First, let me say that I am no expert by any means, but I must ask the question.

Have you considered using a bladder tank?? I am putting together a P7 and have considered this. For some reason I think it will work.

FWIW, 2 guys from Texas came up for a CPA meet, both had P7's With OS55 engines (1 with the Evo performance muffler, the other with a Jett). Both had engines leaning out/deadsticking during the outside loop maneuver. One of the local guys (with a OS .61/Jett) mentioned he had the same problem. He advised them to open the muffler nipple one size (turn drill bit with hand). While it did not completely cure the problem (they still experienced some hesitation), it did stop the deadsticks and both were able to compete both days.

Just a thought...

Wildnloos,

While you didn’t respond to my posts I am so free to show extra information related to your muffler nipple. Hope you or Dave don’t mind.

As mentioned before the tank pressure is directly related to the throttle level of the engine see my post 19.
http://www.rcuniverse.com/forum/fb.asp?m=10637662

If throttling back in normal flight position, the pressure will be released (or relieved?) fast by an airstream through the muffler line to the exhaust system if the airintake in the tank is above the fuel level.
Throttling back short time before or during nose down position can have the result some fuel have to be spilled because the air intake in the tank is below fuel level. This fuel is released through the muffler and is same amount as air that has to expand to get the lower pressure.
Problem is the drag of the pressure release line is several hundred time more now, filled with fuel, than if air is released. So much more time is needed to release the pressure and in that period the engine has a too rich mixture

It will be clear that these problems can be worse with long muffler line and small diameter of the muffler nipple (here he is, Wildnloose), bulky fuel tank, position of air inlet in the tank or using of (high) muffler pressure. Again, the whole story combined with the situation the fuel is all above the engine in nose down ATTITUDE like a water tower and will drown your engine.

(In the past there were carbs with an added special pressure release connection to do this job, real classic pattern!, they knew it all!!)

My opinion,

First of all rule, keep distance between engine and tank as short as possible when not using a pressure regulator, second, tank not too big and after that, third, good plumbing.

When you don’t use muffler pressure think about Evangelista Torricelli http://www.rcuniverse.com/forum/fb.asp?m=8559982
The principle I use in my other Taurus without muffler pressure. Real Dutch, don't spill fuel!!


Cees

I would like to agree with your statement, but I cannot.

The static pressure in the muffler is exerted over all the surfaces of the tank and the tubes, regardless the location of the fuel inside them.
That is the Pascal's law.

http://en.wikipedia.org/wiki/Pascal's_law

You missunderstand that law. The water pressure at the top of a watercolumn is 0 at the bottem it has a pressure due to the weight of the water, the equasion in you link will calculate that pressure. The muffler pressure is not an incompressable fluid andits pressureas used is not based on its static weight. The fuel tank has the same effect in that when the plane and tank are upright the muffler vent has no fuel blocking it and thus the tank pressure is the same as the muffler pressure. When inverted the fuel is now restricting the vent and the tank pressure will be reduced from the muffler pressue by the differance of the fuel head sitting on top of the vent.</p>

I just need to get back to the field and start working my way through these awesome theories!!!

First up is the Uniflow setup. Hopefully I can do it this weekend.

The uniflow setup is good, I use it often, but I doubt it will do much for your problem.  I think it may be more related to cooling of the engine at low idle and high airspeed.  I think the solution may be a hotter plug.

WHOOOOOPIE! WE FIGURED IT OUT! I tried the Uniflow setup and it seemed to sorta work, but the problem is, airplanes throttle back. As soon as I throttled back the fuel pressure dumped into the muffler. Sloppy mess and a way rich motor.

A buddy at the field had a similar problem with his Evolution engines and said his fix was an Evolution glow plug (I was using an OS #8). Luckily he had an extra! I also reverted back to a normal vent-line setup. The Evolution plug changed everything. The engine was running way rich as well. Did a few takeoff-land-adjust cycles on the engine and I finally flew a sucessful outside loop (running 8).

The next couple flights I practiced the Sportsman SPA manuevers. She's tracking great! A few more practice days and we'll give SPA a shot in September (Ft. Worth).

Thanks for all the great advice fellas. Dave

Whats scaryis that plug had probably 50-60 flights on it .

Really appreciate the help Mark!

No problem it was fun next comes the106[>:] or it is for sale