Please be careful if you do try to attain very high speeds on the road or track. I read several years back that when tires are speed rated it is a new tire that has never been used and is tested on a machine. In the real world a tire hits potholes that may cause structural damage to the tire and IMO may reduce the speed that it can attain safely, I certainly wouldn't want to find out the hard way.

 

If you want to find out what your car can do, there are sanctioned Open Road Racing events held in Nevada and Texas. You will need appropriate saftey gear, and will be allowed to go to certain speeds based on your ability, and the safety gear you have.
I just sold a 99 cobra, and could get into the 170's, was allowed up to 165 as a tech speed, and could run and average 150 mph for 90+ miles. To average 150 you need to be able to run approx 160-163 most of the time, they posted known and unknown radars along the course to keep people honest.
The way the Z is geared it should do 170 sometimes with the limiter cancelled, but dont try it unless you have ability, safety gear, a closed highway, and w rated tires. The Cobra had 300 rwhp, but needed more in the winds, etc we encountered. A Zo6 runs out of gears at around 168 and a c5 can do into the 170's. I bagged a z06 in Tx in a race, as the first ones had no trans coolers, would overheat about 30 miles in, dashes would light up, and the party was basically over for them.
Someone said try the salt Flats? If you wanna really trash your car and loose 20 MPH from rolling resistance, and the sanctioning bodies out there are a nightmare.
Here are some sites, www.openroadracing.com, www.silverstateclassic.com, there is also one for the big bend ORR, but it usually does not work, something like bborr.org, run by the city of FtStockton Tx, my favorite course, won 1st at 125 and 145 mph there
John
ps again safety first!!!!

 

THE AMERICAN VERSION MAY BE RESTRICTED TO 155 BY THE UK HAS LOTS OF JAP IMPORTS, THESE ARE RESTRICTED TO 112MPH WHICH I AM SURE THAT YOU WOULD ALL AGREE IS TO LOW? SO I THINK THAT THIS WAS A VERY VALID QUESTION.

 

HKS Speed Limit Defencer for the Z33 (application specific) removes the limiter.

 

The Z is speed limited in the ECU, Technosquare has confirmed this and removes it with their ECU reflash. I believe they actually set it very high like 230+, in essence removing it from the equation. Yes HP, aerodynamics play a part but as someone mentioned so does gearing. This car handles high speeds quite well, just don't blink. Besides the JUN car I believe Skiddazle may have hit the highest speed on the streets at just over 170 with more room to go. Of course his car has the power and the gearing for it.

 

yeah... gearing affects the ratio of engine power that you put down through the tire to the ground.

basically when you're aerodynamically maxed out, your net acceleration is 0. therefore, net force is 0. so the force your car is exerting is equal to the force of the wind, and force of wind is proportional to speed.

if you increase your engine's power output, it takes more air resistance to reach 0 acceleration, which means more speed.

lower coefficient of drag means that you have less resistance at the same speed than you originally did. so you have to increase speed to make the force of air resistance equal to engine force output.

 

a lot of, if not most, automatics do as well...



Most of us probably know what I'm about to say... but when you say proportional, it is not 1:1... (not saying you implied it was 1:1) obviously it isn't a 1:1 relationship... anyone who has taken any engineering courses in college that covered fluids, knows the formulas for drag are extremely complex, and even can be broken down much more detailed and more precisely than just a "set" Cd... getting into the density of the air, etc. But.... a basic model for a vehicle moving fast, and other "fast" items, says the drag force is based on the sqare of the speed.... so to do double the speed, takes ~4x more power. Which makes sense... we know a car with 120hp can reach 100mph pretty easily, but hardly any car would be able to hit 200mph with only 240hp.

Also, something to think about.... I live in Kansas... moved here from Florida... it is amazing how windy it is here... a lot of times there may be 15-20mph sustained winds.... so... if the winds were blowing directly from south-to-noth, and I was driving due north, I'd now have a tailwind of 15-20 and now theoretically could go 15-20mph faster than usual, provided my gearing would let me.... same of course holds true if it is a headwind... but opposite.

 

I have gone 159 m.p.h. in my 03 track. That was what the digital speedometer read, I didn't look at the analog.