How I tune my 2 Strokes. What do you think?
 

G'day All,
This is a How I, not a How to, tune 2 stroke engines.
First off, nitromethane in lower percentages, 5 to 10%, does not add significant power to a 2 stroke, but what it does do, is increase the tuning range, so this is how I tune my motors.
This is for fully run in motors, not new ones.
Ok I like to extend my needle valves, with a short piece of music wire, with the end bent into a ring, or at 90 degrees, this lets me see where my needle valve setting is.
Then I start my engine, run it to full throttle, & slowly wind the needle in, until the engine starts to sag, & note the position, then wind it out, until it sags on the rich side, & note that position, this is the tuning range of the motor, more or less nitro will change this range, then just wind the needle in a few clicks until the motor, is running smoothly. Lift the plane nose high & motor should pick up revs, indicating it is rich enough to allow for the motor to unload in the air, I fly at this setting.
This setting should not need major adjustment, no more than a click or two, to allow for weather variations during the day, & it will be right next week too, & so on.
If that is not enough revs, to fly, either wrong prop or need a bigger motor.
What method do you guys use?

RE: How I tune my 2 Strokes. What do you think?
 

sounds more or less how I tune mine, you should be right on the money.

RE: How I tune my 2 Strokes. What do you think?
 

In addition:
1. I leave the glow starter on for the first run up and high-speed setting.
2. I tack the engine to maximum and then back off 300 to 500 RPM.
3. After setting the high speed I set the low needle using the pinch test.
4. I then let the engine run for several minutes and check transition.
5. Then I set the top end again and then the bottom end again.

Total agreement. When a large adjustment is needed something needs fixing like trash or fuel tubing etc.

Total agreement. I don’t do upside down engines or pumps or heat.

Many who have troubles are simply tuning around a fundamental problem like tank height etc.


Bill

RE: How I tune my 2 Strokes. What do you think?
 

This is fine if you live where the weather doesn't swing very far. It won't work where I have lived in the USA, unless you have a tin ear and can't hear an engine protesting. Of course, you have to know the sounds that I am talking about in order to diagnose their absence or presence. Many do not.

No one has ruined a standard engine by running it a little on the rich side. The only way that you can be sure that the engine is running a little on the rich side is to adjust to peak and then back it off appropriately. Any other technique means that the operator is lazy or fooling themselves. Fortunately, their bad habits do not affect my engines, so I don't really care. I do watch those flying at the local fields to memorize their tuning habits. This lets me know who I am willing to buy a used engine from and those that I would rather avoid.

No offense intended, but those that preach the "leave it alone" philosophy almost invariably have a tin ear.


Ed Cregger

RE: How I tune my 2 Strokes. What do you think?
 

Ed,

I simply don’t agree with the ‘tin ear’ based on the statements that were made. Here is a refresh on the statements.

No offense is intended but the needles do not need adjustment every flight or every day.

Bill

RE: How I tune my 2 Strokes. What do you think?
 

I cannot agree to setting the needle 500, or more RPM rich.

In racing, this is the surest way to lose any race.

If you ask those that win these races; they don't ruin their engines very often from setting them too lean eithers.

I set my engines ~100 RPM rich of max, with the nose straight up.
When I set it level, it will slow 150-200 RPM more (250-300 rich of max).

Setting an engine unnecessarily rich is better than lean, but it will not prolong its life.

RE: How I tune my 2 Strokes. What do you think?
 

If it's an engine I haven't used recently I'll open the needle about an extra half turn to make sure it's rich then go to full throttle after a brief warm up at about 1/2 throttle (I hold the head until it's uncomfortable). Then lean it until it's not making any more appreciable difference (meaning still very slightly rich) before richening up to get a quite obvious rev drop. I never use a tacho but they're probably about 1000 below peak. I don't fly for speed so there's no need for more revs. As most probably know by now I don't use nitro either because it can't give me any benefit. This rather rich setting means I basically never have to touch the needle because of minor (even major) changes in conditions.

For an engine used recently, meaning maybe a week or more and that I know hasn't been messed with, I'll just start it, go to full throttle and do a nose up check just to confirm it won't sag.

RE: How I tune my 2 Strokes. What do you think?
 

300 to 500 RPM rich with the airplane level has worked well for me. I don’t race.

