Funtana s40 with TT F91S

[DMC]

I have a Funtana S40 with TT F91S . After I read the posts on rcu about Funtana and TT 91S I think the engine is good for 3D with this plane. Somehow " don't have enough power to pull out of a hover and loose power on verticals . The engine has about 15 tanks . I tach the engine about 9600 (still running rich) with 14x6 master airscrue with 20/20 fuel . What is the problem ? Need a pump ? Need one way valve between muffler and fuel tank ? Need another prop ? Need recheck the valve clearence ? the engine has a steady idle and it fires quikly and never had a dead stick . I have a on board glow ... does it matter ?

I'm new to 4Stroke and at the field nobody knows how to tune a 4 stroke engine.
Please help .

[Neogenesis]

ok....first off throw away that master airscrew. Buy yourself a APC and you'll be amazed at the difference it will make.

Next.....you can only tune a 4 stroke with a tach. It is nearly impossible to tune by ear. Other than that just use the same procedure as you do your 2 strokes. Bottom end first and then your top end. It's as simple as that.



Neo

[Gus155]

tried a 14x6 master airscrew wood prop on my funtana and saito 80, DID NOT WORK. The saito 80 i have in mine would also swing the 14x6 around 9500 rpm, but will swing the 14x4W at close to 11 000.
Try the APC 14x4W,first. Works very well with the saito.
Dont know the thunder tiger 91 fourstroke, but my saito leans out a lot when hovering.
My set up with the saito 80, running 20% nitro, will turn the 14x4W at about 10 600 rpm. I then turn the needle out to peak at about 10 000rpm, while running wide open level on the ground. When you point it straight up, it leans out to the optimum rpm range between 10 500 and 10 700 prm.

Before you get pumps and check vaves and ouver complicating things, Try the 14x4W, turn the needle out a touch more.
You running tank pressure from the muffler?
might be a good idea to reset the tappets.

[DMC]

My prop is made of Nylon not wood. I have tried the 14x4 W apc but the same problem. With 14x4 w i have about 10500. Same problem... on vertical I loose power.
Gus155 , yes the tank is presurised from the muffler.
Sorry about the language barrier (I'm from Romania )... what is "tappets" ?

PS : Offcourse I use a tach... is imposible to distunguish 8000 from 10000 only by ear.

[casey g]

ok i have a saito 100 and i have it on my funtana 40
i only had that problem once cause we leaned it out a little to much and it could not take it once it gut up a little bit it ran hard on the ground but after take off it did not want to run so i landed and richened it up a little and that fixed it for me

[gabo90]

i have the same problem in my funtana with an os 91fx 14x4 prop, i tried with pipe and lot of things and stay the same,i turned to another prop,a 15x6 and it has a lot of change
i dont like very much 91 engines because of vibration and problems

[Gus155]

	Quote: Originally Posted by DMC
	My prop is made of Nylon not wood. I have tried the 14x4 W apc but the same problem. With 14x4 w i have about 10500. Same problem... on vertical I loose power. Gus155 , yes the tank is presurised from the muffler. Sorry about the language barrier (I'm from Romania )... what is "tappets" ?(Need recheck the valve clearence) PS : Offcourse I use a tach... is imposible to distunguish 8000 from 10000 only by ear.

The tappets are the rockers that push the valves down. On a new four stroke they should be reset after a few hours. Four strokes of this capacity dont run well over about 11 000 rpm.
Sounds like your tt91 is a bit on the lean side. Open the needle valve untill you are getting about 9900 to 10 200 rpm with the 14 x4w. Had similar experience with my saito. will swing the 14 x4w at 10 600, but wouldnt pull out too good, untill i richend the mixture.
I have found that a 13x6 master airscrew "K" series prop also works well.
Good luck, hope it helps.

[DMC]

Thank you for the quick answers. I'will try in this afternoon.