I can tell you what happened with GM's motors and their swirl chambers....

Early 6.2s had smaller holes in their sqirl chambers. This resulted in better fuel mix and better fuel economy, at the expense of power. Later on the hole size was increased which allowed more flow and more power, but mixing wasn't as good and fuel economy took a hit.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.