Why is all this oil all over the belly??

cjensen · Post by **cjensen** » Wed Oct 18, 2006 2:24 pm

Well, that would be because you overheated the piston rings, they all cracked, and your compression in that cylinder is 0/80.

That's what had to tell one of our Malibu customers this week. You can see in the pic that the rings are in pieces, the top of the piston is coated with oil and carbon deposits, the exhaust valve looked the same. This guy didn't take care of his expensive engine, and now has to pay the price.

Sometimes (well, most of the time!) I just love my job! I get to watch engines being torn down and rebuilt on a daily basis, learn from watching, and I also learn valuable lessons from the expensive mistakes of others...

captain_john · Post by **captain_john** » Wed Oct 18, 2006 2:58 pm

Chad, what year was this one? Was it one of the early Conti's that were run LOP?

It seems to me that that practice lead ALOT of Malibu engines to an early grave.

There was something in AOPA Pilot about it last month, I think.

CJ

Post by **Spike** » Wed Oct 18, 2006 3:02 pm

So what did this owner do Chad that caused this damage?

- John

cjensen · Post by **cjensen** » Wed Oct 18, 2006 3:31 pm

This one is a Lyco TSIO-540 powered 1995 Mirage.

We're not exactly sure what caused this, particularly because it was only two cylinders, both on the rear left side. We did top overhaul all three on the left side because #2 was showing signs of the damage that #4 and #6 suffered, with #6 being the worst. The right side was not checked due to time constraints, and the owner wanting his airplane back ASAP.

It will be back for the right side before too long. The compressions were ok on the right side, not great, but acceptable.

However, the owner is well known to treat his airplanes like s#$%, and most likely was caused by his mis-management of the mixture, running it LLLLEEEEEEEEEEAAAAAAANNNNNNNN of peak. Probably a detonation issue, but we're still trying to figure this one out...

cjensen · Post by **cjensen** » Wed Oct 18, 2006 3:33 pm

Oh, these cylinders have just under 600 hours on them. That's about the amount of time turbo Conti 520 and 550 cylinders go, but the big turbo Lyc's usually reach at least 1000 befor they need jugs pulled.

Post by **Spike** » Wed Oct 18, 2006 3:38 pm

Lean of peak 'eh? Im not sure I buy it. Lean of Peak operations and detonation dont really go together from what I understand. Does he have matched flow injectors?

cjensen · Post by **cjensen** » Wed Oct 18, 2006 3:45 pm

Spike wrote:Lean of peak 'eh? Im not sure I buy it. Lean of Peak operations and detonation dont really go together from what I understand. Does he have matched flow injectors?

It's unlikely, but possible. Here's an excerpt straight from a Lycoming bulliten-

With a normally aspirated engine, if leaning is initiated at 75% power and leaning past peak EGT is accomplished, it is unlikely (but not impossible) to induce detonation by opening the throttle to regain power. In our initial examples, both Lindberg and Conrad were operation engines that had little potential for detonation based on the fuel they were using. A highly turbocharged engine is another matter. Employing this same technique will put the engine into a narrow operating envelope where detonation is possible if the mixture is richened slightly.

If you're talking about Gamijectors, no, this airplane does not have them. I don't believe in those anyway. It's a gimmick if you ask me...

Snap · Post by **Snap** » Thu Oct 19, 2006 2:03 am

Why are they a gimmick? I thought they were built on solid data and testing?

cjensen · Post by **cjensen** » Thu Oct 19, 2006 8:55 am

Well, this is my opinion, and only that...I have yet to see ANY Gami installation in ANY Malibu/210/Bonanza/etc. that has truly worked. We have two or three Malibu's with them, and the guys are saving fuel for sure, but they put cylinders on their airplanes every 200-400 hours!!

Over the course of that amount of time, are you saving enough in gas to justify the cost of a set of cylinders??? I think not. I think they do distribute the fuel evenly, but it's causing premature wear of the engine when the guys are leaning back to 13-14gph. Malibu's should burn no less than 19 gph at 65% cruise, 21 gph at 75%, and 23 gph at 80%. Gami's will bring the burn back, but it's detrimental.

Post by **Spike** » Thu Oct 19, 2006 2:47 pm

All Gamis do is even out the fuel distribution, so that all cylinders peak at the same time. Nothing more. If cylinders are being destroyed it is not the fault of the injectors. It is the fault of the person flying the plane. LOP is not an enemy, it is a tool to manage heat and economize.

cjensen · Post by **cjensen** » Thu Oct 19, 2006 2:56 pm

Spike wrote:All Gamis do is even out the fuel distribution, so that all cylinders peak at the same time. Nothing more. If cylinders are being destroyed it is not the fault of the injectors. It is the fault of the person flying the plane. LOP is not an enemy, it is a tool to manage heat and economize.

Exactly. People (not all, mind you) THINK these things allow you to run as far as you can LOP to get the fuel burn down. I'm not faulting injectors... This was purely operator error. They get this error from thinking the Gami's allow this. The problem is that since each cylinder is an individual, getting them all to peak at the same time, may not be the best for each one.