700N with YS91SR a little help

[TryHarder]

My problem is I fly a bit more scale or F3C (at a stretch) and so I got the 700n 3G for stability in the wind and smooth flying rather than 3D which is what I personally enjoy. I was recommended the YS over the OS but now I 'm wondering if I bought the wrong engine or maybe Its my setup.

Bottom line is it works, but.... I'm not liking it.

So it ticks over like I've never seen so quiet and slow and sounds spot on, lift it off idle and its goes horribly lean and sounds like a car misfiring then it comes on the next needle and scares the living crap out of me ! lol !

I'm running the 91SR with an OS8 and Wildcat 20%

Is this engine designed to idle lovely and then just hit the governer, because I don't like it, I have disconnected the governer because the YS's hover throttle position marked on the throttle arm is 40% and the Governer comes in at 30% I found once it popped and missed so I gave it a touch of gas it must and it leapt 15 feet in the air and although I have been flying for about 15 years it sure focused me for a minute my mistake I know.

So I disconnected the governer and messed with the throttle curve and the carb settings it got a bit better but its still won't go through that transition from idle to spooled without sounding awful at any carb setting so I make the throttle curve steeper to help it through and then it really comes on power and spools far too quick for me.

I guess you 3D guys love that insane hit of power and I can understand that if you are flying 3D.

So does anyone have any throttle pitch curve settings that might get me from idle to a nice controlled gentle spool up, or do I need to go back to OS ?

Coming from a raptor 50 OS50 which is just perfect (but a little worn out) I'm dissapointed but I guess I'll get there I just don't know anyone else with a YS.

Thanks !

[MaSt0RaS]

you have to buy the ys 91 ST NOT THE sR..!

[TryHarder]

Yes thats what I am now thinking, time for a purchase and some ebay me thinks.

Thank you.

[epl]

TryHarder , its all in the tuning on the YS91SR. Is the engine broken in yet. My SR was a bitch to start when cold and had to have the hover needle leaned way out for it to start and idle cold. then we lean out the low needle, high needle. The transition from idle to mid on spool up was horrible ,it would blobber and miss and 50% of the time stall. lean out the needles and it was beter but not right.Wouce off this step engine ran smooth and had all the power you wanted. Ran like this for three cases of 30% Cool Power, then it would not start again. A feind that is a YS fan for years was out at our sight and tuned this engine so it starts well has on trouble off idle ,more power and two minute more fight time. Find someone that really know how to tune the YS, Roy also said the YS91ST was easier to tune.

[craig.t]

ATG (govenor)

Chuckie and I were there together, both of us working out the bugs of our SR 91's/N9/ATG's. We both learned about the linear tuning that Chuckie mentioned. Once the engine tuning was resolved, Curtis had me move up the "low throttle setting" of the ATG. This is the lowest point that the ATG is allowed to drop the throttle when it backs off the power.

With a GV-1 you have to tell the governor where the throttle barrel closes and where the full throttle position is.

With an ATG you have to tell the governor where you want the governor to limit its low throttle travel during governor compensation while in flight.

By having the top end too lean the motor would radically overspeed on the top end. The ATG would quickly cut the throttle all the way down to an idle. The rpm would drop enough for the ATG to sense this. When the ATG would try to add throttle again the low/mid needles were too rich, thus forcing the ATG to really slam the throttle wide open again. The engine would hit the lean top needle, overspeed, and force the ATG to close the carb again. Now, add a super fast Futaba 9253 tail servo used for throttle control to the equation and you can see how the oscillation is easily possible. The ATG responds so quickly to changes, the throttle servo is almost instant, but the engine is poorly tuned and responds too quickly at the top and too slow at the bottom.



How do you tune your SR91?????



Turn off the ATG.Govenor

Go to factory needle settings. Adjust the idle for a smooth idle that will spool up without stumbling yet has a nice slow tick over.

Hover the heli and lean out the midrange slowly until it goes lean. Take small steps. The YS will quickly tell you when you have gone two clicks too far. Land instantly from your hover and richen it up one click at a time until it hovers clean.

Slowly do some long climb outs keeping the engine on the midrange needle, not full pitch here. Just check to see you have the needle just rich enough to handle the added pitch for a long time.

Land and check your idle again. Adjust if needed. However, don't richen up the low end to get rid of any hanging on the pipe during your long climb outs. ONly adjust for the idle once the engine settles down.

Now slowly perform some long climb outs that gradually enter full throttle and full pitch. Land to richen or lean the top end only. If the engine hangs on the pipe adjust the TOP end, not the idle needle. As things smooth out do some more aggressive climbs.

When you think you have it, go up and do some heavy loading on the enigine like sustained tic-tocs. Instantly hit throttle hold and see if the engine hangs on the pipe as it autos down. If it does, richen the top needle a click. Repeat.

If the engine never hangs on the pipe, it hovers and transitions nicely, and still idles great the engine is tuned.

Now, Turn on the ATG.

If the engine starts to surge, land and reset the low throttle position. Move it up gradually until the oscillation quits.

Done, Enjoy.

Thanks Curtis for your help at IRCHA.

Tyler

[TryHarder]

Thanks guys,

Well I had the governor off and was just hovering around and a few circles last night, (nervous it was going to cutout but it didn't). I guess after about three good tank fulls I noticed it was running much better getting from idle to hover jet well actually the whole heli had loosened up, or maybe I was just getting used to it, whatever things were improving. So I hooked the governer back up and did some climb outs and it was all fine (man this things climbs hard :-)) I flicked the TH a couple of times and it was still running once landed.

So I think you are right it just needs a bit of breaking in and some careful matching of throttle and pitch to get a nice smooth transition, it still needs a little more tweaking but at least I can get on and fly it and if you shut the fuel and raise the revs slightly on the last flight so it clears itself it starts fine next time. I have to say also its not too bad on fuel but then I'm not trying real hard, and the tickover is sooooo sweet.

Thanks for the advice, guess the bottom line is patience !