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Small tuning issue - 4/28/2012 5:59 PM   
VetteV12


 

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Status: offline 		I'm having an issue with my newly rebuilt Evolution .46NX. I replaced the piston/sleave, connecting rod, and wrist pin. Bearing are fine, carb is clean, ect. I was breaking it in today every thing was going well for the most part. However, it will NOT idle. As soon as the RPM drops to what a normal idle should be it just dies without warning. No hessitation, sputtering, or anything of the sort. After 2 tanks I started to find the sweet spot on the high side and set it 2 clicks richer untill I get more run time out of it. I tried messing with the low speed but that just caused more issues with the idle. So I returned that back to where I had it. It transistions very well from low RPM to high RPM after the engine has been at 1/2 or full throttle for a few seconds, so I know the low speed is good. I've checked for any cracks in the fuel lines (which they are new).

Someone please help me out because every time I tried to come in for a landing and brought the throttle back I was dead sticking it in. I have added a Bison Pitts muffler to it since this engine is now inside of a Stinger instead my old Escapade. It's the muffler made for an OS 46AX but horizon said it would work without issue. I'm using an OS #8 plug and I will try a #6 next time to see if helps. But does anyone have a clue to what could be wrong?


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RE: Small tuning issue - 4/28/2012 8:17 PM   
jester_s1


 

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Status: offline 		That does sounds like your needles simply aren't right. I have that same engine and it's the most temperamental one I've ever owned. Suddenly dying is a classic lean condition at idle, so you have to open it up. The LSN affects the top end even at WOT on these engines, so if you get a decent idle setting but find the midrange is all wacky, it probably indicates that the needle combination is off. It's possible to be too rich on the top and lean it out on the bottom, or vice versa. That will let the engine run well at one throttle setting but no where else. With yours, I's suspect you're too lean on the bottom and too rich on the top.

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RE: Small tuning issue - 4/28/2012 8:31 PM   
VetteV12


 

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Status: offline 		I just re-read my post, I forgot to mention that with the glow plug igniter on it would idle just fine and at WOT it seemed to have more power as well.

I will try your suggestion to make the LSN richer and the HSN leaner. I did think it was odd when I had to turn the HSN about 1/2 turn richer to get it to run right a WOT. I had this engine running just a few weeks ago with the old piston and I didn't change the carb settings.


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RE: Small tuning issue - 4/28/2012 9:17 PM   
JohnBuckner



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quote:

ORIGINAL: VetteV12
I forgot to mention that with the glow plug igniter on it would idle just fine and at WOT it seemed to have more power as well.

WOT.


I had this engine running just a few weeks ago with the old piston and I didn't change the carb settings.




Get rid of that plug and throw it just as far as you possibly can! Not in the bottom of your box either.

And as Jester already stated you are too lean across the board.

Be aware old carb settings from before any kind of rebuild or even just a looksee will be useles and you need to start over with both needles.

I too know little about your engine but I did own one for a short while (maybe thirty flights) on one of those Horizon P-51's the so called trainer and after I got rid of needle limiter and the dumb flywheel it dialed in very nicely by tuning to a pinch. It ran so well those flights someone just had to have it and since I never sell but what ya'll got to barter, it was soon gone.

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RE: Small tuning issue - 4/28/2012 9:37 PM   
VetteV12


 

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Status: offline 		I just ordered some OS A3 plugs on tower and a TT R1. I also turned the needles a bit richer for the next start. We will see how it goes from here.

Do you guys think I could have damaged the new engine with these issues? I had a HUGE puddle of oil under the plane when I was running it in on the ground.


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RE: Small tuning issue - 4/29/2012 1:02 AM   
JohnBuckner



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Status: online 		No I would not worry about that and if at all possible Try to get an experiance hand to help you with these first starts and by that I mean someone experianced with airplane engines and not necessarily car engines.

It appears your location indicates a military base and if so many stateside bases will have some expeianced modelers you might be able to network with, just a thought.

John

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RE: Small tuning issue - 4/29/2012 1:40 AM   
Hossfly



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quote:

ORIGINAL: VetteV12

I just ordered some OS A3 plugs on tower and a TT R1. I also turned the needles a bit richer for the next start. We will see how it goes from here.

Do you guys think I could have damaged the new engine with these issues? I had a HUGE puddle of oil under the plane when I was running it in on the ground.



METHINKS you have a bad pressure connection or a muffler problem with the pressure outlet.

Not too long ago I had a similiar problem. The engine quit on final. (Sp. Tigre 75 a good engine) I filled it up, noticed a lot of fuel coming out, Oh well guess I was pumpimg too fast, and started up again. I use the Tetra Bubbless tank, and when it overflows it does just that! HA! Started up and all seemed OK but thought I would check the idle. Well it DID NOT. Long story to short, the overflow tube - which, with these bladder tanks has to be capped after fueling - had a long split in it, above the outlet inside the cowl. Therefore the muffler pressure was simply pushing all the fuel out the overflow and there was no real draw for the engine when the throttle was retarded kinda like the pilot at that point.

