I took a trip to NYC this past weekend and while on my way there, I had a nice stretch of open Interstate and decided to jump on the throttle. My previous top speed was ~240 km/h. That run was according to my speedometer as I didn't have my GPS with me. This time I made sure to have the GPS running.

In miles:

http://www3.sympatico.ca/akrusvar/2k2Max/Image1.jpg

In kilometers:

http://www3.sympatico.ca/akrusvar/2k2Max/Image2.jpg

Last time I looked at the speedo during this run, the needle was at about 250 km/h.

The car was very stable as the road was really smooth.

Albert

 

thats fast

 

You sure a 164mph is right? Cause that just dont seem possible.

Dixit

 

get ready for a bunch of "your GPS is wrong" comments... nobody will believe it

 

Yeah, I thought about the fact that I'm going to hear the GPS isn't right, but I guess I'll have to re-run it sometime to verify.

I guess there are two possible ways to verify:
1) I get another GPS in the car and try the same run;
2) Put the GPS into another car and try to verify against it's speedo

I had the WAAS functionality turned on on the GPS. I believe that is supposed to make it much more accurate.

Albert

 

Thats serious speed. Is there any kind of margin of error for the gps? Were you on level ground the whole time?

 

Rock on!!


Fred...

 

You're my hero!
I've heard of some sweet top speed journeys but this takes the cake.
The fastest I'ed seen up until now was 156mph(2k2)
The fastest I've gone remains at 138mph fuel cut off.(2000)
Sweet dude you deserve the gold star!

 

when i read this thread about 2 hours ago i was convinced something was wrong. but the fact that your speedo was reading over 155 MPH and your GPS also went that high (and higher) makes me wonder if the speedo and GPS could both be off by that much at the same time.

maybe try to do it again sometime with someone else so they can verify the reading on the speedo at its highest point. maybe even a person with a video camera.

 

....what stretch of Interstate you were on? what time it was?

Brian (not a doubter... just curious)

 

what rpm were you in @ 6th?

 

As far as I understand GPS devices, the error is quite small, especially with WAAS turned on. WAAS only works from a certain latittude North (not sure of the exact lat). Goto http://www.garmin.com/aboutGPS/waas.html for some info.

The ground was very level (to the eye anyway).

Albert

 

I've got doubts that both could be off at the same time. I suppose it's possible. The number really sounded high to me when I first saw it. For the longest time I speculated that the Max would only do 155 - maybe.

I'm not sure that anyone I know would get into the car if I told them that we were going to go on a high speed run. A bracket for a camera would be needed otherwise, and I don't have one of those (bracket or camera).

Albert

 

[edit]***location was up long enough***[/edit]

Albert

 

I'm not sure of the rpm as I wasn't looking at the guages too much. As far as it being in 6th, I'm not too sure about that. What I mean here is that after running 5th right out, I shifted into 6th, but the car didn't seem to accelerate any. It's possible that it did gain a mile or so, but I doubt it.

Albert

 

I just got into the office and decided to check my odometer reading against what the GPS read from the weekend.

On the way back from NYC, my mileage was:

according to GPS - 900.1 km
according to Maxima's odo - 856.4 km

There's definitely something out of whack here. Either Nissan is being really generous and the tire diameter is throwing out the odo (making me happy since I lease), thus making the GPS correct, or the GPS gets optimistic. I'm not sure which it is. If I get some time today, I will try to enter my exact route into Streets & Trips to see what that gives me.

With the difference in mileage, I'm wondering how accurate my fuel consumption spreadsheet is
http://www.cenpipe.com/~akrusvar/000...axtracking.xls

Albert

 

Lets just consider some physics facts for a min before we decide.

1.) The 300ZX TT when the speed limiter was removed was good for about 165. The car had a smaller wind footprint, one reason being the roof line was much lower than the Maxima. The car also was making a true 300 (crank) hp. That should equate to about 250hp at the wheels with figuring in 20% driveline loss.

2.) The 270hp Acura NSX could do about 170MPH. This car had much less wind resistance than even the 300ZX.

3.) The Maxima is a bigger car than the 300ZX or the NSX. It only makes 200hp to 210hp at the wheels stock, hardly adds up to the advertised 255 crank hp. It doesn't matter that the Max is a lighter car. Weight doesn't have much effect on top speed, just accceleration. Just from this little bit of data we can conclude that even if the Maxima had the same wind resistance as the 300ZX it would still need to make 250hp at the wheels in order to hit 165. Figure in the fact that it has alot more surface area and the hp requirements only grow to attain that speed.

