RE: TT .46 Pro problem.
 

Hi!
First! Get rid of the hopper tank! Then use just one tank so you can acctually see that the engine runs as it should. The tank in your case (air boat) doesn't have to be mounted according to the tank-mounting-rule as you don't intend to fly with the boat...[8D].

I know from experience that mounting a tank several decimeters under the carb have no ill effects on how the engine behaves, you just have to open the high speed needle some more!

RE: TT .46 Pro problem.
 

This is simple physics, the hopper tanks stays full because it is a closed system. This doesn't mean that there is enough pressure from the exhaust to overcome gravity.
At lower throttle settings the engine still relies on the fuel draw from the carb, but the hopper tank of coarse keeps its level as there is no way it can change.

RE: TT .46 Pro problem.
 

I have a temp gauge/failsafe connected to my test stand (can be seen in the last picture of the engine) It does temp up nicely even though its cold out, but I may put a small strip of alum. ducting tape around it just in case. Anytime the engine has stalled, its been right around 220 degrees.

On the plug - I'm running the hottest plug I can find - McCoy #59. I have no interest in OS plugs - never had one I liked. If you have a hotter plug than this you can recommend, I'm all ears. One thing to note: This engine will not be ran in winter much - I've just been running it to get it dialed in and broke in well before running it on the boat.. I'm impatient. ;)


The hopper tank is on its way out - its already disconnected and I'm carrying the engine outside to go run it soon. (I'm leaving it mounted but disconnected) I will test it all out and take a video and post back what I find. Thanks for your help, Jaka. I do appreciate it.
I suppose - I didnt think about that...

RE: TT .46 Pro problem.
 

When I got my Jett muffler, it came with a brass gasket. Thinking this would leak less than the stocker, I put it in with the stock muffler. This was how the engine was ran yesterday (3 previous videos). Last night I connected the main fuel tank directly, swapped the Jett gasket for the stock gasket. This was how I broke it in. I figured to go back to the drawing board and go all stock.

MC59 plug, Byrons 15% nitro/18%oil (80/20 syn/cas) with an additional 2-3oz of castor, stock muffler & gasket, 8oz hayes tank
http://s153.photobucket.com/albums/s...t=MVI_0002.mp4

I ran it a few times before this video and got Peaks at 14,100rpm and 14,400rpm but they were quick blips. Average RPM is probably 13,700 or so. There is a delay going from low RPM to high RPM, but If I feather it up to about 4500rpm, it'll transition to WOT instantly now. Idles back down nice and back up nice so long as its feathered beyond idle.. It didnt want to idle below 3000rpm just yet... Still needs more time. I'm letting the case cool so I can swap on the Jett muffler and see how it runs on that.

RE: TT .46 Pro problem.
 

This is only true for high throttle settings, when there is plenty of pressure from the muffler and lots of fuel draw from the carb.
Near idle there will not be enough fuel draw and muffler pressure to overcome the gravity, no matter how much you open up the needles.

RE: TT .46 Pro problem.
 

From the video it sounds too lean on the low end to me.
Would it hurt to mount the tank higher up on the side of the stand, just for testing purposes?

RE: TT .46 Pro problem.
 

I am testing it as it will be ran in the boat. I do think fuel draw seems to be okay now. There is a slight delay at very low rpms but only slight. I have since richened the idle only slightly - Its tuned to give a good clean transition from about 3500rpm to WOT. The main needle is set about 300rpm rich from peak.

RE: TT .46 Pro problem.
 

Feeling confident enough that its running better, I put the Jett muffler & gasket on. The hesitation off idle is gone, and it throttles so much better. Peak RPM only up about a thousand or so, but I'm sure in warmer weather it will perform better. I think Jett claims an OS/TT .46 will turn something like 15,800 on the jettstream with a 10x6 prop, but it doesnt say what kind of prop or fuel.

Definitely a bit louder than stock...
http://s153.photobucket.com/albums/s...t=MVI_0003.mp4

The camera batteries died at the end, so thats why its so short. When we get some 50° or better days, I'll get it back out and try it again and see if the RPM picks up any more.

RE: TT .46 Pro problem.
 

Bob in the Jett forum suggested running a smaller prop - namely a 9x7 or so.. I'm going to pick one up tomorrow and the next nice day I get, I'll flog this thing again. Bob said I should be shooting for 15,500rpm to start with to take full advantage of the pipe, so I'll give it a go and post back what I find with it...

RE: TT .46 Pro problem.
 

