AbuAnas

Hi,

I have an OS 46 that have some delay when I apply full throttle. It takes few seconds before the enging roars into full throttle. I made sure that the throttle/rod works smoothely and there is no bending.

Is there any solution for this problem?

AbuAnas

Motions

I don't know how experienced you are at tuning, but you could be running pretty rich.

redfox435cat

this is a tuning issue and is a mistuning on the high and low end. FIrst set the high end. peak the rpm by leaning out the needle a click at a time then back it off 3-4 clicks. then set the low end. get it to idle and pinch the fuel line and listen to the engine. if it speed up and die it's too rich. if it just dies it's lean. you should get a good 2 second pinch with little to no change in RPM. NOw reset the high end then retest the low end.

rctrax

I have found that what I had percieved as a lag in throtle response was just the distance from the model at altitude from the ear and the time it takes for the sound to arrive at your ear when you punch the throtle. It sounds like a lag but in actuallity is only the time it takes for the sound to reach you.

DarZeelon

Mohammed,


Most OS engines (all their standard ones) come from the factory, with the low-speed needle adjusted excessively rich...

It is preferable to potentially damaging the engine, from an excessively lean condition, but it is up to you to adjust it, so your engine will run and transition properly.

The main problem is many modelers, especially those that have less experience, are afraid to change the setting of this needle, if at all they know where it is... In your engine it is in the center of the throttle barrel/arm and is accessible with a small, flat screwdriver.
If you don't find it there, check the manual that came with your engine, or go to the [link=http://www.osengines.com/manuals/index.html]OS web site to download the PDF manual[/link].

First, you must adjust the high-speed needle to maximum RPM and then back off (richen) it a bit, so the engine will gain RPM when you bring the plane's nose straight up and stay there without sagging.

Afterward, there are several techniques to adjust the low-speed.

Your aims:

After closing the throttle to idle, the engine must speed up very little before settling to a steady speed.
If it gradually slows down, the setting is too rich. If it speeds up more noticeably - too lean.

Make adjustments very small, 1/8 of a turn at a time at most. Retest until the engine sounds good and steady.

When checking for transition, the engine must be cleared out at full throttle, before every test iteration, to prevent an incorrect assessment, resulting from excess fuel accumulated in the crankcase, or a total lack thereof.

Allow the engine to run at idle for 20-30 seconds, then open the throttle rapidly (with the R/C).

It should accelerate to high RPM immediately.
If it hesitates as if choking, it is too lean.

If it hesitates 'wet', or even spits fuel from the carburettor, it is too rich.

Adjust very gradually (1/16-1/32 of a turn at a time).


Good luck!

AbuAnas

Hi,

Thank you guys..

As a system administrator and application developer and I know my way very will around complex systems tuning.. But those engins? DUH for me they look like space technolgies! though I have been in the hobby for 4 years now..


OK now let me simplify what I understood from your advices:

1- On full throttle I lean the engine till I get the max RPM.
2- Rich it by 3-4 clicks.
3- Test by raising the plane. If the RPM didn't raise I should re-lean it little more.
4- Set throttle to idle. Pinch the fuel line. If dies -> Too lean. If speeds up and dies -> too rich.


DarZeelon, good information and advice .. but could you elaborate more on the low-speed setting?


AbuAnas

DarZeelon

Mohammed,


Let's start with the way you understood this and comment on your replies.
I do suppose you have done the break-in for your engine, close to what is detailed in [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]this thread[/link].

Let's also suppose the fuel tank is as close as possible to the engine and its center-line is at the same level as the carburettor's fuel-jet.


Yes, you begin by leaning at full throttle, until maximum RPM is reached (further leaning results in reduction/sagging).

This is usually not enough!

Richen so RPM is audibly reduced by about 300-400 RPM.

You must raise the plane with its nose straight up.
The RPM should rise, but still be 100-150 RPM lower than the maximum you saw in (1-).

If it is faster than that, richen a bit more. Slower - will not hurt your engine, but you could lean a couple of clicks.
Richer is a bit safer, since too lean will potentially cause damage.

I would say:
Pinch the fuel line. If it dies immediately -> Too lean. If speeds up and dies after two seconds and longer -> too rich.

I may elaborate later, but I believe it is quite complete.

jaka

Hi!
I would say ...forget about the pinch test!!! I never seen anyone using this test in all my 31 years in this hobby and I certainly haven't used it myself...it is much to crude method to work well. Just listen to the engine and set it fairly rich and go from there.

Regards!
JanK
Sweden

Build-n-flyer-RCU

My Feedback: (4)

The low speed (idle) adjustment controls fuel flow during throttle-up. Adjusting the high-speed needle will not help with this.

The low speed is actually very easy to adjust once you find the adjustment screw. Look in the end of the throttle shaft on the side where the throttle linkage connects. You will see a screw slot on the inside of the shaft. Use a small jewelers screwdriver to make adjustments. This must be done with the engine stopped because it is close to the prop and vibration makes it hard to hold the screwdriver in the slot.

As stated, OS 2-strokes are ALWAYS shipped with this set extremely rich. Turn the screw 1/8 turn clockwise, start the engine and check the throttle response. If it still sags when you throttle up then shut down the engine, turn the screw in another 1/8 turn and try it again. It is a very sensitive adjustment so go slow. When the engine responds to full throttle without sagging you are there! Once set correctly you will probably never have to adjust it again.

Walt

Sport_Pilot

Actually it works better than tuning by ear, especially with a new engine that you are not familiar with. Sometimes it even works better than when using a tach, at least with a tach that is not very responsive.

redfox435cat

To say the pinch test is worthless on the high end is a reasonable assumption. Still not true. Not as effective on thehigh end I'll give you that. With the low end, it is the best way to check it. Works equally as well on 2 and 4 strokes. The old guys at the field thought it preposterous as well since they were stuck in their ways. Now most of em are doing it. At our field anyhow.

jaka

Hi!
I might be an "old guy" (52), so I think doing it by ear is soooo easy and can't understand why some people would do in any other way.

Regards!
Jan K
Sweden

Sport_Pilot

If you are not using hearing protection, you may find out why in about ten years!

Turk1

Sorry but where is the high end pinch test was recommended?I dont think anybody said pinch the line with full throttle.Sure its easy to adjust by ear.But how one can adjust true idling and good throttling habit by ear?Sure can be said trial and error but why if pinch test says its lean or rich?

AbuAnas

Thank you very much ..

I have another issue when I tried this technique. When I bring the stick to idle the plane just ramble/vibrate and then die.. Though the stick is a little nutch under the middle..

wcmorrison

My Feedback: (2)

You are to far up North. We use it all the time in hot dry Texas. You have that nice dense (cold) air.

Cheers,

Chip

Motorboy

We do it same pinch test here in Norway..

Jens Eirik