So having said all that perhaps there is just some piece of the equation that we're all missing here. The numbers as we have them just don't add up.

 

Yeah it's called a tail wind.

For the record 5th gear in a 2002 will not go past 155MPH (assuming a 6550 rev limiter and stock tires). You would have had to pull that in 6th. There is more torque to the ground in 6th at those speeds than in 5th anyhow.

Just for the record I'm not a doubter. I believe that the GPS is very accurate. I've gotten in many an argument with DaveB about the top speed of the 2002. I think the car should be able to do about 152-157 on level ground with no head (or tail) wind.

Stereodude

 

Man you were moving.

 

Nothing like bringing poor logic into the equation in an attempt to illustrate a point. But I can play this game too.

Consider these facts:

1) A 4th gen with only 190HP (at the crank) was tested by car and driver and recorded a top speed of 143MPH. The 4th gen is less aerodynamic than the 5th gen (by .01).

2) The Volvo 850 T5R wagon or whatever the heck it was called was tested by Road and Track (might have been Motor Trend) to go 157 and 155 (two different cars on two different occasions). If I'm recalling correctly it had about 230HP and the car was certainly a box (bad Cd and it has a lot of frontal area).

If a 4th gen can go 143MPH with 65 less HP and a "Boxy" Volvo can go 155 with ~25HP less HP why does it seem so impossible that a Max could go 164MPH? Granted I think it probably had a slight tail wind (~6-8MPH)but I don't think it's nearly as far fetched as you propose.

I did extensive mathematical calculations and showed that an automatic 02 could hit 147. 2k2themax took his 02 auto to 147.7MPH (GPS measured). The same calculations show that the 6 speed should be able to hit ~152-157. If Akrus had a light tail wind his speed is very possible.

Stereodude

 

Yes GPSs are very accurate for ground speed so lets rule that out of the equation. When I said that we're missing part of the equation I was implying that I don't believe a non modified 2002 Max could possibly attain the speed of 164mph. 155mph for 5th gear does sound very accurate but a stock Max even hitting that speed is overly optimistic.
How in the world do you figure that a car can put down more torque in a taller gear than a shorter one? Wheel torque is a simple equation of Engine torque x gear ratio x axle gear ratio x percentage of driveline efficiency. Lots of VQ35s make as much as 230 ft. lbs. of torque on the low end but about 220 to 225 at the high end (and even less at the redline). Since we need engine torque we can add the driveline losses back to the number. If we use 85% efficiency the number comes out to about 264 engine torque. Lets figure a Maxima motor is spinning at the optimum RPM to make 225 toruqe and is in 4th gear that we'll call 1.0 to 1 gear ratio. Im not 100% sure but offhand i think the axle ratio in the 6speed is 3.8:1.

264 x 1 x 3.8 x .85 (lets use 85% efficiency) = 1004 ft. lbs. of wheel torque.


Now lets go to a much taller gear that we'll call .75 to 1 or an overdrive gear.

264 x .75 x 3.8 x .85 = 640 ft. lbs. of wheel torque




Thats only at the optimum RPM in both gears. Even if you got all the exact gear ratios and figured in the exact engine toruqe at a certian RPM in each gear you'll find that the answer is still the same.

 

I do beleive a stock Maxima can hit 147 or perhaps just over 150 given the righ conditions. If you do calculations you should also know how much hp it takes to make MPH increases such as that. In order to double your speed you encounter 4 times the wind resistance and need 8 times the hp to attain it.

Motor Trend tested the 4th gen to 141MPH. I personally had my stock 4th gen to 140.7MPH (GPS) so I know it will do it.

The drag coefficient is only one side of the story. The manufacturers give that number to you but they don't tell you the surface area of the car. Total drag includes the drag coefficient AND the surface area. Do we not agree that the 5th gen as alot more surface area than the 4th gen?
And wasn't it that same Car and Driver that only got a 222hp 5th gen car to 143MPH? Gee why would a car with 32 more hp only get another 2mph? It's called drag.

 

You've over simplified the equation. At redline the 3.5VQ is not making much torque. Look at your own Dyno curves. 155 in a max in 5th (6550RPM). (160 X 0.809)/3.812 = 33.96. Now at 155 in 6th (5100RPM) (230 x .63)/3.812 = 38.01

Lookie there... At 155 MPH in 6th gear has more torque to the ground than 5th.

