I'm writing a log of my turbo repair here in case it might help some other poor newb. I'm posting a list of references at the bottom.
I have a Piper Saratoga PA-32, with a Lycoming TIO-540-S1AD. It has a very simple turbo setup, with a direct cable interlink between the wastegate and throttle. It doesn't have a density controller or other compensation device. It is a turbo, not turbonormalized, with a max manifold pressure of 36 mmHg.
I have been having an issue of not achieving book performance at altitude, with critical altitude far lower than book value, 16,000 feet. I do get maximum manifold pressure on takeoff at sea level, 36 mmHg. Per Lycoming's service notes, some TIO-540 engines are supposed to hit maximum manifold pressure at sea level with the throttle wide open, and some models will hit it with much less than wide open throttle (Lycoming S.I. 1257E). The S1AD is the latter, and I was hitting the maximum manifold pressure with less than full throttle at sea level, which is the expected behavior.
I read everything I could find on the issue, including all the below documents. I found the Ramair troubleshooting guide and associated links the most helpful.
Fortunately, my system is very simple, so I figured there are only a few things that could cause the problem. Here's a list and the appropriate check for the problem:
Boost pressure leaking out the induction piping, or exhaust energy leaking out the exhaust manifold.
Use a shop vac to pressurize the system and spray everything with soapy water and look for bubbles which are leaks.
(From the Ramair Leak Check Guide)
Wastegate butterfly eroded
Inspect the wastegate butterfly
(From the Piper Maintenance Manual)
Wastegate butterfly not closing all the way
Inspect the wastegate butterfly
(From the Piper Maintenance Manual, or Lycoming SI 1431)
(of note, the Piper manual has you leave the wastegate with a bit more gap than the Lycoming procedure, which just has you adjust it to close against the factory stop screw)
Turbo worn out
Inspect the turbo blade clearance from the housing
(Lycoming S.I. 313B)
The document says, "Extensive tests conducted in the field and in our experimental laboratory have indicated that the over-all condition of the turbocharger can be estimated by the clearance at the turbine blade tip."
I'm not sure if this document applies to my turbo. Lycoming uses different model numbers, but another document specific to my engine directed me to use this guide. I would have Lycoming confirm things before relying on the measurement, but the blade clearance as a gauge of health is a nice idea.
Intake flow restriction
Use the alternate air intake to see if the problem improves. Check the air filter.
There are a lot of other possible causes if your setup has a compensation device like a density controller, slope controller, variable pressure controller, etc. These devices add a lot of additional things to check, which are covered pretty well in the Lycoming troubleshooting guide.
As for my problem, I changed my filter, checked that the butterfly valve was opening all the way, and then moved on to leak checking the induction piping. I found I had pretty significant leaks in the induction piping, both at a loose hose clamp on the duct at the turbo output, as well as leaking around a bypass door. This system has a little door held shut by a magnet on the high pressure side that can pull open with excessive vacuum in case of occlusion of the turbo. The magnet is mounted on a rubber plate that is adjustable and adjusting the magnet further away from the door allowed it to pull tighter shut, fixing the leak. Likely, that door needs a new gasket.
Flight testing it after fixing the leaks yielded much more boost on takeoff. I had to use a much lower throttle setting to achieve maximum MP, and much better boost at altitude. The fix cost me paying my A&P to tinker with me, and an afternoon.
Ramair Troubleshooting Guide
https://www.ramaircraft.com/troubleshooting
Ramair Induction and Exhaust Leak Checks
https://www.ramaircraft.com/manifoldpressure
Lycoming Troubleshooting guide
https://www.victor-aviation.com/pdf...chnicalPublications-Troubleshooting-Guide.pdf
Lycoming Service Bulletin 313B: Periodic Turbocharger Inspection and Maintenance
Lycoming Service Instruction 1431: Adjustment of Fuel Metering and Turbocharger Linkage
Lycoming Service Instruction 1257E: Horsepower, Manifold Pressure and RPM Values
https://bsd-box.net/~mikeg/N8031W/SB_SL/VSP_0075.pdf
I have a Piper Saratoga PA-32, with a Lycoming TIO-540-S1AD. It has a very simple turbo setup, with a direct cable interlink between the wastegate and throttle. It doesn't have a density controller or other compensation device. It is a turbo, not turbonormalized, with a max manifold pressure of 36 mmHg.
