Is “ai” in "j'ai" and “finirai” pronounced exactly like “er” in infinitives?

Question

Is the *ai* in *j'ai* and *finirai* (I am assuming they are the same) pronounced exactly like the *-er* in infinitives: are *manger* and *mangeai* pronounced exactly the same?

Answer 1

It's not the same pronunciation.

-er: [e] manger

It's the same pronunciation with é: un café, un musée, l'été

-ai: [ε] je mangeai, j'ai, je finirai

It's the same pronunciation with è: un chèque, un collège