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Old 07-07-2009, 08:10 PM
eshepardson eshepardson is offline
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Default Lycoming IO 390 engine and Power Flow

With the recent STC for the Lycoming IO-390 for the Cardinal, any possibilities of your PF unit working with this powerplant? Am looking at the 390 for a replacement of a near TBO engine soon, and also want to install the PF at the same time, if not sooner.

Regards,

Eric Shepardson
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Old 07-18-2009, 12:39 PM
dtilman dtilman is offline
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Default Re: Latest Update

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Originally Posted by eshepardson View Post
With the recent STC for the Lycoming IO-390 for the Cardinal, any possibilities of your PF unit working with this powerplant? Am looking at the 390 for a replacement of a near TBO engine soon, and also want to install the PF at the same time, if not sooner.
The Power Flow Exhaust for the C177RG should fit and offer similar boosts in performance on the IO390 as it does for the IO360. We personally haven't done such an installation just yet, but we understand at least one of our deposit holders has the IO-390 engine on order.

From a Certification (a/k/a "Legal") stand point, it would be up to the installing IA (A & P with Inspection Authorization) to determine if the STC for the Lycoming engine and the STC for the Power Flow exhaust are ok together.

This is because most STCs modify the original configuration of the aircraft - as it was type certified. In the 30-40 years since that occurred, owners may have applied many different modifications to their aircraft. As it is impossible to check for every variable, most modifying companies (such as Power Flow and Lycoming) will do all of their required certification testing and evaluation using the basic type certified configuration. This covers the most bases and and keeps the costs as low as possible.

If the owner comes along later and adds a very simple modification, such as an exhaust fairing, the person signing off the aircraft installation can make a judgement call based upon their experience and knowledge as to if any conflict exists. Most people agree that as long as the exhaust isn't contacting the fairing, no problem exists and it will be signed off.

The same is technically true for the IO-390 engine, although it is arguably a little more involved than just adding an exhaust fairing.

Bottom line: If your IA is comfortable and will sign off the installation of the engine and PFS exhaust, it should be ok and approved because they are taking the responsibility for it.

Thank you for your question.
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Old 06-14-2011, 05:42 PM
RG_driver RG_driver is offline
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Default Re: Lycoming IO 390 engine and Power Flow

FWIW, my IA and I discussed the potential issues at length. He did sign off on a Power Flow exhaust on an IO-390. There have been no issues with the combination.
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Old 06-14-2011, 05:48 PM
dtilman dtilman is offline
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Default Re: Lycoming IO 390 engine and Power Flow

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Originally Posted by RG_driver View Post
FWIW, my IA and I discussed the potential issues at length. He did sign off on a Power Flow exhaust on an IO-390. There have been no issues with the combination.
Excellent! Did you fly with the exhaust before you changed the engine? If so - Can you comment on what kind of performance gains you saw with the engine change and then the Power Flow or was it all at once?

Darren Tilman
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Old 06-15-2011, 01:24 PM
RG_driver RG_driver is offline
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Default Re: Lycoming IO 390 engine and Power Flow

Unfortunately, no. I had already purchased the Power Flow and asked my IA to install it at the annual. He found a cracked head at annual, and on further teardown there were other signs of impending failure. The STC for the IO-390 in the Cardinal RG had just come out. Lycoming made me a great offer on a zero-time rebuild of the IO-390. I think my bird was the first in the fleet to get the STC'd IO-390, certainly the first with the IO-390 + Power Flow.

To top it off he discovered the source of a long-standing rigging problem and re-rigged the airplane, so there were 3 significant changes at the same annual. Not my plan, but that's life.

So I can't give meaningful before and after numbers. I can say that the airplane climbs much faster. I've been flying this airplane for 18 years and the performance is markedly improved. It's fairly routine to maintain >1000 FPM at cruise climb airspeeds with full tanks and me flying alone.

Cruise is also better, I used to plan on cruise of 137 knots at 2400 RPM and full throttle. The tuned induction system on the IO-390 seems to work well, I see manifold pressures at altitude that I never saw with the IO-360. I've been keeping the power high during break-in but I have to back it off in bumpy conditions to stay below the top of the green arc at 142 knots.

Once I have some more time on the engine I'll take it higher and try to get some decent cruise and fuel burn numbers; for now I'm staying low and above 72% power whenever I can.

I'm very pleased with the combination and would recommend it for any RG. My IA called the Power Flow the single best performance enhancement I could make; he was right. The IO-390 is a great improvement over the IO-360, more than the 10 HP difference suggests.
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Old 09-03-2013, 09:47 AM
RG_driver RG_driver is offline
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Default Re: Lycoming IO 390 engine and Power Flow

Several pilots have emailed me about this; here is my latest response.

I've had no problems at all. Climb is much better.

The plane was re-rigged at the same time I installed the IO-390 +Powerflow, so I can't be sure how much performance change is due to the power. Now I always cruise at 142 kts indicated - top of the green - and generally have to back off from 24x24 to stay there. I used to flight plan 137 kts true, less indicated, and often saw a bit less on warm days. So the plane is definitely faster but part of that is not flying in a crab.

The IO-390 has a tuned induction system, and the powerflow gives tuned exhaust. I don't know if it is better induction or both, but I can hold 24" MP to several thousand feet; much better than in the IO-360.

The ignition is much better and it always starts on the 2nd turn. I'd recommend replacing the heavy aluminum starter cables with same-gauge copper, the starter seems to pull more amps. Aluminum corrodes over several decades anyway. This is much easier to do when the engine is off the airframe.

The powerflow requires a prop balance. Do this in flight! We discovered that a good balance on the ground gives rather poor in-flight numbers. I'm guessing that the support of the nosewheel changes the vibration mode.

It is a bit tedious; I would go to the field every decent morning over 2 weeks, then orbit the field at 2000' AGL and capture a few readings while holding 25x25 power for break-in. The mechanic would look at the results and change the weights, It took about 10 flights to get it dialed in; we didn't understand why, but eventually found a good balance.

The IO-390 wants 100% power wide-open throttle at low altitude, for 30-60 minutes early in the break-in. I waited for a glass-smooth day and flew 30 minutes out and back at over 160 kts indicated. A bit tense for a pilot who rarely goes outside the green arc.

Good luck! If your IA/A&P is hesitant, there are no problems in my experience. It's up to the IA/A&P to determine if two STCs are compatible; no FAA approval or additional forms required. My A&P discussed every possible issue we could think of; nothing serious, nothing unexpected happened. You might want to talk this over before committing to the purchase. I've corresponded with others who had trouble with timid mechanics.
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