richg99

I'm new to all of this, so please forgive some of these questions..
My TT .28 starts well enough.
I have it on a (probably) too heavy plane at 4 lbs.
My motor never gets above 11,500 rpm flat out., no matter what prop I have on it so far.
Adjusting the high speed needle doesn't seem to add much in the way of rpms.
The High speed needle ...it is very sensitive. If we tweak it just a click, it will drop rpms and stop quickly.
I've tried three props 8.7 9.6 10.6 and the rpms do not change a lot.
It stutters and dies at full throttle way too often.
The manual says it should have a range of 2500 to 18000. My engine's range is 4500 to 11,500
I've used two different glow plugs... the one they included an R-2; and an OS 8
A guy at the field said to take the baffle out of the muffler. We did that, and the plane was a bit noisier ( of course) but did finally lift off of the ground!!
When I was leaving the other day, another guy said to try a 10 x 4 prop.
I am using 10% fuel....somebody said to go to 15 or 20 % fuel???
All I want is slowish scale-like performance.

I'd like to use the engine somehow. I build SPADS and can build another one, in a smaller configuration for lighter weight if that is the only way to get some use from this engine.

Any and all help or suggestions appreciated. Rich

controlliner

How much run time do you have on it? These TT engines are awesome after 1/2 - 1 hour run time. 11,500 sounds low, you should get @ 12-13 K on a 9X4-9X6 with 10%. Also these TT engines really reccommend at least 20% castor oil for the fuel, due to the nickle plated liner.

jeffie8696

I would like to see some more specifics like fuel brand and condition. Perhaps you have contaminated fuel. Or it could be as simple as a plugged fuel filter.

richg99

I'd guess that I am might not have as much as 1/2 hour on it as yet. The fuel is brand new from my local hobby shop. Same fuel runs fine in my OS 46 ax. I'll pull and check the fuel filter tomorrow. thanks and I'd be happy with any additional thoughts or suggestions, too. Rich

jeffie8696

Have you done any bench testing. It helps to iron out any kinks before installing it on the plane.

richg99

No re the bench testing...but...running it at the field, on our start-up benches (during the week so as to not bother the other guys on a crowded weekend) affords me the use/input of a couple of older hands. On my own, I wouldn't know if what I was seeing was good or bad. thanks Rich

rainedave

My Feedback: (1)

If this is the new TT .28 with the cast-on carb body then an 8x7 or 9x6 is too much prop. As controlliner said, try a 9x4 or maybe a 9x5.

The 18,000 listed in the specs is the engine's practical rpm limit (sort of like a redline) and not what you will turn with usable props.

Is this the one you have?

David

richg99

Yes it looks like it rich

jeffie8696

I think the manual is telling him to use a 9X6 or 10X5.

rainedave

My Feedback: (1)

Sounds a lot like an OS manual. That's definitely aimed at lowering sound levels, not achieving optimal performance.

David

controlliner

The transfer ports in these engines (18,and 28) are shallow. They will swing a big stick if you need to but the smaller prop is the way to go. I can't stress this enough, 1/2 - 1 Hour run time in a rich two cycle and these engines will perform way better than an LA. They have a nice thick nickle plating (twice as thick as any other ABN engine). I also believe that using fuel with 20% all castor will help your engine perform better. TT instructions say you can use a castor synthetic blend but they don't seem to believe it is the best way to go.

DarZeelon

Rich,


I do hope you had done the break-in, as it is described [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]right here[/link].

I also hope you are using fuel that has at least 22% lubricant, of which at least half is castor oil.

If you're using all-synth, made in USA fuel (exception: Copper's), you're playing with trouble...


5% extra nitro will only add ~100-150 RPM on top and this engine seems to be missing about 2,000; or about 40% of its HP output...
It is quite obvious something you did was wrong.

jaka

Hi!
What does the instructions say about nitro content!
What you describe sounds like too much nitro.
9x6, 10x5 or 10,5x4,5 , even 11x4 or 11x5 will work , all APC

richg99

Dar, very little of what you wrote is in the TT manual. It does say to use 20 % lubricant, and that is what I am using. The manual specifically does say
QUOTE-
"Proper break-in is critical to the life of any model engine. Because your TT GP series engine // is ABN//...A prolonged break-in period is not necessary. In fact, after a tank or so on the ground, your engine can be flown to break it in." end of QUOTE...

I will be doing a number of things this week..Running the break in after reading your treatise and trying a 10 x 4 and a 9 x 4 prop; ...etc.

Thanks for the help so far. I'll be back. Rich

DarZeelon

Rich,


I know most manuals are not as exacting as my thread... This is probably because they are designed to get the engine through its warranty period safely; not to a 300 hour service life.

My thread is intended to achieve the best longevity (and performance and reliability) from any tapered-bore engine.


These two objectives are not necessarily the same and neither are the ways to achieve them.


The manufacturer would probably want you to replace your engine periodically (with another of his engines), while you would probably prefer the engine to serve you trouble-free for as long as possible, or to fetch a good price when you try to sell it.

This is the objective of my thread.


For failing to mention you must use a lot of castor oil in the fuel mix for any bronze bushed engine, the manufacturer should be hit on the nose, with a boxer's tools of the trade...[sm=punching.gif]