[email protected]

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Ok since you sound like you know what you are talking about, NO PUN intended, What do you think about performance mods on motors. Here is what I have been told and think. Porting on the intake side doesnt always mean larger and smoother is best, infact most intakes are large enough and alot of them are too large. Some roughness in the runners actually make the gas and air mix more turbulant, is that better? Make sure the carb and intake runner match perfect. The exhaust is better mirrow smooth as well as the inside head dome. Make sure as well the exhaust port matches the header inlet perfect for the transition. I have been using full ceramic bearing in my motors for about a year, without a failure. These are full ceramic, inner, outer and balls, with no seals. I get about 300-500 rpm more with these bearings. Any other ideas???? Thanks

Crash90

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Pe. Are you suggesting that we do not need to run non synthetic for break in?

pe reivers

Yes I am.
Give me one good reason why I should not.

rmh

Tho somemay not agree - On all my own performance gassers (ALL run tuned pipes-all are rotary valve -of some type) they all start and stay with 32-1 Syn typically the Mobil one -
compression improves little by little from new to present - nice tight seal easy free flip overs -
This is not a carte blanche recommendation - just noting that on my stuff it works very well.

Crash90

My Feedback: (17)

That's interesting. As a new gas engine owner I just thought it was necessary. Thanks.
How about running a break in prop? Necessary?

[email protected]

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I have always been told to never break in any engine without it being under load, but engines on engine dyno's do not so???????

rmh

hold on -- engines on a dyno are under load (that's what a dyno is---a calculated load device.)
Of course you could remove the load but pork a?
Ideally the load matches the intended (design parameter) load
On these little aircooled (actually fuel cooled ) things - you run em up n down the load (thru the rpm band -a and make sure they don't overheat .
I run mine from square one -on the pipe with the prop I will use just vary the load so the engine does not overheat .
The only time I use a bench -is in sorting out prop/pipe combos

Crash90

My Feedback: (17)

Very interesting. This is new to me. I was about to buy a break in prop for my DA50. Seemed like a waste to spend the money on a CF prop that I was only using for a few gallons of gas. Thanks for the input guys.

skiman762

I knew the EPA was after the 2 strokes they will win soon since the model airplane market is so small it won't survive
the lawn care market is seeing more and more 4 strokes along with the marine stuff
If they are happy with that we may get to keep going if there is someone to supply us
There can't be a huge market or the lawn care makers would be making a rc version of their engines my guess is they know 2 stroke are doomed [&o]

freeonthree

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I ran about 1/2 tank of pennsoil 2 stroke with TCw3 at first, but it left a residue on the belly of my new Stearman, so I poured the rest of that gallon into my 73 Chevy flatbed, it will drink anything. I then switched to QuickSilve full synthetic @ 100:1 as my friend Greg suggested, and im pleased as punch. Runs better, and no more crud on the belly of my new plane. If it takes a year for the ring to break in, I don't care, it runs like a jewell, and will idle at 1000 rpm until you turn it off. I think thats pretty impressive myself.

freeonthree

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That would look real cute on my Stearman. lol

altavillan

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Crash; Selecting the prop you are going to use is a trial and error thing. There is no one size fits all. Each different plane needs a different prop. Be aware that if you are running a large prop for the engines ability you need to be able to tell when an engine is running hot. A smaller prop reduces overheating posibilities to some extent and is advisable if you have little gas experience. With experience your ear can give you a good idea of when an engine is running hot. Like Dick said above he runs a prop he's decided to run because he has experience. But he'll be the first to admit sometimes your first prop pick isn't the last. So pick a prop, use it, see if the engine is turning in the rpm range you expect, and make sure it isn't getting hot. For DA 50 you'll be somewhere between 22x8 to 23x8 for aerobatics. Maybe a thin 23x10 for scale non aerobatic and very little WOT. A phone call to DA is a better place to learn what fits best. You will learn with time how to select props.

