Originally Posted by
shortride
One consideration is that these late model engines have the ability to adjust the ignition and maybe valve timing and fuel control under different conditions. This could explain some of the performance characteristic differences.
The gearing explains it... Lower gears apply more torque at a lower speed to the rear wheels, which will provide more acceleration. Pair that with a heavier vehicle and the lower gears will attain similar acceleration to a lighter vehicle with taller gears, though at the cost of highway mileage and top speed.