Quote:
Originally Posted by 19bonestock88
I did seal all the unnecessary gaps when I built my Kamm and it provided a loss of about 4%, as it was built... I meant to revise and retest it but never did, focusing on measuring the gain from lowering the car...
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From reading up on kammbacks and stuff on this site your results make sense now. With most sedans (unless yours is abnormally boxy) air remains attached for several inches down the window before detaching, with more aerodynamically shaped cars such as the '01 and newer Civics having more of this (tuft testing revealed ~50% attached airflow on my own Civic). With having the kammback on there you aren't adding any attached flow that isn't already there, and the flow is then detaching further away from the glass surface than is was without the kammback, and thus creating greater drag.
It seems that unless 100% perfectly designed, kammbacks don't really help sedans that much unless they extend beyond the rear of the car and lower than level with the trunk; essentially a mini-boattail.
Just my $0.02...and all from Ecomodder research too.