I have been having an issue of not achieving book performance at altitude, with critical altitude far lower than book value, 16,000 feet. I do get maximum manifold pressure on takeoff at sea level, 36 mmHg. Per Lycoming's service notes, some TIO-540 engines are supposed to hit maximum manifold pressure at sea level with the throttle wide open, and some models will hit it with much less than wide open throttle (Lycoming S.I. 1257E). The S1AD is the latter, and I was hitting the maximum manifold pressure with less than full throttle at sea level, which is the expected behavior.
I read everything I could find on the issue, including all the below documents. I found the Ramair troubleshooting guide and associated links the most helpful.
Fortunately, my system is very simple, so I figured there are only a few things that could cause the problem. Here's a list and the appropriate check for the problem:
Boost pressure leaking out the induction piping, or exhaust energy leaking out the exhaust manifold.
Use a shop vac to pressurize the system and spray everything with soapy water and look for bubbles which are leaks.
(From the Ramair Leak Check Guide)
Wastegate butterfly eroded
Inspect the wastegate butterfly
(From the Piper Maintenance Manual)
Wastegate butterfly not closing all the way
Inspect the wastegate butterfly
(From the Piper Maintenance Manual, or Lycoming SI 1431)
(of note, the Piper manual has you leave the wastegate with a bit more gap than the Lycoming procedure, which just has you adjust it to close against the factory stop screw)
Turbo worn out
Inspect the turbo blade clearance from the housing
(Lycoming S.I. 313B)
The document says, "Extensive tests conducted in the field and in our experimental laboratory have indicated that the over-all condition of the turbocharger can be estimated by the clearance at the turbine blade tip."
I'm not sure if this document applies to my turbo. Lycoming uses different model numbers, but another document specific to my engine directed me to use this guide. I would have Lycoming confirm things before relying on the measurement, but the blade clearance as a gauge of health is a nice idea.
Intake flow restriction
Use the alternate air intake to see if the problem improves. Check the air filter.
There are a lot of other possible causes if your setup has a compensation device like a density controller, slope controller, variable pressure controller, etc. These devices add a lot of additional things to check, which are covered pretty well in the Lycoming troubleshooting guide.
As for my problem, I changed my filter, checked that the butterfly valve was opening all the way, and then moved on to leak checking the induction piping. I found I had pretty significant leaks in the induction piping, both at a loose hose clamp on the duct at the turbo output, as well as leaking around a bypass door. This system has a little door held shut by a magnet on the high pressure side that can pull open with excessive vacuum in case of occlusion of the turbo. The magnet is mounted on a rubber plate that is adjustable and adjusting the magnet further away from the door allowed it to pull tighter shut, fixing the leak. Likely, that door needs a new gasket.
Flight testing it after fixing the leaks yielded much more boost on takeoff. I had to use a much lower throttle setting to achieve maximum MP, and much better boost at altitude. The fix cost me paying my A&P to tinker with me, and an afternoon.
Ramair Troubleshooting Guide
https://www.ramaircraft.com/troubleshooting
Ramair Induction and Exhaust Leak Checks
https://www.ramaircraft.com/manifoldpressure
Lycoming Troubleshooting guide
https://www.victor-aviation.com/pdf...chnicalPublications-Troubleshooting-Guide.pdf
Lycoming Service Bulletin 313B: Periodic Turbocharger Inspection and Maintenance
Lycoming Service Instruction 1431: Adjustment of Fuel Metering and Turbocharger Linkage
Lycoming Service Instruction 1257E: Horsepower, Manifold Pressure and RPM Values
https://bsd-box.net/~mikeg/N8031W/SB_SL/VSP_0075.pdf
