[PHOEBISIS]

Hey,did you guys take a look at the date I wrote that?April 15-and now I'm being beseiged!!
Well,according to the article sleightofhand posted the link to,I am wrong on the covers,but right on the tailgate.
Titan4X4aggie,I understand the" why" on decreased pumping losses for a lower restriction intake,but you only get a decrease in total intake resistance at WOT,at part throttle operation(where everyone-except NASCAR- measures mpg) the total intake resistance will be unchanged,so pumping losses will be unchanged.How can this be,if the filter is lower resistance?Simply,the throttle plate is the main source of resistance in the system at part throttle.You want less resistance to get the same amount of air in at a given load-just open the plate a bit more!!On a carb motor it is a little different, since fuel flow is dependent on airflow-drops in pressure etc.In short(ha,ha)a lower restriction air filter won't lower the intake pumping losses at anything but WOT with EFI.
Exhaust side,well, isn't so easy to defend my position,and once again at WOT you can get more hp,and probably more mpg.At part throttle,I just don't think so.Usually an exhaust system that gives more peak hp,will give up a bit of low end hp-torque.This usually means the filling at those RPMS- is a bit less-probably because of sound wave tuning..Bigger diameter-or shorter- tubes mean better high RPM power,but less low RPM power.The MCycle manu folks have developed devices to overcome this in their 4 strokes,but I don't think the cars use anything like that.I think you probably lose the gain you get from the decreased exhaust resistance,because of poorer "extraction tuning"

Well,who knows.On the covers,I might have to concede,but the tailgate stuff-no way(except for the weight in low speed stop and go).Thanks,Charlie