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Topic-icon Seneca 2 with Merlyn Black Magic wast gate overboots

  • Stephen Murphy
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6 months 1 week ago #1316

Hello all. Just picked up my 1980 Seneca 2 with Merlyn wast gates. New to turbos so I have some questions about the Merlyns behavior. I just want to make sure they are behaving the way they were designed. I should mention that I have the Pressure Limiter (POP off valve for overboots protection).

My questions are these.
1) Seems these throttles are VERY sensitive and I've never had them anywhere near full open. IS this normal operation or do they turbos need to be adjusted a bit. I have pretty good control of the boost all the way cup to 16K (that's as high as I've gone).
2) What are sings that the Merlyn wast gates are "sticking"? I pulled the RPM back to 2300 and WHAM! one of the engine overboots and the engine were set at 32. One of them "Jumped". Is this a sign of a sticky wast gate? What can I do to ensure they work smoothly? I have heard mouse milk is good but I have no idea where to put it if that is the case.
3) Aslo, any help on climb and cruise setting for your engines. I wold love to hear how people fly their planes, but only then ones that didn't need a top overhaul at 400 hours! LOL. Power cruise setting I'm curious about. I'm thinking the 65% rout to save the engines but I've heard that 75% run right is fine. Any thoughts?

4) What kind of numbers are you getting at cruise, (KTS, TIT, CHT's, EGT)

I have to say, I love this plane but taking some time to get to know her so to speak. Treat her carefully or else she'll end up like a bad girlfriend, high maintenance.

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6 months 1 week ago #1324

Hi,
Mouse Milk is applied to the shaft ends of the turbocharger wastegate butterfly. Just squirt a little on each end of the shaft where it projects out of the housing.
I'm going to try to get Piper Flyer member David McKenna to weigh in on your questions. He flies a Seneca with the Black Magic turbo controllers.

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6 months 1 week ago #1326

Thanks for the response. Being new to the plane I'll take any information I can get my hands on!

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6 months 6 days ago #1329

I have flown my Turbo Arrow IV with a Merlyn for more than 20 years. I believe your Seneca also has Cont TSIO 360's. The sensitivity of the throttle is normal. Below the flight levels you won't need full throttle. At 65% 0r 75% I usually use about 2/3 throttle at 30" @ 2300 for 65% and 34" @ 2300 for 75%. I have had the aircraft up to 20K and still had full power. I'm not sure what the limit of boost is for your Seneca, but my boost limit is 41".

I climb at 75% ROP. At times I climb at 100% when needed as I do not have a limitation at 100% power.

I fly longer flights in cruise lean of peak (LOP). As a graduate of GAMI's Advanced Pilot Seminars, I am a firm believer in LOP operation. CHT's are what I use to monitor my engine operation and I typically operate in the low 300's LOP. Operated LOP properly you can expect lower CHT's, lower internal cylinder pressures, and lower fuel burn. This equates to longer engineering life. I typically run about 50 LOP at 65% HP. Rich of peak I operate at 75% or 100% without reservation. GAMI generally advises to either run LOP or very rich for operation with a turbo charged engines. Please don't take my word for it, Take GAMI's seminar and learn how and why to operate your engines LOP.

I have never experienced the "sticking" you describe so I have no comment. Call Merlyn. They are very helpful on the phone.

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6 months 20 hours ago #1332

I own a Seneca II. I installed the Merlyn waste gates as soon as I bought it. First, there was one reply saying to spray mouse milk on the waste gate butterfly. The Seneca II has a fixed waste gate, there is no butterfly valve. It is just a bypass that allows a certain amount of exhaust gases to bypass the turbo charger. It is manually adjust on the ground. The Merlyn waste gates has an internal bellow and replaces this bypass tube. It senses upper deck pressure and MP to change to amount of bypass gases. It gives a little higher critical alt. The throttles are very sensitive and will take some time getting used to. If you feel you have some sort of problem with the waste gates, Call Merlyn. Suzanne is the owner and will most likely answer and is very knowledgeable. If she can't answer the questions, she will most likely put you in contact with Hugh. I've spoken to him several times and he knows his stuff. I've flow as high at FL210. The only thing I've noticed is I can't get the MP up running 2300RPM when I'm at Altitudes above around 17 or 18k. So I run the engines at 2400RPM and whatever the MP setting is for that ALT, Temp and RPM. I'm also running LOP with GAMI injectors. Usually around 25deg on the lean side. I burn around 20GPH total. Merlyn's phone number is (509) 838-7500. Hope this helps.

Jamie

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6 months 20 hours ago #1333

Also, as a side note, My engines are well over TBO. The previous owner was changing cylinder almost every annual. Also a top OH. He sold it because it was coming up on TBO and didn't want to spend the money. Since I've been flying this plane (2 1/2 years), I've had to replace 1 cylinder. All my compressions are in the 70s. I borescope the cylinders and send out my oil for spectra analysis each oil change. I also use CamGuard as directed. Since using CamGuard, there has been a significant reduction in the metals in the oil. While changing the cylinder I inspected the interior of the engine. All cam lobes and lifter faces are in great shape. These engines will run forever if well taken care of and flown properly and often. The most important is not letting the plane sit too long between flights. I try and fly mine at least one a week for at least an hour or two. This gives enough time to burn off and moisture in the crankcase. Also keeping you cylinder temps low, but not too low. Somewhere around 320F but no higher than 380F. Your plane looks great. I see you also have the Micro VGs too. I have also installed those on mine. Anni Brogan is the person to speak with at Micro AeroDynamics. The Seneca II is a great plane. I love mine. It's a stable platform, and plenty of room. (I'm 6'4" 300# LOL).

Happy Flying,

Jamie

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