TSIO-520-NB throttle and turbo control questions....

[wombat]

How does the linkage from the throttle knob work to control the throttle and turbo?

Does the throttle control have two stages, one for the actual throttle and one for the turbo?    

Does the turbo automatically try to maintain 2" of upper deck pressure over the intake manifold pressure?

Something else?

Does anyone have diagrams of this?

 

This is for the install on a Mooney Rocket

Edited April 1, 2023 by wombat

[Fly Boomer]

1 hour ago, wombat said:

How does the linkage from the throttle knob work to control the throttle and turbo?

Does the throttle control have two stages, one for the actual throttle and one for the turbo?    

Does the turbo automatically try to maintain 2" of upper deck pressure over the intake manifold pressure?

Something else?

Does anyone have diagrams of this?

 

This is for the install on a Mooney Rocket

As far as I know (not a mechanic), you set the desired manifold pressure with the throttle, and the waste gate opens or closes as necessary to keep the manifold pressure where you set it.  Very much like the prop control — set desired RPM, and the prop governor adjusts blade pitch to keep RPM where you set it.

[wombat]

There has to be some mechanism for controlling manifold pressures below ambient pressure though, so you can't just control the wastegate with the throttle control.

 

Let's say I wanted to climb from sea level at 25" of manifold pressure.... When I start the throttle is partially closed and the wastegate is fully open so the turbo is spinning as slowly as possible.     As I climb, the throttle needs to open more and more until it's fully open, and then the turbo needs to start spinning faster by closing the wastegate.    At some point if I keep climbing I'll exceed the critical altitude of the turbo and the wastegate would be fully closed and the manifold pressure would start dropping.  (This altitude may be above the service ceiling of the airplane)

[M20F]

The throttle linkage has nothing to do with it.  Turbos are either like mine manual (crank in 20” of boost at sea level, feel the horses run) or it is automatic and the wastegate opens/closes automatically to keep a manifold setting. 

[N201MKTurbo]

The TSIO-520-NB has a variable pressure controller and does have a throttle connection to the pressure controller.

[N201MKTurbo]

https://aeroforce.aero/wp-content/uploads/2023/01/400888-0000-HET-guide-complete.pdf

 

[wombat]

Thanks, @N201MKTurbo.   So it sounds like the throttle control in the cockpit in this case will connect to the 470836-18 or 633388-10 pressure controller and that pressure controller will actuate both the waste gate and engine throttle as necessary (Through oil pressure and a system of cams and followers, respectively) to achieve the absolute pressure set by the cockpit throttle control.

I'm assuming then that the controller is set to keep the actual engine throttle as wide open as possible and the turbo wastegate as open as possible (Lowest boost) to achieve the desired absolute intake pressure.   But as a pilot I don't actually have control over these things directly and I can consider the control in the the cockpit to be simply setting the manifold pressure however I want.   As long as it's within the manufacturer's allowed operational parameters, of course.

[N201MKTurbo]

16 minutes ago, wombat said:

Thanks, @N201MKTurbo.   So it sounds like the throttle control in the cockpit in this case will connect to the 470836-18 or 633388-10 pressure controller and that pressure controller will actuate both the waste gate and engine throttle as necessary (Through oil pressure and a system of cams and followers, respectively) to achieve the absolute pressure set by the cockpit throttle control.

I'm assuming then that the controller is set to keep the actual engine throttle as wide open as possible and the turbo wastegate as open as possible (Lowest boost) to achieve the desired absolute intake pressure.   But as a pilot I don't actually have control over these things directly and I can consider the control in the the cockpit to be simply setting the manifold pressure however I want.   As long as it's within the manufacturer's allowed operational parameters, of course.

I believe it will keep the upper deck pressure an inch or two above the manifold pressure. Not quite as good as a slope controller that doesn’t have a throttle connection and has a manifold pressure sense line. They are both absolute controllers, so they won’t change upper deck pressure as you climb and descend.

The controller doesn’t control the throttle, just the wastegate. The throttle is controlled by the cockpit control. There is a link from the throttle valve to the pressure controller. The throttle position also sets the upper deck pressure. As you increase the manifold pressure with the throttle, the pressure controller will increase the absolute pressure up stream of the throttle valve.

[kortopates]

31 minutes ago, wombat said:

So it sounds like the throttle control in the cockpit in this case will connect to the 470836-18 or 633388-10 pressure controller and that pressure controller will actuate both the waste gate and engine throttle as necessary (Through oil pressure and a system of cams and followers, respectively) to achieve the absolute pressure set by the cockpit throttle control.

