You should not fake whiplash injury
Why? Because it is very easy for both medical and legal professionals to catch you out with this, as many people have tried before and not succeeded can attest, this is a useless exercise.
Do not fake whiplash injury with the intention of receiving compensation settlements
This does not work, for more information on the criteria for whiplash compensation please see this whiplash information page.
I would suggest you read this before making a claim to ensure you are not wasting any time.