Noise is an issue in almost any country, and if it is not yet today, it will be tomorrow. Race tracks have already closed down, or are under threat because of noise problems. In 1995 IFMAR, the World organization for RC racing, asked the manufacturers to come up with solutions to reduce the noise-level of 1/8 scale gas powered racing cars. Serpent took up the challenge and in close co-operation with the University of Delft, developed the universal Induction Noise Silencing Box, the INS-BOX. In combination with an effective (*) exhaust silencer, the INS-BOX is able to reduce the overall sound level with up to 4 decibels. If 10 cars would be using the INS-BOX at the same time, like in a race, the overall noise-level would drop with 5 to 6 decibels!
Noise is measured in decibels. The decibel scale is not linear but logarithmic. For instance, total silence would be 0 dB, a silent room 45 dB, a person speaking 60-65 dB, a car 80 dB, an airplane 90 dB. From a silent room to an airplane is only doubling the amount of decibels, but what you hear is much more than double the noise. There are different scales used with decibels. This depends on the type of sound and the environment it is produced in. For noise-level measurements used to set acceptable standards for the human ear, the "A scale" is used. The noise level depends on the distance between the noise source and the point of measuring. The closer by, the higher the noise level. The standard distance for measuring noise levels of cars and machines is 10 mtrs. The universal norm for industrial noise levels has been set at 80dB(A) at 10 mtrs. A noise level of 83dB(A) compared to 80 dB(A) is experienced as double the noise by the human ear!
Current 1/8 scale gas powered cars, using IFMAR homologated exhaust pipes are measured at 89-90 dB(A). This high noise level depends very much on the engine rpm. With the ever increasing rpm's, the noise level went up from 84 dB(A) in the early 80-ties, till 90 dB(A) at this moment as engines are now capable of running well in excess of 40.000 RPM.
In 1995 IFMAR set a target of 85 dB(A) at 10 mtrs. to be achieved by 1997. With the use of the INS-BOX this can be achieved, providing an effective exhaust silencer is used. Models 082, 089 and the 053 have been found to be effective. EFRA has asked all the manufacturers of exhaust silencers to issue their exhaust pipes for re-homologation and will publish a new list of silencers that can be used from June 1998 onwards. It is expected that EFRA and a number of their member countries will make the use of an induction noise silencer like the INS-BOX, in combination with a homologated exhaust silencer, mandatory in 1998.
RC cars have 2 sources of noise, the exhaust system and the inlet system. With the use of homologated silencers, the exhaust noise has been effectively reduced to 84/85dB(A). The induction noise however, has no silencing device and with the ever increasing rpm's, the induction noise has gone up to close to 88 dB(A). The 2 noise sources together produce the measured overall noise-level of close to 90 dB(A). It is obvious that reducing the exhaust noise level further would not affect the overall noise level. Only reducing the induction noise would be effective in terms of overall noise reduction. This is what the INS-BOX does. The box is designed to filter out the 700Hz frequencies and its harmonics. These frequencies are 'weighed' very heavily in the 'A" scale used for measuring the 'industrial noise levels' such as cars. The INS-BOX was designed using complex acoustic formula's to calculate the volumes and shapes of the 2 chambers and the size and length of the holes (pipes) which connect the 2 chambers.
Because of the optimized design, the INS-BOX unit does hardly affect the performance of the engine, it only reduces the induction noise. The performance was measured in various ways: by taking lap-times (no difference), by using data-logger technology (no difference), and on the test bench (approx. 3% difference). What can be felt is a very little loss of throttle response at low speed. But this will be the same for everybody of course. Running the car with or without the INS-BOX has no influence on the setting of the carburetor, which is proof that the air-flow is not restricted. Using the INS-BOX has no effect on the engine temperature as it does not restrict the airflow and the engine is not running leaner.
The INS-BOX is equipped with a high quality and effective foam filter to clean the air before it enters the engine. Insert the foam filter from the top in the lower case, the rubber filter-grommet must snap between the lips. This provides a firm and positive fixation of the filter. Do not use glue for this purpose too.The foam filter must be treated with the special filter oil which is included in the set. The INS-BOX is designed for this foam filter. Other foam filters may not fit and should therefore not be used.The box itself works as an additional protection against dust and can also be used in rainy conditions. It does not provide full protection against heavy water under all circumstances, the foam filter may still get soaked.Tie the INS-BOX down to the carburetor by wrapping a tie-wrap around the rubber part which fits over the carburetor. After installation on the engine, the top-part of the INS-BOX box can easily be removed by squeezing the lower case slightly, thereby freeing up the upper part. To re-install, gently press the upper part back in the lower case until it snaps into the groove of the lower case. Do not modify any part of the box as it will have no effect on performance but it will disturb the proper silencing function of the unit and the noise level will go up again.
Serpent has developed the INS-BOX for all RC racers, independent of the brand of car or engine used. This product is not marketed as a Serpent product, and therefore you will not find our brand name on the INS-BOX. IFMAR, EFRA and other organizations have already recognized and approved the INS-BOX as an effective noise reduction device. We at Serpent hope that you will appreciate our efforts to reduce the noise level of 1/8 scale racing cars and that you will start using this device, even voluntarily. This is our contribution to a better 'gas on-road' world.
