a few detail m20m questions

[pkofman]

Well I  finally received the m20m.. Outstanding !  Fantastic..

but it has as always a few snags and i want to ask a few somewhat newbie questions.... Im looking for exact answers

 

1 Does taxiing with virtually no power count in the 3-5 minute turbo cool down period or should I add find minute before shutdown

2 My MP gauge backlight is not working.. ill have to send it out to have it fixed.. To be honest i find it hard to read , Is there a good simple ( nothing in aviation is simple !)  replacement for the E. I Inc MP gauge without getting into a  $$$$ JPI type system,

3 Is transitory Overboot acceptable on takeoff, can the engine take it for a few moments or not. What is the max MP i should shoot for . I was using  38 but i think i went over that for a bit for a short bit on departure.... Im sure there is allot of experience and comment on this....

Maybe simple questions but I'm not clear, and perhaps I'm being too particular, but i would like to be sure to understand this.

Thank you all and Merry Xmas 

Peter

 

[Danb]

Peter there's a recent thread on turbo cooldowns, some believe no cool down somewhere do the cool down. I count the taxi time as time to cool. Pull up some of DVA's posts on engine operation in Bravos he has quite a few good remarks. I never go to 38" my full power is 35.5"

[mike_elliott]

14 minutes ago, pkofman said:

Is transitory Overboot acceptable on takeoff, can the engine take it for a few moments or not. What is the max MP i should shoot for . I was using  38 but i think i went over that for a bit for a short bit on departure.... Im sure there is allot of experience and comment on this.

Have Clarence set the wastegate to be under redline at full throttle std day

[DVA]

2 hours ago, pkofman said:

1 Does taxiing with virtually no power count in the 3-5 minute turbo cool down period or should I add find minute before shutdown

2 My MP gauge backlight is not working.. ill have to send it out to have it fixed.. To be honest i find it hard to read , Is there a good simple ( nothing in aviation is simple !)  replacement for the E. I Inc MP gauge without getting into a  $$$$ JPI type system,

3 Is transitory Overboot acceptable on takeoff, can the engine take it for a few moments or not. What is the max MP i should shoot for . I was using  38 but i think i went over that for a bit for a short bit on departure.... Im sure there is allot of experience and comment on this....

(First, thanks for the plug Danb)

Merry Christmas Peter, nice present you got there!

As Dan mentioned I wrote a few articles that may be of some assistance. I have them in my blog area, here.

As for #1, you’ll find the thread on this and see there is no consensus, and no proof either, that a cooling period after taxi is needed. But during taxi, my strong opinion is that anytime you are taxiing you should be running extremely lean, to the point of slight engine roughness to minimize idle period plug fouling.

#2. If you don’t want to invest in a full JPI or other engine monitor, you can add the JPI Slimline MP Gauge for about $350 + install. Very easy to read with alarm function.

#3. 38’ is the MAX allowed for that engine, not the MAX takeoff pressure. If you are routinely seeing that much MP on takeoff power, you need to have the density controller and the waste gate modulation circuit adjusted. My blog post on this engine will help answer some of your questions, I hope.

The TIO-540 Engine Manual specifically states that the pilot should not reduce throttle on take off rolls in an attempt to control MP maximums in favor of having it adjusted properly. Unless there is a very high over boost, over two inches per Lycoming, you should not be adjusting throttle as it also reduces fuel flow which is critical at this point in the operation to help maintain detonation margin. As you will see from the charts I have in the post, the AF1B makes full 270HP well below 38” of boost - this is one of Lycoming’s highest performance engine designs. Some people think the AF1B is a derated TIO-540 engine, they are wrong per Lycoming. It is an uprated engine 250 HP engine and therefore needs to be treated very carefully. Mooney jammed this engine into this airplane for all intents and purposes to make the Bravo’s numbers.

Just for fun, here is Lycoming’s SB-592 on how to handle turbo overboost conditions.

That said, I would not allow my AF1B to exceed 38” under normal situations. On takeoff mine will be between 35”-36” depending on OAT and PA.y

Have fun with your new toy!

 

[PaulM]

#1 I start the 5 min timer after taxing off the runway..

#3 There is a table in the Lycoming manual (page 5-25) for setting the MP vs the injector outlet temperature.   Depending on the OAT you will get between 35-38"   The adjustment is very touchy and you will only hit 38" on a hot day. (not a standard day)

And Lycoming has published this procedure:

https://www.lycoming.com/sites/default/files/Turbocharger Density Controller Adjustment.pdf

A momentary overboost is ok, due to bootstrapping surge, but that indicates that either the oil wasn't > 100  or that you were very ham fisted in the initial roll.    A persistent overboost would indicate that the setting is too high and should be adjusted. 

(and the things DVA says) 

[co2bruce]

When I owned a 231 we counted taxi time in our cool down time. Do not overboots on takeoff, a few seconds shouldn't hurt, watch it.

 

[Danb]

[Tony Armour]

Not familiar with the mp backlight but I would think any avionics guy could Repair it. If mine went out I would have a go at it for sure (and of course have my IA sign it off)

[LANCECASPER]

The gauge is at the bottom of the instrument panel so you should be able to pull it from underneath and replace the bulb. It's not a very deep instrument.

 

[pkofman]

20 hours ago, Danb said:

Ha! of course the answer is right in front of my eyes..... thanks for pointing it out..

Ill do a deep dive on the manual.....

Merry xmas .. Pete