Piper Flyer Association - Technical Know-how, Serious Fun read more

Topic-icon Turbo induced engine surging

  • David Crass
  • David Crass's Avatar Topic Author
  • Offline
  • Subscriber
  • Subscriber
More
1 week 3 days ago #2086

I am a new owner of a 1999 Piper Saratoga II TC. I'm trying to solve a problem with the engine surging. By surging, I mean that the MP will start oscillating 3-4" after smooth, gradual throttle changes. I don't recall that the RPM's were changing. The engine has about 100 hours since overhaul and the Tempest massive electrode plugs were installed about 9 hours ago. The turbocharger wastegate (which was not replaced at engine overhaul) was found to be sticking after soaking in "Mouse Milk" so the wastegate and the actuator were replaced. Induction and exhaust systems were checked for leaks, none found. The engine continued to surge intermittently on the next flight so the turbocharger controller was replaced and all lines checked for condition. MP and Upper Deck lines were clean and dry. After installing the new controller, the engine will still surge during the ground run by my A&P . This aircraft has the TIO-540-AH1A engine and as I understand it, is configured such that there is not a connection between the fuel servo and the Turbo system which is somewhat unique to this series engine. My A&P has talked to two different technicians at Lycoming who were no help with troubleshooting the surging. We plan to do another test flight in the next few days and we will record MP/RPM combinations that induce surging, and verify that RPMs are not changing during a surge event. Any guidance would be greatly appreciated!
Thanks in advance!
David

Please Log in to join the conversation.

More
6 days 8 hours ago #2091

Hi David;
I apologize for not replying sooner. I'm digging for answers--will query some experts. I'll get back to you.
Steve

Please Log in to join the conversation.

More
6 days 7 hours ago #2092

Do you get fluctuations in the TIT or any of the EGT indications? If those are rock solid, then the issue is likely down stream of the turbo, i.e. on the induction side and not the exhaust side. Do you have an engine monitor that records?

Please Log in to join the conversation.

  • David Crass
  • David Crass's Avatar Topic Author
  • Offline
  • Subscriber
  • Subscriber
More
5 days 22 hours ago #2093

TIT is steady. I don't have an engine monitor so I don't know what EGT's are doing. I'm on the calendar at the avionics shop next month for a major upgrade which will include a JPI EDM-900, sure wish it was already installed! I've been in touch with Paul New, Tennessee Aircraft Services (awesome guy by the way, did a major repair on my Cardinal RG). He's familiar with slope controllers that are on many of the Cessna P210s. My AH1A series TIO-540 has a slope controller. Paul pointed out that when increasing power on a turbocharged aircraft always lead with mixture, then prop, then throttle in that order. I know for sure the first time I experienced surging I did not enrichen the mixture before I advance the throttle. Paul advised that would cause a very lean mixture which could contribute to the surging. In reflection, the RPMs were likely oscillating some as well, I just don't remember. My A&P did observe RPM oscillation when he induced surging on the ground run by abrupt movements of the throttle. Absent of an engine analyzer, I've mounted a GoPro to have a record of the gauges for the next test flight. Unfortunately, we were unable to fly today. Thanks for the input, I'll follow up with an update after the test flight next week.

Please Log in to join the conversation.

More
3 hours 3 minutes ago #2102

Hi David;
I've got a couple of suggestions.
First, it's possible that there's a restriction of some sort in the air delivery system--either the induction filter is clogged or there's something in the ducting between the air filter and the turbocharger. That's a pretty easy check.

There may also be a leak in your induction system. To test for leaks, first disconnect the hoses to the controller and plug the holes in the induction system. Then pressurize the system with about 10 psi, and spray soapy water along the system. Any place where the soapy water is blown away is a leak; bubbles are OK.

One expert recommended that you disconnect the upper deck and manifold pressure hoses and make sure they are clean. Carbon can clog the lines.

As I re read your post, it appears as if you have already gone down this list.

It's also possible that the bearing in the center section of the turbine are coked up which will prevent the turbine from spinning at rated speed or be slow to spool up. That wheel should spin freely. You should be able to feel any drag. The following is from the service manual:
TURBOCHARGER DECOKING.
Mouse Milk lubricant may be used for decoking the turbine and compressor drive shaft by the following
procedure:
1. Disconnect the oil inlet and outlet lines from the turbocharger and allow all oil to drain.
2. Cap the oil outlet port on the turbocharger.
3. Pour the Mouse Milk into the oil inlet port of the turbocharger and allow the unit to soak overnight.
4. Drain all Mouse Milk from the turbocharger and flush the unit with engine oil.
5. Prime the turbocharger in accordance with Turbocharger Lubrication System Priming.

I believe the turbo (turbine) wheel is not able to spin up fast enough. The slope controller is a good controller because is manages the speed of the turbo in relation to a differential between upper deck pressure and manifold pressure. The upper deck pressure is the pressure out of the turbine. The manifold pressure is the pressure downstream of the throttle butterfly.

This controller varies the speed of the turbine wheel (by controlling the opening and closing of the wastegate) so that approximately 2 inches of manifold pressure above what the throttle position dictates is available. That's a good thing.
Here's a description:
Sloped Controller

The sloped controller is designed to maintain the rated compressor discharge pressure at wide-open throttle and to reduce this pressure at part throttle settings. [Figure 3-22] A diaphragm, coupled with a spring-supported bellows for absolute pressure reference, is exposed to deck pressure and intake manifold pressure through ports located before and after the throttle, respectively. This arrangement constantly monitors deck pressure and the pressure differential between the deck and manifold pressure due to a partially closed throttle. If either deck pressure or throttle differential pressure rises, the controller poppet opens and decreases turbocharger discharge (deck) pressure. The sloped controller is more sensitive to the throttle differential pressure than to deck pressure, thereby accomplishing deck pressure reduction as the throttle is closed.

Since you've done everything except check for restrictions in the intake sys/air filter. It sound like it's time to attempt to adjust the controller.



The controller has an adjustment screw in the bottom of the controller. I believe turning it in will close the wastegate at a lower differential, but am not sure. Any adjustments must be very slight, before running to determine whether the adjustment was effective.

Good luck,

Please let me know what you find.

Please Log in to join the conversation.

Time to create page: 0.250 seconds