Stereodude

 

You have several flaws in your math.

1) Velocity is cubed in the formula. You lose 8x the HP to the wind. You need 8x the HP to go the same speed.

2) The frontal area of a 5th gen is not more than a 4th gen.

3) No, it's not called drag it's called gearing and power curves. You can't simply look at the Peak HP and TQ and assume it has all of it available.

4) 143MPH in 5th in a 222HP 5th gen occurs at 5950RPM. We all know that that version of the 3.0L VQ does not make it's peak HP until redline. The 4th gen's 190HP engine had a similar power curve to the 2002. At ~5900RPM (same gearing the 5 speed) it made a greater % of it's peak.

You're looking at this problem in 2D. There's another aspect that you're missing. You have to look at the gearing and how much TQ/HP is on tap at the RPM's the car it running at. I've already shown how a 2k2 has more torque to the ground in 6th at 155Mph than 5th.

Stereodude

 

Yes, we're just not sure exactly how fast.

SR20DEN: I fully understand what you are getting at with your comparisons. I am definitely not an expert on what is beneficial/detrimental to top speed, so I can't say that your comparisons are easily comparable. For example:

You mention that weight does not have "much effect" on top speed. I would think that it would as the horsepower can be put to better use.

I was always taught that torque gets you going and horsepower keeps you going.

Somewhere we need to bring into this equation the effect of gearing.

Road & Track claims 175 mph for the NSX. Quite different from 170. This isn't a big point, just thought I'd mention it.

You touch on frontal area and roofline as critical components to high speed. I believe that you neglected rolling resistance due to tire width among other things. It's been proven that the underbelly of a car has a huge effect on drag as well.

In the end, I'm not sure what to think of the GPS reading. I think that Stereodude's estimate of 155-157 sounds reasonable to me. The only mod on my car is the Frankencar intake. How much that extra 10hp (or so) to the wheels is worth, I'm not sure. Anyone know what the drag co-efficiency of the 2k2 Maxima is?

Albert

 

I was talking about an older 270hp NSX that Motor Trend once tested. It was from memory anyways so I could be off by a few.

And I didn't want to throw in too many details into the equation because there are literally hundreds.

 

I can understand what you mean by there are too many details. We could definitely argue this to the end of time. I just have a hard time believing that my GPS would be wrong. Equally hard to believe is the readout that it's giving.

Albert

 

I'm sure that you were going 164. I don't doubt the GPS.
It's an oversimplification. HP and torque are mathematically related. You will reach your maximum speed with you no longer have enough available TQ to overcome the force that the wind/friction is placing on your car. TQ and drag are both forces. When you displace a force over time you have power. Drag can be related to the power used to overcome it. Power in a car is the TQ * (RPM/5252).
I've been trying to do this. There's no guarantee that the NSX or the 300ZX were at their peak HP points when they hit their top speeds.
Believe the GPS reading. I'd bet money you had a tailwind. The Cd is .34 I think.

Stereodude

 

ok at redline which we agree is 155mph in 5th gear.

At 6550 RPM my dyno graph showed about 158 ft. lbs or torque.

158 x .809 x 3.812 = 487

and 5100 RPM for 6th is about 200 ft. lbs.

200 x .630 x 3.812 = 480

How is 480 more than 487 using the ratios you ahve supplied?

I understand gearing and power curves. The VQ30 5th gen is a Maxima I havent personally driven. Every other Nissan product I have had usually tops out right at the hp peak in 5th gear. Maybe that one doesn't.

 

The GPS isn't wrong. I've provided a reasonable explanation.

*sigh*

What is this forum coming to? We had lots of threads about the top speed of the car. No one believes the math (provided by me). They say it's too high. I'm all washed up. It just can't be. "Someone should go run it and see." So Someone (you) goes out and actually tries it. Now we have the "nope, can't be" responses rolling in. How much more proof has to be provided. The empirical tests that the naysayers demanded show the car to be faster (or at least as fast) as the math.

