Name that Tune

Name that Tune

Get Tuned In

Most of today's R/C cars, trucks and buggies are supplied with some type of tuned exhaust system or expansion muffler. Gone are the days when many RTR's actually came with a small model aircraft-type muffler, and a tuned exhaust system was an optional aftermarket accessory. A tuned exhaust system is an easy way to improve performance, reduce noise and keep your vehicle clean by routing the exhaust to the side of the chassis. Let's take a look at the different types of systems that are available and how to best use them, and see what may be the best type for each particular application.

The term "tuned pipe" was actually coined by 2-stroke motorcycle engine tuners, who learned an exhaust system could be made to a certain length and shape that would actually help the exhaust gases escape from the combustion chamber, thus increasing horsepower. By experimenting with different shapes, they learned the power band of engines could be improved. You'll notice that tuned pipes for model cars come in many different shapes, depending on the performance goals of the particular product. Exhaust system types include:

Component

This type of system is comprised of a header, tuned pipe (either plastic or metal) and a silicone coupler that connects the two. The advantage of this system type is the ability to "tune" the overall length of the pipe/header combination. For example, the overall length of the tuned pipe/header assembly can be made shorter to improve top speed performance or longer to increase low-end torque and "standing start" acceleration. As a general rule, the overall pipe/header length can continue to be shortened for optimum full-speed performance increase until the engine becomes increasingly difficult to needle (tune). At that point, the overall length can increase by 1/4" to 1/2" and the coupler secured with wire ties. Never allow the tuned pipe and the header to make contact; always leave at least a 1/4" gap between them, which will allow some flex and "give" in the event of a hard impact with another car or object. However, some engine tuners will go so far as to cut material off the header pipe (in small increments of 1/8" to 1/4") in search for the "ultimate" tune. This is recommended only for experienced racers with the proper tools.

Link-type (One-piece)

Gaining popularity within the last several years are the one-piece ("link-type") systems that feature a fixed coupling method using small springs. The benefit to using this type of system is the strength of both the seal and the overall system; this type of exhaust is rarely damaged or broken in a crash. The downside of the link system is its lack of adjustability, in that the overall pipe/header length is fixed and cannot be adjusted. Most 1/8 and 1/10 on-road chassis from manufacturers such as Serpent, Mugen and NEO use link-type systems on their vehicles. They've found that the benefits of strength and virtually no maintenance far outweigh the lack of adjustability.

Helpful Tips

No matter which type of tuned exhaust system you may have, here are some tips that will allow you to achieve maximum results and durability from your system:

1 Inspect the seal between the manifold (header) and your engine. Regardless of rear-exhaust or side-exhaust installations, it's most important to have a leakproof seal between the crankcase and manifold. For side-exhaust engines, make certain the gasket that seals the exhaust port/manifold area is in good condition. If the manifold did not originally include a gasket or if the gasket has become worn or damaged, you may use a high-temperature silicone sealer (found in most auto parts stores) to form a leakproof seal between the header and the exhaust port. Also make sure the screws that secure the manifold to the crankcase are in good condition. For rear-exhaust applications, check the condition of the manifold seal to ensure there are no holes or tears. Rear exhaust systems use springs to secure the manifold to the engine. Check these often for signs of unusual wear or stress.

2 Inspect the pipe coupler for tears or leaks. On component systems, the silicone coupler needs to be in perfect condition to prevent leakage. Change the coupler often and make sure you use only the highest quality tie wraps, such as Dynamite's Thermal Grip Coupler Ties with metal clasps to prevent the coupler from becoming loose. On link-type systems, check the seals and springs used on the pipe/ manifold joint for wear and replace as necessary. Some manufacturers offer "rebuild" kits that contain the necessary seals and springs for these exhaust systems.

3 Inspect the tuned pipe for creases, holes or other causes of potential leaks. Crashes, tumbles or just the stresses involved in operating a car can cause metal fatigue within an exhaust system. Checking these components often can help keep small problems from turning into a larger one. Small pinholes or cracks in tuned pipes can often be repaired using JB Weld™.

4 Check the pressure tap to make sure no dirt or debris has become lodged inside the tap. Simply removing the pressure line and inserting a thin piece of music wire can accomplish this. Also make sure the pressure tap remains securely mounted to the pipe at this time. A small bead of JB Weld can be applied to the base of the pressure tap where it meets the tuned pipe to secure this area (if necessary).