Hot Cylinder??

[Iceman]

We have a Mooney with an IO-550G that has a hot cylinder and I was wondering if we should be concerned or not. The hot cylinder according to the JPI is #5 (copilot side in front) and only on climb out (5th to flip over on LOP). The cylinder reads 40-50 degrees higher than all the other cylinders. I was told at Oshkosh that the #2 cylinder is always the hottest on these 550 engines and that the #5 cylinder was giving a false reading because of a lack of airflow around the sensor. They said one way to fix the problem is to cut a hole 2x2 inches right in front of the #5 cylinder in the baffling to help circulate the air around that cylinder.

What should we do? (The baffling is in very good condition with no visible weak areas.)

Thanks

Chris

 

[Ken Ibold]

What other detective work have you done? I presume you've already checked the injector and the sensor. Do you have GAMIs? The "false reading because of lack of airflow around the sensor doesn't seem right, but I'd have to defer to others with more knowledge. I would cut the baffling as a last resort, in any case.

 

[Dave Siciliano]

Chris:

It's great to dig and you should find out. On each plane and engine set up, there seem to be unique remedies. On, my A-36, it was number 4 that was hot. That was an IO-550B. On the P-baron (IO-520) our number 5s were hot until we found a remedy.

Does the hot cylinder temp get over 380? If not, you're well within the limits I follow. If so, then you really need to hook up with someone that does a lot of this and has fixed others. Cutting holes in the front of baffling can alter air flows in other areas. Not always that simple. It can also affect the airworthiness certificate if not properly performed.

Best,

Dave

 

[Len Lanetti]

Chris,

There is a Mooney specific email list for tech issues. You can sign up by boing to

www.mooneypilots.com

Lots of Mooney mechanics monitor the postings. Good luck.

Len

 

[Iceman]

What other detective work have you done? I presume you've already checked the injector and the sensor. Do you have GAMIs? The "false reading because of lack of airflow around the sensor doesn't seem right, but I'd have to defer to others with more knowledge. I would cut the baffling as a last resort, in any case.

No Gamis...performed their test and was below the threshold recommended for using gami's. < .5 gph diff I think.

I also agree that cutting the baffling should be the last resort. At oshkosh we talked to the engineer that designed the 550 (not sure which version). He said that normally number 2 would run the hottest on climbout and the reason number 5 was reading high was there was a dead spot in air movement right at the top of cylinder 5. He continued to say that the rest of cylinder 5 was properly cooled and it should not shorten the life of that cylinder.?. He pointed out that the bonanza has a small hole cut in the baffling that takes care of the problem on their new aircraft.

The strange thing is that the cylinder is one of the last ones to peak and the temps have a close spread which would indicate that the sensor is working correctly.

 

[Iceman]

Does the hot cylinder temp get over 380? If not, you're well within the limits I follow. If so, then you really need to hook up with someone that does a lot of this and has fixed others. Cutting holes in the front of baffling can alter air flows in other areas. Not always that simple. It can also affect the airworthiness certificate if not properly performed.

Best,

Dave

Yeah the temp climbs to ~400 if we keep our airspeed up (120+) up to 425 if we use best climb on a hot day. It is also a pain because when climbing if we try to keep 5 <380 the other cylinders are <340 which is wasting fuel/hurting performance.

 

[Dave Siciliano]

Yeah the temp climbs to ~400 if we keep our airspeed up (120+) up to 425 if we use best climb on a hot day. It is also a pain because when climbing if we try to keep 5 <380 the other cylinders are <340 which is wasting fuel/hurting performance.

Don't give up on it Chris. As a matter of fact, we were told the Baron couldn't climb on a hot day at gross without exceeding 400 plus. Just went to Mexico and back and didn't have that problem. Cruise climb is a help, but if the airflow isn't correct, it won't correct this problem.

Ask your engineer buddy if he's going to guarantee the cylinder to TBO--think you know the answser.

I can recommend BDS and GAMI. Of course, they will normally only work on planes with their kits. Is this a factory baffle set up, or did someone else install it and have the STC? I did find a mod the factory did to the P- Baron on certain models, and it did involve putting a hole in the front baffling, but the factory had diagrams and under their certification authority could perform such mods. Please research it well and go to someone besides Bubba that says he can cut a hole where ever you want it. Make sure a reputable IA is comfortable with signing it off. I have seen cases where folks modified the baffling and moved the problem from one place to another.

Dave