RE: Saito 125 poor performance problem
 

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ORIGINAL: rlmcnii

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And this volume is not forced out of the crankcase... Only a very small percentage of it is. This volume is not drawn into the crankcase as the piston rises either.

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I assumed not, thus the statement concerning the efficiency of the process. If you are correct, and I do not doubt that you are, the process is very inefficient.

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You're welcome, Rlmcnii.

This has nothing to do with low efficiency...

Please imagine a fully isolated syringe, with its piston pulled all the way back and your finger plugging the only exit...
If you push the piston in, to compress the air that is inside, it will heat up.
If you release the piston, it will return nearly (friction) to its previous, fully extended position. No great work loss!

The work done, as the air expands and cools is equal to the work done when you compressed it and caused it to heat up.

This is in general what happens in the crankcase of a four-stroke engine...


This is off-subject, but was necessary to clear up a misconception.

RE: Saito 125 poor performance problem
 

What were these needle adjustments??

All of this talk about sealed bearings, cross-drilled sealed bearings, drilled crankshafts, and Saitos spitting more oil than other four-strokes gives rise to a couple more thoughts:

1. A Saito can spit no more oil out than it takes in. For that matter, neither can any other four-stroke.

2. All of the oil that goes into a Saito, or any other four-stroke, must come out. Or, is this not correct? Do four-strokes, other than Saitos, somehow make their oil vanish? I ASSUME that they do not. I could be wrong. Is it possible that the other four-strokes are just taking in less oil than a Saito? My personal experience with other four-strokes is too limited to know. I recently helped an older friend set up a Magnum four-stroke and with the needles set, per instructions, for the initial running that engine was taking in much less fuel...and oil...than any Saito with which I have had experience.

3. New Saitos (I believe hs said his was new) have their LS needles set very rich. And, exhaust large amounts of oil, both in the exhaust and through the crankcase breather, until the LS needle is properly set.

4. For some reason a lot of folks are reluctant to properly tune their Saitos. That is, they are reluctant to sufficiently lean the LS needle. Probably because they usually require what seems to be an inordinate amount of turning to get them properly set.

5. Could it be that the engine under discussion here, since it has the crankcase effluent running back into the intake track, is being impeded in its operation just because of the amount of non-combustible oil (and other by-products of combustion from the blow-by gasses) being dumped into the intake track? Perhaps it needs a little finer tuning.

As a little addendum to this this post: I have noticed that a properly tuned Saito does not put out an inordinate amount of oil at all, either in the exhaust or in the effluent from the crankcase. My Saito-powered planes accumulate no more, and usually a lot less, oil on the airframe than other glow-powered planes after a session of operation. Probably because a well-tuned Saito is not taking in any more oil than a well-tuned anything else.

Also please note: All of the above could be wrong...just the early-morning musings of a rookie R/Cer.

pax vobiscum.

RE: Saito 125 poor performance problem
 

I think we have to dispel the misconception that oil from the breather being recycled into the inlet causes loss of power.
It does not.YS engines do it.Oil ratio goes up and you adjust for it..If breather oil is dirty and contains dangerous impurities, then the oil is substandard or the engine has tremendous wear.
If it is the case then YS , OS, ASP, Magnum and full sized engine manufacturers should be sued for poor engineering.In fact the good thing is that residual fuel left over is recombusted and blown out thru the exhaustThere is also no direct opening from the breather into the crankcase to introduce outside air that could cause corrosion, a fact I found in saitos with their rather large breather nipple.
Oil that is not burnt is ejected out thru the muffler. Oil quantity ejected is the same for all engines with the same oil content and tuned properly. Its just that the oil is ejected thru the muffler instead of the breather and muffler.
On a footnote, saito engines left the LS needle purposely rich for running in. It does not effect the topend rpm of the engine if only the HS is adjusted. The topend will suffer if the LS is adjusted later on.A close look at the carb will tell you why.

RE: Saito 125 poor performance problem
 

Well, it does take energy to pump oil, even residual oil. So, saying that it takes no power is incorrect.