Now all these fuel lines of today are really garbage. If you find it in some auto parts store, the 1/8 black neophrene (Sp ?) rubber is excellent for both Gas and Glow fuel.
Kind of hard to find now days. The old dark pink line was good but the blue stuff AIN"T! I am not fond of the fancy color stuff the car guys use. The black stuff does have a problem when used and stored on a model for a long time - like MONTHS - but it is overall the best-of-all.

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RE: Small tuning issue - 4/29/2012 1:50 AM   
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Status: offline 		I wouldn't try to tune a newly rebuilt engine. If you have a new piston and sleve you need to break in the engine all over again high rpm then low rpm etc for several tanks 2 or 3... then go fly and then start to tune for max performance. finishing up at about 10 flights.....things are still seating together and will change, which will mess up your tuning

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RE: Small tuning issue - 4/29/2012 2:19 AM   
VetteV12


 

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Status: offline 		JohnBuckner, Yes I'm military but all the guys I used to fly with are either deployed or have PCSed. I have tuned 5 or so airplane engines and I used to race 1/10 scale stadium trucks. I know how to tune for the most part, not saying I'm a master or anything but I can usually tune and engine by sound alone. My last resort will be taking to the LHS. However, I'm a crew chief so I don't give up easily.

Hossfly, The Stinger is band new, I just finished the build on friday. I always take extra time to look the tank over and lines before calling it good. I had an issue with a split line once way back on my trainer and I haven't over looked a fuel line or tank issue since lol. I can assure you that they are good. As far as pressure in the tank, that's what I'm curious about. I read a post on rcgroups that when using the Bison Pitts muffler like I am most guys had to pinch off one of the exhaust pipes to get enuf pressure in the tank. I really don't want to do this but I will if nothing else works.

jetmech05, I did run 2 full tanks and about 2/3 of a 3rd tank before trying to tune and fly. I know that things will change as it loosens so I wasn't looking for stellar performance. I just wanted it to run and idle like any engine should.


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RE: Small tuning issue - 4/29/2012 4:50 AM   
JohnBuckner



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quote:

ORIGINAL: VetteV12

that's what I'm curious about. I read a post on rcgroups that when using the Bison Pitts muffler like I am most guys had to pinch off one of the exhaust pipes to get enuf pressure in the tank. I really don't want to do this but I will if nothing else works.




Ya know this is also a possibility and one of the reasons I generally avoid that type of muffler myself, But I have run across several two stroke set ups with various engines and various pitts or box mufflers with double outlets that the fellows were having troubles with and were improved by plugging the second outlet.

These types of mufflers tend to be treated as 'One size fits all' but thats not really the case. At any rate it is really simple to just stick a plug, cork or whatever in one side and give it a go.

John

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RE: Small tuning issue - 4/29/2012 4:54 AM   
Gray Beard


 

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Status: offline 		If it idles well with the glow driver on then dies when you remove it the problem will usually be just as John pointed out, a bad glow plug. Until that is replaced you can adjust all the needles you have on the engine and it won't idle. What you described is a plug on it's way out, gasping for breath!

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RE: Small tuning issue - 4/29/2012 6:58 AM   
Firepower R/C


 

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Status: offline 		I say glow plug also, then if problem still persists, plug one pipe on the muffler. I have had several Evolution engines with a pitts... they need GOOD back pressure for a solid tune- once I figured that out about the Evo's, it was smooth sailing from there!

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RE: Small tuning issue - 4/29/2012 7:44 AM   
VetteV12


 

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Status: offline 		Thanks for the advice everyone. When the plugs come in from tower I will try again and let you all know how it goes. I'm bumping the heat on the plug up to see if runs better. All my other engines like the hot plugs so I'm also thinking the #8 I have in there is too cold

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RE: Small tuning issue - 4/29/2012 10:01 AM   
jaka


 

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Status: offline 		Hi!
OS 8 or Enya 3 are all good glow plugs that suits a two stroke engine running on 5-15% nitro.
OS 3 is a little to "hot" (pre ignition) if run on 15% nitro.

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RE: Small tuning issue - 4/29/2012 12:31 PM   
ddewey


 

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Status: offline 		+1. To Firepower's post.
In our club it has become standard procedure to plug one Pitts opening to get back idle.
If you look at the area of the two openings in the Pitts and compare to the stock muffler you will probably have the equivalent of double the siz opening of the stock muffler. The engine runs at the high throttle because it pumps up enough back pressure to the tank to flow fuel. At lower RPM there is not enough to pressure to supply fuel=no idle.
I cut small wooden or cork plugs to fit the opening, red RTV them in flush with the end, then drill a small hole in the side of the pipe to run a servo screw into the plug to secure. It is cheap and easily removable. Has worked on a couple of O.S. and Super Tigers with Pitts.
Good luck!






