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Author Topic: What is wrong??  (Read 1288 times)

Offline Steven Kientz

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What is wrong??
« on: April 22, 2012, 11:43:36 AM »
  Having a problem with a new Evo 36. Brodak 3.5oz(?) wedge tank, setup for pressure. Stock rnva, not sure if I'm using small or medium venturi and tongue muffler. To fuel, I pull the pressure and overflow lines, filling thru the feed line. Fuel runs out the pressure line. Thought maybe it is a tank issue, so I pulled same size Brodak  tank off of another plane, with the same results.
  I know alot of people have replaced the stock Rnva with regular nva, don't really know if this will help this problem?
 Still figure it's operator error, just not sure what I'm doing wrong. Almost ready to change to plastic clunk tank since I have better luck with those.

Steve
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Offline Douglas Ames

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Re: What is wrong??
« Reply #1 on: April 22, 2012, 11:58:33 AM »
So what problem are you having, a run issue or tank filling issue?
Are you sure you have the lines ID'd correctly?
I think the Evo .36 has some kind of lock on the NVA to keep your mix. set.
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Offline Steven Kientz

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Re: What is wrong??
« Reply #2 on: April 22, 2012, 12:06:30 PM »
Ihave both run and fill problems. Has only ran once(20 sec.) on a test stand(engine/tank mounted to plane). The stock rnva does have a"preadjusted"setting, easy to bypass that and use as a regular Rnva. Most of the time it will not draw fuel when hand flipping. I guess I should pull the engine and put it on a test stand until I get the problem corrected. I have a few other planes I can fly. 

steve
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Offline Bill Morell

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Re: What is wrong??
« Reply #3 on: April 22, 2012, 12:20:49 PM »
Giving the engine a "proper" break in going beyond 20 seconds would probably be a good place to start.
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Offline Steven Kientz

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Re: What is wrong??
« Reply #4 on: April 22, 2012, 12:25:08 PM »
Planned on that, but ran out of things to do inside this winter , so I mounted the engine and tank. I figured once it warmed up, I'd run some fuel thru it, before flying it.  The 20 sec. run was because it quit and would not restart.

steve
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Offline Steve Helmick

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Re: What is wrong??
« Reply #5 on: April 22, 2012, 12:29:04 PM »
Is this Brodak tank a uniflow? You have the muffler pressure line going to the uniflow vent, and you're fill through it? The overflow tube is on the bottom of the tank, and you're uncapping that to fill? Can you post a picture of the tank installation?

I don't have an Evo, but I think most have reported using the smallest venturi, unless they put an aftermarket NV assy in the front. If you do that, use a venturi that is .257" to .272" bore with a .156" spraybar, and give it some bench time. I cannot help but suggest trying the 11 x 4.5 Thunder Tiger Cyclone propeller...it's that wonderful. y1 Steve
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Offline Steven Kientz

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Re: What is wrong??
« Reply #6 on: April 22, 2012, 12:35:35 PM »
Pressure line on top, overflow on bottom. I have been pulling the line off the Rnva and fueling thru it. Am going to the garage and pull the engine. Will check the venturi size while I am at it. I could retrofit a Brodak nva to the venturi.

Steve
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Offline Steven Kientz

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Re: What is wrong??
« Reply #7 on: April 22, 2012, 03:08:06 PM »
  Changed to a GMS rnva and os spraybar in a evo venturi(med.), known combo from another engine. Still wouldn't draw. Changed tank height(on test stand), actually started once (backwards) when backflipped. I did notice that the os spraybar covers the majority of the venturi id. I have had enough for one day, will try tomorrow after work. I will also try different fuel tomorrow.

Steve
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Offline dennis lipsett

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Re: What is wrong??
« Reply #8 on: April 22, 2012, 04:01:17 PM »
You have a leak someplace. Could be the tank pick up, fuel line, etc. Check everything. Switch to a known good tank if you don't want to dis assemble your present tank.I seriously doubt that the needle valve isn't open enough, but make sure that it is .
I have 4 Evos and do not run the remote NVA with them nor do I run any of the supplied venturis. They are in my opinion all too large. I've used a Just Engines Jen venturi/nva set up from an Irvine and that works perfectly in my Oriental and will needle perfectly . For the others I had Jim Lee make up true sprinkler venturis and used Randys needles with perfect results. The engines are fine but the fuel delivery needs to be looked at. Others have taken the venturi of choice and drilled through and used a conventional NVA. The engine is priced well and if it had the correct delivery system it would be a certified winner.

