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  1. #1

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    Nitro engine boggs out when throttled

    So to start directly with my problem, when i throttle my engine the slightest bit it dies out. I am running a vx .16 (noobish i know) So i know there are a few issues with my setup like and old glow plug. But also I'm using a mixture of a nitro airplane fuel (25% nitro 20% lube) and the Blue Thunder fuel(20%) The car ran fine until i decided to break it down for a cleaning. So during said cleaning the needles on the carb got moved about, so i set it back to factory settings( HSN 2.5 turn LSN flush) I have checked out the clutch and it looks fine to my eye ( i didn’t really know what to look for) Another thing to add is that when idling there is almost no smoke or oil splitting out the exhaust, but when i open her up, there is an immense mass of smoke and few sputters of oil. I am planning on upgrading my engine, but i wanted to get all i could out of my current one, is it time for a change? Its about a year old and so far I've probably ran about a gallon through it.

    Update: Ive tried leaning and richening both the HSN and LSN to no avail.




  2. #2
    JohnP2's Avatar
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    RE: Nitro engine boggs out when throttled

    I don't think a gallon warrants being time for a new engine. Based on what you stated, it sounds too rich. The lack of smoke at idle is perfectly normal. Your choice of fuel could be a culprit. Have you tried running it with a straight fuel (as opposed with a mixture)?

    If you are able to post a video of it, that will also really help. Are you taking the temps of the engine? If so, what are they? You also noted that you're using an "old glow plug". Have you tried a new one?

    Thanks
    Mugen MBX6R, HB D8T, Losi 8 2.0, Savage X 4.6, Losi 810, Hyper 7, Exceed Forza
    http://www.youtube.com/user/NitroRCNerds

  3. #3

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    RE: Nitro engine boggs out when throttled

    Well all the fuel I had left was a little of both of the two stated above, so I just mixed them together. This weekend I will pick up a new glow plug and some fuel. If the problem persists ill upload a video. Oh and the temps are at about 215 F according to my crappy device. When water hits it, it sizzles of in about 2 or 3 seconds.
    Thanks for the help

  4. #4

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    RE: Nitro engine boggs out when throttled

    Okay so I tinkered with it today and I remembered that when I first got the engine, I had the same problem. So I also remembered having to richen it quite a bit to fix it. So I tried richening the HSN to about flush with the collar and it works almost perfect now. The only thing is it eats up fuel rather fast. The only way I think I could describe the flow-rate is if there is a bubble in the fuel line, it moves about 1cm a second. I also took a temp reading of from 262F to 293F. So is it at all possible that if I was running it too rich it would somehow bogg like I said? And does everything sound about normal?

    Update: Richening the HSN only helped alittle bit, its back to bogging out at about 3/4 throttle

  5. #5
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    RE: Nitro engine boggs out when throttled

    I'd suggest to just keep tinkering with it. I have four engines, and they all run at different temps. However, if you drove it WOT for a few runs and it is at 215, that seems a little low (mine average 250-300 at max temps).

    You might consider replacing the tubing as well. Just keep ruling things out (tubing, glow plug, fuel mixture, etc) and you'll eventually get it. ;-)
    Mugen MBX6R, HB D8T, Losi 8 2.0, Savage X 4.6, Losi 810, Hyper 7, Exceed Forza
    http://www.youtube.com/user/NitroRCNerds

  6. #6

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    RE: Nitro engine boggs out when throttled

    Will do But just to be clear, im not harming the engine unless I hit the upper 280 to 320 degree range right?  The thing is, if I am running rich im afraid to lean it out more because im already at about 275.  However is theres still a good stream of blue smoke. I have 2 other engines that run very nicely with slightly less milage and they never have required so much trial and error.  But thats also probably because they are much nicer ones too.

  7. #7
    JohnP2's Avatar
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    RE: Nitro engine boggs out when throttled

    I would go more toward what you see/hear than the temp. As an example, if you are getting good smoke, it sounds okay and you are at 295 (after speed runs) then I personally would not worry about it. However, using that same scenario, if you are at 350, then you'd want to richen it some regardless. From what I've learned the engine will let you know if you are extremely lean or rich without needing to take the temp. I used my temp gun either when breaking in, or when I suspect it might be a tad lean. If you go way to lean, you'll know it without need the temp. Again, that is just my experience. Thanks
    Mugen MBX6R, HB D8T, Losi 8 2.0, Savage X 4.6, Losi 810, Hyper 7, Exceed Forza
    http://www.youtube.com/user/NitroRCNerds

  8. #8
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    RE: Nitro engine boggs out when throttled

    If it takes off wiihout a lot of power and bogs around 3/4 throttle, it's probably too rich.

    If it takes off with great gusto but suddenly quits at 3/4 throttle, it's probably too lean.

    One way to get high temperatures is to run with too lean a HSN and too rich a LSN. Try turning in the LSN about 1/2 turn, and then tinker with the HSN to get decent top speed.

    Go back and forth a bit more to keep improving things.

    I typically find the LSN has to be set somehwere between the factory setting (typically flush) and 1 turn in. The HSN often has to be set leaner than factory specs if it is to take throttle at all.

    If your LSN is far off, let it idle and listen to the rpms. If it slowly rises, your LSN is too lean. If it slowly idles down, your LSN is too rich. The PINCH test is another way to do a rough LSN adjustment. Pinch off the fuel line near the carb and the engine should quit after 3 to 5 seconds. If it idles for 20 seconds or more, you're close to a rough LSN tune.

    To get the final LSN setting, just tweak it a bit until the engine acts snotty when you nail the throttle from idle.

    Finally tweak the HSN for the best top speed, and then back it off maybe 1/8 turn (make it richeer). A screaming engine at WOT isn't the most healthy thing. I tune mine a little down from screaming.

    As far as temps go, my rule of thum is it shouldn't go over 300degF after a couple of 100 to 150 foot runs in grass. But there's no real rules about temps. The handy thing with a temp gun is for when you are learning. Sometimes you just dont' know what's going on and measuring the temp gives you an "indication" of what's happening. Once you get a little better, try to stop using a temp gun and go by sound, smoke and perfomance.

  9. #9

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    RE: Nitro engine boggs out when throttled

    So I've fixed most of the problems now.  Its only on occasion that it dies at WOT and when it does, richening it usually fixes it. I assume its because the engine isn't getting enough nitro.  The other issue i found was that there was a tiny pinhole in the fuel line, so when the engine really starts pumping fuel, it sucked some air in and goes lean.


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