At a high level, the changes are:
- Preventing easy overtake of someone not drafting to reduce the effectiveness of “slingshotting” someone and lower the acceleration.
- Dynamic draft coefficient (CdA) changes - Zwifter’s frontal area relative to draft is adjusted depending on the situation, accounting for a) attacking and b) high draft situations
- Changes to maximum draft possible and the draft cone - by changing the way the draft cone is calculated in specific situations, we can help the pack feel smoother and more realistic to attain the original goals of PD4.
If you’re looking for specific numerical changes, we aren’t disclosing those. Our changes from PD4 to PD4.1 are actually super small numbers tweaks guided by the main goals David set out in the original post, all coming together to produce the overall feeling we’re looking to achieve when riding in the packs on Zwift. “Small tweaks” are generally something like (and I’m making this up just for an example) changing the effect of headwind on the rider when surrounded by a number of riders by .01 or .1, reducing draft cone size by .025m, etc.