Will this actually block engine and road noise in a car?

It reduces vibration and mid-range noise on floors, doors and firewalls. It will not silence deep exhaust drone the way a heavy butyl mat plus mass-loaded vinyl does. Use it as a first layer and add mass where bass is the problem.

Can it go in an engine bay or near exhaust heat?

Closed-cell foam with a foil face handles moderate radiant heat, which is why it is used on firewalls and ductwork. Keep it off direct contact with exhaust pipes and headers, where surface temperatures exceed what the foam tolerates.

Clean and degrease the surface, let it dry, then peel and press the adhesive backing down firmly, working from the center out. Cut pieces with a utility knife or scissors before peeling. Roll or press the sheet to push out trapped air.

The closed-cell structure does not absorb water, so it suits basements, ducts and outdoor panels. Seal cut edges and seams if the sheet will sit in standing water or constant spray.

How much area does one roll cover?

One roll covers roughly 3.5 square feet. Measure your doors, floor pans or duct runs first and plan on multiple rolls for a full vehicle or a large duct system.

Does it work for soundproofing a room?

It helps with echo and vibration on shared walls, doors and duct chases. Full room soundproofing needs mass and decoupling, so treat this as one layer in a larger assembly.