The Lycoming IO390 project was worked with the Cardinal Flyers group long before the engine came to market... Lycoming hired a mod shop in Texas to get the STC, and that was well underway even before the engines were commercially available.
It’s really a 15 HP increase over the stock IO360A, because the FAA changed the tolerance band on engine horsepower between certification of the IO360 (plus or minus 2.5%) and the IO390 (minus 0%, plus 5%). Lycoming took advantage of the 2.5% to call the IO360 a 200 HP engine... it’s really more like a 195. But the IO390 really makes 210.
At the time of roll out of the upgrade program, Lycoming promised (!) that they would keep an engine in inventory... so folks who discovered a sudden need (engine failure, prop strike) could avail themselves of the upgrade. Unfortunately, that went by the wayside... when my engine crumped a couple of years ago, I called the factory... they couldn’t even give me a date for when I might receive an IO390 if I placed an order... their idea was place an order, and in a couple of weeks we’ll let you know our production schedule. What? I ended up going with a more controlled (so I thought) field overhaul.
The IO360A and the IO390 have the same external dimensions... so the engine fits well. That’s the same for the relevant Mooney models, since they also had IO360A. The Cardinal’s stock oil cooling on the RG is “interesting” so the STC modifier added a bigger oil cooler, which many Cardinal folks had done in the field, thanks to Firewall Forward making that part of their high compression piston mod available free to Cardinal Flyers members. Unfortunately, the STC only includes one particular oil cooler... whereas FWF included the entire class of oil coolers, irrespective of manufacturer. So if an aircraft already had a bigger cooler, but not just the right one, there was either a field approval opportunity or a new cooler in one’s future.
As an aside, Tornado Alley Turbo really solved the oil cooler problem, and engine cooling air availability as well, with the Cardinal Cruiser update... we’re hoping they make that part of their STC available separately. They’ve said they’re entertaining it.
Speaking of compression ratios... the IO390 is 8.9:1, a higher compression ratio than the 8.7:1 of the IO360A... It would be very challenging to run the engine on mogas; very rich mixtures (or very lean ones) plus significant reduction of allowable CHT would seem to be required, and most likely water injection.
Owners report that the roller cam engines run very smoothly, and with lower CHTs (which makes sense, since the compression ratio is higher, more energy is being removed from the combustion gas). Oil temperatures tend to run warmer a bit. And just as some IO360A owners have periodic exhaust valve guide wear problems (I am one), some IO390 owners are seeing that problem as well.
I don’t know enough about Arrows to know if the 180 HP airplanes’ cowling is big enough for the IO390; certainly, I would expect the 200 HP airplanes sporting IO360C’s to be big enough, since the dimensions are nominally the same.
The performance increase for a power improvement will always be more noticeable in climb than cruise. Climb is pretty linear... in this class of airplane, each additional horsepower adds about 10 FPM in climb rate. That agrees well with the pirep above of the upgrade from 195 to 210 HP adding 150 FPM to climb rate. However, cruise speed only increases about the cube root of the power increase... The 7.7% increase in power, then, would be expected to deliver a 2.5% faster cruise speed... 4 knots or so?
>> It can't be much wider than an O360 parallel valve engine if it fits into a Mooney without modification.
We only know that it only fits in the IO360A equipped Mooneys without mod, since the IO360A/C and IO390 are the same width. The angle valve IO360A and IO390 are about 2” wider than the parallel valve O360 engines (or IO360B or D).
The FAA in Washington DC’s guidance to FSDOs is to NOT field approve horsepower increases greater than 10%. Since this is less than that, finding the right FSDO, always key, could lead to a field approval for an IO390 in a 200 horse Arrow. If you want to upgrade a 180 HP ship, having puzzled out the cowling issue, you’d need to accept a manifold pressure redline that limits the IO390 to 198 HP... whether that redline is observed in practice is between you and your god, and any FAA guy riding in the airplane.
