262 -MB engine operation

[Bryan1016]

First turbo...TSIO-360-MB engine.

For decent from altitude, I pull the throttle to 20".  As I descend, airspeed increases and manifold pressure creeps up like in a normally aspirated engine.  Is this normal?

Thanks,  Bryan

[Zwaustin]

As you descend yes MP will creep up as you don't need as much throttle for the desired setting down lower. I have an LB and usually descend without pulling much power to keep speed up and eliminate shock cooling potential. From there I reduce MP an inch or two every couple minutes as needed. I cruise close to 26 inches (have intercooler) and a quick pull to 20 inches would be too much cooling on my engine. 

[Bryan1016]

Zwaustin,

Thanks for the reply.  The -MB engine has a manifold pressure controller system.  Any 252 folks out there?

Thanks!

Bryan

[Zwaustin]

1 hour ago, Bryan1016 said:

Zwaustin,

Thanks for the reply.  The -MB engine has a manifold pressure controller system.  Any 252 folks out there?

Thanks!

Bryan

Ah, had not remembered it had that and the later induction system. Someone who flies one will surely have more specific model advice for you then but can it normally maintain/ hold steady MP with a large altitude reduction? I don't know the answer to this but am curious how efficient the controller is for my own knowledge. With that being said I still would not recommend pulling too much throttle out at once for descent as done on a non turbo engine. If I recall correctly the 360LB manual calls for a reduction of 1-2 inches per 2 minute period but perhaps your is different and allows abrupt power pull. It doesn't take much for rapid cylinder cooling when at a high altitude. 

[carusoam]

It may be helpful to include details like inter coolers and pressure controllers if you have or don't have them...

Just trying to be helpful...

Best regards,

-a-

[pkellercfii]

My experience with my '89K, a factory 252 powered by a TSIO-360-MB engine, is that it appears that the turbo wastegate does seem to come full open below 5000' MSL at 20" or so on MP. Below that, yes, it does behave like a normally aspirated engine in that the MP will creep up in descent. Above 10,000' MSL, MP is rock solid on descent.

--Paul Keller

'89K @ RLD

[dlmorris]

I have flown a 262 conversation for over 15 years (thousands of hrs). First, a comment; assuming you are using book power settings and operating at typical altitudes for this model  (mid-teens) Any sudden throttle reduction regardless of reason will significantly reduce engine life. 

As to the MP increase in decent from 20 inches, I would first confirm your prop is the correct model for a 262. The 231 had a 216 prop. The 252/262 requires the 221 prop. Some conversions were signed off with the old prop. Rpm and MP increases in decent if the 216 prop is still on the plane.

Assuming a correct prop, I would have your wastegate controller checked. It should progressively open as you decend into thicker air. 

Best solution, discontinue the throttle reduction practice. Gradually reducing MP from 20 miles out has been my practice and my engine has over 1600 tach time hours on it and going strong.

[Bryan1016]

Thanks for the feedback everyone.  Prop is the 221.  I will check altitude where the controller creeps next flight. 

[jackn]

On June 8, 2016 at 3:13 PM, Bryan1016 said:

First turbo...TSIO-360-MB engine.

For decent from altitude, I pull the throttle to 20".  As I descend, airspeed increases and manifold pressure creeps up like in a normally aspirated engine.  Is this normal?

Thanks,  Bryan

This is normal. I think 20" is too low for a long descent.

 

[jackn]

Also, I would recommend attending a Mooney Safety Foundation PPP. You will really get to know how to operate your plane. 

[Zwaustin]

13 minutes ago, jackn said:

Also, I would recommend attending a Mooney Safety Foundation PPP. You will really get to know how to operate your plane. 

I second this recommendation. I did one in Dallas last year and it was well worth it in time and money. all Mooney specific and you get a bi annual review and IPC done while your at it. 

[Bryan1016]

Safety foundation PPP...never been to one of these, but sounds like what I need.  I've been running 28"/2500 based on an old article I read, no GAMI's yet.  Trialing different settings for approach speeds. 

Topic divergent...Recently flew an A36 Bonanza for small company.  Very glad to be back into a Mooney.  The Bo is easy to fly, but drops like a brick without that 550 spooled up.

[jackn]

28/2500 is fine, but I only use that setting if I have a strong headwind. Otherwise, I usually run at 26/2440. It just sounds better and I use 3 gph less fuel. Speed drop of about 10 kts. For approach, I'll use 16.5-17 depending on headwind. 

I fly with a friend in his A36 w/550. Nice plane, burns fuel.