anything obviously wrong.  I could spin it as well.  I also checked to see if the waste gate was stuck, but it moved freely.  The overpressure relief also seemed fine, and a mechanic said he had never had an issue with those anyway.

So, I took it up again yesterday.  On takeoff, the manifold pressure was about 28", the same as it was prior to starting.  In the air, I tried a few different settings.  At WOT and 2500 rpm, the manifold pressure was 30"; at WOT and 2200 rpm it was 32".  So the turbo is giving some pressure, but no where near all it should.

Anyone else have this experience?

[EricJ]

No upper deck intake or exhaust leaks?   An intake leak would likely be fairly large to do that so might be easy to spot.

 

[AH-1 Cobra Pilot]

21 minutes ago, EricJ said:

No upper deck intake or exhaust leaks?   An intake leak would likely be fairly large to do that so might be easy to spot.

 

Definitely nothing noticeable.

[MikeOH]

A SWAG (I'm not an A&P): Is it possible that something collapsed in the exhaust (flame tube?) partially blocking exhaust flow so that the turbo can't fully spin up?  Are the EGTs normal?

[N201MKTurbo]

I would mouse milk the waste gate.

[AH-1 Cobra Pilot]

16 minutes ago, MikeOH said:

A SWAG (I'm not an A&P): Is it possible that something collapsed in the exhaust (flame tube?) partially blocking exhaust flow so that the turbo can't fully spin up?  Are the EGTs normal?

All the temperatures seem to be normal, although the #3 & #4 cylinder temps are higher than the rest by a few 10s of degrees.

[Z W]

Had it once due to an air intake restriction caused by a poor air intake box repair. Restricted air intake prevented the turbo from spooling up to full power. Also caused the alternate air door to open and that light to come on.

Could be a lot of things, unfortunately, but there's one.

[M20F]

You have a leak, smoke test it. 

[Schllc]

It could be an induction leak,  it’s harder to find at the higher pressures, but check all of your clamps and hoses. I have no idea what the setup is on a 210, but I have had to chase these before on my io-540-s1a5 and it can be a little from multiple locations or a lot from one or all the above.  Start with the easy obvious places first, hose clamps.

how do you check the relief valve?

[hubcap]

Have you verified the gauge is reading correctly? 

[exM20K]

If that is an induction leak, it is a big one.  Soapy water and the exhaust side of a clean shop vac will quickly show if that is the issue.

I’ve had small induction leaks from over-enthusiastic clamping of the intake tubes, from the upper-deck pressure lines to the injectors, and the hardest to find: a nicked MP hose for the G1000 MAP gauge.  I recently helped a neighbor diagnose a leak in his T210, and in all these cases, the symptom was lapsing MAP by -1” per thousand feet.

being 3+ inches below takeoff MAP sounds like something else is going on, and I would have discontinued the takeoff. I’m unfamiliar with the TSIO520 setup, but in the 550’s it is pretty straightforward to test the wastegate with, IIRC, shop air.

 

Was the fuel flow, takeoff, and climb performance normal? If so, it would seem to be a gauge issue.

-dan

[Schllc]

It doesn’t take much, looks like all boost was gone with 28-30” being atmospheric pressure at sea level. I had a loose hose clamp and split boot and that’s all it took to lose boost in mine. I fixed the hose clamp and had full on the ground, but when I went up above 7 I couldn’t hold full MP. 
it takes less than you think. 

[AH-1 Cobra Pilot]

12 hours ago, hubcap said:

Have you verified the gauge is reading correctly? 

The power output is proportional to the gauge reading.