Not quite. Your throttle control is directly controlling throttle position not the controller. Its just that the controller is also connected to the throttle such that it reduces deck pressure for partial throttle to keep deck pressure a bit above manifold pressure based on throttle position. This was the tubo isn't working as hard at partial throttle positions.

 

34 minutes ago, wombat said:

I'm assuming then that the controller is set to keep the actual engine throttle as wide open as possible and the turbo wastegate as open as possible (Lowest boost) to achieve the desired absolute intake pressure. 

Not at all, partial throttle on the cockpit throttle control equals partial throttle in the manifold no different than if there was no turbocharger. The controller automatically adjust the wastegate to provide the desired deck pressure. The desired deck pressure is adjusted by the throttle position linked to the controller by cam and levers

Here is an article by Mike B that explains how these work: https://www.avweb.com/ownership/troubleshooting-the-turbo-system/.  

[wombat]

It's starting to make sense @kortopates   In Mike's description, the upper deck pressure is always at much as the turbo can do given the exhaust flow up to the maximum upper deck pressure, which is just a little above maximum intake manifold pressure.  That fits the "Fixed Absolute Pressure System" in the  PDF that Rich attached.

In the case of the TSIO-520-NB, which is a Variable Absolute Pressure System there is a the addition of the linkages and cams that take the throttle position and provide that as an input to the pressure controller, so the pressure controller will vary the upper deck pressure to just enough to overcome the fluid friction losses of the intake system.  This is the "Variable" part of the variable absolute pressure system.

Sounds a bit inefficient to use the turbo to boost the upper deck pressure then restrict it with the throttle again.   But I don't know how much power we're talking here.

If the ambient pressure is 29", I've got the throttle halfway open, turbo is boosting to maybe 34"  and because the throttle is 1/4 closed, it restricts it back to 30".  As I open the throttle more, the upper deck pressure will increase, and the difference between upper deck and manifold will decrease.   But running at say 25" at FL210 and having the throttle partially closed still sounds wasteful.   So the shape of the cams and angles of the linkages would determine the map of throttle position to target upper deck pressure.   And the more closed the throttle, the greater the differential between upper deck and manifold pressures would be.  At wide open throttle, it would be the most efficient with least differential.

 

 

The description of the system in the PDF Rich attached is:

VARIABLE ABSOLUTE PRESSURE SYSTEM (TWIN ENGINE, WITHOUT COVER): 

Operation: The variable absolute pressure controller (direct sensing, without cover) works much like the nonvariable absolute pressure controller in that it senses deck pressure, compares it to a reference absolute pressure, and adjusts the wastegate butterfly (controlling turbocharger speed) to maintain sea-level horsepower at varying altitudes. It differs from the nonvariable version, however, in that it is directly linked to the engine throttle, and through a system of cams and followers, adjusts itself to varying power settings, achieving the optimum deck pressure for a given throttle movement. A pressure relief valve, set slightly in excess of maximum deck pressure, is provided to prevent damaging overboost in the event of a system malfunction. A sonic venturi, if installed, is incorporated to provide a constant source of compressed air to the cabin pressurization system. An intercooler, if fitted, is added to cool the compressor outflow and increase cylinder charge air density.

[kortopates]

25 minutes ago, wombat said:

In Mike's description, the upper deck pressure is always at much as the turbo can do given the exhaust flow up to the maximum upper deck pressure, which is just a little above maximum intake manifold pressure.  That fits the "Fixed Absolute Pressure System" in the  PDF that Rich attached.

Yes, that's the APC and Mike describes the APC and then the VAPC right after the APC.

 

26 minutes ago, wombat said:

In the case of the TSIO-520-NB, which is a Variable Absolute Pressure System there is a the addition of the linkages and cams that take the throttle position and provide that as an input to the pressure controller, so the pressure controller will vary the upper deck pressure to just enough to overcome the fluid friction losses of the intake system.  This is the "Variable" part of the variable absolute pressure system.

The inefficiency with the APC is that its always working pretty hard o produce full UDP even though the engine isn't using it with partial power throttle. But when it working harder at partial power it's really the altitude that determines how hard the turbo is working and less so on how reduced throttle is.

But when you go to the VAPC the turbo is no longer always putting out redline UDP and just putting out a bit more than manifold pressure, that where the improved efficiency comes in since the turbo is now working proportionate to both altitude and throttle setting - not just altitude like the APC. 

34 minutes ago, wombat said:

Sounds a bit inefficient to use the turbo to boost the upper deck press

Every turbo adds a certain amount of overhead to provide the boost. But the rewards of 100% rated power up to the critical altitude is well worth it. The engine HP rating is already taking this into account as well. But of course if your cruising along and you loose the the turbo you are going to instantly see that overhead in the form of a intake manifold pressure dropping to a few inches below ambient atmospheric pressure due to turbo now adding just back pressure and a fuel system that is creating an overly rich condition. Added complexity with the emergency procedures goes along with their overhead so to speak making it important for turbo operators to understand them.