freeonthree

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32:1 with full synthetic ? That must be a blend... full synthetic should be 80 to 100:1
Too much oil can stick your ring. Not sure what ya mean by easy flip overs, mine has loads of compression, and it always starts on the first flip when it's at all warm. Cold is like, choke on, 3 or 4 flips to start and die, choke off, and 3 or 4 flips to running, every time, but once it's got any warmth in it at all, it always starts on the first flip.

freeonthree

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Put an 18x8 on your SV26 and fly you pants off. Excessive rpm never did any engine any good. The power band on these puppy's is between 6500 and 7500. Theres nothing to be gained outside that box but noise.

rmh

well if that's what that engine turns -so be it --

Tired Old Man

My Feedback: (1)

Thre's zero need to use a non synthetic oil during the break in. Why rush the break in? I don't know about you other floks, but like Pe and Dick I prefer to have the best possible lubrication running through my engines from the first spin. I just can't understand the reasoning where some manufacturers tell the customers to use a lower quality oil during the break in or first few gallons of use. Perhaps they want the engine to wear out faster so they can sell more. That's the only logical explanation. Tell your significant other you put sand in the Vaseline to help loosen things up sooner. They'll think you're crazy too

Who said synthetics have to be run at 80 and 100-1? If you remember the three purposes of oil it would be reasonable to presume that more oil would do some of those jobs a little better. Especially in cooling and cleaning. More oil does not necessarily create more carbon. The way the engine is tuned, loaded, and run has more to do with carbon development that the quantity of oil, although some oils generate carbon tracking long before others. The design of the exhaust system also can contribute or delay carbon development.

Using the size prop you intend to fly with loads an engine during the first few hours much better than using a smaller one. Using a smaller prop for running in is something left over from glow engines and tapered cylinders where you want to keep them from heating up and sticking. It's useless for gas engines.

blw

My Feedback: (3)

This used to be the common logic for car engines from the 1970s. Run regular oil until the engine broke in, then switch to synthetics.

skiman762

I'm ready to see the answers from Pat on his quiz
so I can see how little I know

freeonthree

My Feedback: (1)

Thats what I read in several sites, 6500 to 7500, and from my tests, their right, at least with a 15 lb biplane anyway. When it was proped to turn 8200, it took forever to get rolling, and sounded like it was spinning it's guts out in the air. It pulls so much harder now, and the flywheel affect of the larger prop ( 18" ) helps it to idle real slow. I love that !

Tired Old Man

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There have been some pretty good answers to the questions. Some of the answers took off to places I never thought they could but that's kept it interesting.

Answer #1:

The loose piston and the tighter piston can run at exactly the same rpm from the first spin. The engine with the loose piston has a slightly better heat tolerance but ultimately it's a no gain situation since it can only permit a very little amount of additional heat before ring damage occurs, which is at the same temperature as the engine with the tighter fit piston. Water cooled or air cooled, a piston ring can only take so much heat for so long before something happens, and it's the same amount of heat in both types of engines.

Answer #2:
The break in process between a loose fit and a tight fit piston is the same. The ring is breaking in, not the piston.

Answer #3:
The piston does not require a break in since it should not be in contact with the cylinder wall.

Answer #4:
In a perfect world no part of the piston should make contact with the cylinder wall. One of the things oil is used for is to maintain separation of metals and a well lubricated engine has a thin film of oil separating the piston from the cylinder. Unfortunately it's not a perfect world and some engines rock the bottom of the piston as the rod carries through the stroke on the crank, slapping the piston skirts ever so slightly.

Answer #5:
Three hours or less running the engine at variable rpm levels between 3,500 rpm and 5,500 rpm, with short cooling cycles at idle rpm to assist thermal cycling. The harder material is the cylinder, with our rings generally being made of iron or other softer metals. The ring only has the ability to knock any miniscule metal fibers from the cylinder that were left from the honing process. Other than that the ring wears before the cylinder does.

Answer #6:
The piston rings and any parts that were cast. Which leads us to #7.

Answer #7:
The piston ring over the short term but the greater benefit goes to all the cast parts. Casting is a process where two or more metals are melted into the same pot. During the (for lack of the correct term) "alloying" process those metals do not come together in their natural forms so their molecular structures are modified, weakening the original metal in many cases.