Dennis
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Offline Balsa Butcher

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Re: What is wrong??
« Reply #9 on: April 22, 2012, 04:02:15 PM »
My suggestion is using the smallest venturi if you are using a remote needle valve. Even with that they are a bit thirsty (but powerful). 4.5 ounce tank is recommended but first you have to get it to run. Pressure check tank for leak. It may be new but poor soldering happens. Prop suggestion is good, APC 10.5/4.5 is another good one. These like to rev but will stay in a strong 4 cycle. Did I mention to use the smallest, not the medium venturi that comes with the engine?  8)
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Offline Steve Thomas

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Re: What is wrong??
« Reply #10 on: April 23, 2012, 03:30:15 AM »
Steve, have you tried just leaving the feed line attached to the spraybar and filling through the pressure line? 

Maybe I'm misunderstanding your problem, but it sounds as if you have a uniflow tank, and the other end of your 'pressure' line exits somewhere in the apex of the wedge rather than near the top of the tank.  If this is the case then it's highly likely that fuel is venting out your 'pressure' line when the tank is only about half full (or even less if the tank's on a model that's sitting tail-low). It could be that you have feed problems because the amount of fuel at the pickup is marginal.
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Offline Tim Wescott

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Re: What is wrong??
« Reply #11 on: April 23, 2012, 08:57:59 AM »
Quote from: Steve Thomas on April 23, 2012, 03:30:15 AM
Steve, have you tried just leaving the feed line attached to the spraybar and filling through the pressure line? 

Maybe I'm misunderstanding your problem, but it sounds as if you have a uniflow tank, and the other end of your 'pressure' line exits somewhere in the apex of the wedge rather than near the top of the tank.  If this is the case then it's highly likely that fuel is venting out your 'pressure' line when the tank is only about half full (or even less if the tank's on a model that's sitting tail-low). It could be that you have feed problems because the amount of fuel at the pickup is marginal.
That is what it sounds like to me, too.  I fill a uniflow tank through the vent (aka pressure) line until fuel comes out the overflow line.  If you try to fill a uniflow the way you describe, you'll get it half full or less, and only pull a few drops of fuel out of it before your feed line is sucking air.  Most folks probably do it the way I described.  There may be other ways, but whatever you do, the only line that should be letting air out while it's filling is the overflow line.

It ain't full until the overflow line is squirting fuel!
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Offline Steven Kientz

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Re: What is wrong??
« Reply #12 on: April 23, 2012, 03:34:38 PM »
    Found the paperwork for the tank, standard vent(uniflow?). Long day @ work today, will have to look into it tomorrow.

 Thanks everyone
Steve

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Offline Tim Wescott

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Re: What is wrong??
« Reply #13 on: April 23, 2012, 04:45:11 PM »
Standard vent usually (as far as I know, at least) means that you have a fill/vent tube that goes down from the top to the bottom of the tank, an overflow tube that goes up from the bottom, to the top of the tank, and a pickup tube on the rear outside of the tank (right rear if you look from behind on a conventional rotation airplane).

Post a Brodak part number?

It's still not full until fuel is squirting out the overflow.
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Offline Bill Little

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Re: What is wrong??
« Reply #14 on: April 23, 2012, 07:09:39 PM »
On uniflow tanks, I fill trough the vent line with the plug off the overflow.

On a standard vented tank I fill through the vent line with the plug off the overflow.

The fuel feed line never comes off.

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Offline Steven Kientz

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Re: What is wrong??
« Reply #15 on: April 25, 2012, 03:57:00 PM »
Well it finally started tonite. Changed fuel(new jug), also notice leak around glow plug. Tighten that and played with the nva a little and it ran 1 tank thru it. Did notice one head bolt is loose(blowing out fuel). Will fix that tomorrow. Start my month end overtime tomorrow9thru Monday), so very little airplane time.
    THANKS to all who helped, I'm the only C/L guy at our field, although engines are engines.  I wish I had the time to join J. Sheeks and Clancy Arnolds club, lotta knowledge in that group.

Thanks again
Steve
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