Jezmo

Yep, every application and engine is different. Mine can't run with less oil because it has bushings on the rod. That's OK though because I have four other oils, three of which are synthetic, that don't create this problem so I will leave the remaining Mobil 2T to you guys that really need it.

On the conversations with the 4 engineers at major engine makers, were you having such major problems that it took that many to figure it out. Just joking. Have a great one.

RTK

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Believe me it can be done. Twins more so than singles. Poor baffling and/or a lean run is all it takes. Saw a guy toast a new engine running it too hard on the ground trying too adjust the needles.

Tired Old Man

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I work in a field that uses a lot of gas engines for it's flying machines.

freeonthree

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Yes, i've been filled in on that. You had me going there for a while. lol I was thinkin that you were extremely rough on engines when you said 40 in 6 months ! lol
Sounds to me like you have a pretty good handle on what these little engines can and cannot take.
One question, are you guys using full synthetic or petroleum based oil ? OK 2 questions, what throttle setting are these engines run at, 1/4, 1/2, 3/4, or ..... I think you said 500 hours to worn out, thats pretty good actually in my mind. Hmmm... I fly maybe 10 minutes per flight, mostly half throttle, I ain't gunna live long enough to wear out any engine of mine I don't think. I dont even run my weedeater wide open. I got 10 years out of the last el cheapo weedeater, and it was running decent when I snagged the choke off of it for my SV26. Talk about getting your $99.00 worth of service out of weedeater eh... lol
Im only running the new weedeater on 100:1 full synthetic now, and the chain saw too. The plane runs so good on it, I can't resist.

Tired Old Man

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Full synthetic from day one. The ratio varies with weather (ambient temp) conditions. I'm not a proponent of 100-1 ratios with any oil or engine but it does work. It does not leave any room for tuning or cooling errors.

I can't be very specific about throttle positions but suffice to say they run the full spectrum.

freeonthree

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OK, well, 500 hours between rebuilds is pretty good in my opinion.
As to the fuel mix, just for example, my friend who taught me to fly in 2002 (Greg) has been running his Brison 50 on 100:1 full synthetic, as Brison recomends, for 4 or 5 years now, and he pounds on it pretty hard in the Pitts. My SV26 seems to love it as well. Im not at all worried about hurting my engine. Needle settings ? well, he aint touched his needles in years. Thats the other reason I wanted to go to gas. Actually, so far, I have been running my low end leaner than Greg because I don't like the 4 cycle sound so much. If you fatten to blubber, then lean to clean, on the fat side, you really can't go wrong I don't think. Gregs Pitts will go like heck after a 30 second warmup, but I need to warm mine up good before it will transition, but as I said, I don't dig the 4 cycle sound.

RTK

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I try to run "most" of mine lean on the bottom and just a "tad" rich on the high. A lean low will take some warming up before it will transition and there is nothing wrong with that. A lot of 4 stoking bothers me for some reason.
As for oil, I would not run anything at 100:1. I tend to like the oils mixed in the 32-50:1 range and I buy my quality oil accordingly

freeonthree

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But thats not full synthetic is it ? I was a little concerned until I put a drop of the 100:1 gas /oil mix between my thumb and finger and rubed em together. This stuff is so slippery, I dont think I have anything to worry about. Nitro fuel is not even close to the lubricity of this stuff, and this fuel doesn't attract moisture like nitro fuel, so the bearings should last many many years. Right now it's like 45-50 degree's, but in the summertime, I will go to 80:1, but Greg has never bothered with that, and it gets over 100 degree's here all the time in the summer. His brison 50 sounds the same today as it did when it was new, and he pounds on it pretty hard most of the time in my opinion, but he says Nah...
In case I havnt showed this yet, here's my Stearman with the cowl being fit. It won't be long now, and it will look normal. Just want to make sure this muffler will stay together and tight first. I think im in love, I never felt this way about a plane before. Am I sick ? lol

Jezmo

I like to hear em running two stroke when WOT and then four stroke for just a second or two when I pull the throttle back just slightly until the plane slows down enough to load up the engine again. Then she's right back to two strokin.

Tired Old Man

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The old Brison company noted 70 or 80-1 synthetic ratios in the manual. If he's been running it 4 or 5 years it's an old Brison like the ones I have. If it's been years since the needles were checked it's time they were looked at. Tell him to quit being so lazy and pull the cowl off once in awhile You never know what's been living in there if you don't[X(]

All of the engines we use benefit from a warm up prior to tuing or going for the blast off after starting. Mixture settings change as the engine expands during warm up, and idle rpm will be higher after warm up than immediately after starting. Engines with leaner oil mixes warm up a lot faster, which should be a warning indicator all by itself. Dependable mixture settings and idles don't occur until ater the engine reaches cht's between 80-90c, or 176-194f. There goes the theory that engines running at cht's of 200f and below are healthier...

Tune them to run slightly rich of peak rpm. Maybe 100 or so below peak, and all should go well. Flying tells all of course.

