Whats this valve under the frunk for?

[atikovi]

With the black cap. Assuming it has something to do with air suspension.

 

[brainhouston]

air suspension fill valve

 

[atikovi]

Yes I assume that, but what for? The air suspension has an air pump. Is it used if the pump fails? How much psi do you add?

 

[brainhouston]

officially its for nitrogen fill but it runs fine on air
yes its also useful if compressor is dead but it might still require operating solenoids manually...
the tank should have a label with max pressure, i believe its 200psi