These days, when youre shopping for an engine overhaul, youre really shopping for cylinders. All the rest of the stuff that goes into an engine, the crankshaft, the cam, the gaskets and the mags are surely important but when the airplane goes into annual every year, its the cylinders that get the most scrutiny forward of the firewall.
Overhaul shops offer their customers guidance on cylinder choice but from our reader mail, we sense that many owners consider picking the right jugs to be a shot in the dark. They like the idea of a factory engine but worry that the cylinders wont last, especially on Continental engines.
How about Superior Millenniums? Are they really as good as some owners claim? Are ECIs line of attractively priced cylinders a good bet? Whats an owner to do?
We think the best way to answer these questions is to ask other owners about their experiences with cylinders and thats what we recently did. As part of our ongoing research on cylinders, we queried Aviation Consumer readers about their experiences with cylinders on relatively recent overhauls. We heard from owners of 249 aircraft-not 249 owners, since some own more than one airplane. We e-mailed owners a questionnaire and also posted it on the Aviation Consumer Web site.
The executive summary: the level of customer satisfaction with cylinder quality in general is, to put it generously, underwhelming. None of the companies making cylinders seem to be driving the quality control ball over the fences, although ECI comes close. ECI and Superior lead the customer satisfaction race, with Lycoming behind and Continental a dismal fourth, according to our survey.
What We Did
Our impressions of cylinder quality are formed by e-mails and letters that trickle into the office; far more of these are acidic complaints than love letters to the cylinder makers. To balance the equation, we published a 12-question survey on our Web site and made note of this on our online sister publication, www.avweb.com.
We asked readers what kinds of airplanes they fly and how many hours a year, when they bought the last overhaul, what cylinders it had and how those cylinders have fared over the course of the long march-at least one hopes it will be long-to TBO and beyond. When additional detail was needed, we contacted the readers by e-mail or telephone. We also did some phone research with engine shops and, of course, the manufacturers.
We sorted the survey responses by major manufacturers and well provide a detailed section characterizing reader reports on each brand and type of cylinder.
Were most interested in this bottom-line question: having bought your cylinders in the first place, would you buy the same brand again? The calendar age of the surveyed overhauls varies but predominantly, they were done after 1998 .
Engine Components, Inc., a long-established San Antonio parts and overhaul house, hasnt taken the onslaught of intense competition on cylinders lying down. Even as the factories have pumped new jugs into the market at reduced prices, ECI has expanded its cylinder line, most recently with the new Titans for large displacement engines.
Although ECI has had its share of quality biffs including cracking cylinders, casting porosity issues and the heat treating foul-ups we described in the March, 2004 issue of Aviation Consumer, the cylinders get high marks from owners and some shops. One shop we spoke to loves them, another swears by Continentals products.
We heard from 25 owners flying with new ECI cylinders of various types, plus 11 more using Cermi-Nil-treated overhauled cylinders. The Id-buy-again approval rating is an admirable 80 percent, an impressive achievement in the world of cylinder marketing. Although we think cylinder quality should be better than it is, we also think any approval rating in the mid-70s and higher is a home run.
For a jug-to-jug comparison by engine type, we examined how the ECI cylinders fared on large displacement Continental engines, specifically the O-520 series. Seven of the owners who replied had variants of this engine on aircraft ranging from Cessna 210s to cabin class twin Cessnas.
Six of the seven told us they were happy with the ECIs and one Cessna 414 owner described them as wonderful, an adjective we dont often hear in the same sentence with cylinder.
While other manufacturers have stuck to the basics in building cylinders, ECI has pioneered overhaul and metal treatment methods. Some 15 years ago, it marketed a process called CermiCrome, a surface anti-wear treatment that turned out to be a bust. While some owners got acceptable service from CermiCrome, many more experienced a premature slide into low compression, erratic oil consumption and oil-fouled spark plugs.
In 1997, ECI yanked CermiCrome off the market and began offering a new process called CermiNil, a variant of a process called Nikisil developed in Europe and used with some success in high-performance cars. CermiNil involves plating the bore with nickel and silica and although its more expensive than traditional chrome plating, its also more environmentally friendly.
Obviously, owners considering the CermiNil treatment recalled the CermiCrome experiment and many wonder how CermiNil would hold up. According to our survey, owners are happy if not enthusiastic with CermiNil. Of 11 owners who said they had CermiNil cylinder, nine (81 percent) said they would recommend them to a friend. Not bad.
On the other hand, one owner who had chrome cylinders on one engine of his Cessna 310 and CermiNil on the other said that although both engines remained serviceable, compressions on the chrome cylinders were stronger.
Alongside ECI, Superior Air Parts has come to play a significant role in the new cylinder business. Unlike ECI, Superior offers only new cylinders and its product line is currently more limited than ECIs, when overhauled jugs are thrown into the mix.
