Top Speed

[doodledo824]

IN THE WINTER I HIT 135 RELATIVELY EASY ON THE PULASKY SKYWAY HERE IN JERSEY. 4TH GEAR PULLED STRONG TILL ABOUT 123 OR SO . I THEN PULLED 5TH TO ABOUT 135 I THINK IT IS CAPABLE OF 140 WITH A LITTLE MORE STRETCH OF ROAD AFTER 130 THE PACE SLOWED CONSIDERABLY I GUESS DRAG MUST BE PLAYING A ROLE...HOWEVER THE OTHER DAY ONMY WAY BACK FROM SCHOOL I TRIED DOING THE SAME THING AND IT SEEMED TO TAKE FOREVER TO DO 135. I NOTICE A HUGE DIFFRENCE IN PERFORMANCE ON MY P11 IN THE SUMMER. THE CAR FEELS SLUGGISH WHILE IN THE WINTER IT'S VERY LIVELY.

[Brian P]

what are the tires rated for? ive got the t with the Potenza 195/60 15s.

[Brian P]

oh, and the top speed of the car is a direct function of the diameter of the tires, multiplied by the final gear ratio and current gear ratio, times engine rpm... and like you said, engine rpm can and often is governed, either by a chip in the ecu, or by your willingness to go over redline.


Formulas:

TireSidewallHeight = 2*(TireWidth/25.4)*AspectRatio/100
TireDiameter = TireSidewallHeight+WheelDiameter
MilesPerHour = RPM*TireDiameter*PI*60/(GearRatio*63360)

195/60 15
195 = tire width, 60 = aspect ratio, 15 = wheel diameter.

a java calculator that uses the above is found here: http://www.geocities.com/z_design_studio/

about aerodynamics... the G has a pretty good coefficient of drag going for it... .30 if i'm not mistaken, that is on par with a corvette. since the top speed of the tires is a function of the engine and transmission, aerodynmics doesnt have much to do with it. i think at like 100 mph, an average car would need to produce 70hp just to maintain speed, as opposed to traveling at 35mph, when it would only need to produce 7hp (thus the reason behind slowing down for better gas milage). so i guess in a way aerodynamics COULD limit the top speed... when the amount of hp needed to maintain speed equals the max hp the engine is producing... yeah i guess you could get your speed limited. but even with 140hp, i bet the G could overcome air resistance due to its steamlined design and a transmission that puts a good % of the engine power to the wheels.

[Kenny-G]

The Potenza RE 92 came with the stock G20t is H rated, that means you can run 129 mph safely for 30 mins....( I think it is 30 mins.....or 1 hour..I don't remember, that is how they rate it tough ). I got Potenza RE 730 and it is Z rated, so I can go faster I want with my G not to worry about my tires overheated.

[slickkedar]

Ok, so using Brian P's method (thanks).........here are the speeds
At about 7k rpms, the top speed with factory tires is about 160 (??- you might want to check yourself).........

[endfro]

I dunno about all G20s.

But my older brother used to own my G20, he drove from Minneapolis MN all the way to Ithaca NY with a friend to stay for a week.

On the way back (while going through canada) a canadian patrolman pulled my brother over clocked at 145mph. I'll talk to my bro, hes got pics of the spedometer hitting 130 and the revs kept going up.

Fastest ive taken mine is 115. I dont wanna get pulled over goin real fast. =]

[Brian P]

well according to my calculations, my auto '99 with the low profile tires will max out at 7000 rpm (redline) at 177.66 mph. and if i'm feeling REALLY stupid, i could (theoretically) rev it up to 8000 rpm (well, the ecu probably wouldnt let me) and top out at 203 mph.

whats funny is that the speedo tops out at 125 mph, but according to my calcs, 3rd gear goes all the way up to 124 mph. then youve got your overdrive.

I verified my numbers by using that Z car applet thingie. according to those formulas, I am correct. i know it seems very strange... and for an underpowered car like the G, it would probably take 20 minutes to reach those speeds since the gearing becomes so low. if you were driving around on a high speed oval, there is a good chance that you might never see 178 mph because when you hit the turns, the added friction would likely tax the engine enough so that it could not accelerate further during turns.

so basically, assuming those formulas are correct, and that the ECU governor wont screw with ya too much... yeah, this car really goes that fast... but then again, i'm sure most cars could.

[slickkedar]

it might work with those calculations, but if you look in the back of the new SCC, it shows how much of a difference the cd (coefficient of drag) makes........i really doubt we could get anywhere near 177

[GtRider]

i own a 94 g20t automatic
one day i waz coming home from work and i pushed my car all the way and it clocked 120mph.
is that good or bad?
all i got is an intake and advanced timing!

[Sleepy]

dude thats not bad ran my to 140 stock other then some timing advancement my a 2001 g20

[jprimera]

My mother 1999 auto primeragxe with 17 timing did 200kmh no more in a very strait road (the same that I test my car)we test with a gun machine laser (police friend) and the car did not pas the 200kmh (199,450) the tachometer were at 204kmh.

[JustinP10]

Well, I entered in the info from the FSM to the calculator and got some very interesting results.

Info from FSM:
1st gear : 3.063
2nd Gear: 1.826
3rd Gear : 1.207
4th Gear : 0.926
5th Gear : 0.733

Final Drive: 4.176

Here are the speeds at which the car would be travelling at 7500rpms (stock redline in the P10) with 205/45/16 tires and stock 195/65/14 tires

205/45/16 (195/65/14) *in miles per hour
1st : 41 (42)
2nd: 68 (70)
3rd: 103 (106)
4th: 134 (138)
5th: 170 (175)

That to me seems very high. I don't remember second topping out at 70mph, i thought it was more in the 60-65mph range? and I thought 3rd tops at right at or slightly under 100mph? Or could it just be that my tires have worn down enough for me to notice that big of a difference? Either way, 170 seems REALLY REALLY REALLY high for our cars.

[T4 Primera]

Either way, 170 seems REALLY REALLY REALLY high for our cars.

Of course they won't do 170mph - the calculator does not take horsepower, drag co-efficient or rolling resistance into consideration. It's just a straight gearing calculator

[JustinP10]

Originally posted by T4 Primera
Of course they won't do 170mph - the calculator does not take horsepower, drag co-efficient or rolling resistance into consideration. It's just a straight gearing calculator

I don't think it would take that much hp to top our cars out in 5th gear. A couple list members ran their NX2000 in the Silverstate race and they managed to race their NX to the top of 5th gear, and I am pretty sure they are N/A powered and they were even running slightly larger tires IIRC, so it is definitly possible. Their gearing runs out right around 150mph so it's not too much different from the G20's, just slightly smaller. I think a small turbo would easily power a G20 to the top of fifth gear, probalby with the just the majority of the bolt ons it would be possible too. I just thought that our gears ran out before 170mph. I didn't realize there was that big of a difference between the SE-R tranny and the G20's.

[T4 Primera]

I don't think it would take that much hp to top our cars out in 5th gear.

Did some rough calculations on this 170mph (5th gear @7500rpm on 205/45/16s) in a G20 thing and you would need 208 wheel horsepower just to overcome wind resistance. Add more at flywheel for drivetrain/rolling resistance losses
Formula: Power to overcome aero drag = 1/2*air density*cd*cross sectional area*velocity CUBED.
air density = 1.177kg per cubic metre
cd = 0.30
cross sectional area roughly = 2 square metres
velocity = 76 metres per second = 170mph