M20J with M-20 Turbo Operation

[DaveM]

Apologies if this has already been asked but can't find it.

Anyone out there with an M20J Lycoming IO-360-A3B6D and the M-20 Turbo kit installed?

If so, are you able to get full takeoff RPM without exceeding 30 inches manifold pressure at a sea level airport?

The AFM just states Normal Takeoff (100% Power) 30"Hg MAP and 2700 RPM

[N201MKTurbo]

If you are exceeding 2700 RPM at 30 inches, you need to adjust the prop governor. Nothing to do with the turbo.

[N201MKTurbo]

I can normally get full RPM at 25" or so. It sounds like you have a power issue. Is your timing correct?

[DaveM]

Timing is good.

Problem is, sea level airport, throttle in for takeoff, hit 30" before full throttle.

Full throttle and manifold pressure goes off the clock. Gauge ends at 30 but the needle rolls well past this.

Manifold pressure gauge reads normal at shutdown.

Everything I have read so far indicates that a turbo normalized Lycoming with this type of fixed wastegate (bypass) will be throttle limited to 30" on takeoff at a sea level airport.

Just trying to see what other experiences are.

[carusoam]

Welcome aboard Dave!

How familiar with turbos and aircraft engines and mechanical things are you?

Full power takes a few things…. Some we can measure easily….

1) airflow, defined by MP

2) fuel flow, needs a fuel flow gauge, not everybody has one….

3) RPM, Governor controlled…

4) The mechanical aspect comes with some delays and overshoots that the PIC needs to control…

5) If your MP is going past redline…. There is a control for that…

6) If rpm is going past redline… there is an adjustment for that…

7) If FF isn’t where it needs to be… it can be adjusted up or down following a mechanic’s procedure…

8) Often, when a complex airplane is new to the pilot….  Transition Training (of some form) is often a great way to become familiarized with all of the plane’s systems…

 

PP thoughts only, trying to fill in a base line for the discussion…

Best regards,

-a-

[DaveM]

Thanks for responding

I'm a mechanic looking after this airplane.

Its based at a sea level airport on the west coast of Canada.

Takeoff from this airport, throttle is limited by the manifold pressure.

Prior to getting to full throttle it hits 30" so turbo is putting out.

Fuel flow is low due to throttle position.

RPM is low due to throttle position.

Stuffing the throttle all the way will overboost the engine.

Have adjusted the fixed wastegate to lower boost at takeoff, which gets us full RPM and Fuel flow but then sea level manifold pressure ceiling is reduced.

Overpressure valve is a 470930-9018.

I have been unable to find the relief specs of this valve. Have sent an email to Quality Aircraft to see if they can tell be the spec.

Again, everything I have read on this type of turbo system indicates it will be throttle limited at a sea level airport.

Just trying to find out if this is the norm or does the system rely on the overboost valve to limit MP on takeoff.

[carusoam]

Great details Dave!
 

Thanks for sharing them.  That will help get the response you are looking for.

Often we have the RayJay guy around here… @tomgo2.  Who can point some people in the right direction for maintenance on turbo systems…

Rich above… is the guy with the experience that closely matches what you are looking for… @N201MKTurbo

Go MS!

Best regards,

-a-

[N201MKTurbo]

1 hour ago, DaveM said:

Timing is good.

Problem is, sea level airport, throttle in for takeoff, hit 30" before full throttle.

Full throttle and manifold pressure goes off the clock. Gauge ends at 30 but the needle rolls well past this.

Manifold pressure gauge reads normal at shutdown.

Everything I have read so far indicates that a turbo normalized Lycoming with this type of fixed wastegate (bypass) will be throttle limited to 30" on takeoff at a sea level airport.

Just trying to see what other experiences are.

You are limited to 30”. 
 

The upper deck pressure controller is set to ~32”, which is above red line.

You cannot just shove the throttle to the stop. You have to set the throttle to 30” and no more.

[N201MKTurbo]

59 minutes ago, DaveM said:

Thanks for responding

I'm a mechanic looking after this airplane.

Its based at a sea level airport on the west coast of Canada.

Takeoff from this airport, throttle is limited by the manifold pressure.

Prior to getting to full throttle it hits 30" so turbo is putting out.

Fuel flow is low due to throttle position.

RPM is low due to throttle position.

Stuffing the throttle all the way will overboost the engine.

Have adjusted the fixed wastegate to lower boost at takeoff, which gets us full RPM and Fuel flow but then sea level manifold pressure ceiling is reduced.

