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Old 11-28-2011, 12:46 AM   #1
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Default First R/C Car....need help!!

Hi, ive just purchased my first nitro on-road RC car, and im having a few issues. Also, im new to these forums and this is my first post

Ive just finished running in the engine, all went well.

a few questions,

1. there is alot of thick petrol comming from the exhaust, almost like oil.

and the main issue is the gearbox, it seems really sluggish. and its not even that fast, its a 2 speed.

the manual says to oil the diff etc, but it came with no oil and the hobby shop didnt mention anything about oiling, they just told me to run it in.

Thanks for the help guys!!
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Old 11-28-2011, 10:19 AM   #2
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Originally Posted by onlinegamesnz View Post
Hi, ive just purchased my first nitro on-road RC car, and im having a few issues. Also, im new to these forums and this is my first post

Ive just finished running in the engine, all went well.

a few questions,

1. there is alot of thick petrol comming from the exhaust, almost like oil.

and the main issue is the gearbox, it seems really sluggish. and its not even that fast, its a 2 speed.

the manual says to oil the diff etc, but it came with no oil and the hobby shop didnt mention anything about oiling, they just told me to run it in.

Thanks for the help guys!!
This is going to be a long post because, since you are new to the hobby, to really answer your questions you're going to need to understand how your engine works.

The petrol you're seeing from the pipe is, indeed, unburnt oil coming from the engine and this is normal. Here's why.

Your nitro enigne differs from the engine in your car in the fact that it is far more simplistic in it's operation. While there are a number of ways in which they differ, your first question address the lubricating system. In your car engine, you have an oil system that pumps oil through the parts of the engine that require lubrication. This oil is kept seperate from the fueling system.

In a nitro engine, the only part that needs lubrication is where the piston meets the cylindar (called a sleeve in r/c engines since it is replacable) wall. Because this is the only area where lubrication is critical, and due to the small size of the engine, the lubrication system is incorporated into the fuel. If you look at your fuel's contents, you'll see a certain percentage of it is oil...usually about 8-14% depending on brand. This oil lubricates your engine as it runs and helps keep it cool. This oil causes your engine to produce white smoke while it is running. If you do not see white smoke when you are driving your car, you are running your engine too lean and it is not receiving enough lubrication.

The second question you have, about the car's sluggishness, also has to do with your engine's fueling. When your engine is new, the manufacturer has you set your needle to a possition which will be "rich". This means your engine is getting more fuel than it needs to run at it's best. They do this for two reasons.

First, for break in, you want to have the additional lubrication that a "rich" needle setting will provide. Since your break in should consist of just idling (first 2-3 tanks) or no more than half throttle driving (second 2-3 tanks) not much air will be moving over the engine and thus it will run hotter than normal. This default rich condition will help prevent the engine form overheating.

Second, running rich will not damage your engine even though performance will suffer and the car will feel "sluggish". Running lean CAN damage your engine and thus it is safer for the manufacturer to start you off at a "rich" setting.

Once your break in period is over, you will need to tune the carburetor to get optimal performance from the engine. NOTE: ALWAYS follow the manufacturer's SPECIFIC instructions when tuning your engine. What I'm about to cover is GENERAL tuning information and your engine MAY differ.

You may have one, two or three needles on your carburetor. Most engines have two while some "beginner" engines may have one and more high end engines will have three. No matter how many you have, the main needle is called the High Speed Needle (HSN). This needle is the tall one that is up by your air cleaner and is where you attach the fuel line from your tank to the carburetor. This needle controls overall fuel flow into the engine and any other needle you may have on your carburetor will only further restrict or control the flow from this needle. Thus, if you lean this needle, you lean ALL the needles on your carburetor. The HSN must be adjusted first.

To adjust your HSN, you must first let the engine get to it's operating temperature. Then make a few full throttle passes. You should have pleanty of blue smoke from the exhuast during the pass. If you do not, richen the high speed needle. (Turn the needle counter-clockwise to "richen" the needle and clockwise to "lean" the needle. Make adjustments in 1/8 of a turn increments.) If the car is sluggish but you are seeing a lot of smoke, bring the car in and lean the HSN 1/8th of a turn.

After you make an adjustment, you need to drive the car for a bit for the enigne to adjust to the change you've made. After making a change, drive it around for a bit then make 2-3 more full throttle passes like you did before to see what the change did. You can then lean or richen the HSN again and repeat the process.

