Throttle curves and carb mix

[simon1]

After finally getting my tail servo sorted and free of binding, I now seem to have trouble in getting the tt39 engine tuned right. Which seems to be a common theme with this engine. The last 3 flights I have had, a full tank of fuel each time, has resulted in my engine being hot to touch and impossible to hold your finger onto it for more than two seconds without burning it!

Now I'm not losing power in flight, which would indicate my engine isn't overheating? And seem to have decent power and smoke from exhaust. It doesn't idle very well though, bit lumpy, which is again what iv heard of these engines.

So do I still richen it? the high end needle I think is the one i need to richen because low end needle seems rich already. Lots of smoke whilst idling.
My reference usually is the raptor technique site which I think is great, my normal throttle curve is 20 45 55 65 100 ( I no 100 is alot but don't get near it anyhow Any others with this engine? and there throttle curves?

cant seem to get it right on or does this engine like to run hot?

cheers

[Adrian]

The tt engines seem to run hotter than an os engine, i have one tt and its deffo hotter than my three os ones

[Rotorhead]

Unfortunately its one of those things that needs to really be looked at in person to fix it, if there is actually a problem..... kinda hard to tell from a forum post.

But..... I'd check things like the o rings in the carb first off, you didnt say whether it was a new engine or an old one, but it could in either case be that there is a leak somewhere causing your problems.

It could also be just down to the weather, recently temperatures have been all over the place, one day its nice out, the next day your fingers are dropping off, and it does mess with the tuning of engines unfortunately.

It could be the fuel you're using, wrong type or a bad batch etc, a friend of mine had a TT39 that was having trouble, no power, a bit hot etc, and it was all down to the fuel he was using, wrong type, as soon as we changed it and retuned it, it was perfect.

[simon1]

Unfortunately its one of those things that needs to really be looked at in person to fix it, if there is actually a problem..... kinda hard to tell from a forum post.

But..... I'd check things like the o rings in the carb first off, you didnt say whether it was a new engine or an old one, but it could in either case be that there is a leak somewhere causing your problems.

It could also be just down to the weather, recently temperatures have been all over the place, one day its nice out, the next day your fingers are dropping off, and it does mess with the tuning of engines unfortunately.

It could be the fuel you're using, wrong type or a bad batch etc, a friend of mine had a TT39 that was having trouble, no power, a bit hot etc, and it was all down to the fuel he was using, wrong type, as soon as we changed it and retuned it, it was perfect.

The engine I think is about 2 years oldish, I bought the heli 2nd hand in may this year and I think it was about 18 months old then.
I think the fuel is rubbish and thats some of the problem, its a mixed bag of two fuels with different percentage mixes. I got it given and told it was up to scratch just for learning on.
Now its gone im looking to get some more fuel, opitfuel? not sure what percentage mix though, im just about doing figure of eights, slowly
What fuel would you suggest for the rappy 30v2 with the tt39 engine?

cheers

[Birdie4x4]

12 or 15 percent should be fine untill you start to work it hard.

[simon1]

12 or 15 percent should be fine untill you start to work it hard.

cheers

[Baldie]

Hi, Use Optifuel 12 in mine and it runs great.
Will agree with others though, It does run hot. Its my first nitro and i worried about the heat at first ( Can just about keep my finger on backplate for 2 sec immediately after a flight), But making it richer to cool it made it run bad. So i backed it up until it run well then richened it a click and left it. its still going great after 13 litres ... .

Recently had the engine out to install a gov., And looking inside at the bearings / piston there is no sign of overheating. The backplate test is really subjective, ie a guy i work with has asbestos fingers and could probably keep his pinky on the backplate for an hour.... !. To this end, for comfort now i use a cheap laser thermometer now on the back of the head occasionally after a flight and usually get about 108-119 Deg C, Which as far as i have read is fine for this engine.

Simon

[simon1]

[quote=Silverlyx;397872]Hi, Use Optifuel 12 in mine and it runs great.
Will agree with others though, It does run hot. Its my first nitro and i worried about the heat at first ( Can just about keep my finger on backplate for 2 sec immediately after a flight), But making it richer to cool it made it run bad. So i backed it up until it run well then richened it a click and left it. its still going great after 13 litres ... .

Recently had the engine out to install a gov., And looking inside at the bearings / piston there is no sign of overheating. The backplate test is really subjective, ie a guy i work with has asbestos fingers and could probably keep his pinky on the backplate for an hour.... !. To this end, for comfort now i use a cheap laser thermometer now on the back of the head occasionally after a flight and usually get about 108-119 Deg C, Which as far as i have read is fine for this engine.

Cheers mate this is a really informative post for me, I do the finger test on the back plate and it is about 2 secs then its ouch hot!! I think the low end needle is still a bit rich doesn't idle at low stick, with mid trim when started, need a bit of trim to keep it ticking over.

When I first start it up I have to keep puching the throttle, on the deck to seem to warm the engine up abit, need to keep it about 70% throttle then I can hear the rpm change and im off!! Once its warmed up then I lift off at mid-stick, which is what I want. So im guessing just too rich at low needle.

cheers
simon