[Orginally posted this on the Racing forum, but I am getting no responses there, so I thought I would try here...]

Just got home from the 2005 Silver State Classic Challenge in Nevada. We finished 4th in the 130mph Class out of 12 cars (averaged 130.2294mph for 90 miles, 4.3 seconds too fast from the 130 mph target speed).

When going through the "top speed" trap, I expected that the car would shut off at 155mph (since I have heard many places that the stock ECU kicks in to spoil the fun at this speed). However, I was watching the digital speedo in the first gauge pod tick up, 153, 154, 155, 156, 157... The GPS that we use (since it is more accurate than a normal speedometer) showed 159 and change.

I had to back down after that, but the limiter never kicked in.

So, my first question is, since I still have not re-flashed the stock ECU, why didn't the limiter kick in? Not that I am complaining, but I just found it very surprising...

I was running stock size rear tires (Nexen 245/45R18, full tread, less than 1500 total miles on them), and slightly different size front tires (245/40R18). Air pressure was bumped up to about 39 psi front, 38 psi rear.

My second question is: How does the limiter sense speed? Via the rear wheels or the front wheels? Is it gear and engine rpm based, transmission rpm based or wheel rpm based?

Can any of you Z techno-geeks tell me what is going on?

Thanks.

 

I hear ya man, I was pushing 155 on the digital speedo before I let up and it felt like it had more left, no sign of a limiter. If i were to guess i would say the limiter may run off the engine rpms.

 

Took It Up To 145, Got Scared.. Had To Let That Bmw Go.. No Sign Of Limiter!

 

To me the limiter is nothing like a governor on some cars. Governors cuts the engine into slowing you down about 5 or 10 mph before the engine cuts back on. A limiter is a fuel cut meaning it starts slowing down the injectors and it doesn't put as much fuel into the engine to keep you from going any faster. I've been to 161 on my digital read out and it would not give me any more. When I first got my car I was thinking to myself this car will do more than the speedometer says and as soon as you put the car in 6th gear after redlining 5th. You can tell the power has cut back alot from 5th to 6th gear. It creaps up in speed in 6th unlike 5th it climbs. I bet with a reflash the Z will do about mid 170's if not more if there was a good stretch of road.

 

How much and where do you flash the ECU?

 

technosquare

 

Limiter is set at 159, trust me

 

how do u know its at 159 ?

 

That is not quite true, it all depends on wind speed and roads... all basic physics- straight road no to minimum wind i hit 165 on stock. At those high speeds it is hard to gain mph, need more power, with stock rev limiter i hit 165 at around 6200 thats when the Z's power curve starts to drop. Get the reflash and MORE POWER!!!!!
I sure hope this is the last top speed thread
WARINING: When you go those high speeds PLEASE REMEMBER to have High speed rated tires!!! VERY IMPORTANT, stock tires cant hold will burst at that pressure, so please keep that in mind... tire suggestion bf goodrich T/A KD!

 

i got a reading of 157 on the digi. i was at about 5500 rpm and it felt liek it had more... smooth as glass i was really hopin to see 160 but 157 was good enough for me

 

how did u hit 165 i had the same conditions ?

 

http://www.alteredatmosphere.com

 

I ran that when i was N/A and had 285 rwhp, and roughly 330-340 crank hp, thats alot more power than stock. More power helps in top end.

 

ya but i'm saying that the car didnt' limit my speed (well not directly) but the computer did i'm just wondering like y with mods would the computer let u go faster

 

No, because that is where the fuel cut off is, when the computer kicks in the governer and basically stops the car

 

The cars are probably drag limited, not computer limited, so essentially with the power made from the factory it will go no faster, however with extra power mods it will top out even higher Maxima SE and GLE Models are not limited except for drag, I would wonder why nissan would limit their sports car

 

no cuz it felt like it had alot left it was still pulling

 

The car is DEFINATLY limited by the ECU (at least on the 03s). I've seen the ROM disassembled and there is a speed limiter function built in (based on speed sensors, not RPM). I believe that it pulls spark not fuel though. Pulling fuel at high RPMs can cause lean conditions if the throttle is still down, which is dangerous. I've only looked at the 03 ROMs, but I would be willing to bet that all other years have kept the limiter. I'm guessing it's a US safety regulation, but that's just a guess.

 

Oh yeah... 1st post on this board

 

ignore cars speedo, at those speeds it will probably read 10mph over what your really doing. Use gps. UK cars tested by magazines etc hit 155mph (250kph) and no more. Remove the speed limiter and it will apparently do a genuine 167mph.