One thing to note, the engine will run it's best when it is TOO LEAN. Thus it is very easy for beginning nitro engine drivers to keep chasing that "perfect tune" where they get the most speed and wind up over-leaning the engine. You should ALWAYS see a nice trail of blue smoke at Wide Open Throttle even if the engine seems to run a bit better when it doesn't have this smoke. Here are some signs the engine is running too lean:
  • No blue smoke from the exhaust.
  • Engine runs fine for a few minutes then shuts off and will not start until the enigne has cooled off. (This is a moderately too lean condition.)
  • Engine "cuts out" when you give it full throttle but then starts back up when you let go of the throttle. (This is a severly too lean condition!)

If you experiance ANY of these conditions, richen your HSN by 1/4 turn.

There is an optimal temperature range your engine should operate at. This range is determined by the manufacturer but all nitro engines usually have simliar ranges. In addition to the above information, you can also perform the "water test" to see if you're within this operating range. After the engine is up to temperature, place a couple of drops of water down in the head of the engine right next to the glow plug. These drops of water should "dance" there for a couple seconds before evaporating away from the heat. If they turn to steam immidiately, the engine is too hot and you need to richen your HSN. If they take longer than five seconds to evaporate, you're a little rich and can lean your HSN out slightly.

Once your HSN is set you can tune your Low Speed Needle(LSN), if your engine is equiped with one. Refer to your instructions as for the location of this needle. It usually is in the end of the carburetor "inside" the area where your linkage attaches to the arm to move the carburetor.

To adjust, make sure you have your HSN adjusted properly and bring your engine up to operating temperature. Then do one or two full throttle runs to "clear out" the enigne. Bring the car to a complete stop and let the engine idle for 30 seconds. Once the 30 seconds is up, give it full throttle. The car should take off normally or only slightly slower than normal. If it is very slugglish, or the engine dies when you give it full throttle or before the time is up, the LSN is too rich. For most enignes, you turn the LSN clockwise to lean it and counter-clockwise to richen it. (NOTE: Some carburetors are the reverse of this so MAKE SURE you follow the instructions provided by your manufacturer specfically!!) Make very small adjustments to this needle when changing it (1/16th to 1/8th turns only).

Like with the HSN, make sure to drive your car around a little after making an adjustment to the LSN to let the engine adjust to the change. Make a couple more full throttle passes then again bring the car to a complete stop and repeat the process until the car launches well and there is still pleanty of blue smoke at less than half throttle driving.

The third needle, if equipped, isn't a needle at all but is reffered to as either the low speed needle seat or the mid range needle. I will not go into this needle as this is something for more advanced drivers. The factory setting will be fine for 99% of drivers anyway.

This should cover your questions about the oil from the pipe and the sluggish performance of your engine at the moment.

As for your diff oil, this is something that you CAN do. The car should have come with some oil or grease already in the diff if you bought a Ready-To-Run (RTR) car. I'm assuming that you did get an RTR.

If the car came with Gear Diffs, and almost all nitro cars do, for now you are probably fine as these diffs don't need to be re-greased very often. To do so would require you to remove the diffs from the car, open them up, and fill them with diff oil.

Now if you are racing AND the differentials in your car are sealed, you can fill them with different weight oils to "tune" them to change the way the car handles. Again, as a beginner this is something you don't need to worry about at the moment but if you wish you can read through posts here to get a better idea of how that adjustment works.

I know this is rather long but I felt these questions needed to be answered in depth to help you expand your knowledge as a new hobbiest. Good luck and please feel free to ask more questions if you have them.

Last edited by Robotech; 11-28-2011 at 10:35 AM.
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Old 11-28-2011, 12:22 PM   #3
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Yep......that was a loooooong post!

Don't you hate it, when you sit down and type that much, lose your internet connection, and didn't save a copy?
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Old 11-28-2011, 12:25 PM   #4
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Btw, it won't shift into 2nd gear, until you have the engine broke-in and tuned properly.
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Old 11-28-2011, 01:18 PM   #5
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Btw, it won't shift into 2nd gear, until you have the engine broke-in and tuned properly.
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Old 11-28-2011, 03:13 PM   #6
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Originally Posted by red7fifty View Post
Btw, it won't shift into 2nd gear, until you have the engine broke-in and tuned properly.
I didn't mention this only because he never said it wasn't shifting, just it wasn't fast, but you bring up a good point. I'd also like to mention that your 2-speed could also be out of adjustment and shifts so quickly that the car is basically trying to start out in 2nd gear. Double check your instructions and make sure the 2-speed is set correctly. With my cars, I usually "turn off" the 2-speed (mine you can adjust so that 2nd never engages) during break in and then, once the engine is tuned properly, adjust to the 2-speed to engage where I want it to.
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Old 11-29-2011, 02:56 AM   #7
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Very nice explanation.

In any case maybe he'd better for the next time to mention manufacturer and model for car and engine.
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