Occasionally as a tuning cross check I pull the longest up line the airplane will hold and listen to the engine. After landing the engine will sometimes be adjusted one click in the appropriate direction. Also occasionally I listen to the engine for rich/lean on the taxi back to the pits after a flight. The fuel will be low, the engine fully warm and at high idle. A very minor touch to the low speed needle might be made depending upon the engine sound on taxi back.

Although the up line test will feel and sound slightly different as temperature and humidity changes adjustments are only made occasionally maybe every few weeks. Everyone tunes slightly different based on the objective. Needle tweaking might be entertaining but not much is accomplished by most.


Bill

RE: How I tune my 2 Strokes. What do you think?
 

[quote]ORIGINAL: BillS

300 to 500 RPM rich with the airplane level has worked well for me. I don’t race.

I agree with Dar, 500 rpm is far to rich for any engine, glow or gas. You're doing it more harm than good. You only need to be 100-200 rpm on the rich side at the most

RE: How I tune my 2 Strokes. What do you think?
 

Dar is correct. 500RPM is bordering on 4 cycling and will not allow an ABC or ABN engine to get up to operating temperature. This could cause scuffing or galling of the liner (peeled liners on O.S.?) and cause more harm than good. However, ringed engines would love it!

Phil

RE: How I tune my 2 Strokes. What do you think?
 

Wow! Didn’t mean to start a fight over such a simple issue. A few hundred RPM is not worth debate.

RE: How I tune my 2 Strokes. What do you think?
 

G'day All,
I can see I have started the debate I was hoping for,
1) If you know the tuning range of your particular setup, ie prop, fuel, stc, you don't need a tacho, most around here don't have em or need em, & it's easy to hear when the engine sags, at the lean end & rich end of the range. If done like this, & I'm talking general flying, NOT competition pattern or racing, the high speed needle is almost guaranteed to be rich rather than lean, & that is what we are after, so the motor will keep running in the air.
A lot of guys just adjust em to the point where they are as lean as possible, then wind the needle out a couple of clicks, & have no idea what the tuning range is, or even that there IS a tuning range for their motor.
2) I was only stating my setting method for the high speed needle, low speed requires a better ear & different technique, to set, maybe I'll annoy everyone with a thread on that later.;)

RE: How I tune my 2 Strokes. What do you think?
 

Try more like 2000 below peak. Most of my engines I run in a 4 stroke all the time, even my ABN OS VF's, so I know what happens to them. They just keep on keeping on :). I tune my Rossi 45 to run in a continuous 4 stroke in level flight because I know that in a reasonably steep climb it'll lean out into a screaming 2 stroke. I hate to think how lean it'd be in a climb if I tuned for only a few hundred below peak.

RE: How I tune my 2 Strokes. What do you think?
 

G'day Downunder,
Maybe you tanks are a bit low.

RE: How I tune my 2 Strokes. What do you think?
 

Not this one. I set my low end right the first time and never touch it again in any given season. The high is a simple adjustment that I do recheck every time I fly but not more than a click or so is required. Why mess with what works.

RE: How I tune my 2 Strokes. What do you think?
 

G'day Cyclic,
This was only for tuning high end mixture, not low end, I did state, for fully run in motors, that would have their low end set already,
I just get frustrated watching guys fiddling with needle valves, before every flight, now matter how well the motor ran during the flight before.
They just can't stop fiddling.
Generally the mixture is a set & forget thing, at least for that day.
Just can't get through to some people.;)

RE: How I tune my 2 Strokes. What do you think?
 

Hey what time doyou have down their? is' 10:45 sat night here

RE: How I tune my 2 Strokes. What do you think?
 

G'day Cyclic,
16.55 here, Sunday, 7-1-07, Bloody hot, very little wind, have had a great days flying, in fact I had to replace a glow plug in my 160, finally wore it out.

RE: How I tune my 2 Strokes. What do you think?
 

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And nowhere have I indicated that I believe that they do need changing for every flight, although I have seen highly tuned racing engines that need "checking" before every flight.

Most of my engines get tuned during the first flight of the day. If I see/hear a deviation in the engine's performance, I may recheck it again. Sometimes a failing glow plug will change how the engine needles.

Unless the weather has changed an extreme amount, once a day should be just fine.


Ed Cregger

RE: How I tune my 2 Strokes. What do you think?
 

