What is the biggest difference between Audi 80 and Audi 90?

I noticed that Audi has both 80 and 90 models, but they seem very similar. Can someone explain the main differences between the two?

The main difference between the Audi 80 and Audi 90 is their respective engines. The Audi 80 had a 2.0-liter engine while the Audi 90 had a 2.3-liter engine. This may not seem like a big difference, but it results in a noticeable increase in power and acceleration for the Audi 90.