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tuning a vmax 46, HELP!!!! please!

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Old 06-01-2006, 04:51 AM
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casey_tribe
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Default tuning a vmax 46, HELP!!!! please!

Hi im new to this so if im in the wrong area, i apoligise, i have a stinger plane with a vmax 46.
im having trouble tuning it properly, i can get it to run nicely sitting on the horizontial, but as soon as i tilt it in an up ward direction it wants to die as if it is running to lean, i then tune it in the verticle position, get it running nice, bring it back to horizental, and now it is far to rich?[:-]
I have just replaced the fuel tank and lines,all o rings in the carby and the fuel with new fuel, i think it made some improvement but that could just be me,
any ideas?

Thanks

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Old 06-01-2006, 05:52 AM
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Default RE: tuning a vmax 46, HELP!!!! please!

Is the engine broken in? Do you use muffler pressure?
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Old 06-01-2006, 06:56 AM
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Default RE: tuning a vmax 46, HELP!!!! please!

Sounds to me like your clunk line is too long, and when you hold it vertical the clunk is sucking on the back wall of the tank. I normally go for about 1/4 inch clearance. That or the clunk line may have a split near the front, although thats unlikely if youve changed all the lines.
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Old 06-01-2006, 07:55 AM
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Default RE: tuning a vmax 46, HELP!!!! please!

The symtoms you decribed here are not all that uncommon.

First, are you running the Vmax muffler ? Or an after-market muffler ?

What prop are you using ?

Is the fuel tank in a conventional location (Behind the firewall) or is it mounted away from the engine (near CG) ??

Assuming a conventional setup for a moment, with nothing more than a 10x6 prop ....

What you decribed is an engine with limited ability to draw fuel, or insufficient muffler pressure.

It needs either a bit more backpressure, or a bunch more tank pressure
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Old 06-01-2006, 10:29 PM
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Default RE: tuning a vmax 46, HELP!!!! please!

thanks for your help bob27, wilkigmc and soarrich, i am using the muffler that came with the engine, the tank is directley behind the fire wall, the chunk line is fairly long, ill shorten it up and see if that helps, and as for increasing the muffler back pressure, what would be the best way to do that? steel wool? again thank you for all your help!!
Pat!
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Old 06-01-2006, 10:30 PM
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Default RE: tuning a vmax 46, HELP!!!! please!

thanks for your help bob27, wilkigmc and soarrich, i am using the muffler that came with the engine, the tank is directley behind the fire wall, the chunk line is fairly long, ill shorten it up and see if that helps, and as for increasing the muffler back pressure, what would be the best way to do that? steel wool? again thank you for all your help!!
Pat!
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Old 06-01-2006, 10:47 PM
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Default RE: tuning a vmax 46, HELP!!!! please!

casey
how many tanks of fuel have you ran through this engine?????
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Old 06-01-2006, 10:55 PM
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Default RE: tuning a vmax 46, HELP!!!! please!

If you're using the stock muffler, you don't need more back pressure. Are you using a 10 x 6 prop, if you have too big of a prop it would act the way you describe. Your tank center line should be about 3/8 inch above the needle valve, and the tank should be 10~14 oz, (Sorry I don't think in metric). You never said if it was broken in, is it? If you see black in the oil residue, thats aluminum wearing, that's bad. Here in the USA OS is real good about replacing defective engines, you might want to send it back.
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Old 06-02-2006, 04:12 AM
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Default RE: tuning a vmax 46, HELP!!!! please!

Hi thanks soarrich, i had a 11x6 prop and have changed it to a 10x6, that made a big diferance, i tryed to creat some more back pressure by putting a leingth of oil and heat restant hose, dident do much except stop my plane frome getting covered in oil,
I also lifeted the tank.

And JS615 , i have run a least 20+ tanks through it, i run 4 tanks through it as the book said, and i dont think that i have eva seen any black crud in the oil comming out the exhaust, but mind you i think i have always had it running way to rich all along, whan i land it, there is oil dripping off the tail plane, it eaven started to seep under the covering and stained the balsa. i thing itsall good, seams good but if it sounds like i may have skiped something or something ive done sounds dodgy please dont hesertate to let me know.


So for now its running sweet, thank you for all your help again!!
Many thanks
Pat
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Old 06-02-2006, 08:11 AM
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Default RE: tuning a vmax 46, HELP!!!! please!

Glad to hear you have it running ok.

The Vmax engines have a muffler similar to the Tower muffler - semi-tuned exhaust.

The 11x6 was definately way too big. The engine has to turn up well over 14,000 rpm with that exhaust to run right. Over 15,000 would be ideal. You might even want to try a 9x7 and let the thing wind up a bit.

Worry not about the backpressure. The problem as you have seen was the prop.
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Old 06-02-2006, 09:13 AM
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Default RE: tuning a vmax 46, HELP!!!! please!

I have three of these engines,,a vmax .46 and two vmax .52,,, they all needed at least 5 tank fulls of fuel ran through them before they ran right,,,, but after that they run like tops...no problems at all,,,, i belive these are gms engines,, tower engines are the same also i think...
If you are still haveing trouble just send it back,,, and have them fix or replace it.....
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