As for 500 hours between rebuilds or worn out, that's totally dependant on how the engines are run and treated. I've seen some that didn't make it 30 hours before they had to be torn down, with an average t.b.o. before a top o/h to be in the area of 120 to 200 hours . Those running the snot out of them will have shorter times between over hauls, especially those that heat them up and keep them hot flying lots of hovering and torque rolling 3D. The circle flyers, like warbirds, can expect a lot more than 500 hours of total engine life if they started with one of the better engines. Then again, the first nose in impact sends the engines back for parts and labor anyway, and that usually happens long before they are worn out

Regarding the melted ring lands. I haven't seen that very much in air cooled "flying" 2 strokes. When it does happen the piston wall usually has transferred a lot of aluminum to the cylinder wall as well, indicating that the owner ran it so lean or low on oil the engine was melting. Rarely will it be from poor cooling inlet air. With some of the engine types you noted, in many cases the pistons have secondary compression rings and oil rings. They run drier and hotter at the tops. Perhaps due to over head valves and such. For our stuff we get excited when we have a two ring piston. Those are the best for heat transfer and maintaining compression as they heat up, but like anything else can get toasted by poor operational methods too.

The ring materials that are used in our model engines are not anywhere near the quality of automotive stuff. At least one manufacturer uses two different qualities of rings in their engines. One type is absolutely terrible and unfortunatey the buyer will never know which one they are getting in an engine when it's shipped.

freeonthree

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You hit the nail right on the head.

RTK

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There are full synthetics made to mix any where from 32:1 to 100:1 depends on manufacturer. Lately I have been using penzoil air cooled at 40:1 and have been very very pleased.

freeonthree

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He has had the cowl off for things like hoses and stuff, but it always runs perfect. Greg says you should never have to touch the needles on a gas engine once there set, unless something changes. Suttle adj's for outside temperature is not what im talking about.
I agree with him because I have never touched the needles on our old weedeater, and it lasted 10 years. I did kit the carb once, but it didnt need any adjustment afterwards, it still ran mint. Im new to flying weedeaters, but im learning...

freeonthree

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Do you ever find any residue on the plane, or is it as clean as the family car ?
Only thing coming out of my exhaust is hot air. I can put my hand at the pipe, and it always comes back bone dry. This is truely a dream come tru for me...

rmh

It is obvious , not everyone uses their engines in the same manner.
also - the industrial engines which are in a shroud with a forced flow - run cooler (or at a more constant temp)-
Sticking these things , (with out forced flow shroud)in the front of some models STOPS correct flow thru the fins. the air just skates around or stagnates.
getting this right in gassers is seldom done.
On motorcycles -look at the relative fin area on a 100cc bike and on a 100cc model engine-- totally different ballgame
and there is also a whopping difference in total case/crank you name it mass.
Personally I fly NO conversion engines - all are purpose built from square one -but that's my choice - Ido believe a GOOD conversion engine typically has piston n sleeve which will cool better - tho the rest of the setup typically does not appeal to me.

freeonthree

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The old Brison company noted 70 or 80-1 synthetic ratios in the manual.

Thats weird, Gregs manual says 64;1 and 100:1, 64:1 being petroleum based oil, and 100:1 for synthetic. I read it myself before I tried it in mine. He threw it down in front of me and said "read it, its right there" and I did, and he was right ! It's the manual that came with his engine.

pe reivers

If you are happy with the manual and 1:100 ratios, so be it.
Tests have shown, that best fuel economy was obtained with 1:30 fuel oil mixtures or even more oil. That means, that at these ratio's, friction is lowest.
If you run more friction, the engine gets hotter, wears faster. That's a fact of life. The piston also has less heat transfer, so runs even hotter (air cooled!) Heat flow from piston jacket to cylinder is the only thing that keeps the piston from melting. If the piston crown inside is black, you are close to desaster. If it gets ashen (death ash), You are courting it. Before making all the statements that you do, I would rather not hide behind Graig's broad back, but inspect my engine so I know what I talk about.
If you are happy with 1: 100 and shorter engine life, so be it. I would not do it your way, and a little oil mist out of the exhaust system does not bother me. That is what keeps my engines alive.

Tired Old Man

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Gary must have changed his manuals sometime after the ones I have. No biggie, he's not there to talk to about it anymore so we can't go there to ask about the change. As for checking the needles, I suppose that if an engine always ran at the same geographical location all the time it would be fairly happy left unmolested. I know that the carbs we use will tolerate an extremely large altitude differential on a good basic tune.

I've got some pictures somewhere of pistons that had been running 100-1. The reason for the ratio is something I can't go into. When I dig them up I'll post a couple after cropping to get the backgrounds out. They perfectly depict what Pe was describing.

Rcpilot

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Leaning your oil down to avoid having to wipe the plane down after a day of flying seams pretty ridiculous to me.

Sorry, "ridiculous" was the nicest thing I could think of. I can't post what I REALLY think of that logic.

I've been trying to stay out of this one, but I just can't do it anymore.

