Gentlemen.

Do any of you know this carburator?

http://planemania.dk/motorer_braends...21_049_da.html

Thanks

Looks like (maybe ) an MVVS carb...what do you want to know about it?
From what I can decipher, it appears to work with or fit engines from 3.5 to 8 cc's...

Hey Proptop.

It's for my TT Pro 46. Like Dabigboy, I have midrange problems with my engine. Mine was put away for over one year without any after run oil. I put in new ball bearings and cleaned it up. I'll try without pressure on the tank and remove the fuel filter. If that dosn't help, I'll try a new carburator. I've tried everything else without any luck...

http://www.rcuniverse.com/forum/m_76...tm.htm#7662041

Yes it is a carburator for 3,5 to 8 ccm engines. If it is a MVVS it should work just fine

I'll ask the dealer.

Hey Lille-bror...
Hmmm...I've never had mid range problems with any of my TT .46's? Got 2 of them now, and had 2 more previously, that I traded stuff for...
Just thinking here...perhaps your low speed needle is loose/leaking/not set quite right?

I also have an MVVS .49 (8 cc ) and the carb neck is 13 mm
I don't recall right now, but is the carb neck of the TT .46 also 13 mm?

Perhaps Dar, or Pe or Jaka can confirm if that pic of yours is an MVVS carb? It looks a lot like the carb on my .49 but not quite exactly.

Bror,


It is an MVVS #3216 carburettor.

It is quite inexpensive, has a 13 mm diameter spigot and a 7 mm bore.


This is one of the most linear carburettors in existence, but I am not sure it will fit unaltered onto your TT, which may have a carburettor socket of a different diameter.


The older MVVS carburettor had an idle-stop screw, which this carburettor doesn't and a simple intake 'horn'; which in this carburettor has been replaced with an elaborate, double-curved horn. It has much better manners and linearity than carburettors that cost 3-4 times as much.

I can vouch for the MVVS carbs as being very linear, no fat midrange and the instructions are precise as in they tell you just how to set them. They don't just say, "turn the screws and see what happens".

Thanks all.

If you are bored, you can check a video I recorded last Friday. Turn up the speakers a bit high to hear the engine.

http://www.youtube.com/watch?v=JL3d80uSj3g

The outside temp was 1 dregrees Celsius. With the alu-tape on the top, it didn't go down in RPM when the glow driver was remowed (A3 plug).

I've tried OS8, A3 and F plugs. Fuel without nitro and 12 - 25 % synth oil. The first time I tried Cool Power 7 % nitro it ran great. The next time and until now, it's back with rich midrange. Also 10 % nitro with 12 % synth oil.

3 different tanks. APC 9/8, 10/7, 11/5 and 12,25/3,75 props.

Last night I cleaned the carb ones again, and sealed the 2 O-rings towards the spraybar with Loctite 5699. The 2 O-rings on the needles are cowered in castor oil to eliminate air leaks (I can't by a new O-ring set here in Denmark any more).

No change with or without the head shim.

It's not a adjustment issue.

A gentleman in Denmark suggested testing the engine without tank pressure...


I just wondered, that Dabigboy´s engine also runs like s***. His engine didn't (like my engine) run for a long time...


Thanks

The "mid range" on the engine in the video sounds fine. During most of the video the engine is at what I assume is full throttle, with a little idling and a bit of mid range stuff (when your tach shows about 7K) which sounded fine.

It actually sounds like the engine is overheating to me - it's sagging back from a peak of somewhere in the mid elevens back into the tens once it gets hot. Which prop were you running in the vid?

I would lose the ally tape and try the run with all else equal again.

I would add to Grant's words...

It seems you never attempted to get the idle down, from around 3,000 to ~2,000 RPM, which this engine is capable of sustaining...

The prop seems to be a rather large, 12.25x3.75W, which has enough rotational inertia to get idle down to 1,850...


And the mid-range does not seem to be getting too 'fat'...

Too much prop. Try a 10x6 and see the difference.

Also fatten the mixture up a tad. You're running it way too lean. You don't have to over lean this engine when running a 10x6. I'd like to strangle the person that spread the rumor that these engines run best with an 11x6, or heavier, prop. These engines are designed to scream, not be lugged down like a John Deere garden tractor. If it isn't spinning at 13 to 14k with a 10x6 and spitting a little extra fuel, then it is over propped and too lean.

I'd have to run a few gallons of fuel with that European super lubricant before I could believe that such a low percent, volumetrically, is adequate. I'm beginning to wonder if this low percentage of oil can account for so many Europeans engine problems.

I have nothing against Europeans. After all, that's where my ancestors came from.


Ed Cregger

What???? Do we have many engine problems? who? when? where?

I leaned as much as possible in the top and in the bottom, to be sure that it wasn’t rich settings, that was the issue. It was not too hot after the top end adjustment.

I would never run the engine like that in the plane.

The alu-tape was put on, after a test without it – again, just to be sure, that it wasn’t overcooling, that was the problem. If I pinch the fuel tube a little, when the engine runs at 6000 RPM and then go to WOT, the transition is perfect.

I used APC 12,25/3,75 prop.

Cool Power 7 % nitro, 17 % synth oil. After the video I tested the 10 % nitro mix with 12 % AeroSynth3 oil. I noticed a metallic sound after readjustment from the engine with that fuel – I’ll go back to 18% oil. The engine doesn’t run faster with less oil.

The idle at 3000 is too high, I know. I can easily get it down to 2200.

If an engine runs perfect, the transition from midrange to WOT should be as smooth, as the transition from idle to WOT, right? To me, the transition from midrange hesitates a little.

I’ll put back in the plane and give it a try.

Always nice to have inputs from other people.


Thanks gentlemen

Next time I'm in the US, I'll pop in for a strangling.

The TT .46 pro runs fine with an APC 11 x 6 (about 11.5 - 12K), an MA 11 x 6 (mid to high 13K), an APC 12.25 x 3.75 (11.5 - 12 K), an APC 11 x 5 and an APC 12 x 4 (both mid to high 13s). The only application you'd run a 10 x 6 or a 9 x 7 on a TT .46 Pro is in a Q500 or similar.

We used to run 10 x 6 props on our baffle piston .40s in the seventies. A modern .46 is in a whole-nother realm, powerwise.

Please tell me: If you have a little 3D plane, like my Hangar9 Tribute 36, you should use a large prop, right? Approximate 12/4 on a .46 engine?

In our neck of the woods, the two most popular props for a TT .46 Pro in a 3D application are the APC 12 x 4 and the APC 12.25 x 3.75. The 12 x 4 has less rotational inertia and lets the engine do about another 1500 - 2000 rpm at peak. It pays to try both to see which is best for your model and your flying style.

I like a 12x4 on a .46 engine for small 3D planes. I think I like an 11.5x4 even better!

Thanks Ken and Harry. You are very kind.

Gentlemen.

Freakingfast has made, for me that is, a very interesting post concerning mufflers:

http://www.rcuniverse.com/forum/m_50...tm.htm#8415069

I was not aware, that a simple baffle could make an engine runs differently. All I have learned until now, was perhaps a lower tank pressure and perhaps an increase in the top RPM.

Things that make U go "hmmm"

I thing I've solved the problem.

I put the removed baffle back into the muffler, and the transition was perfect.

I don't know if the sealed O-rings in caburator made any change, but I doubt it because they seemed to be in a good condition.

Thanks again, gentlemen.