Tuning issues OS50

[waqr]

Hi!

I have an Align/OS 50 engine (without GOV) in my Trex 600 and it runs great (I think) It idles well and responds well on full throttle. However when decreasing throttle quickly it kind of almost shuts off. It is always recovering byt it feels a bit unsafe to have it like this. Current setting on the needle is 1,25 turns. Since I just bought it I have only tried it in normal mode. Here is my settings

Norm
TC: 0,20,40,75,100
PC: 45,47,50,75,100

What could cause it to almost die when decreasing the throttle?

[waveydavey]

Your curve is your problem, in normal mode that's just what your going to have unfortuantely. The needle settings are around right for the OS50, but whats happening is that you are starving the engine of fuel. Are you flying about like this, if so you might want to consider an idle up curve

[waqr]

Tuning issues OS50

Thanks!

What TC do you recommend for idle up when not using a GOV? Today my IU is:

PC: 0,25,50,75,100
TC: 85,75,50,75,85

Thanks

[KevDavies]

Personally i would have said the idle needle is too rich. When you shut any engine it should pretty much settle to an idel straight away or drop down to nearly the idle then settle the rest.

I know when ive had this with nitro buggy engines adjustment of the idle needle has sorted it. I would suggest removing the main blades and bringing the engine to near a decent headspeed and then chop the throttle, and adjust the idle mixture until it settles correctly. On all my previous helis I always had a good tick over and a reliable one that I knew wouldnt cut on me during an aut so I could bail out.

[Andy from Sandy]

What no-one knows from your TC and PC numbers is what they mean on the model. How much pitch do you have when the PC = 50 and at the same point where is the marker on the engine carb?

What waveydavey is alluding to is that as you bring the collective stick down to reduce pitch you are also closing the throttle. This then reduces the headspeed which will make the model fall out of the sky and not fly down with a constant headspeed.

[waveydavey]

Problem is Kev under load shutting fuel off from the engine is going to do exactly what the OP is seeing. It won't come straight down to idle and in this weather in England I would be richer than that on an OS50 never mind Sweden. All of my 50's have ran a few clicks either side of the OP's depending on the weather so I don't think it's the richness at all. If it was too rich under an unload condition it should settle quickly into an idle, as a tuning thing I would say it was too lean Just my opinion though and I'm often wrong.

[waveydavey]

Thanks!

What TC do you recommend for idle up when not using a GOV? Today my IU is:

PC: 0,25,50,75,100
TC: 85,75,50,75,85

Thanks

I have no idea as Andy says we have no idea how the model is setup so the figures could be miles out and would be meaningless. Idle up curve looks okay apart from you're not using the top end at all. Open the curve out at the top and bottom to 100,100 and bring the middle up a bit. You're going to find it difficult with a 5 point curve to stop the head overspeeding in descents but I'm sure you know that.

[KevDavies]

Problem is Kev under load shutting fuel off from the engine is going to do exactly what the OP is seeing. It won't come straight down to idle and in this weather in England I would be richer than that on an OS50 never mind Sweden. All of my 50's have ran a few clicks either side of the OP's depending on the weather so I don't think it's the richness at all. If it was too rich under an unload condition it should settle quickly into an idle, as a tuning thing I would say it was too lean Just my opinion though and I'm often wrong.

MMM. I read it as when he shuts off on landing he nearly cuts then it comes back. Maybe I read into it wrong. And dont worry about being wrong, Im always wrong LOL

[bladeboy400]

tacho the head then adjust to what full throttle point you want as your idle 1 and 2 then copy either side of mid point and adjust to suit what load you put it under, send me your address i will send you an align govner i have never used if you need one.

[coolice]

Hey.

It could be that your mid point is too lean, but with no mid range needle to adjust you need to run your idle slightly richer.
From past experience the 50 Hypers always have a lean mid range when the idle is set for a clean idle and the high end needle is around where you have it.
What could be happening is as you're coming down through the mid range region on the carb its starving the engine of fuel, the latter can cause the rpm to rise prematurely due to it running lean and also even stop abruptly. If it's too rich you normally get a plume of smoke and the engine struggles to raise its rpm cleanly, coughing and spluttering in the process.

Check your engines rear crankcase area, you should be able to keep your finger on it. However if it's too hot to do so you're running lean. On the other end of the scale if it's too cold, you're running too rich.

Engine tunings a fine art, if it sounds and looks right it probably is, but there's a lot of area inbetween to get through first.

Also check your fuel lines and any fuel filters, if these are blocked/perished it won't help the engine run smoothly and throttle cleanly.
Don't forget your pressure line from exhaust to tank, another culprit in some engine troubles.
.

[waqr]

Thanks for all replies!

My personal opinion after reading all your replies is that the low end is a bit to rich since it sounds like the engine is stuttering when lowering the thorttle stick from full throttle.

My pitch is rouhly -3 - +11 in normal and -11 - +11 in IU. At mid stick I have 0 degrees of pitch and the marker is on the second marker in the carb (hence in the middle)

[waveydavey]

That's what I said, not quite as eloquently I give you that Ian

[waveydavey]

Thanks for all replies!

My personal opinion after reading all your replies is that the low end is a bit to rich since it sounds like the engine is stuttering when lowering the thorttle stick from full throttle.

My pitch is rouhly -3 - +11 in normal and -11 - +11 in IU. At mid stick I have 0 degrees of pitch and the marker is on the second marker in the carb (hence in the middle)

Where is the idle needle setting, take stock setting as being 12 O'Clock, it wants to be around 12:30 depending on what pipe, fuel and the temperature. The 1.25 is around right although maybe a little lean for Sweden in the Winter. As you haven't got a mid range the main needle takes this role and if coming from a lean condition to a lean condition then you are going to be running rough in the mid range. Remember when you are hovering you are on the main needle not the bottom