I go for 500 down form peak if you don't go this far you don't have any room for error. Many engines get a different fuel flow from full tank to near empty tank and 100 or more off peak will ruin your engine. You can have fuel splashing and fuel foaming to consider too and as you fly there are many more things happening in the air so you should take this into consideration and adjust your needles to compensate for near empty tanks etc. The model fuel system is for from precise it is amazing that it works as well as it does because it is very crude in design. Just think about it we use exhaust gass to pressurize our tanks for fuel delivery. This gas can vary in temp and pressure greatly. We use a carb that looks more like a water faucet in design and works about the same, no way can it meeter fuel acurately. As we fly the fuel in the tank under goes GForce posite and neagative, just look at the puff of smoke as you turn your plane and think can the force that causes that extra smoke be in reverse. There are many many more things to consider when adjusting needles but these are just a starting point and I don't mean to say I know a lot about this because noone here knows much about this. Most of us (including me) know just enough to get ourselves into trouble.

RE: How I tune my 2 Strokes. What do you think?
 

If you tune the high-speed needle nose-straight-up, so the greatest effort is needed by the engine to draw fuel, there absolutely is no need to over-richen the mixture setting with the plane in level attitude.

Just 100 RPM rich is enough, which will go up to ~300 rich with the plane in level attitude.

...And it will never become too lean in any attitude.


Now, if you don't have the fuel tank 'smack against the firewall', just buy a fuel pump/regulator.

Don't even bother trying to adjust it... The attitude mixture variations will be too large.

RE: How I tune my 2 Strokes. What do you think?
 

I run mine up and lean to peak. Then I back them off about 1/3 or 1/4 turn.

It's easy to find the exact peak. Lean it one click at a time. Listen to it pick up RPM. Lean it another click. IT will pick up more RPM. Keep leaning it 1 click at a time and listen to it. Take your time. Give it 10 seconds each time you lean it. Listen to it.

Eventually, you'll get to a point where you lean it 1 click and nothing happens. Go ahead--lean it one more click. Still--nothing happens. One more click and it'll slow down. It just went lean.

Now you know where max RPM is. And you also know where too lean is.

Back it up 2 or 3 clicks to max RPM. Now back it up about 6 or 8 clicks. That will be about 400--600RPM off peak. Go fly it.

My low end is tweaked for absolute perfection. I hate an engine loading up on me or dying on throttle up. I adjust my low end for absolute perfection. I can sit there and idle on the bench for 10 minutes. Move the throttle stick and perfect transition. Thats the only way to adjust an engine.

An engine that is a little rich on the top end will NEVER die or COOK on you. NEVER.

But, you take it up one time when it's too lean--and you just added a whole season worth of flying to the engine--in about 5 minutes.

It's totally okay to run a 2-stroke engine a bit rich on the high speed needle. It doesn't have to be slobbering and farting all over the place. Just a few clicks rich from peak. You won't hurt a thing.

RE: How I tune my 2 Strokes. What do you think?
 

Gentlemen,here weather getting colder and about 8 C (46 F) and windy now and under such cold, carbs getting insane if fuel having full 20% castor.Because thicker castor than normal ,clogs those tiny passages while engine is trying to suck at midranges.So I saw low speed needle needs some good richen if pilot needs some 3D maneouvers with dynamic throttling. During second and third quarter of throttling,engine cant suck enough fuel to compansate the intake air and quickly bogs down.High speed needle cant compansate this alone.

RE: How I tune my 2 Strokes. What do you think?
 

G'day All,
The one point that you all seemed to miss, was the tuning range of your engines, ie, the position that your needle is turned IN to get it fully lean, & how far you need to turn it out to get to the richest setting.
When you know that range, you can tell at a glance, where you are, as far as tuning the top end.
Most seem to say, lean it out to peak & then back off, 1/8 turn, 1/4 turn, 3 clicks, 5 clicks, 200 revs, 500 revs, whatever, but no-one knows the tuning range of their motors! Some motors, depending on the amount of nitro used, can have a tuning range, up to 3/4 of a turn of the needle valve, some may only have 4 clicks, or less.
That was the point of my post,
Thank you gentlemen, most enlightening!

RE: How I tune my 2 Strokes. What do you think?
 

Well I don't know about you :) but I tune by listening to the engine and not by looking at the needle valve. The amount of movement of the needle valve from peak to blubbering rich is of no consequence. What is of consequence is the result when you turn it, however much that may be.

I agree the idea of saying peak it out and back it off x many clicks is pointless because of all the variables but 500 below peak is 500 below peak whether it's 3 clicks or 3 turns. But if you can tell just by looking at your needle valve how it's tuned then don't turn your back at the field cos I might just give it an extra 1 turn tweak (rich of course, I'm not that evil :)).