OS LA .15's finicky?

[cipoll717]

I read recent threads, and have heard previous comments that indicate there is a high amount of frustration with the running performance of the OS LA .15.

I've owned about a dozen of these engines over the last 2-3 years. My experience has been overall very satisfactory, and wonder if we can shed some light on: is there a real problem, what may cause it, and what others are doing to overcome it?

I know there is an issue with the back plate, and there are several fixes that are successfully used.

My experience is that if you take one out of the box, fix the back plate, run 2-3 tanks of fuel through it, it will almost always turn 17.5k reliably. There is a great 'break-in' procedure on the Georgiacombat site that provides additional details.

Over time, the engine will begin to lose a little power due to wear and tear. We are pretty hard on these engines, and I suspect this weardown is due to simple fatigue, but also a great extent to all the crap that ends up in the carb upon dirt naps. At this point, my remedy is to simply use a higher nitro fuel, and this will extend the useful life of the engine. Initial performance is fine with 10-15% nitro, but overtime up to 25-30% nitro can maintain performance. Also, I use nothing but top grade fuels (Powermaster, or if not available, Wildcat).

Thus, in my experience, these things seem to run satisfactorily 'right out of the box', and for a long time. I'd be interested in what others experiences are, and what 'fixes' are used- maybe we can overcome the problems associated with this engine being considered finicky.[?][?][?]

On the subject of the LA's durability:
I flew a fair amount of combat over the last two years, and guess that I go through about 3 engines a year. About half of my losses were not wear-out related (crash damage). I flew about 60 combat heats last year, and at least that many club combat heats. So doing the math, I get about 40 heats per engine. Since about half of my losses were due to engine wear-out, that translates to about 80 flights per engine before wear-out. I usually just scrap an engine for parts at this point, but get about $10 worth of parts (used carb, muffler, needle valve). So this translates to about $55 for 80 flights before wear out. So thats about 68 cents per heat. Does this seem like a high figure relative to other engines?[?][?][?]

Mark

[Lee Liddle]

I agree with the backplate, break-in and no prob getting to 17.5k.. You do need to open up the baffel. My engines have lasted longer though. What kills the engines is dirt and LEAN RUNS. If ya keep it pretty clean and don`t run it lean, it should last for hundreds of runs.

[boiler]

I flew 174 rounds of ssc last year at meets plus practice rounds and I'm still using 5% nitro. Towards the last part of the season I had to start closing the throttle to keep under 17500. I guess they run cooler and last longr with lower nitro.

[Lou Melancon]

Mark,
My take is that the .15s don't have the fuel draw ability of larger engines and are also more subject to vibration related fuel foaming.

You can't get consistent performance till you have a working fuel delivery set up. Many folks stop working with the engines before they get a working fuel delivery system in place.

[sgilkey]

i tend to agree that based on what i have seen, a big part of the problem is the fuel delivery system, not the engines themselves. you can have foaming and not even know it. if you have foaming, you will get erratic runs. I believe these engines are more prone to foaming due to the plain main bearing which creates more vibration (i'm sure you've all heard the main bearing rattle of a plain-bearing model engine at part throttle) due not only to increased radial clearance, but also more fore-aft clearance. the Big Mig Norvel 25s had a similar issue with vibration and foaming.

if you put a quality ball bearing engine on some ssc planes that were struggling with poor engine performance, you might see the problem go away. I would say in general, the Mag 15XL (not a quality BB engine, but BB nonetheless) is slightly less foam-prone, but it's leaky and sensitive HS needle more than makes up for it.

the plastic backplates stink. i've had the same backplate problems on 40LAs so it's not peculiar to the 15, and i have had no backplate probs with my 15FPs. however i believe even the OS CVA has a plastic backplate??? maybe the lower level of vibration makes it more suitable for that engine? don't know, haven't run one.

the 15LA has a plastic carb nozzle that is simply pressed into the aluminum carb body that is very prone to loosening over time. grab one and try to rotate it, it's pretty common that you can. this can create an air leak. seal it by globbing JBWeld around the aluminum/plastic joint- RTV will fall off.

other than that the 15LA is not a horrible engine, but plain bearing engines running this level of rpm need care in the fuel system to perform reliably.

I've got 20 FPs, 9 LAs, and 8 Mag 15XLs, plus some cats and dogs like TT. It's still the rare engine that exceeds 17.5k. maybe i just don't have the touch. as a group, the LAs are more powerful than the others, but i like the reliability of the others better. i don't love any of them.

[cipoll717]

Good feedback about the potential foaming issue. It sounds to me like most feel, with a little initial attention that these engines do perform well. As such, I would offically declare these engines not-finicky!

Scott- interesting that you have problems getting 17.k! Yet, you are able to get a lot more out of the little 1/2a engines than most people. What's your trick?

Mark

[Hat Trick]

I rarely get near 17,500 either.

[lightning]

Hey Mark, I have never exceeded 17,500 and I run 15% Powermaster. I replace the backplate with the FP aluminum one and use a remote NV. (The 40/46LA housing with the 15LA needle in it). However Lou's point is well-taken - I have never tried bladders so maybe I do have a foaming problem. My issues have always been that in order to fly a full round I have to launch way rich (really helps the power at take-off!) so by the middle to end of round the engine leans out and starts to fly. Of course my streamer and almost everyone else's have gone by then.
Count me as one who has to disagree with your "non-finicky" conclusion!
I use the 25FX for comparison. Full power for the entire round and certainly very tolerant of needle valve "tweaking". Problems - virtually nil! Fixes as it comes out of the box - zero (unless you count cutting off the RNV from the backplate so it doesn't break of as a result of the first crash!)
Maybe we should allow CVAs for SSC as long as we keep 'em below 17,500 on the spec prop. max power is only at 18,000.

