RC Car Engine Basics



Nitro powered RC car engines can be a little confusing at first because of the different types, sizes and engine specifications. In this section, I'll give you the basics on the following:

1)RC engine sizes explained
2)Slide versus rotary carbueretors
3)Needle adjustments
4)Turbo RC engines
5)RC engine ports

Nitro RC Car Engine Sizes Explained
Nitro engines range in size from .12 to .32 ci(cubic inches) and are available in small block and big block. You may also see engine sizes like 3.0 and 3.3. These are sizes in cubic centimeters(cc). For instance, a 3.0 cc engine is the equivalent of a .18 ci engine. The 1/10th scale rc cars use small block motors and the 1/8 th scale rc cars, buggies and trucks use the big blocks. Putting out between 1.5 to 2.7 horsepower, these engines are extremely powerful for their size. Note: Big and small block motors are determined by the actual size of the motor.

Slide Versus Rotary Carbueretors
The two types of carbueretors(carbs)used are the "slide" and "rotary", which refers to the type of valve used as the throttle. The slide type opens faster and gives a quick, "punchy" response which is more popular for the on road rc car. The rotary carb gives a smoother response more desirable for the off road rc cars and buggies.

Needle Adjustments
The typical rc engine has three needle adjustment settings: the high speed, low speed, and idle adjustments. The idle setting adjusts only the throttle at idle or stop. The low speed needle(lsn) and high speed needle(hsn) adjust the air/fuel mixture ratio at different speeds. Adjust each, starting with the idle first, then the hsn next, until you get the best performance. To avoid overheating and engine damage, take care not to adjust the lsn or the hsn too "lean"(low fuel to air ratio which happens when the needle is adjusted by turning clockwise). Remember, your fuel also contains your lubrication, so a lean setting means less oil as well. When properly adjusted, you'll have a nice trail of blue smoke when accelerating. *Note: Some of the high end engines may have a fourth setting for the mid range speed.

Turbo RC Engines
Turbo engines have cylinder heads that are beveled instead of flat and use "turbo" glow plugs that match the beveled surface. This allows the glow plug to sink further into the cylinder which creates greater head pressure and more power. Turbo's are more popular with on road cars because off road use results in more dirt which can get down into the beveled area, thus making it harder to clean.

RC Engine Ports
Engine porting in it's simplest explanation is the elimination of exhaust gases by well placed and designed slots cut out of the engine cylinder and the piston itself. This is done to increase horsepower at different throttle ranges, usually toward the middle and upper end. The number of "ports", the design, the angle of the cut, and the placement all figure into the overall performance. Porting is most popular with off road enthusiasts who want peak performance at different throttle ranges. Most rc hobbiest send their engine out to be custom modified or buy engines that come new with porting already done. Novarossi is one of the most popular high end engines with many porting options available.

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