Hate bringing up old threads but they recently raced the Duratec class at Bathurst at the end of last year (2012) and the general rumours were speed reads in the 265kph range (around 165mph) down conrod straight. Remember thats with a tyre that has grooves and no downforce...
The problem is they are nearly getting too fast for the track and this video shows what happened in qualifying that weekend
http://www.youtube.com/watch?v=eyb2UHmbmDQ It's really too dangerous around there in open wheelers yet they raced F3 there. Mental.
...and heres another clip of the star of your Bathurst comeback videos spinning around in a kent car
http://www.youtube.com/watch?v=QzjJ-6GNdmo