I am pretty sure that the problems you have at low rpm, surging and dying on acceleration, is due to the low tank position. If you can live with it then fine, otherwise try to raise the tank. Remember that the engines usually leans out a little when it moves, compared to being stationary.

Regarding a suitable prop I think you can leave that for final testing on the water, just get a good selection to try out with. It will be an optimization of static thrust (large diameter) with good acceleration from a stand still versus a higher pitch (smaller diameter) and high top speed, but a slower acceleration from a standstill.

RE: TT .46 Pro problem.
 

It doesn't surge though it may sound like it from the video. Wearing gloves makes it tough to hold onto the throttle linkage so it sounds like it's up and down. Also, it quit stalling off idle. The tank is low, yes but Dub Jett even said it should draw fine that low. It isn't perfect yet, by the engine has only seen a half gallon of fuel.

RE: TT .46 Pro problem.
 

Hi!
Sounds as if the engine is not getting enough fuel when you give throttle in the first video. Open the idle needle slightly!

Running a hot plug with as much nitro as 15% is no good performance wise.
My recommendation is to use either 5% nitro and a Nova Rossi 4A or 4 plug (medium hot) Enya 3 or 4 , OS 8 plug works too or...to use the fuel you now have (15% nitro) and use a colder plug , like a Rossi 6,7 or 8.

Best 10x6 propellers are the British RAM or German Graupner "Cam-prop"! This is when you use your engine in a plane (Q-500 racer) but I think those will give best performance in a boat too. Aim for 14500-15000rpm using no nitro (80/20) fuel and a 10x6 RAM prop together with a Nova Rossi 4 glow plug and removed head gasket.

9x6 or 9x7 is also a good size and then the APC is the prop of choice.

RE: TT .46 Pro problem.
 

As your boat gains speed it will need more fuel.So sucessful ground running may be meaningless. If there are no bubbles in the hopper tank, then the hopper tank is not needed as it is only for seperating the air from fuel from the main tank delivery. Putting a hopper tank onver the engine serves no purpose, if you think so then get rid of the hopper tank and loop the fuel line above the engine. Same thing happens with the hopper tank as the head from the hopper tank to the engine is canceled out from the extra head to the tank.

However there is increased resistance to the fuel by the hopper tank, the extra loss from fuel entering another clunk and discharging through the ven increases the pressure required.

RE: TT .46 Pro problem.
 

In the last 2 videos, the hopper was disconnected. I was running on the main tank 6" below the engine. The idle was slightly lean before these 2 videos so it was richened a tad. I put the engine away after the last run. I will run it more later this week in the present configuration with another prop and drop the nitro some. The 15% is all I had left but I'll get some 5% today too.

RE: TT .46 Pro problem.
 

I thought about it after my last post, but I've got 5 gallons of methanol. I need to use up this 15% fuel so I think I'll thin it down with straight methanol down to 5% or so and add extra castor. My cars won't run very well on this I don't think.

Also - I emailed TT about the tank placement and they suggested using a fuel pump. Depending on how it does, I might just get a pump and try it.

edit: I have about 1/2 gallon of 15% nitro byrons gen2 aero fuel that I want to use up. To mix it down to 5% nitro, I figured it out to using about 11oz of the byrons fuel (which ends up being 1.65oz nitro and 1.98oz oil and the rest being methanol and whatever additives byrons uses). If my math serves me, I'll add 4.42oz of castor oil, and add 16.58oz methanol. This will give me 5% nitro (1.65oz in 1qt), 20% oil (6.4oz in 1qt), and the 75% remainder methanol and additives (23.95oz) I did the same calculations for 10% nitro as I'd try running both to see how marginal of a difference there would be. I could make a 1/2 gallon of 5% and a 1/2 gallon of 10%. I dont want to try running FAI fuel until its warmer out. Today (Tues. 3/8) is supposed to be around 40° so I think Ill be out testing again today. Its not as warm as I want but since I ended up with the day off, it'll give me something to do and put a little more run-time on the engine. I also have an APC 9x7, and an APC 10x5 balanced and ready for testing. The 9x7 was really tough to balance.. (This one is tiny!) The 10x5 was way out of balance which I find odd.. The bigger props I have for the K&B .65 (APC13x6 and 13x7) were almost right on right out of the package which seems odd.

RE: TT .46 Pro problem.
 

Hi!
Justr open the low speed needle some and use the correct fuel and glow plug!

RE: TT .46 Pro problem.
 

I'm going to start with that, kind sir. Mixing the fuel I have down to 5% nitro is what I plan to do as shelf fuel is expensive and I have no use for it in my r/c cars.