[wombat]

Oh, believe me I understand the overall benefits and costs of having a turbo.    With luck (Well, good maintenance on behalf of the seller) I'll own a plane with a turbo this time next month.

[N201MKTurbo]

Rockets are fun to fly. They go very fast. Don’t haul a lot.

[carusoam]

1 hour ago, wombat said:

Oh, believe me I understand the overall benefits and costs of having a turbo.    With luck (Well, good maintenance on behalf of the seller) I'll own a plane with a turbo this time next month.

Get a good Transition Trainer…

Somebody with Mooney turbo experience…

You are asking great questions….

There is a bunch of practical stuff to get familiar with regarding turbo ops and maintenance and preflight….

There is also a bunch to know for flying in the Flight Levels…. O2 system, O2 level measuring, Back up systems….

 

Much will depend on what you get for a turbo waste gate controller… some are more manual than others…

The most automated one is nice, but not completely automated at all….

Overall, it is really cool to have a turbo, or a pair of turbos….   …

and a MP controller…. Throw in an intercooler when able… get good instrumentation to support it all….

Know what mouse milk is…

Get ready to do a lot of reading for the new bird!

Post pics when able!

PP thinking out loud, I would love to add a pair of turbos to my Ovation…. 

Best regards,

-a-

[wombat]

The plane I'm looking at is N5773S.  It's still up on controller.com at the moment.

[carusoam]

One of the cool things about buying a bird from GMax…. (Where this and another Rocket is listed)

They are a wealth of knowledge when it comes to buying a Mooney from them….

They can bring you up to speed with everything about the bird in general… and they usually know the specifics about the individual bird as they typically buy it before selling to a customer…. Not just handle it…or rep it.

They are able to arrange training for you… and any equipment updates you might want to consider during the buying process…

 

The tough decision….

It is always a good idea to get your PPI from an independent source of the person selling the plane….( Four eyes vs. two)

GMax is both the best pre-flown Mooney seller, and the best Mooney service center in the world…. Together in one place.  So not so independent…

 

I learned about M20Cs while speaking with Jimmy’s partner (David), in the late 90s…

I was back a decade later learning about Ovations with David and Jimmy….

Got the O’s PPI done at DMax…

Did the transition training with Bob Cabe…

A really good memorable experience…

I last saw Jimmy at a Mooney gathering in KOSH…. Pre-pandemic…

Best regards,

-a-

[Fly Boomer]

18 hours ago, wombat said:

At wide open throttle, it would be the most efficient with least differential.

That's how Mike Busch runs the TSIO-520s (not NB) on his 310.  He controls the power with mixture.  Sometimes deep lean of peak.  He says he is more interested in longevity than speed.  Frequently heat is the constraining variable -- especially as you go higher.

[wombat]

Yeah, I've found Mike's stuff to be very reasonable and what he advises is normally what I try to do.  Hard to run LOP on a Continental O-470 though.   When leaning, one of the cylinders starts missing before the last one even reaches peak EGT, let alone get even the slightest lean of it.

 

But what you are saying about him running WOT all the time was part of the reason I was thinking it was possible to get the throttle all the way open before spooling up the turbo.   If your throttle doesn't open all the way until 35", running at 25" at FL180 with the turbo providing 12" of boost and the throttle partially closed seems wasteful.

 

Well, if I do end up buying this plane, I guess I'll see how it runs LOP.   

[Fly Boomer]

On 4/2/2023 at 10:24 PM, wombat said:

Yeah, I've found Mike's stuff to be very reasonable and what he advises is normally what I try to do.  Hard to run LOP on a Continental O-470 though.   When leaning, one of the cylinders starts missing before the last one even reaches peak EGT, let alone get even the slightest lean of it.

 

But what you are saying about him running WOT all the time was part of the reason I was thinking it was possible to get the throttle all the way open before spooling up the turbo.   If your throttle doesn't open all the way until 35", running at 25" at FL180 with the turbo providing 12" of boost and the throttle partially closed seems wasteful.

 

Well, if I do end up buying this plane, I guess I'll see how it runs LOP.   

Your TSIO-520-NB should be fine LOP.  That said, less than perfect mags, harness, plugs, injector balance, etc. can derail those plans.  Things I read -- not a mechanic.

[carusoam]

Hard to run LOP on an O-anything…

Probably why they installed the I on every O, if available…

Both are good…

Just the IO goes LOP better…

-a-