I always look upon my glow engines as being similar to the old rotary engines of World War 1 with their total loss oiling systems. It helps me tolerate their spraying of that nasty oil all over my model. <G>


Ed Cregger

RE: Saito 125 poor performance problem
 

By what method does one re-combust that which has been combusted?

RE: Saito 125 poor performance problem
 

Most glow oils will not "burn" during the combustion cycle. That is one of the reasons that they are chosen for model fuel. By being expelled unburned, they remove heat from the engine, as with all total loss lubrication systems. So, all that is really happening with glow four-strokes that funnel their lower crankcase oil back through the intake tract is that they are taking the chance of introducing swarf from the lower crankcase into the upper crankcase and they are ensuring that most of the waste oil goes out through the muffler, instead of a hose that is directed toward the ground. In the process, they are robbing a miniscule amount of energy from the engine's output. Not enough to be concerned about, I'm sure.

Until someone shows me absolute empirical proof that some of the oil is burned, I'll stick with my present opinion. Has anyone actually tried to ignite model lubricant with a heat source at the same temperature at which our engines operate? Good luck.


Ed Cregger

RE: Saito 125 poor performance problem
 

You must remember that not all fuel is burnt the first time round,minute amounts escape being burnt due to leakages, incomplete combustion etc, this portion including combustion byproducts which are not neutralized are the culprits in causing corrosion,oil alone does not cause corrosion.
The presence of swarf in the crankcase signals a breakdown of the engine if it is present in 4strokers, it also means YS engines would be destroyed in no time and we should avoid buying these engines! In actual fact,swarf inevitably ends up causing massive damage to the piston and liner as it thrown up by the vortices present in the crankcase without it being drawn into the combustion chamber.
I think we're getting off topic here anyway!! A quick recap,I think we're all trying to help Highside and I hope he resolves his engine anomaly soon,I'm curious if the solution is the same as mine. Cheers and compliments of the season!!

RE: Saito 125 poor performance problem
 

I have to disagree... Look at it this way.

Your cylinder can only take in so much volume on the intake stroke. If you were running some ridiculous amount of oil (say 95%), you wouldn't be able to get much methanol in the cylinder at all, would you?

Naturally, I don't think a glow engine could even RUN with 95% oil, but I think this helps to illustrate how more oil in the mixture will equal less power output, all things equal.

One more thing.. Adjusting the needle valves only change the proportion of air to fuel/oil mixture. It does NOT change the volume of air and fuel mixture that can enter the cylinder on the intake stroke!

RE: Saito 125 poor performance problem
 

The needle valve adjusts the engine for the best air/fuel ratio for proper combustion so only the combustible portion of the fuel is taken into the equation,which is how we tune our engines.We shouldn't stretch the oil content to 95% as an example!! Its more like saying that 18% oil content performs better than 20% oil content!!The fuel/air mixture for both fuels at optimal performance is equal except the fuel with less oil will have less lubrication available. The amount expelled by the breather is minimal compared to the amount blown out by the exhaust.

RE: Saito 125 poor performance problem
 

AND,

The little droplets of oil, swarf (?? cool), and un-combusted (but soon to be combusted?) fuel are all competing for space in the total volume of the intake charge. Their presence in the charge volume does nothing more than reduce the amount of air (read OXYGEN!) entering the engine.

As our glow engines are already tuned rich-of-peak (modeler's lingo for rich-of-stoichemetric.), the presence of the effluent from the crankcase does nothing but drive the mixture further from stoichemetric. Does this enhance power output??? I sure don't know.

Plus, as EC points out, one must consider pumping losses.

Never had a YS engine, but do they not use some system(driven by crankcase pressure?) to pressurize the entire, including air (read OXYGEN), intake charge entering the engine. In that case, as is demonstrated by the power output of those engines, the loss of combustion efficiency and pumping losses are more than compensated for by the increased mass of fuel burned on each power-stroke.

If, indeed, the entire intake system of the YS is pressurized, then they are a horse-of-a-bit-different-color than is a Saito running at atmospheric pressure. hs's 1.25 runs at atmospheric pressure?

Things do get a little crazy around the solstice, don't they?