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RE: Small tuning issue - 4/29/2012 2:18 PM   
jester_s1


 

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Status: offline 		Mine ran best with a #8 plug, but feel free to try something else. I agree with the others that your plug is probably bad. If an engine runs better at the top with the driver attached, you're either sloppy rich or have a bad plug.

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RE: Small tuning issue - 4/29/2012 2:23 PM   
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Status: offline 		Just a thought as I also have one of these engines. My understanding was that these engines use the longer/extended plug? I use the Fox miracle plug or the O.S. "F" plug with absolutely no problems. Might be worth a try. Good luck.

Randy

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RE: Small tuning issue - 4/29/2012 3:32 PM   
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RE: Small tuning issue - 4/29/2012 3:33 PM   
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Status: offline 		I would put another OS8 in it and run it.  It sounds like the same plug is still in the engine that was used to break it in, so I am betting the element is contaminated with minute particles of aluminum and nickel from the piston and sleeve seating.  This is quite common, and I always run in my engines on the bench for 3-4 tanks and throw away the plug before I put the engine in a plane.

I am also not a big fan of Pitts mufflers.  As I have posted before, I have never seen an engine run really well with one.  Some engines can run pretty good, others poorly.  Some plug one outlet for more pressure so the engine can idle, but what does that do to the top end power??  I would try a stock style muffler if you still have tuning issues after you replace the plug.  If you need an in cowl type muffler that actually makes power, call Dub Jett.  He makes a really nice one, but it is kind of spendy.  Good luck.

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RE: Small tuning issue - 4/29/2012 7:30 PM   
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Status: offline 		no one mentioned the rubber o-ring under the carb.
give that a look. might be loose, might be torn or nicked.
got to mash the carb down tight as you tighten it up to mash the o-ring and get a good seal.

i know from experience that a leak there will effect idle.


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RE: Small tuning issue - 4/29/2012 7:56 PM   
Gray Beard


 

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+1. To Firepower's post.
In our club it has become standard procedure to plug one Pitts opening to get back idle.
If you look at the area of the two openings in the Pitts and compare to the stock muffler you will probably have the equivalent of double the siz opening of the stock muffler. The engine runs at the high throttle because it pumps up enough back pressure to the tank to flow fuel. At lower RPM there is not enough to pressure to supply fuel=no idle.
I cut small wooden or cork plugs to fit the opening, red RTV them in flush with the end, then drill a small hole in the side of the pipe to run a servo screw into the plug to secure. It is cheap and easily removable. Has worked on a couple of O.S. and Super Tigers with Pitts.
Good luck!






I keep hearing of people doing this to there mufflers to get more tank pressure when using Pitts type mufflers. I have never had to do it and I used several different brands and makes of them over the years. Some are just a box with two pipes and some like the Bison are baffeled like a real muffler. There are single pipe mufflers designed to fit planes just like the Pitts. Why buy a Pitts then automatically plug up a pipe?? I just don't understand this.

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RE: Small tuning issue - 4/29/2012 7:57 PM   
Firepower R/C


 

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Status: offline 		I actually "tune" my pitts mufflers by CAREFULLY crimping down both outlets while the engine is running full throttle until a slight decrease in rpm is detected, then open them back up with a screwdriver just enough to get the rpm's back. This has always given me a solid idle and performance that is at least on par with a stock muffler. As a plus, there is no risk of a plug EVER coming out. You will also need to retune as you do this, as the back pressure will change as you crimp, obviously.

For what it's worth-

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RE: Small tuning issue - 4/29/2012 8:27 PM   
Gray Beard


 

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quote:

ORIGINAL: Firepower R/C

I actually ''tune'' my pitts mufflers by CAREFULLY crimping down both outlets while the engine is running full throttle until a slight decrease in rpm is detected, then open them back up with a screwdriver just enough to get the rpm's back. This has always given me a solid idle and performance that is at least on par with a stock muffler. As a plus, there is no risk of a plug EVER coming out. You will also need to retune as you do this, as the back pressure will change as you crimp, obviously.

For what it's worth-

Some years ago Sullivan used to send out there Pitts mufflers without a pressure nipple and they had pipes about 6 or 8 inches long. You just cut them to tune the muffler to the engine. I always cut them at an angle with the back pipe shorter then the front. Max RPM and as soon as it dropped a little you quit cutting. Most of my engines did not require the pressure nipple at all. If it did I just drilled and tapped the front of the box for it. My first choice is always the Bison Pitts style muffler though. I found them to work perfectly out of the box. I never tried to tune one at all.

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RE: Small tuning issue - 4/29/2012 11:59 PM   
JohnBuckner



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Status: online 		It takes two seconds to stick a cork in one tube. If there is any reason at all to suspect poor fuel delivery performance when using any aftermarket box muffler with two outlets then this should be among the very first things to try, its painless and instantly reversable.

If ya, ain,t got a cork then whittle one from a tree branch. I know we don,t have much of them in these parts but heck betcha I could cut one from the old out house door real quick

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RE: Small tuning issue - 4/30/2012 1:36 AM   
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