Based on positive reader feedback, we have consistently recommended Millennium cylinders as a reliable choice, if not the best-value choice for the typical overhaul. Sometimes its more cost effective to overhaul a first-run cylinder, knowing full well that the quality may not match that of a new Millennium or Lycoming jug. Our survey seems to suggest that this is still good advice.
Forty-three owners reported overhauls with Millennium cylinders and of that total, 32 or 74 percent said theyd go with Millenniums again if given the choice. Again, thats high praise but thats not to say theres no rumbling in the ranks of Millennium owners, even from some who say theyre satisfied.
One Cessna 182 owner told us he encountered soft compressions in his Millenniums at 650 hours. The other cylinders on the market have all had problems, he complained, but I would probably not choose Millenniums again and would try ECI instead. I definitely would not use Continental cylinders, given the quality problems they have had since the early 1990s. Shops and some owners have complaints about stingy warranty coverage, something Superior says its improving.
Based on this survey and on ongoing reports from the field, our view is that Millenniums are still a good choice and although some owners have encountered the same premature wear problems that owners of Continental cylinders report, these arent nearly as widespread.
As has Continental, Lycoming has been aggressively invading the new cylinder market for more than a decade, rolling back prices on new cylinders and offering competitive deals on factory overhauls.
These efforts have proven successful but in the process, there have been stumbles, including the massive crankshaft fiasco of 2002-2003.Even as it labored to shake off the stench of the crank recall, Lycoming never let up on its aggressive ad campaign touting high-quality, reliable parts at competitive prices.
Has the company delivered? With regard to factory-0new cylinders, we would offer a lukewarm yes. Lycoming seems to generate few complaints about cylinders that dont last but we found customers werent bubbling over with enthusiasm for new Lycoming cylinders.
We heard from 21 owners who bought new Lycoming cylinders recently, for engines of all sizes. Some of these cylinders were installed on field overhauls, some on factory overhauls. Of the total, 13 or 62 percent of the owners say they would buy Lycoming cylinders again.
More telling, in our view, is that of the five who said they wouldnt buy Lycs again or who werent sure, the responses were fair-to-middling negatives, not the shrill, no $%^^%$ chance that buyers of other cylinders-gone-wrong seemed to feel.
Digging into the survey comments, we didnt find much in the way of serious complaints, nor did we find the kind of premature wear patterns that seem to dog Continental owners. Although we didnt uncover complaints about warranty issues, some owners feel Lycoming should do a better job of answering phone calls and letters to the factory. We agree. We find Lycoming difficult to deal with at times.
Companies whose products arent viewed favorably in surveys such as this occasionally complain that open-ended queries tend to attract only those who arent happy with the products. The happy customers never contact us.
While theres some truth to this, we hasten to note that this limitation applies equally to all companies so if theres a problem out there, an open-ended survey will find it.
And, in our view, Continental continues to have problems with its cylinder quality and many owners who buy them continue to be dissatisfied with their durability. Hardly a month goes by that we dont hear a complaint about Continental cylinders and we think our current survey plumbs the depths of the problem.
We heard from 85 buyers of new Continental cylinders, more than from any other single brand or type. Of that total, an alarming 56 or 66 percent told us they wouldnt buy Continental cylinders again, a customer satisfaction level thats nearly the diametric opposite of Lycoming, ECI and Superior. These findings were so staggering that we felt compelled to dig more deeply into the data and comments offered by readers.
There are patterns in our data and also some surprises. Heretofore, we had concluded that premature wear in Continental cylinders was confined to the large-displacement O-520 and O-550 series and was more common in the higher horsepower versions. While that remains generally true, we also found complaints among owners of smaller displacement engines.
Of those who said they wouldnt buy Continental cylinders again, three were on O-360-series engines, a dozen owned O-470 engines, 29 owned some version of the O-520 engine and seven owned O-550 engines. There were a smattering of other types to fill out the total.
Pre-mature wear in smaller displacement engines seems less common but it seems more the norm than the exception for owners of O-520 engines, turbocharged or normally aspirated. There seems to be a magic number between 300 and 500 hours when new Continental cylinders begin to show more wear than an owner expects. Some owners who fly frequently reach this stage in under two years and, understandably, they arent happy about it.
Thats not to say there are no success stories for buyers of Continental cylinders. Indeed, some owners told us theyd absolutely recommend TCMs new cylinders. One airline operator-Cape Air-uses Continental factory reman engines exclusively and routinely reaches extended TBOs of 2700 hours. (See the sidebar.)
But none of this accounts for why so many customers are dissatisfied with Continental cylinders. Our survey seemed to reveal two significant areas of abnormal wear in new TCM cylinders. Valve guide or seat wear which leads to leakage around the exhaust valve and/or cylinder bore wear that results in loss of compression. Without actually examining the cylinders, we can only rely on owner reports which, in turn, come from mechanics.