RE: Saito 125 poor performance problem
 

We are not talking huge dollops of oil pouring out from the breather!! Its like saying 18% oil gives better performance than 20% oil content.I have ran my saitos with the modification without any loss of power.OS surpass II engines and OS alpha engines turn equal or higher rpms than engines without recirc. oil which by argument shouldn't be the case.These are real world figures not classroom theory.

RE: Saito 125 poor performance problem
 

I'd say that 18% oil WILL perform better than 20% oil, everything else being equal. This would be very difficult to prove, since the oil reduces friction, and lowers the operating temperature as well.

However, it remains that the oil content is NOT a power producing component of the fuel/air mixture, so the more oil you introduce into the mix will produce less power. I have to add that a small amount of extra oil, such as what comes through the breather, shouldn't make much difference in power potential. Still, it WILL reduce the power potential somewhat, the same way that reducing methanol content will. In fact, that is EXACTLY what it does!

However, drilling into the carb body may have been the whole source of his loss of power. Who knows how this has actually effected the overall power potential of the engine?

If this were MY engine, I'd get a new carb body, put the stock muffler back on, and then run it to see what my power output was. Or else, I'd just accept what I had created... Not all experiments have positive results!

RE: Saito 125 poor performance problem
 

So would I.

And then, I would very carefully inspect every bit of tubing in the fuel system and reduce the plumbing in the fuel-system to the bare necessities.

RE: Saito 125 poor performance problem
 

Good point, rlmcnii!

The K.I.S.S. system was taught to me early on, and it is still just as true as it ever was!

RE: Saito 125 poor performance problem
 

Ken, i did the same to my saito 125 and did not experience a drop in rpm at all. I tapped the inlet manifold and connected a tube to the breather.No rpm loss and less mess. I was tired of cleaning up the mess.Its installed in a WM senior sports 90 and running 10% nitro and 20% nitro occasionally.
I'm converting a saito 115 next.

RE: Saito 125 poor performance problem
 

Sounds reasonable.

Some of the oil is burned or vaporized, especially the synthetics used in model fuels. I use 8% Klotz synthetic oil in my FS-52 and the exhaust has very little oil in it. The engine is being lubricated adequately. I run 20%-25% castor oil in my four stroke diesel conversions and the exhaust is very dry. I would have to say a good part of the castor must be burning, but then again, the engines use less than half the volume of diesel fuel than glow fuel.

Yes, this is typical for break-in procedures.

Saito carbs low and high needles tend to interact. If you don't know this then you will constantly chase settings and never come to a good tune. Saito engines in general have much higher compression ratios than other engines and in my opinion must be run rich in order to prevent preigntion and or detonation.

No, I don't think so. The crankcase recirculation idea is not new. OS has been using it for more than 15 years on various engines. Besides, he tested the engine with the vent disconnected from the intake and found the same problem. The volume of oil compared to the volume of methanol is small. Do the math figure out how many BTU we are talking about estimate engine efficiency and give a theoretical power figure. And this figure will only be correct if the suspended oil is not burning at all. If the oil that is suspended and not in contact with metal engine parts is burning, and some of it is, it is also contributing to power. A simple test would be to run an engine for a few minute on straight alcohol. There will be enough oil in the crankcase to prevent damage for a minute of so. I know most of you won't risk an engine like that but I will. I'm running 8% oil now. I might go to 5%. I've heard about people running 2% in Saitos and running hundreds of hours. Four stroke lubrication is different than two stroke even though they are both total loss.

RE: Saito 125 poor performance problem
 

Yes I do agree, things over your side are sometimes a little crazy!!

Ken, this is my what i did to one of my saito 125.

RE: Saito 125 poor performance problem
 

OK, I'm not really surprised to hear that. The small amount of oil from the breather shouldn't make a significant difference. However, you said that more oil won't make ANY difference, and it does. It reduces the amount of actual power-producing material that can be introduced into the cylinder. In small amounts, it may not be noticable, but it DOES make a difference.

