to the REALLY FAST FD owners......
 

.......a question.

Did you keep the undertray complete? Did you do anything in particular to reduce lift at high speeds? Or is this even an issue?

I have had my car to 153 tops, and it feels rock solid. However, I have seen some posts from those that have cars that go over 170 (claimed) talk about the "floaty" feeling.

I have been in only a few cars that actually did 150+ (my FD, a Jag XKE, a supercharged '96 Camaro, and a '74 TransAm with a 500 hp 455) and the odd thing is, the lighter cars like the FD and the Jag actually felt better at high speed. Seems like weight would HELP, unless the whole aerodynamic characteristics of each car are actually very significant.

Regardless, I guess my real question centers around was the FD engineered for the 160 mph range or does it perform very well at insane speeds?

And it brings into question the functionality of the air dams and wings. I saw a report that indicated that R1/R2 and Touring models actually had a higher drag coefficient than base models, due to the wings and different air dams.
So, is the drag from EFFECTIVE downforce, or is it unwanted drag?

Great post. I am waiting to see what the tech guys say about this one :)

My top is 173mph on flats, i ran out of room :(

I've had my car up to 140mph (speedo indicated) on the back straight at Moroso International Raceway, stock 95 PEP suspension (essentially touring). Very stable. Ironically, I've had it up to 165+ in a few "other" situations where the front end did feel light. I feel this is mostly due to the power steering (95%) and to the lack of a R1 front lip (5%). Adding a more agressive front end with more downforce should be balanced out at the rear. Don't do one without the other. There's also the inherent danger of top speed testing and you'd better make sure the car is thoroughly prepped and it'd done in the proper venue. But the way to go may be the removal of the power steering. One fellow RX7 enthusiast commented that it made a world of difference on the track. Not much fun in parking situations.

while we are on the subject, I just read from RX7 yamaguchi book that stock r1 spoiler was desigend to reduce lift at rear end to get more high speed stability while drag coefficent increased slightly.

I don't mean to sound like a jerk, but I believe that's the general idea of a spoiler. Hence the name.

I think you'll find that a lot of spoilers are strictly aesthetic. But that is not the case with the R1 spoiler.

for those who have broken over 170mph on the flats, how much hp do you have and would it take to push the car to maybe 180?

I dont have much, only about 320 rwhp, but I had a few miles to get up there :)