Tettra Tank Issues in Pat XL / 90LX  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Tettra Tank Issues in Pat XL / 90LX
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Tettra Tank Issues in Pat XL / 90LX - 10/3/2005 5:06:26 AM   
jon_focal_plane


 

Posts: 72
Joined: 4/11/2005
From: Tucson, AZ, USA
Status: offline 		Bob,

I removed the Jett Bubbleless 12 oz tank for a Tettra 18 oz tank in the Pat Xl. Re-tuned on ground everything ok. Had two dead sticks. Took it back to the test stand. When plane is horizontal, no problem. When at idle and the plane is tilted up or down and given full throttle, the engine quits. If already at full throttle, will perform fine at any tilt angle. Got it home and inspected the method Dubb used for his Bubbleless tanks, that is the pickup end in the tank, I thought I had the problem licked. No dice. Took it in the back yard, same problem. I'm running the Tettra tank with just the one pickup line into the tank. Any ideas?

Jonathan

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RE: Tettra Tank Issues in Pat XL / 90LX - 10/3/2005 2:12:39 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Jon,

Im not sure what might be wrong. The tetra works pretty much the same as the Jett tank.

Be sure that you are getting 100% of the air out of the tank before filling it. Thats about the only thing that can really go wrong.

Make sure the outside of the tetra tank is not leaking - where it might be losing pressure altogether when at lower rpm. If that happens, there might be somesorta back-flow action going on. Im not sure. Worth a look.

One other thing to try if nothing else works - install a small checkvalve in the muffler pressure line to the tank. Formost makes an inexpsneive small one, and a YS checkvalve will work too. That will at least minimize any backflow.

On the last tetra I put together, I used a long plastic barbed fitting as my feed tube through the tank stopper. No clunk or clunk line. But that was on a 10oz tank.

Let me ask around, I will see if anyone has run into this also.

Bob


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

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RE: Tettra Tank Issues in Pat XL / 90LX - 10/3/2005 3:14:15 PM   
jon_focal_plane


 

Posts: 72
Joined: 4/11/2005
From: Tucson, AZ, USA
Status: offline 		Thanks for the feedback Bob,

Follow up info: I inspected the tank before repeating the test. Exterior of tank was in good shape, no leaks. Inner lining was not leaking. I removed all air before the test. I had about 1/4 fuel load in the tank. I will probably need to retest it at various tank fuel loads to see if there is a dependency. I just realized there might be another issue. Although there were no bubbles in the line from the tank to the needle valve, there were some bubbles between the needle and the carb. Not sure why that wasn't sending alarm signals off to me; you get focused on one thing and lose sight of the big picture. I'll replace the line and make sure the needle nut is tight.

Jonathan

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RE: Tettra Tank Issues in Pat XL / 90LX - 10/3/2005 3:51:32 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Jon,

Sounds good.

one thing Ive noticed - it is usually best to start with a 100% full fuel tank. This way there is no way for air to 'work' its way back upstream after you make all of the fuel line connections. In fact, it is the only way to ensure there is no air in the tank. It only takes a little bit of air in the tank to really mess things up.


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to jon_focal_plane)
       Post #: 4

RE: Tettra Tank Issues in Pat XL / 90LX - 10/4/2005 4:35:35 AM   
jon_focal_plane


 

Posts: 72
Joined: 4/11/2005
From: Tucson, AZ, USA
Status: offline 		Inspected the lines, no leaks. Will have to wait till next weekend for further testing. I think the neighbors enjoyed the sound of the Jett 90 cranking.

Additional info: I removed every bit of air before flying or testing. Always fly on a full tank.

Jonathan


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RE: Tettra Tank Issues in Pat XL / 90LX - 10/7/2005 1:07:36 AM   
jon_focal_plane


 

Posts: 72
Joined: 4/11/2005
From: Tucson, AZ, USA
Status: offline 		After replacing the fuel lines and filter, I retested. Level, with full tank, engine responds well, no bubbles whatsoever. At idle, when you place the nose high or low and go to full throttle, the engine dies. Looking closely while the engine is off and moving the nose high or low, I can see a strong pull when I go nose high and a push when I go nose low (small bubbles tell the story). That tells me I'm leaning when I put nose up and flooding when I go nose down. Seems rather intuitive; I think this happens to some degree with any tank installation. But it didn't kill my engine with the Jett 12 oz Tank, or for that matter, any other plane I own with any variety of tanks. Am becoming disappointed with the Tettra tank. Will probably go back to the Jett 12 oz or a larger non-bubbleless installation. Shucks!

Jonathan

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RE: Tettra Tank Issues in Pat XL / 90LX - 10/7/2005 2:37:52 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Wow......thats really weird.

since its a nose up/down thing.... its gotta be the fuel tank, or id say check the needle packing nut ... make sure that is tight.

In the Ext Speed forum, look up Madscientist. He has a 18oz tetra in his F-16. Seems to be working ok. Maybe compair notes ?



Bob


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to jon_focal_plane)
       Post #: 7

RE: Tettra Tank Issues in Pat XL / 90LX - 10/17/2005 2:52:29 PM   
jon_focal_plane


 

Posts: 72
Joined: 4/11/2005
From: Tucson, AZ, USA
Status: offline 		I went back to the 12oz Jett tank this weekend. Didn't experience any of the pitch sensitive issues. It may be a 'distance from the carb' issue since I couldn't push the Tettra tank as far forward as the Jett. Still kinda bummed I couldn't use the Tettra though.

Jonathan

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Your life may just depend on a mere scrap of information!

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       Post #: 8

RE: Tettra Tank Issues in Pat XL / 90LX - 10/17/2005 3:23:55 PM   
bob27s



Posts: 4819
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Thanks for the update Jon.....

Yeah, I was hoping that big tank was going to work out well. Shouldnt have been a bit problem.

I guess we found some limitation not previously known.

Bob


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Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to jon_focal_plane)
       Post #: 9

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