Stereodude

 

I already stated I beleive that car can attain 147 to 150+. I just don't beleive it can do 164 even ina tail wind without being modified. If you know the exact equations for the car doing 147 then why don't you run that equation to do 164 and tell us how much hp is required. Lets not throw in the gearing and optimum engine rpm, but just the required hp. And arent there a few people who have already hit 150 MPH?
Besides that, some of your math is flawed (im not saying all of mine is perfect either). The 6th gear thing isn't hitting on much IMHO. I have had my car to almost 140 once or twice and it's nearing the redline already. I had alredy tried shifting to 6th at that speed and the thing just died because there simply wasn't enough wheel torque to push it anymore.

Sad to say I am happy that you are getting as frustrated as me with this debate. But I would rather work with you than against you.

 

I was using the numbers that I remembered from someone elses dyno curve. My point still stands. It is possible to get get more torque to the ground in a higher gear depending on the power curves the engine. From your curves it doesn't happen exactly at 155MPH, but there is a point at which it happens in each gear. That's what determines the shift point of the car.

Stereodude

 

I love you guys.....

Everyone gets soooo scientific when it comes to this stuff. You guys are great. I learn more here than watching Mr. Wizzard.

Well I have done work with GPS systems and even tested my car with one. Actually my car read about 1.4 MPH lower than the GPS when I was traveling. Now I did Use a Garmin GPS12-MAP, which used at least 6 satellites to gain its pinpoint and movement. Notice at least 6. That creates a very effective mapping and speed designation.

Now the Etrex unit like my man used here is a little different. It uses I think only 2-3 satellites to project its movement. The numbers are going to be a little less accurate for this unit.

The accuracy involved here is only pinpoint related. The actual speed should be quite close. I would say there is probably a 3-6 mph zone of error for the unit, one satellite could have dropped off for a second leaving only two satellite to send signal and the unit could have misjudged it's movements. It is tough to say, but the numbers are still more accurate than what the cars speedo can provide.

 

Exactly, more wheel torque at the wheels in a higher gear depending on hp curves and gearing aka shift points, I agree. I was just showing that the maxima isn't geared on the high end to make that possible (at least my specific car). We could (if we had the time) run the wheel torque equations in every gear at many different RPMS and find out the optimum shift points but that's probably a waste of time.

And were you calling the 2x speed = 4x drag = 8x hp wrong? Look it up if you don't beleive it.

 

An E-trex is a 12 channel device. It can track up to 12 satellites. It is just as accurate as any other 12 channel device. It is far more accurate than you suggest.

Stereodude

 

I'm not really frustrated. I think it's ironic.

The HP to run 164MPH is relative to your air speed. A 95HP Civic could go 164MPH with enough tail wind. Given an 80MPH tail wind it could go 164 easy. The engine would only need to provide enough HP to go 84MPH.

If you think my math is flaw prove it.

Stereodude

 

Hmm... Drag (HP) = 6.75e-6 * Cd * A * V**3

Cd = drag coef
A = frontal area (sqft)
V = velocity (mph)

Now where's that 4x at? Drag is measured in HP needed to overcome it. If we double V, the drag is 8x as much. 2^3 = 8.

Stereodude

 

I see we have to leave no grain of sand unturned. Your 80mph tail wind would have to encapsulate the entire car while going in the exact velocity (remembering that velocity is speed and direction) and for the entire distance it takes the vehicle to achieve that velocity.

In order for his car to hit 164 and only have the hp to do 150 he would have had a 20 to 30 mph tail wind that just wouldnt quit. And for a few miles in a straight line might I add. Thats why it's difficult to buy into.

The forumla I quoted was posted in Motor Trend Magazine on a few occasions. The flawed math I was seaking of was your 6th gear makes more toque example.

 

yeah, yeah, I'm replying to my own post... flame me for it but I just had to say

told you so!!!

I'm a freakin' psychic! Paypal me $10 and I'll answer life's mysteries by IM.

This is comical. Someone shows 150 on his dash speedo and everyone freaks out "we *all* know Nissan speedos are off by 38.4mph! Do it with GPS." Now it's done with GPS, in the range calculated by stereodude, and "your speedo AND GPS must both be off. Have someone else follow you, with GPS, and tell the cops when/where so they can get it on radar but make sure they used a tuning fork recently! And turn around and run from them again in the other direction so you get a two-way run and average them."

Seriously... who wrote "tailwind" (stereodude?)? It seems everyone agrees 155-157mph is likely the limit. All it would take is a 7mph tailwind to get to 164mph. Akrus already said it's possible there was a 7mph breeze. Why is there still an argument about this?

 

OK ok

THIS explains everything!!