per Number: 2005-01-3803
DOI: 10.4271/2005-01-3803
Author(s):
Sam Zimmerman - University of Idaho
Dan Cordon - University of Idaho
Michael Anderson - University of Idaho
Steven Beyerlein - University of Idaho
Thanks 93
In terms I can understand
being a non-geek ......it would appear that it is true that such a fitting can not only effect noise, but flow of the intake and can affect the actual running efficiency of the motor. A great deal of research into this has apparently gone on by the geeks at Mazda and as the cost of the modification is small, they have included it/them.
"Acoustical tuning of intake manifolds is a common practice used to achieve gains in volumetric efficiency in a pre-determined region on the torque curve. Many methods exist for acoustical tuning of the intake including a variation of the Helmholtz resonator model by Engelman as well as the organ pipe models by Ricardo and Platner. In this work a new intake tuning model has been developed using an Impedance Transform Model along with a minimal set of limiting assumptions. Unlike the models of Engelman and Platner, this model can accommodate any intake geometry. The model can also be used to analyze specific points in the intake system or the entire system rather than just the intake runners. Model verification consisted of resonance testing of three different Helmholtz resonators as well as dynamometer testing of a Honda CBR F3 four-stroke SI engine using three different intake system geometries. The different intake systems and Helmholtz resonators were designed such that each would produce different resonant frequencies for proper model verification. The model accurately predicted the resonant frequencies of each different Helmholtz resonator and the torque peak produced by each intake system iteration."
There is a mention also from someone who reported a 25% torque drop in the sub -4000rpm range
.
Not easy to accept but not something you'd want to happen for the sake of a little extra sucking noise .....