I only have hot plugs, and anyone locally does not carry Enya, or Rossi plugs. I will not use any OS plugs ever. I've used them before and I do not like them. I've got K&B hot plugs, 1 Fox hot idle bar plug, and a bunch of McCoy #59 hot plugs. These are my test-mule plugs. Since I'll have more time, I'll keep the Jett muffler on it and try out the different plugs I have on the 5% fuel mix as well as the two other APC props I have for it. I will come back with videos and results. When the boat is ready for runs on the water, I will test with APC props and once I find the one prop that makes it run out the best, I will order 1 or 2 Graupner Cam-props in that/those size(s) and perhaps a few glow plugs that you had mentioned. Those Graupner props look super efficient. I looked them up online yesterday. They didnt seem to have the sizes I was looking for (9x7, 9x8, 10x5).. Would I have to use the metrics or was I reading the site wrong?

RE: TT .46 Pro problem.
 

I have a side question regarding fuel draw and muffler pressure. I've seen some airplanes running exhaust extensions/deflectors over 12" long. I can't remember what forum I had seen it talked about but wouldn't doing something like this add a little backpressure to provide better muffler pressure to the tank? Should fuel flow not be sufficient on a given engine to get proper RPMS, could one do something like this without taking a huge performance hit or would the gain in pressure be too low to make it worth trying?

RE: TT .46 Pro problem.
 

Try it...then you will know! Simple. Capt,n

RE: TT .46 Pro problem.
 

Hi!
Long exhaust extensions will only increase heat build up inside the engine (which is no good) and reduce power significantly. The only time an extensions works without loosing power is when you have tuned pipe!

RE: TT .46 Pro problem.
 

Okay.. I was pretty sure there was a downside to it. Thanks, Jaka!

RE: TT .46 Pro problem.
 

Alright. Bob27s in the Jett forum suggested a 9x7, so I put one on and ran it. I thinned the 15% byrons down to 5% nitro / 20% oil, 9x7 APC prop, MC59 plug. Transition sounds rich to me, but you be the judge. Max RPM in the video is about 100rpm rich from peak. (Running on main 8oz tank only with muffler pressure/no checkvalve)
http://s153.photobucket.com/albums/s...t=MVI_0009.mp4
I tried the K&B hot plug, but didnt bother with a video - peak RPM's down to 15,700. Didnt bother trying the Fox idle bar plug - my hands got too darn cold.

edit: This is the very first run with the 9x7 prop. I ran it a short while before I took this video to warm the engine up. I got an even 16,000 peaked, so I richened it about 200rpm.
http://s153.photobucket.com/albums/s...t=MVI_0005.mp4

RE: TT .46 Pro problem.
 

To me the transition sounds much better than before, glow engines should always sound a little on the rich side.

The Fox idle bar plug is for another, older, type of engine design (baffled piston, non-schneurle ported), the idle bar will most likely give a lower performance than a plug without it.

RE: TT .46 Pro problem.
 

To me, it seems rich. Only slightly, but still rich. According to everything else I've read about adjusting plane engines said you adjust the idle mixture for a clean, instantaneous transition which is what I had in the video you commented of it being too lean (though my fingers fumbled the throttle some). As long as it doesnt stall and load up at idle, I'm fine with it. The engine was screamin' today. Haven't seen those kind of RPMs from an airplane engine yet. My Car engines will do 30,000rpm all day long but the sound of this .46 on the pipe seems so much different. I think its got a neat sound to it. This muffler rocks, IMO. Hopefully the engine blossoms a bit more to maybe get that 10x6 humming in the 15,500-15,800 range. (Probably a bit optimistic, but hey.. one can hope.)

The only reason I bought the fox idle bar plug last summer was for my K&B sportster .65 drone engine. The midrange is so blubbery rich within the limits of the idle mixture disk that it stalls out sometimes. I figured it worth a try in hopes of keeping the engine from dying on the water. (another airboat) Being it wouldnt even run on it, I swapped back to the MC59 that I run in everything else and modify the carb a little and it runs better. I think it needs a new (current design) spraybar/barrel.

RE: TT .46 Pro problem.
 

Sounds pretty darn good to me!
Just a wee bit rich is a good thing...because once it gets moving, the prop will unload a little bit...maybe not as much as it might in an airplane, but actual testing on the boat will tell.

Temp changes will effect tune as well...but you already know that.

I'd say she's pretty good now...about as close as you need 'er to be. The rest of the fine tuning can be done while running the boat, I would think?

How fast do ya think you could get your air boat going on the snow?;)