You have to be kidding if you feel you didnt quite capture that impression of speed - I think the last two look like their really flooring it, and the first two still look like theres alot of speed.
The second could be alittle sharper, but having said that with the focal lengths used Im amazed you could track these things as they went by. Also you got the wheels with alot of spinning blur which is great.
More vibrant colours would be desirable but I guess you have had the same weather as we're having up here so not alot can be done about that.
Very good & thanks for sharing