Heat cycling the engine during the break in permits the various metal molecules to migrate back to a structure closer to what they were originally, making for a stronger cast component, and one that can better handle various heat stresses.

Bearings do not break in, and as noted by someone else, wear. However, in the better quality engines the fit and alignment of parts is so good that you will wear the rings out long before you wear the bearings out. It's not unusual to replace rings two or three times before the bearings are showing critical wear. That amounts to literally hundreds of hours of running time if the engine is not run lean or hot, and if quality oils at reasonable ratios are used. Air filters a great benefit as well.

Moving on;

I'm certain that someone, somewhere is going to bring up questions or statements about oils, which is best, and what ratios, but I have no intention of beating that horse again. If you want to run a lot of oil it's easy to figure out when you have too much. The engine just won't run well and will foul plugs no matter how you adjust the needles. On the other side, too little oil will make it's case somewhere down the line with worn out parts, scored or melted pistons, low compression, and stuck rings. Contrary to an earlier statement, I (and I'm sure others) can attest that 70 and 100-1 ratios most definately can stick piston rings and there is plenty of evidence to prove it. It's all in how you tune and run them that determines what's going to happen.

As for breaking in...do it in the air with the prop that's right for the plane and avoid hovering and torque rolls for the first hour or so. Use a good oil regardless of type. The break in oil should be what you intend to run the rest of the time. If you want to use a little more, why not? You sure won't be hurting anything.

freeonthree

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Its not the ring that suffers, it's the piston. It gets too hot, expands and seizes in the cylinder. However, if the end ring gap is not sufficient, and the engine gets too hot, the ends of the ring will come together and break the ring because it cannot expand anymore. It would be hard to overheat a 2 cycle plane engine that is not over proped, and has sufficient oil in the gas. Just look at the pounding weedeaters take. Plane engines get lots more air. I've never seen any of mine even close to too hot. My revo is another story, i've seen at at 270 several times before I got the tuning correct. My planes are always under 200 when I check em, and thats super cool.

Tired Old Man

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I've gone through about 40 engines in the last 6 months that proves the piston is not the issue, it's the ring. They get hot, they loose their tension, and they stick. Every time. If you're getting the engine so hot that the piston is expanding into the cylinder wall then you've gone far past general over heating or moderately lean running. Sticking pistons is a catastrophic condition that only occurs in extreme situations. Typically extremely lean running and/or lack of lubrication. Many engines can attain temps of 228c (442f) for a singular extended period and not stick a piston if lubrication and mixtures are in line. The rings will be toast but the engine will otherwise be ok.

freeonthree

My Feedback: (1)

I unfroze many seized engines, and the rings were still ok. But once the piston collapses (at the ring lands) the ring sticks, and gets smeared onto the cylinder wall. I.ve seen that many times. That and the ends of the ring coming together and breaking the ring because the lack of end ring gap. I have never seen signs of scoring just because a ring got too hot. Im retired from the motorcycle/automotive industry though. These little engines may not be quite so tough. Normally if you lightly seize a large 2 stroke, Motorcycle or scooter, as soon as it cools, it's good to go again, unless ya really roast it. Maybe were both right, and I have just never seen the situation your talking about, or i've been mis-diagnosing some of the results i've found. Outside of lack of oil in the gas, or bad tuning or vacume leak, I don't think you can overheat one of these little engines. I've never hurt one. Come to think of it, outside of a timing belt on a pinto, i've never had an engine failure.

Tired Old Man

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You win. All I do is gas two stroke airplane engines. Lots of them.

freeonthree

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nah, you win... im sure they have different characteristics than larger mills have. Im pretty new to this gas engine thing (weedeater style). Im lovin it though. Flying for penny's is awesome !
40 engines ? What da heck are you doin to em ? I've been flying since 2002, and I havn't lost an engine yet. Actually, all my engines still run fine, even my picco 26 in my Revo, and the stock .15 from it still runs perfect too ! Guess i've been real lucky. All my planes have Saito's though, and one Magnum 70, and now this wonderful SV26.