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STEVE ELLS replied to the topic 'Turbo induced engine surging' in the forum. 14 hours 33 minutes ago

I do not know if there are restrictions in the oil lines to the turbo and wastegate.
There is a requirement to put a restrictor at the engine in the oil pressure line to slow the loss of engine oil if that line fails.
I suppose it makes sense to have on in all the engine oil lines but I believe that since the oil lines from the engine to the controller and from the controller to the wastegate are designed to provide sufficient flow to cool the turbine center bearing, so my guess is that there isn't one in those lines.
I just talked with Main Turbo and was assured that there are no restrictions in the oil lines of the turbo system. There is a check valve above the turbo that is designed to prevent oil from puddling in the center section (then leaking out past the seals into the compressor and turbine wheels) when the engine is off.


STEVE ELLS replied to the topic 'Turbo induced engine surging' in the forum. 15 hours 7 minutes ago

Sounds like a good plan.
Please let me know how things turn out.


David Crass replied to the topic 'Turbo induced engine surging' in the forum. 15 hours 28 minutes ago

My A&P/IA wanted me to check with you and ask if either of the oil lines on controller are supposed to be orifice fittings. Lycoming tech mentioned it to him and it's mentioned in the trouble shooting guide but the Lycoming tech couldn't confirm or give any guidance.


David Crass replied to the topic 'Turbo induced engine surging' in the forum. yesterday

Thanks for the recommendations. We've checked for restrictions in the upper deck and manifold pressure lines, they were clean and clear. I'll work with my A&P to pull the induction filter and check it and check for any other intake restrictions. We'll also check for Induction leaks with air pressure and soap. It's now making sense to me that there is likely coking in the center section of the turbine. I did a ground run Saturday and another one today. Before advancing the throttle beyond 1200 RPM I allowed the oil temperature to reach 100 degrees. Both times I could achieve 38" MP on the initial runup but as I continued additional runups, I was unable to achieve 38". On the subsequent runups, oil temperature continued to increase up to a maximum of 180 degrees and maximum MP decreased to 37", then 36" then 35.5". These were all done with a gradual throttle increases such that surging did not occur.

Is it possible that as the turbine temperate increases to normal operating temperature and coking is present, the tolerance is reduced and therefore the turbine is unable to achieve full rpms which results in the observed reduced maximum MP? We'll perform the decoking procedure and I'll let you know the result. I appreciate the insights!


STEVE ELLS replied to the topic 'Turbo induced engine surging' in the forum. yesterday

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:
Mouse Milk lubricant may be used for decoking the turbine and compressor drive shaft by the following
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.


STEVE ELLS replied to the topic 'Looking for Dynon Pocket Panel' in the forum. yesterday

Hi Michael
The D-3 pocket panel is sold new for $879 at many aviation vendors such as Aircraft Spruce and Specialty


Robert Marks replied to the topic 'Piper Turbo III/IV cowl' in the forum. yesterday


Pics on the way......



BOB HIDLEY replied to the topic 'Piper Turbo III/IV cowl' in the forum. yesterday


I'm planning on repainting my Turbo Arrow III and am really impressed with the paint scheme on your plane that I saw in Piper Flyer. Could you email a couple pictures and include the wing tips which don't show in the magazine?

Bob Hidley


Robert Marks replied to the topic 'Old paint and interior going bye-bye' in the forum. yesterday

Wow! The exterior shots made me hungry for a baked potato. I'm just starting a new panel on my Arrow IV. Make sure we see the after shots too!



Michael Harris created a new topic ' Looking for Dynon Pocket Panel' in the forum. 2 days ago

Looking for a Dynon Pocket Panel for our Pa-24. Would like a complete unit with mounting/power cord. Contact mike
text 281-543-2512.


Harley Kleemann created a new topic ' Old paint and interior going bye-bye' in the forum. 2 days ago

With lots more left to do...


STEVE ELLS replied to the topic 'Removing the overhead trim handle on at 1967 PA-28-140' in the forum. 3 days ago

Yes, I do.
The trim handle is just like the door handle in that a spring clip is inserted into a slot in the handle. The clip holds the handle in position on the splined part of the door or trim shaft. Actually it prevent the handle from sliding off the splined shaft.
I use a small T shaped pick to pull the spring clip out of the handle. You will have to push up on the plastic around the trim handle to see and get at the clip. Often times you won't be able to push the plastic far enough up to see the clip, but it can be viewed using a small mirror and flashlight.
Hook the pick under the clip--which is roughly U shaped and pull. It's a spring so it may "jump" once you pull it clear of the handle.
To get a better idea of what these clips look like go to your local auto parts store and ask for some door handle clips.
To re install, there are two ways. You can install the clip in the handle and apply enough pressure to spread the clip over the tapered end fot the trim wheel shaft, or you can put the handle up into position and by using a small pair of needle nosed pliers push the clip into position.
Happy Flying


Mark White shared 2 photos in the Mark White's photos album 5 days ago

Smaller than my old 260 Six but good to be back in the ownership community.

Photos are being loaded.
Doug Linville shared a photo. 5 days ago

Doug Linville shared a photo. 5 days ago

Well of course the one you own:)


David Crass replied to the topic 'Turbo induced engine surging' in the forum. 7 days ago

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.


Kristin Winter replied to the topic 'Turbo induced engine surging' in the forum. 7 days ago

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?


STEVE ELLS replied to the topic 'Turbo induced engine surging' in the forum. 7 days ago

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


STEVE ELLS replied to the topic 'Change a Passenger Reading Lightbulb' in the forum. 1 week ago

Good, thanks for telling me.