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Author Topic: ...engine surges...  (Read 931 times)

Offline Bootlegger

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...engine surges...
« on: October 10, 2013, 12:27:58 PM »

  Guy's I have an O S 32 S X engine on a H9 pt 19, and the darn engine surges. The tank is a metal 4oz with uniflo to the atmosphere, running 5% Sig 20% oil half sny/half castor, thunderbolt idle bar plug 10x4 prop.

  So far I have put muffler pressure in the tank, changed the glow plug, again T B idle bar, changer fuel brand and it still surges.

  My next thought is to change the tank to a plastic clunk and try again.

  Any suggestions? Thanks a lot, Gil
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Offline Joe Yau

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Re: ...engine surges...
« Reply #1 on: October 10, 2013, 01:58:18 PM »
Quote from: Bootlegger on October 10, 2013, 12:27:58 PM
 Guy's I have an O S 32 S X engine on a H9 pt 19, and the darn engine surges. The tank is a metal 4oz with uniflo to the atmosphere, running 5% Sig 20% oil half sny/half castor, thunderbolt idle bar plug 10x4 prop.

  So far I have put muffler pressure in the tank, changed the glow plug, again T B idle bar, changer fuel brand and it still surges.

  My next thought is to change the tank to a plastic clunk and try again.

  Any suggestions? Thanks a lot, Gil

Which 10x4 are you running?   I had an engine surge problem with a Evo .36 a while back.   It would only do it with a 11x4 wood prop I was using (less load), switching to a 11x4 APC (wider blade or more flywheel effect?) then it ran steady.
« Last Edit: October 10, 2013, 02:21:35 PM by Joe Yau »
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Offline Bootlegger

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Re: ...engine surges...
« Reply #2 on: October 10, 2013, 02:47:15 PM »

 Thanks Joe, I am running a 10x4 APC prop, I have run 10x5 APC and also 10.5x 4.5 APC props on the engine, so I am gonna keep looking, and again thanks for the advice..
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Offline Steve Helmick

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Re: ...engine surges...
« Reply #3 on: October 10, 2013, 04:20:13 PM »
Sounds like it's not broken-in, or running lean, or not enough oil in the fuel, or...you're not running with the R/C throttle, are you? I could see a leaky venturi/spraybar or throttle doing that, or even perhaps a loose backplate. If you're using a venturi, is it a tight fit into the case, and how big is the bore and spraybar (if it goes through the venturi bore)?

The engine should run fine on any of those props, tho that doesn't mean that the airplane will also be happy with them.  D>K Steve
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Offline Bootlegger

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Re: ...engine surges...
« Reply #4 on: October 11, 2013, 05:55:58 AM »

 Steve, it is well broken, and the fuel has been run in several other engines, I have installed a .272 venturi, and it is tight in the case, I am using a Tiger needle nva.

  This morning I pulled the engine and the back plate and head bolts are tight, also yesterday I was starting it with one backward flip of the prop.

 One thing that I didn't check was bubbles in the fuel line, in the past if the uniflow vent was too close to the feed line it would "draw" air from the uniflow vent.

 Today I hope to take the back off the tank and check the uniflow line and set it at 1/2" forward of the feed line.

 Will try and see if that works.

 Again thanks for the help/suggestions...
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Offline Jim Thomerson

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Re: ...engine surges...
« Reply #5 on: October 11, 2013, 04:08:38 PM »
I've been having similar problems with two different engines on a diesel powered OTS profile.  The tank is partially into a cutout in the wing, a little difficult to get to. I am thinking the tank is not rubber banded on tight enough, and is vibrating enough to make erratic fuel sloshes and foaming.  I'm going to tighten up the tank rubber bands and give it another try.
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Offline Steve Helmick

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Re: ...engine surges...
« Reply #6 on: October 11, 2013, 04:31:52 PM »
Another thought on Gil's problem is a loose glowplug, but since he's changed it, probably not the case. I have also seen cases where people mistakenly put in a short reach glowplug and the engine ran, but not well, touchy to the NV, etc.

Like most ARFs, the Hangar 9 PT-19 has a weak nose (also too short, generally, but the .32 SX may be heavy enough to make it balance) and is prone to fuel foaming problems. A good filter (CrapTrap) can sometimes make a difference on foaming problems. I've never even considered using the Armor-All trick, but you might give it a try. What I have readd about it is that most people put in MUCH too much, 3 squirts instead of 3 drops. Details matter!  y1 Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Bootlegger

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Re: ...engine surges...
« Reply #7 on: October 13, 2013, 05:29:36 AM »

 I put the engine on the bench with a different tank, and got the same runs!
 Next , tried another engine and it ran fine, with the same tank, so I am thinking engine.

 I also pulled the back off the hard tank and cut another 1/8" inch off the uniflow line, man that engine settled down like it should.
 Installed the engine and metal tank back on the model and went flying, could not get a"smooth" engine run, so I am thinking that maybe the front end is " shaking", might get to check that the next few days.

  Want to say THANK S again for all the sage advice/help. 
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