Overpressure valve is a 470930-9018.

I have been unable to find the relief specs of this valve. Have sent an email to Quality Aircraft to see if they can tell be the spec.

Again, everything I have read on this type of turbo system indicates it will be throttle limited at a sea level airport.

Just trying to find out if this is the norm or does the system rely on the overboost valve to limit MP on takeoff.

The pressure relief valve is set to about 32 inches. The fixed waste gate should be set almost all the way closed. It should be set to give a critical altitude of 19000 feet. All the way closed gives a critical altitude of about 21000 feet.

What is the fuel flow at takeoff power? I get about 18 GPH.

[DaveM]

Thanks

Appreciate the response.

So, takeoff throttle position along with fuel flow and RPM will be limited to whatever you get at a sea level airport.. No short field takeoff's down here.

Also, just checked the pop off valve per SB 592. Reads 46lbs for full open and pop off valve head is at 0.3215 instead of 0.20.

May have a pop off valve issue as well.

best rgds

[DaveM]

Just now, N201MKTurbo said:

The pressure relief valve is set to about 32 inches. The fixed waste gate should be set almost all the way closed. It should be set to give a critical altitude of 19000 feet. All the way closed gives a critical altitude of about 21000 feet.

What is the fuel flow at takeoff power? I get about 18 GPH.

Can't tell you as we can't get full throttle because we hit the 30" limit, which gives us 15 gph approx

[DaveM]

Just now, philip_g said:

If I'm reading this correctly the problem is you can't get full rpm at take off because you can't exceed 30" of MP? 

Correct

[N201MKTurbo]

53 minutes ago, DaveM said:

Can't tell you as we can't get full throttle because we hit the 30" limit, which gives us 15 gph approx

What MP do you get at full throttle? Perhaps the pressure controller (pop off valve) is stuck shut. You should get 32” if you get more than that, it isn’t working right.

Advanced Turbo Components overhauled mine. They didn’t have capability to do it, but they got the info from the OEM and approval from the FAA in two hours flat! The most amazing thing I ever saw. That valve is unique to this STC, there are only 35 Or so in the world.

[DaveM]

6 minutes ago, N201MKTurbo said:

What MP do you get at full throttle? Perhaps the pressure controller (pop off valve) is stuck shut. You should get 32” if you get more than that, it isn’t working right.

Advanced Turbo Components overhauled mine. They didn’t have capability to do it, but they got the info from the OEM and approval from the FAA in two hours flat! The most amazing thing I ever saw. That valve is unique to this STC, there are only 35 Or so in the world.

Can't tell you that. Scares the crap out of us.

Gauge ends at 30". If I use the graduations as a ballpark and the indicator is linear, then north of 35"

Would have to ship it from Canada, so what did Advanced Turbo charge you?

Aircraft Spruce Canada sells an overhauled unit for $633.00 Canadian Peso's

[N201MKTurbo]

1 hour ago, DaveM said:

Can't tell you that. Scares the crap out of us.

Gauge ends at 30". If I use the graduations as a ballpark and the indicator is linear, then north of 35"

Would have to ship it from Canada, so what did Advanced Turbo charge you?

Aircraft Spruce Canada sells an overhauled unit for $633.00 Canadian Peso's

It was like $350, but that was 10 years ago.

I think you found your problem.

[DaveM]

16 minutes ago, N201MKTurbo said:

It was like $350, but that was 10 years ago.

I think you found your problem.

Will comment here when I get it figured out.

[DaveM]

On 8/22/2021 at 2:57 PM, DaveM said:

Will comment here when I get it figured out.

Just found found this from The Aviation Consumer dated 2001

The M-20 system, which sells for $23,389 for the kit plus another $2500 to $3500 for installation, is about as simple as turbocharging gets. It uses a Rayjay/Consolidated turbo with a fixed wastegate but no turbo controller. Boost is fixed at 30 inches, controlled entirely by a pressure relieve or pop-off valve on the outlet side of the turbocharger. (Lycoming developed a similar design for the Seminole and Comanche.) The designs chief advantage is simplicity; there are fewer parts to install and maintain and, especially, no turbo controller to fuss with.

[KSMooniac]

You still have to limit throttle travel yourself and stop at 30"... You're not supposed to firewall it and depend on the pop off valve to vent the excess.

You should be able to get full RPM well before 30", and the fuel flow is a function of mass air flow, not directly from throttle position. You might have a fuel servo and/or governor issue to investigate.

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