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Just one engine question. I always wondered why.

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Just one engine question. I always wondered why.

Old 08-20-2007, 07:33 PM
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Sacagawea
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Default Just one engine question. I always wondered why.

I was wondering why rc nitro engines have all these needles and nobs you have to adjust, why can't you just start it and go like a weed whacker engine? Because those are 2-stroke engines too, and I think the nitro engines would be alot less complicated if they were more like the weed whacker ones. It may seem like a dumb question to some of you but I always wondered, plus I mainly drive electrics so i'm really no expert.
Old 08-20-2007, 07:40 PM
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Default RE: Just one engine question. I always wondered why.

Nitro fuel is a lot more unstable and sensitive to billions of factors than gasoline. rc'ers seek best performance with minimal weight and in order to get that, you need what engines have today.
Old 08-20-2007, 07:49 PM
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Default RE: Just one engine question. I always wondered why.

Weedeaters have a type of compensating carburetor as well...
The Walbro, or Zama, etc. have a diaphram that acts as a fuel pump and there are passages inside the carb that help to (somewhat ) regulate the fuel flow...
If you have extreme weather changes, the weedwhacker will also run lean or richer than optimal, and a little tweaking of the needles helps.
They're also sensitive to the oil ratio.

A typical glow (AKA "Nitro" ) engine is designed to be easy to operate, and be cost effective to manufacture, and not too overly expensive to purchase by the end user. If they (the manuf. ) were to add a more complicated carb, would you want to spend 50 or 100. (or whatever ) more dollars for it?

The same, typical, 2 stroke glow engine only has 2 needles...very simple actually once you get the hang of it.
With some practice and experience you will be tuning your engine by reflex, or almost automatically...it just takes some time to learn how...
Old 08-20-2007, 08:52 PM
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Default RE: Just one engine question. I always wondered why.

Weedeater 2 strokes run on a mix of petrol and oil and nothing else. Glow engines though can run on a mix of just methanol and oil or you can add nitro to the mix in different amounts. For every type of fuel mix the carb needs a different needle setting to get the mixture correct.
Old 08-20-2007, 11:22 PM
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Default RE: Just one engine question. I always wondered why.

The other major difference is the weed whacker has an ignition system which makes a spark at a predetermined time in the cycle and nitro/rc engines don't. Another factor is weed wacker engines have a fan of sorts to provide cooling and rc engines rely on air flow created by the vehicle actually moving. Alcohol burns cooler than gasoline and likewise has les btu's per unit than gasoline.
Old 08-20-2007, 11:29 PM
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Default RE: Just one engine question. I always wondered why.

our weedwacker has an hsn and lsn, and weedwackers arent ment to go fast. all racing vehicals have fine tuning adjustments like that, its just a little different
Old 08-21-2007, 12:02 AM
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gubbs3
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Default RE: Just one engine question. I always wondered why.

Number 1 reason: Performance. As purpose built racing engines more than one needle is required to keep the engine at its top level of performance.

There are a few engines out there that do use single needle carbs. A few budget airplane engines have only one needle and an "air bleed" screw which simulates a low speed needle adjustment but is much less effective (makes it nearly impossible to get it wrong). Older HPI rtr motors came with single needle carbs. Those engine would run, but not well. They were almost always too rich on the low end which made throttle response terrible.


Tuning an engine really isn't all that hard. It can be a bit overwhelming at first but most people usually get it figured out after toasting their first motor .
Old 08-21-2007, 03:58 AM
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Default RE: Just one engine question. I always wondered why.

oh boy i hear ya there gubbs.
Old 08-21-2007, 07:59 AM
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SAVAGEJIM
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Default RE: Just one engine question. I always wondered why.


ORIGINAL: gubbs3

Tuning an engine really isn't all that hard. It can be a bit overwhelming at first but most people usually get it figured out after toasting their first motor .
Oh yeah! But fortunately, there are tuning vids with sounds that tell you how to identify if an engine is running good or if it running poorly and how to tune to correct the problems.

I wish I had such tuning vids so I could avoid burning up my first engine (that poor little .12 RD logics Toki engine, the hell I put it through!).

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