stunthanger.com

Engine basics => Engine set up tips => Topic started by: Mike Quinn on May 18, 2024, 01:51:32 PM

Title: Inverted motor - Needle valve inside or outside circle
Post by: Mike Quinn on May 18, 2024, 01:51:32 PM

Hi

I’ve got an inverted  OS 46 in a Nobler.  Does it make any difference if the Needle is on the outside or inside ot the circle ( as in which way round the spray bar is inserted)?  I’m guessing not as the holes in the  spraybar stay in the same position in the venturi so any pressure differential to the tank will be the same right?

Cheers

mike

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: Colin McRae on May 18, 2024, 04:40:20 PM

I don't think it makes any difference. Just keep the fuel tubing from the tank to the NVA efficiently routed and as short as you can.

I have a 40LA on a Nobler with the NVA inside. Then a 46LA on a Vector with the NVA outside. I don't notice any difference in the engine runs.

And in both instances the NVA's are front type, not the rear needle setup.

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: John Skukalek on May 18, 2024, 08:41:36 PM

When I put the spray bar fuel pick up side on the inside in order to get the needle on the outside away from the muffler on a 46 LA. It gave me problems. I believe that once in the air the fuel flow decreased(causing the engine to go lean) due to resistance caused by centripetal force.

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: Ken Culbertson on May 18, 2024, 09:37:22 PM

I have run it both ways and found no difference.  I do like to keep the fuel line as short as possible which puts it on the outside of the circle for most tanks.

Ken

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: Colin McRae on May 19, 2024, 06:10:05 PM

Quote from: Colin McRae on May 18, 2024, 04:40:20 PM

I have a 40LA on a Nobler with the NVA inside. Then a 46LA on a Vector with the NVA outside. I don't notice any difference in the engine runs.

One thing I forgot to mention. I run muffler pressure on my LA engines. Not sure if there will be a difference (NVA inside or outside) if only suction or ram air is used on the tank.

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: john e. holliday on May 19, 2024, 07:37:04 PM

For years and years I have always located the needle where I can get it without interference from the muffler no matter what make or size of engine.  Remeber to build fuel tank accordingly.  Even when I use muffler pressure or uni-flow. D>K

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: Trostle on May 20, 2024, 06:58:37 PM

A good rule of thumb on where to place the needle valve would be to use the shortest fuel line needed to get the fuel from the tank to the engine.  For metal tanks and with an inverted engine, that would normally dictate that the needle valve would be to the inside of the circle.   For some plastic tanks, with the plug holding the fuel lines near the center of the tank, needle valve placement does not make much different, then the dictating factor would be to locate the needle valve opposite of the exhaust/muffler.

Keith

Title: Re: Inverted motor - Needle valve inside or outside circle
Post by: Mike Quinn on May 22, 2024, 03:03:41 PM

Hi

Thanks chaps.  Its an RC clunk tank on muffler pressure if I forgot to mention. 

Cheers

Mike