Here is how I break in a new gas engine:
Husqvarna chainsaw oil mixed at 32:1

Start it up and adjust the high end for peak RPM. Back it off the thickness of 2 screwdriver blades or until it will just barely fart and pop once about every 10-15 seconds while running wide open. I know thats rich, but not enough to create a bunch of sludge inside the engine.

Adjust the low end for peak RPM and back it up until it loses about 100RPM. Should transition cleanly.

Now go fly the **** out of it.

I vary the throttle settings and mostly just fly circles and loops for the first 2 or 3 gallons. Cruise around in circles at 1/2 throttle. Climb slowly to high altitude and then throttle back to idle. Dive at a 45* angle and throttle up to full power on the bottom. Fly it around in circles wide open for a couple minutes. Back off to low throttle and loaf around for 4 or 5 minutes.

The whole point is to heat it up and cool it down. Full power for a few minutes and the glide around at low power to cool it. Back to full power or 3/4 power for a bit and then glide around or dive in to cool it off at idle or 1/4 throttle.

After about 5 or 6 gallons, I cut back to 40:1. Same oil. Been doing that for a LOT of gallons and I ain't jacked one up yet.

Seriously guys, it's not that hard. If it was rocket science, there would be a lot of broke lumberjacks in the world. Y'all are making it WAAAAAY to complicated.

Edit:

Okay, not ALL of you are making it too complicated. Just some of you.

freeonthree

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I guess we all come to our own theories as a result of our experiences, and what we read and hear from others. I went flying today also, the plane flew great, and the engine purred like a kitten. Guess we'll just have to see how long it lasts. I fattened up the low end a tad, so now it 4 cycles like Gregs, and im gunna try that for a while. Sounds funny when I slow down, but it still runs smooth. It seems to take about 1 minute of warmup before it will transition perfect, and another minute of flying before it really gets with the program, so I don't think it running hot, it takes too long to warm up to be running hot. It's way more cold blooded than my Saito's. I have had the plug out when fitting the cowl, and it looks perfect. The center insulator is a nice tan color, and the plug is clean. As a professional mechanic, I can tell if an engine was running hot just by inspecting the plug, and my plug says no. I will continue to inspect it from time to time though.

freeonthree

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I agree, leaning down on the oil for that reason, would be silly. Nope, I didnt say that, I said I switched to synthetic oil because the non synthetic at 32:1 slimed the belly of my plane. I quit using nitro 2 strokes for that reason, and went to Saito 4 strokes.

Tired Old Man

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For those that like 100-1 ratios, here's three example engines that changed the way a lot of things were done. As for specifics, suffice to say that they ran more than 15 minutes or so at a time, and all of them should have lasted a lot longer than they did. Generally low time engines as these things go. The oil was a top of the line synthetic designed and specified by the manufacturer to be usable at 100-1 ratios. The piston that looks wet around the edges had fuel pumping through it due to a windmilling propeller for quite a distance. The appearence of chipped edges is where carbon had broken free from the piston. Every engine had a partially stuck ring.

BTW, they all flew and sounded great, and there was very little oil residue on the aircraft after extended periods of operation. The plugs were checked and changed far more frequently than most people flying R/C would ever consider. All of them flew great right up to the point they quit running. Many, many more experienced the same issues with similar results. All those had stuck rings too.

Now I'm not going to try to tell anyone what they should or should not mix their gas and oil ratios at. But I won't run any of mine at 100-1 anything. I've got three twins and 5 singles and I don't need to buy any of them again. Now if I needed an engine for a new plane buying another engine is another story altogether BTW, 50 to 70-1 synthetic mixes leave a little oil on the bottom, but a little clean up is cheap insurance. Anymore my personal outlook is that if I'm seeing some oil on the bottom I'm in the ballpark for a workable oil ratio.

RTK

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Well that's your problem right there, your not supposed to let mold grow in those engines. Might be penicillin on the top of that one piston

Oh, ya might want to tell them what your favorite oil is at this point

freeonthree

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I bet the spark plugs were trying to tell you smoething, and it wasn't just to change them either. You had a serious problem there. I just came back from Gregs, and we discussed this topic, and even pulled the at least 4 year old origional plug out of his Brison. It looked great ! The center insulator was a nice tan, and the plug was very clean. No material was even close to being disfigured in any way. There was a small amount of black buildup on one side of the outter ring, but it wiped right off with a finger, and thats after being in the Brison 50 for over 4 years ! The appearance of the plug tells me that the engine has never been overheated as well. Im willing to run exactly what he's been running, and thats 100:1 with QuickSilver full synthetic. I aint gunna argue with success like he's had with it. The plug don't lie, and i've been reading spark plugs most of my life as a professional mechanic.

Tired Old Man

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Ever try checking a plug in the middle of a 15 hour flight? I never said they flew short flights. The conditions were noted after periods of "extended" running. Just giving fair warning of what's happening to engines at 100-1. It just takes some time to become apparent, and fortunately we have telemetry to help us see when it's coming.

Like I said, I'm not going to tell anyone what they should use or at what ratio. But there are reasons some ratios are better than others.