[Lou Melancon]

Once set up correctly the LA .15 is a very consistent engine. It will run the entire combat day without tweaking the needle. To get this level of consistency you need to:
<ul><li>Seal the backplate either by replacing it with an FP backplate or some other method </li><li>Have consistent fuel delivery, with either a bladder system or using a tank mounting method like the one used by Chris Quinn and Tim/Alex Treneff, they never have engine run problems. </li><li>Remount the needle and spraybar so that they are not in harms way in a crash </li></ul>
Finally make sure all potential areas that can leak don't: especially around the neck of the carb, and the head. The supplied JIS (cross point or Japanese phillips screws) work fine but it is hard to tighten them if you do not have a JIS screw driver. Replacing them with hex bolts works fine but over time is slightly more expensive than a JIS tool.

The funny thing is that where SSC is flown a lot folks don't have engine problems. Where it is not flown folks have engine problems. My conclusion is that it takes some time and effort to get them to a level of consistency, but it can be done and now it is actually easy because so many folks have shared their methods of success.

[sgilkey]

Mark I disagree with your declaration, for the chosen application, a vibrating plain bearing engine, as part of a power system that includes fuel delivery, is indeed finicky. I compete in all classes of combat and claim unequivocally (how the heck do you spell that) that the SSC engines are the fussiest, the possible exception to that being the 1/2A engines (too early to tell). this excludes the Norvel 25 which has virtually vanished from serious combat use due to its notorious finickiness (another plain bearing vibrator and fuel foamer). I have more effort into isolating the fuel system in our SSC planes than all the other classes combined, which in general consist of me either cramming a completely uninsulated clunk tank into a hole in the fuselage, or sticking it to the side of the fuse with 2-sided tape. do that with SSC suction tank and you're sunk. bladders solve the foaming issue and if you want to go that way, they make a lot of sense.

[boiler]

Keith I found to get a consistant fuel supply from a tank you need two things. Mount the tank on foam so it sits up slightly from the crank and about the same level as the carb. Second, do not tie it down too firmly and lose the benifit of the foam. You need a slightly rich setting at launch but can check rpm with the needle and then back off or leave the needle alone and do the pinch. The same is true from my experience with bladders. Just a tad rich at launch so you don't get a lean run and burn them up. Tanks have other places where you can develope air leaks that will cause problems. Tracking them down is sometimes challenging for me. I have one wing set up for a bladder and either put that on the plane or put a temporary bladder tube where the tank sat. I didn't use a bladder at my last 3 meets and had good engine runs. Had to partially close the throttle at the last two meets. I do have the fp backplates. I also use allen head bolts and locktite. The only air leaks I have to worry about are at the carb. By the way the cvx uses the plastic backplate as well. It is slightly different than the LA but if you need a spare needle valve, buy the cva and cut the need off of it because it was 50 cents cheaper than the LA the last time I ordered from tower.

[sgilkey]

i don't know why i don't get the power out of our ssc engines, but with 30+ samples and a lot of testing of fuel, plugs, head spacing, etc it is what it is. i don't do anything inside our engines, just careful prep and cleaning. everything i know about 1/2A engines is in my threads on the forum. my experience with the Norvel and AP is consistent with what i have read on the various 1/2A forums, the Norvel is generally more powerful. if you're not seeing that i suggest you check your head spacing. i've done nothing else.

[RH]

I clean out every bit of the muffler baffle and enlarge the stinger to get all the flow I can. I run a clunk tank and some claim you will reduce your tank pressure by doing these muffler mods. I mount my tank similar to Bob's, sitting on about an inch of foam loosely held in place with 3-4 wraps of electrical tape. With the tank this high, gravity feed seems to make up for any pressure loss from the muffler mods. I always have to clamp the fuel line after I fill the tank to prevent gravity feed flooding.

I always turn close to 17.5k at a mile high and when I come down off the mountain to some thick air, the Rs are way up there.

We have found up here that the green Cool Power 25% is MUCH less prone to foaming than the pink fuels.

[Cajun]

I agree with removing the baffle, but I would be carefull of drilling out the exhust stinger. I have done this on a number of engines, with success, but never knows if I have gone far enough until I've gone too far. Go a few thousanths too far and you've ruined the muffler pressure. This is immaterial if you're using a bladder, but troublesome if you're running a tank.

Personally I don't do anything to La.15s but take out the muffler baffle, move the RNV, and seal the backplate. With decent climatic conditions and quality fuel I have never seen one that would not break 17.5K and have tached several showing over 19K on the blue prop. Two years ago at the Paris meet almost everyone there had to go to 5% or 0% fuel to get under 17.5K. At the Houston Jetero meet last fall I did a lot of the taching and observed several engines turning over 18K, and every LA.15 was at or over 17.5K. Many of he pilots had to dial the throttles back to get legal.

The LA.15 is one very good engine for the money and undoubtedly the best for SSC. It doesn't compare favorably with the reliability of the FX.25, but then, very few do[:0], regardless of size.

[EK]

I run my clunk about 1/2" short of the tank length, a 1/4" thick piece of foam underneath the tank and zip tie it tight to the fuse. A squirt of Armorall in the fuel and the warmup/needle set run first thing is with a half tank and I'm looking for a click or 2 rich (get a rpm rise on the pinch). The rest of the day is within a click or 2 of that setting depending on how much the temperature changes. Every time I get in a hurry and set the needle with a full tank, I fight it all day.

Squirrelly runs and I'm looking for the air leak. Usually the result of a dirt nap.(I know, I'm the King)