Elwyn
New arrival
Posts: 20
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Post by Elwyn on Oct 23, 2004 14:49:11 GMT -7
I've got a TT15 I finally got around to installing on a profile ship this weekend. I put about 15 minutes of run time on the engine before putting it in the air. It sounded fine upright and inverted and during an inside loop but when recovering from inverted with a half outside loop it would try to quit. I'm using a 2 OZ uniflow tank set a little higher than the engine centerline and not running a muffler or pressure. The prop is an APC 8-4. I didn't have time to fool with it much today and I didn't try any other manuevers that would put a negative G load on the engine. Any ideas as to why it tries to quit during a recovery to upright ?
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Post by jj5167 on Oct 23, 2004 15:14:55 GMT -7
Elwyn, I don't think I could really help you, but I really feel your overproping with an 8x4. I use 7" props on all my .15's and the two .12's I have on my Tigercat. Right now I am using 7x6 wood props, but have had good luck with APC 7x4's too. Also, is the pickup clunk hanging up on the back of the tank?
Joe
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Post by minnesotamodeler on Oct 23, 2004 17:01:57 GMT -7
You say the tank is set just a little high. That would of course make it a little low inverted. Is the engine starving, or flooding, in those outsides? I'd experiment with moving the tank up or down, depending on how the engine reacts.
--Ray
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Post by Garf on Oct 23, 2004 17:04:03 GMT -7
Is it a hard tank or a clunk tank? Either way, you first need to decide if it is going lean or rich. Also close the needle and pressurize the entire fuel system with a bulb or syringe to find any pinhole leaks.
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Elwyn
New arrival
Posts: 20
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Post by Elwyn on Oct 23, 2004 18:16:43 GMT -7
It's a Brodak uniflow tank. Not sure if it's going lean or rich. I had the feeling that it wasn't getting enough fuel when it tried to quit but that may not be the case. The RPM's sounded aboout the same upright and inverted but we didn't time the laps to check. I only put up three flights. It probably could use a bit more break-in. I'm running Powermaster 10/22 fuel and I'm not sure about the plug type. I put it in the engine 4 or 5 years ago but I never ran it till today. Next time I go out I'll check for leaks and play with tank height.
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Post by jet on Oct 24, 2004 5:50:54 GMT -7
I have always found, on profile airplanes, that the uniflow outlet needs to be very close to level with the hole in the spraybar. I do not understand the success I see people having with off-center tanks.
Jim
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Elwyn
New arrival
Posts: 20
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Post by Elwyn on Oct 30, 2004 18:31:41 GMT -7
I lowered the tank quite a bit and the engine is much happier now!
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Post by Garf on Oct 30, 2004 22:15:46 GMT -7
Tank position is affected by a multitude of factors, some of which most of us are unaware of. I try not to overanalize this, but make the adjustments that make the engine happy and let it go at that. I will leave the reasons why to those who really care about that sort of thing.
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