Quote:
Originally Posted by XutvJet
Other things that can make this process a bit confusing and complicated is the fact that turbo cars do not make the same power in every gear. Turbos are dependent on load to generate boost. Most cars are dynoed in the 1:1 gear (a higher load gear) which gets us the power numbers we're using for these calcs. However, in gears 1 and 2, less boost is being made because the torque multiplication of those lower gears greatly reduces the load on the engine (i.e., it doesn't have to work as hard), thus less load on the motor means less boost that can be ultimately generated. There's no physical way to generate more boost in those gears short of changing out the turbo.
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I have no reason to doubt your app regarding the boost levels in different gears. However, your explanation makes no sense to me. The load is the same in every gear - it's the torque of the engine applying force to the road and pushing against the weight of the car. The weight is the same in every gear. In lower gears the force on the road is greater because of gearing is different, but that just means the car accelerates more quickly. It doesn't mean the load is any different.
Part of the difference might be turbo lag. At max throttle you spend so little time in first gear that the turbo might not have time to reach full boost. Maybe boost drops during the shift to second with a manual, then it gets a bit higher in second before you have to shift again since you spend more time in second. And so on. But, to my seat-of-the-pants sense, the turbo spins up quickly enough that this doesn't seem like a full explanation.
It might also be the computer limiting boost in the lower gears, although it would be hard to understand why an app would have that information as I doubt BMW releases it.
Anyone have a better explanation?