if i could find a really, and i mean REALLY cool cop that would be willing to radar me, i will help put this debate to rest. My speedo said 160. I agree that could be wrong. But I also agree that it could be right. Any police around that want a little off duty fun with their radar?

 

sorry if this has already been posted but im not reading all these posts.......to put a end to the debate of it being a drag limited top speed or it being a speed governer there is a safe easy way of testing this. jack the rear end up and support it very well. once you have made it sturdy rip through the gears. if its limited it will cut off at the governer. if its drag limited it will go to the cars gearing limit. you will see top speeds higher then real life if its drag limited because you are eliminating the wind resistence.

p.s. the rsx type S is geared for 183mph in 6th gear.....stock it is drag limited to 147mph........with rasing the redline to a modest 9000rpm and going to 235/45/17 tires its top speed will then be 203mph but would require a shitload of power to reach it (just had to through in some RSX facts LOL)

 

my top speed is lower now that my underbody diffuser (beneath engine) is off.. even though i am putting more power to the wheels from mods!

i think many people do not understand the power of wind and and airflow

 

From my bike racing days, I remember a figure around 90%. This number is the percent of total energy expended to overcome wind resistance while pedaling at 40 mph.

Taking into account that rolling resistance would be much higher for a car with fat tires, at the speeds we are talking, wind resistance would be the dominate controlling factor at limiting speed. Since inertia is very high, the only factors providing resistance would be mechanical resistance (engine, bearings, etc.), friction (low compared to velocity), and wind resistance. At 165 mph I would guess that in excess of 95% of all energy put to the ground is consumed in moving air over and around the car.

just my 0.02

 

Hello Toykilla,

I think its great you have seen 160. I've only been 130 here.

I am moving to Germany in April and am having my Z shipped over. I look forward to seeing what its top speed is...I recently added the Veilside V1 lip and wing and NISMO sides, to hopefully aid with down-force at high speeds. (I know it will go slower now with the increased drag)I also hope the rear wing can hack it. I heard that somebody had a Veilside rear wing fall apart at high speeds. It will be fun to find out legally what the Z is capable of.

I too have had lots of seat time (ten years) on Honda CBR 900s and a 929 at high speeds. Good, clean, wholesome fun......Tad

 

I think that Nissans 156 is absolutely correct and is drag limited. Toykilla, manufacturers always add a small percent to their speedos. This is done for legal reasons. If your speedo showed 50 and you were pulled over for doing 55 in a 50, you could sue Nissan if you could legitimately prove that your speedo was calibrated too low at the factory. You rely on the manufacturer to correctly calibrate the speedo because no one knows exactly how fast they are going seat of the pants. So, it would make sense that in actuality you were traveling close to 155mph when you read 160mph.

 

Im down, where ya from?

 

Tire wear and it's affect on tire diameter alters any sensor speed detection. No computer can know this.

 

The Z's speed sensor is at the wheel and not the tranny. So if the tire size changes the indicated speed will also change.

 

I have done this twice now. The highest my digital speed will read is 159, even though I stayed on it for about 30 seconds trying to hit 160, it simply stopped accelerating at 159-therefore we are speed limited. The first time I did this I used a long downhill stretch and at the rate I hit 159, the car surely would have gone higher but it cut me off at 159. My analog speedo reads 160 when i do this. We are speed-limited not drag limited, if someone without a speed limiter has the ***** our cars can go over 160mph-although it may take a while after 155....

 

im thinking i need a roll cage and racing seets now.. i wonder whose going to test the FI top speeds ?

 

Fly by, if the tire is new it rotates slower...if it is worn it rotates faster, how does the computer know this? Not saying you're wrong just think we misunderstood each other.

 

That is what happens when the car is drag limited. The car stops accelerating. When there is a limiter, it will feel like you hit a brick wall. My E55 was limited to 158. I accelerated to 158 and then it cut the fuel momentarily. The engine had enough momentum to take me to 159, then back to 158 and I backed off of the throttle. My FX is drag limited. On the same stretch of road going up a slight incline I hit the mid 130's and it wouldn't accelerate anymore. I've read that the top speed in the FX45 is ~142 and it is drag limited. As far as speedo accuracy, the E55 digital readout was always the same as my GPS readout, throughout the range I tested it. My Porsche speedo is right with the GPS readout up to ~80mph. The 911 speedo is about 10 mph too high at higher speeds (above ~120). In 7 1/2 years and 110K miles, I haven't yet found the drag limited top speed in the 911. It should be ~171 but gets a bit hairy in the upper 150's (160's on the speedo). I should have my 350ZR in the next 1-2 weeks and once it is broken in I'll try a top speed run on the same quiet stretch of interstate.
rich
'03 FX 45 w/tech, Black/Brick
'96 911 C4 Cab
'04 350ZR MT, SS/BO w/18's & NAV - on the ground and awaiting shipment to the dealer.

 

I have to disagree with you. If the Z didnt have a limiter and I stayed on it for 30 seconds and and it couldnt accelerate past 159 then I would agree it is "drag" limited, but in our case its not that it cant go faster the ecu wont let us, hence the speed limiter. Just because the Z doesnt cut back out speed doesnt mean we are not speed limited. My dads 2002 Stratus R/T(I know its slow) is speed limited to 130, it takes forever to get there but if you hit 130 it will cut back engine power and drop you to about 120. Just because the Z doesnt do this, doesnt mean it doesnt limit our speed. We have a speed limiter at 159, the winds or drag at that speed are not what keeps us at this limit....the car could do a little more stock, who knows with diff levels of modification.

 

I have seen one reference in print, doesn't ask me where, and it said the top speed of the Z is 170mph drag limited under ideal conditions. Ideal conditions are few and far between. The limiter is actually 155/6 depending on the source, if someone has touched 160mph , it must have been downhill or with a tailwind, which happens. I would like to drive it on the Autobahn with the limiter removed, but anywhere else other than a track is out of the question anywhere else for me.

 

I don't understand why this is such a debate. Technosquare has said themselves that they have removed the speed limiter. http://www.technosquareinc.com/350z.htm
Some are wondering if it is drag lmited...eventually it will be drag limited. But the ECU DOES limit the speed.


for the lazy here's the quote:

"Speed Limiter Removal
The speed limiter is removed. The stock limiter was set at 250Km/h (156 MPH), so for all practical purposes, we could have left it alone. But we decided to remove it, just in case someone feels the need to go beyond that."

 

How much do you really think a fraction of an inch is going to change the speedo? MAYBE 1 MPH? It's already off more than that anyways! The speedo is an estimate just like a cops radar is. That is why you rarely get a ticket for less than 5 over. Everyone knows there is some play in that. I mean, if you're going 10 MPH over the limit, you pretty much know you're speeding. But maybe not if you are just a little above that. Even computer programs have a range and not one specific value for any occasion.

 

Interesting discussion.

I'm just curious WHY a car manufacturer would limit the speed, when they're limiting it at such high deadly speeds anyway. Do they really think, "Well, 156 is a lot safer than the true top speed of 167 so let's limit it there."

Really? What is the thinking behind this? I could see if the top speed was 156 and they limited it at something like 115 (even though no one would want to buy the car) but why limit it so close to the drag limited speed?

 

I doubt that. The Z06 has a lot more horsepower, weighs less, and tops out at 171. Alberto has had his car to 159 and it doesn't sound like there was much if any left.
rich

 

The Z is electronically speed limited...