stunthanger.com
Engine basics => Engine set up tips => Topic started by: Allan Perret on March 01, 2017, 03:00:27 PM
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Whats your opinion, do they work for Stunt ?
Because if they do ....
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I've never had a problem with the std. LA40S remote needle.
I suspect it's a folk myth that you have to change them to a venturi mounted NVA.
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Whats your opinion, do they work for Stunt ?
Because if they do ....
Worked every time I tried them, Fox 35 to 25LA. The only problem I have seen is that for the ones molded into the backplate, on a profile, they get broken off in an inverted crash, which breaks the backplate as well. The type on a bracket is fine, far as I can tell.
Brett
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So this is why I asked about this. I'm thinking a bracket mounted NVA can be adjusted vertically eliminating the need to make the tank adjustable. Moving the NVA with respect to tank position should have same effect as moving tank relative to a engine mounted NVA. Not a big deal for profiles, but on full fuse birds its a big plus. Not having to move tank for adjusting means you can use the full space for tank volume and installing a fixed tank should be easier in general.
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So this is why I asked about this. I'm thinking a bracket mounted NVA can be adjusted vertically eliminating the need to make the tank adjustable. Moving the NVA with respect to tank position should have same effect as moving tank relative to a engine mounted NVA. Not a big deal for profiles, but on full fuse birds its a big plus. Not having to move tank for adjusting means you can use the full space for tank volume and installing a fixed tank should be easier in general.
Does not work that way, you need to move either end, (pick up, uni, or inlet into venturi ) but not the middle.
And NO it is not the same, the remote NVA works fine on a non cycle motor, running a wet 2 cycle, or sometimes a all 4 cycle, but.. the remote NVA does not work as well as standard when running an engine cycling, it has a slight delay, making the motor slightly dumb.. and is not as quick to respond. It/s close but not quite there, Does it work OK for your use??? maybe so maybe no , The only way to tell is to try the setup on your airplane and see if you like it.
Randy
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Does not work that way, you need to move either end, (pick up, uni, or inlet into venturi ) but not the middle.
Randy
I thought it would have been dependent on where the pressure drop occurs, which is in the NVA (restriction) ? Maybe that with a remote NVA there are two pressure drops, one in the NVA and another in the spray bar hole.
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I've only tried two remote NV's, one from an OS .29X (old Max III speed engine), and a bone-stock OS .25LA. I didn't like either, for starting problems mostly. I think the .25LA one leaked a lot of air, so when I choked the engine and got the fuel up to the venturi, the fuel would run back away from the venturi by the time I put the igniter on.
The .29X deal was about 55 years ago, so I can't remember much except that it went away very quickly. For both, I recall that the NV response to adjustments was painfully slow and totally unacceptable. The .25LA unit suggested to me that the Magnum and ASP remote unit is one heck of a lot better made, and that is difficult for me to admit.
As Randy said, that's not the way to avoid adjusting for tank height. Moving the uniflow tube inside the tank is the only option, other than changing relative height between tank and engine. Not many will move the engine instead of the tank! H^^ Steve
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Well, Steve, I have moved engines on Boxcar Chiefs to adjust for tank height but that is an unusual situation.
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My experience with rear mounted needle valves when Sean was younger is that you need to choke the engine more when starting, and if you don't have the tank exactly right, it takes a loooong time for the engine to quit. That is tank height and back end canted out a bit, to get a clean cutoff. This was mainly on OS.40FPs.
Type at you later,
Dan McEntee
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I've noticed that when I keep the fuel tubing between valve and engine short, about 1/2", it has no ill effect to engine run. But I talk about rear intake engine.
I think that's even better than normal needle valve, as regulator is less affected by heat and maybe engine vibration.
L
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The suction head at the engine's intake is independent of needle valve location. What matters is where the fuel opening into the venturi is. Typically, this is the same place the needle valve is, but it doesn't have to be.
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Less likely to suffer finger cuts with remote set up. Great invention!
Floyd