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Engine Questions

Old 03-27-2005, 08:32 PM
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no1speshal
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Default Engine Questions

Hello Almighty helpful people...
I have a list of questions that I need answering and everyone at my flying field is usually too busy for me to ask them. So, I will ask the invisible people, because you all are much more helpful! : )

First question: I have an MVVS 61 with a sort-of tuned pipe. I actually know nothing about pipes, but it looks like a butane fluid tube with a pressure tap and an exit. This engine has a lot less power than my Tower Hobbis 61, which lends me to wonder what I am doing wrong. If it is the pipe that is causing it to slow down, where can I get a regular muffler for less than my total personal worth? Also, what size prop should I be using on this?

Second Question: I have a Super Tigre 91 that has a J'Tec muffler, pitts style, I think. This engine must hate me. I am convinced of this because it never does the same thing twice. I can, however, tell you what it does the most. It just dies. There are no signs leading up to the ceasing of combustion, only the vast silence that follows. It usually dies just after tuning it on the ground, right before flight...OR...when it is flying and I reduce and then add throttle. So, here is a breakdown of this engine and its mishaps: When I am flying it at level attitude and I throttle down for a touch and go, it is fine. However, when I go to take back off, it will run for about five seconds (just enough for it to make for a sketchy landing) and then die. That is, if I make it into the air. It also dies on me when I am tuning it on the ground, richening it or leaning it for daily variations in temperature. After I tune it, hold it nose high for lean out checks, do the pinch test and other ground like stuff, I will taxi it out to the runway and right before I take off, it will die. SEE, I told you it hated me! What am I doing worng on this engine?

Now, both engines are run on the same fuel. It is Cool Power 10% nitro. The MVVS is swinging an 11x6 prop and the Super Tigre is swinging a 13x6. I originally had a 14x6 on the Super Tigre, but the manual says that I over propped it and I thought it was over heating. I am using OS #3's or #8 plugs, I can't remember which, but I am at about 3 feet above sea level here in Florida, so that is what I was told to use.

Can anyone out there in the RC universe help me? I am so frustrated over these two engines I just want to scream. All of my other engines are about the same, so I expect I am doing whatever I am doing to all of them. With the exception of my new Evolution 61 which I love because it runs sooooooooooooo good. I will buy another Evolution engine just because of this one. Thank you all in advance. Thank you very much for your help...God knows I need it! : )


Red
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Old 03-27-2005, 09:01 PM
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Doug D.
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Default RE: Engine Questions

Well first of all your running to much nitro thru your MVVS unless you have installed some head shims. The MVVS line of engines where designed for no nitro because it's to expensive in europe. Contact the guys a Morris hobbies and order at least two head shims for your .61 before going any futher. Unless you switch to FAI or zero nitro fuel. You will notice a difference. And while you have them on the phone ask them how to adjust the mini pipe you have. They can be very helpfull. They have been for me.
Yor problems on the ST .91 sounds like a tank problem. I could be wrong, but it's a good place to start. Your clunk should be at least a half inch away from the back of the tank. Make sure nothing is restricted as well, i.e. pinched or blocked fuel tubes. Do you use an inline filter? If not make sure nothing is floating around in the tank to get caught in the carb. I've seen this happen a couple of times until the tank was cleaned out or a filter was used.

I'm sure you will get more places to look at from the rest of us.
Good luck and let us know what you find.
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Old 03-27-2005, 10:52 PM
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Cyclic Hardover
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Default RE: Engine Questions

Sounds to me like your engines are not dialed in. Anything else is a waste of time and money. I see this constantly. Those who's engines are not dialed in and those who think they are but still way off.
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Old 03-28-2005, 10:01 AM
  #4  
redfox435cat
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Default RE: Engine Questions

Yea to much nitro for the mvvs use 5%, as far as the muffler, their the same as the rossi muffler and it is about the best their is. Sound be me like you ruined the engine with to much nitro.

Your 91. You say you can go to idle then dies when you advance to full.

Doesn't it surge then die or just die?

If it surges then dies then your idle is rich

If it slows down and dies it's lean


The best way to check this is at an idle pinch the fuel line, if it has a remote neddle valve pinch the line between the needle and the carb.

Again if it surges then dies then its rich slows down and dies it's lean

Another way is to let it sit there and idle

if it gradualy slows down and quits then lean the idle. if it speed up before it quits then richen it.

After the low end it set reset the high end. advance to full. lean out the needle until it peaks then back it off about 20 degrees.

Trie the transistion a couple times. it sould advance from idle to full fairly smooth

Have another guy hold the model pointing it up 45 degrees it shouldn't change rpm

This is the one mistake I see again and again is no one touches there idle screw. your idle screw can affect the high end as well.
Otherwise clean everything out and try another glow plug


BEfore you go out the feild next take some canned air and blow out the venturies on the carbs of both engines
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Old 03-28-2005, 10:03 AM
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Default RE: Engine Questions

I don't know anything about MVVS, but it sounds to me like your ST is out of tune. ST engines require adjustment of both the low end and high end throughout the throttle range. The first thing that I would try is adjusting the low end needle just a little bit richer (1/26th to 1/8th turn) and then retune the high end. Work them back and forth and you should cure your problem. The key word here is; PATIENCE, PATIENCE, PATIENCE.

It is too bad that your fellow fliers at the field don't have the time to help you.

Regards,
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