>> Most engines coming out of the Lycoming factory for over 10 years have been roller tappet engines
Well, that’s certainly true for new and reman’d engines. The factory overhauled engines are largely conventional sliding tappet engines. But the IO390’s, as noted, are all roller tappet. If you buy the STC from Textron, they require you buy a reman engine. But if you buy an overhauled IO390, you’re going to essentially get a reman, ‘cause there isn’t good core availability. But then... STC issue.
Stoots in Alaska has an STC to install the IO390 on the Cessna 175:
http://stootsaviation.com/New_STC_IO-390A1A6_210HP.php
>> Cardinal owners accept the opportunity cost of cracked [gear] actuators eating the entire yearly operating budget in a single mx action; I'd just bite the bullet and buy a 182RG.
There’s a lot of misinformation in one sentence! There’s no gear actuator cracking issue on Cardinals; that *is* an issue, with an associated AD, on 172RG and 182RG aircraft. If you look at the Cardinal design, it’s ingenious... it allows the actuators to float, so that you don’t get the lever-arm-reaction forces that cause cracks; the actuators are rounder, too; square corners crack more. If you choose the 182RG over the 177RG to avoid actuator cracks, you’re moving the WRONG direction.
>> I need cheaper cylinders, read parallel...
The great hope there is Superior’s project to get aftermarket angle valve cylinders approved. It’s been starting and stopping for years... We’ll ask for an update at Sun ‘n Fun.
>> the difference in the gears between the 177RG and 182RG: the actuation system on the mains isn't even close to being the same. The 177RG’s more common complete failure is the rod end bearing on the end of the lone main gear cylinder, which resembles a regular hydraulics cylinder
That’s a failure that derives from an improperly spec’d part, with a grease fitting. The grease fitting hole is a stress concentrator. Cessna issued a service bulletin 40 years ago (!) to replace all those cracky rod ends with non-cracky ones... some people are slow to get the memo, however.
>> I really don't see why Lycoming even bothered to develop the 390 and 580. For the minimal rated power increases over the previously existing engines...
They did the 580 for sister company Cessna, who wanted a 206 engine that could still meet certification criteria even if the compression ratio had to be de-rated for use of mogas. That didn’t work out real well, but that was the aim. Once you had tooled up for 580s, the 390 was like falling off a log.
>> With the number of Arrows around, a person would think that obtaining an STC for the 390 in the Arrow would possibly have made more financial sense than to do it for the Cardinal and Mooney
We were in discussions with Lycoming at the time they were making those decisions. They put feelers out to the relevant aircraft type clubs, and also visited the type clubs and looked at the airplanes. What they saw was that Cardinal folks (the first 390 STC) and Mooney folks (five months later) were more fanatical. So it was a multiplication problem: total number of flying airframes times craziness of owners which results in total number of expected engines sold. The Arrow folks apparently didn’t impress them as being as fanatical as brands C and M.
Pretty sure Lycoming was unimpressed with the eventual sales result... but then, folks don’t run out and buy a new engine just because one’s available; they might upgrade at overhaul time. Lycoming didn’t fully account for that in their market analysis as far as I can see. And not having on-the-shelf engines available as promised? A big dissatisfier.
>> the goal with those STCs was also to go after particular markets that were heavily PMA'd from an engine perspective e.g. using aftermarket cylinders
That doesn’t hold; the IO360s these IO390s are replacing have angle valve cylinders. There isn’t an aftermarket supplier...
>> part 23 killed my dream of engine retrofit.
It shouldn’t! The FAA is approving STCs for installation of ASTM (!) certified engines in Part 23 certified airplanes. That’s pretty exciting... the O320 equipped 172s and 177s should be hungry for Titan’s 180 HP IO340, which is an overhaul upgrade of the stock O320E2D those airframes shared...
>> doesn't seem like either the Mooney or Cardinal group is a big enough segment to make it worth pursuing [the IO390]. On the other hand, it might have been a good decision to help offset the development costs
The uncertified XIO390 was introduced in 2003. The IO390 was certified on 30 March 2009. The Cardinal STC was granted in July 2009, the Mooney STC in November 2009. Also in that November, Commander Aircraft received an STC for its model 112B. The Alaskan Cessna Skylark (175) STC is mentioned above.
Paul, in Berkeley