Some cylinders were replaced or repaired in as little as 20 hours but of those owners who provided us with estimated hours at time of replacement or repair, the average came to about 560 hours. Yet even this number is somewhat misleading because some owners reported more than one soft cylinder at various times in the engine run. The 20-hour replacement noted above was due to faulty machining on an intake valve seat, not premature wear.
And the problems arent limited to new TCM cylinders used on field overhauls. Even factory new and remanufactured engines from Continental have encountered premature cylinder wear. Said one owner: Purchased a factory new Continental engine thinking I was getting the best I could buy. At 187 hours, I had three cylinders below 40 PSI and three below 60 PSI. After pulling the cylinders, the exhaust valve stems measured out of limits, causing them to not seat properly.
Whats Going On?
From our interviews with owners and engine shops, one theory that consistently emerges is that Continental made cylinder manufacturing changes in the early 1990s that diminished durability. Our own examination of new Continental cylinders last year revealed what we view to be manufacturing anomalies, although we cant be certain if these would always lead to premature wear or not.
As we reported in the May, 2003 issue of Aviation Consumer, we found that on a test TSIO-360 engine we equipped with both ECI and Continental cylinders, both cylinders showed what we consider to be excess valve guide wear in only 160 hours of flight time. The Continental cylinder had lost all of its choke and showed more bore wear than did the ECI cylinder.
Further, we disassembled and measured three factory new Continental O-520 cylinders and found that although these cylinders were accurate in bore dimensions, the valve seats themselves fell short in the area where the valve contacts the valve seat.
Measuring the six valves at four dimensions yielded 24 datapoints. Of this total, only three met Continentals own stated specifications. The valve-to-seat contact fit is especially critical on exhaust valves, which depend on full contact to dissipate heat to the cylinder head.
Would this be a likely culprit in leakage past the exhaust valve? We think so but others arent so sure. Penn Yan Aeros cylinder expert, Jud Dean, told us hes not convinced that valve seat machining in new TCM cylinders is the problem, although he confirms noticing the soft cylinder trend sometime in the mid-1990s. He believes rocker arm sideloading against the valve stem ovalizes the guide and eventually makes it impossible for the valve to seat.
Yet another perspective comes from Doug McKay, at RAM aircraft, which specializes in overhauls of high-performance Continental engines. RAM uses new Continental cylinders exclusively but ships them off to ECI for nickel plating before installing them, a step McKay believes is instrumental in all but eliminating warranty claims on Continental cylinders. McKay says for RAM, Continental cylinder longevity is as good as it has been in 30 years. RAM does one other thing we found interesting: the shop laps the valves before installing the cylinders, a process thats a rarity these days.
Continental: No Comment
We provided Continental with a copy of our findings two weeks before our press deadline, but the company declined comment.
Weve promised Continental an opportunity to respond more fully and were committed to doing that in a future issue.
With any aviation product or service, we think its unrealistic to expect 100 percent of customers to be satisfied. No business or product is perfect and theres no point in pretending some buyers wont be disappointed. But in judging customer satisfaction with engine cylinders, whats good and whats merely acceptable?
In our view ECI and Superior are doing admirably well by having seven or eight of 10 customers say they would buy cylinders from these companies again, given the chance. Considering how iffy cylinder longevity seems to be, we view an approval rating between 70 and 80 percent as a vote of confidence sufficient to recommend any of these cylinders as a good choice for an overhaul.
Lycoming merits a so-so, in our estimation. A 62 percent satisfaction rating isnt top-drawer and we think Lycoming could improve on that, especially if they were more responsive to phone calls. We think they did well in handling the crankshaft recall and they now need to apply that attitude to day-to-day operations so that owners feel theyre getting a fair shake on technical support after the sale.
New Continental cylinders are obviously another matter. When two-thirds of customers say they wouldnt buy a product again, we cant in good conscience recommend that you should. Continental has advanced efforts to educate buyers on the right way to evaluate wear in its cylinders, which we applaud, but we can sympathize with mechanics and owners who are skeptical of the esoteric method TCM recommends for checking compression.
And we can hardly blame any owner for not wanting to fly with cylinders with compressions in the 50 PSI range. Continental is competing with other manufacturers whose cylinders dont require what we view as a highly tolerant means of assessing wear. (Were referring to the calibrated orifice method described in TCM service bulletins.)
This puts Continental at a disadvantage relative to ECI and Superior. Given the sophisticated means of diagnosing and correcting manufacturing and engineering shortfalls available these days, we think Continental is overdue for fix and we would like to see them address the durability issue.
If you do opt for Continental cylinders or a factory remanufactured engine, the best way of assuring longevity may be to fly a lot. A hell of a lot. As evidenced by the Cape Air experience, flying as often as possible may be the single best way to get long service out of Continental cylinders.