Why cant I select some options in the engine sand box?

[whitelighter]

Im halfway through designing an engine in the sandbox with the tutorial videos.

Its all been going well (1947 tech year) but when I get top aspiration i cant select anything. So I skipped and I cant select the mixtures or the exhaust so I cant complete my engine.

What am i doing wrong?

[BlastersPewPew]

Did you select VVL-VVT options, if you do not select NO VVL it wont unlock the further options. Every segment needs to be selected to "unlock" the further ones, I run into this often when I need to add more airflow to the engine and I have not selected my brakes yet.......