meanings of certain words
Older cars were the worst offenders;though a sizable number of quite new cars were also definited as gross polluters,they were simply badly TUNED.California has developed a scheme to get these gross polluters off the streets:they offer a FLAT $700 for any old run-down vehicle driven by its owner.

what does TUNED and FLAT mean in this passage?

Thank you!

Question

meanings of certain words
Older cars were the worst offenders;though a sizable number of quite new cars were also definited as gross polluters,they were simply badly TUNED.California has developed a scheme to get these gross polluters off the streets:they offer a FLAT $700 for any old  run-down vehicle driven by its owner.

what does TUNED and FLAT mean in this passage?

Thank you!

Answer

TUNED in this sense means how efficiently the engine burns fuel. A well tuned engine is more efficient and does not pollute as much as a poorly tuned engine.

FLAT in this sense means no more or less than $700. ONLY $700.