However, note that you introduced the breather into the MANIFOLD, not the carb body. I imagine you are using muffler pressure or some other means to pressurize your fuel system too, right? If you had experienced a large loss of performance after making the modification, wouldn't you have bought a new manifold, so you could get your engine back up to stock performance?

I just think that this is a failed experiment, and in order to get back to what the stock performance was, he should go back to the stock configuration.

RE: Saito 125 poor performance problem
 

I think he went back to stock and got the same result. I did not say that large amounts of oil will not affect performance- please show me my post where I said that, I thought it was you who mentioned 95%!! I was looking at breather oil expulsion volumes.
The fact of the matter is that the experiment worked for me because i knew it would. I tapped the manifold because tapping the carb body wrongly could cause leaks in the throat. That would mondo trouble!!

RE: Saito 125 poor performance problem
 

Ok compared to all these other people I can tune quite well, and can prove it. Ive got a webra 120 that went through eight owners before i got my hands on it and tuned it right! It would idle fine, but when you would try to throttle up it would increase rpm's a but then drop dead! For me my low speed needle rarely called "MID RANGE NEEDLE VALVE!" was half a turn too lean. I strongly suggest you make an attempt to tune your low speed aka mid range needle while running the engine. I can all most guarantee you that this will solve your problem.

RE: Saito 125 poor performance problem
 

More oil in the fuel will not reduce the static power but wont let the engine unload as well once in the air. There is a certain amount of oil needed in the fuel for the glow airplane R/C engines to give the maximum performance and last and that is something between 15-20%. Too much oil and you will lost instant throttle response, midrange reliability and unloading qualities in the air. Too little oil and you will lost torque and idle reliability because our glow engines run a little bit like an diesel engine and will lost compression with less oil in the fuel and simply run too cold. Thats one reason why good old thick castor oil is such an great additive for syntetic fuels. If one must connect the crankcase nipple to the carb it should be connected to the carb body cone "inlet" where it sucks air and fuel and before the throttle drum. The OS200FS has done it the wright way. Connecting to the intake manifold is not good as there are pulses going forth and back and the oil drops are just in the way.

RE: Saito 125 poor performance problem
 

I don't believe that he changed the carb back to an unmodified one.

As for the oil, I'm glad to hear you agree that a large amount of oil WILL affect performance. It follows that a small amount of oil will affect it too, even if you don't notice it.

I objected to you saying that additional oil doesn't make ANY difference. What you MEANT was that you didn't NOTICE any difference.

RE: Saito 125 poor performance problem
 

Well if you try running 95% oil, you'll probably have a dead starter or tired fingers!! Oil within breather expulsion volumes NOT any amount of oil ,will not have a significant difference to performance-that is what I SAID in all my posts and what I have noticed in my converted engines. Nuff said already.

RE: Saito 125 poor performance problem
 

I agree...

RE: Saito 125 poor performance problem
 

A few points...

It's been my experience (after much experimentation) that less oil does result in *more* power at least when reducing it down to the levels I currently run (about 12%-14% depending on the engine).

The cause of this is probably two-fold. Firstly the fact that there's less incombustible oil entering the engine means a greater volume of air/fuel can be drawn in hence you get more power. Secondly, the pumping losses associated with drawing the oil in and pushing it out are reduced (which is also why lower-viscosity oil will produce more power than high viscosity oil - for a given ratio).

I tend to think that the Saitos are designed with a higher blow-by than many other 4-strokes which explains why they often (in my experience) have more oil exiting the breather. Yes, it's true that oil-in must equal oil-out but in the Saito, more of the oil exits via the breather than in many other engines where much of that oil would have exited via the exhaust.

The YS engine is a totally different kettle of fish it's pretty much like a 2-stroke where the intake charge passes through the crankcase - lubing the bottom end in the process. The YS doesn't rely (or want) blow-by to provide its bottom-end lubrication.

If you want to recycle your crankcase oil then the best place to re-inject it into the engine is (as someone else quite rightly pointed out) on the open side of the carby in the velocity stack or before the throttle barrel. That way you don't affect the dynamics of the intake manifold or introduce possibly harmful (to performance) pressure pulses into the intake system.