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

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    The Best Entry-Level Pipers

    Longtime Piper pilot and Piper twin owner Kristin Winter discusses the cream of the crop in entry-level Piper aircraft. (Photo: James Lawrence)

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    Short Wing Pipers

    Out of a poor economy came a series of aircraft that were better than expected. (Photo: Peter Lubig)

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    The Piper Navajo

    After initially feeling intimidated by the size of the Navajo, contributing editor Kristin Winter found that it really one of the easiest and most gentle aircraft she had flown. (Photo: Paul Bowen)

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  • "...nothing can replace the skill and confidence you get using spare training time to do weird things."

    - Kevin Garrison

  • "It costs fuel to carry fuel in any airplane..."

    -Thomas Block

  • "All of the PA-28-180/181 aircraft are great airplanes."

    - Kristin Winter

  •   "My happy place is metal and T-shaped and smells like 100 octane"

    - Kevin Garrison


STEVE ELLS replied to the topic 'Turbo induced engine surging' in the forum. 3 hours 1 minute ago

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. 3 hours 54 minutes ago

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


replied to the topic 'Piper Turbo III/IV cowl' in the forum. 4 hours 5 minutes ago


Pics on the way......