A tunable stamped collector was developed to improve vehicle performance, drive-by noise and subjective noise quality, and reduced thermal stress concentrations. The stamped collector is located at the junction of the legs of the down pipe/catalytic converter assembly for a transverse mounted V-6 engine and acts to equalize the leg length of the down pipe, as well as provide acoustic tuning volume. This collector differs from most other methods to equalize leg lengths on transverse mounted engines in that it has a tuning chamber incorporated into the design itself, which allows for specific noise frequencies to be reduced.
Performance characteristics were measured for a conventional down-pipe and the stamped collector using the following analysis techniques:
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Frequency analysis of tailpipe noise emissions.
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Drive-by noise emissions.
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Horsepower measurements using an engine dynamometer.
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Finite Element Analysis to determine temperature distributions, stress distributions, and normal modes of vibration.
Down-pipe leg equalization becomes important on V6 or V8 engines (and particularly front-wheel drive East-West powertrains) because engine/exhaust system packaging usually results in unequal lengths of the down-pipe. This unequal pipe length can result in a degradation of subjective noise quality, as well as an increase in drive-by noise levels. By utilizing this collector, engine horsepower and torque was increased, subjective noise quality was improved (through the reduction in odd order noise frequencies), drive-by noise decibel levels were reduced, and stresses induced by temperature gradients were reduced.