Transmission + motor question
 

First I am wondering whether the 6th gear on the new Z is just for cruising or if you can actually pull in it. Next has anyone found out the top speed of the sport package Z without the limiter. Please don't bother telling me where you came across this piece of information. I can only hope you aren't risking your life and property on anything but a private road or drag strip. Finally is the 6 speed manual a sequential transmission. In other words do you have to lift off the accelerator as you put in the clutch? Pardon my lack of knowledge... I haven't really been looking at Z's until recently.

Thanks,
David

The 6-speed is a full manual. As for having to lift off the accelerator during shifts, know that the car is a fly-by-wire car which means that your gas peddle is not directly connected to the throttle bodies. Those are controlled by a computer. I don't know if the computer allows you to shift while still on the accelerator, but it might. Some manufactures disable that (like GM). That is known as a "No-Lift-Shift" A.K.A. "Power Shifting".

There's enough power in the car that if you're in 6th gear and the RPMs are above 3000 that you should be able to put your foot down on the gas and get decent acceleration, enough to pass a car doing the speed limit, I'm sure. Below 3000 and it may take a while for the car to start picking up speed.

Sorry, can't answer your top-speed question.

Thanks fro the reply. Alot of sportier/ more performance oriented vehicles will have the sequential gearbox (I just think it would be a nice thing to have on my next car if i wanted to accelerate realllllllly fast) i know it is available on the BMW M3 and M3 GTR... I am in the market for my next vehicle and I'm considering buying a standard despite the fact I live in Houston.

No problem. Sequential gearboxes are expensive. I doubt you're going to find that on any car under $50K. Those kinds of transmissions usually start at $8K for an entry-level sequential. They're nice, but with a little practice you'll be able to accelerate really fast with a standard trans. :)

VW has it... ^

6th gear is just for cruising, it in fact a lot of the times I'm in 5th on the freeway around 70mph. This car doesn't come alive until about 4500rpm, after 5000rpm it's a beast!! You would want to downshift to 4th for passing, or stay in 5th depending on your RPM's

And if your going 65 and you really want to pass someone fast, downshift to 3rd, this puts you right in the sweet spot of the powerband. 3rd gear is good to almost 100MPH @ Redline, according to Road & Track data specs. Here is the gear list:

Transmission:
6-speed manual
Gear Ratio
Overall ratio
(RPM) Mph
1st 3.79
13.99
(7500) 42MPH
2nd
2.32
8.56
(7500) 69MPH
3rd
1.62
5.98
(7500) 98MPH
4th
1.27
4.69
(7500) 125MPH
5th
1.00
3.69
est (7300) 155*MPH
6th
0.79
2.92
est (5800) 155*Electronically limited.
Final drive ratio
3.69:1

I think it depends on what you mean by "pulling." You can accelerate in 6th, just not that hard. I usually cruise in 6th between 85-90. If I leave it in 6th and step on the gas, it'll accelerate pretty decently. Mind you, if I really wanted it to get up and go I'd drop it into 5th. The gearbox is non-sequential. It's a conventional MT (vs. DSG, for example).

Thanks. I'd really like to get the top speed question answered, my swag would be somewhere in the range of 170-175MPH on a smooth drag strip. I'd also like to know where 6th gear @ 7500 RPM puts you in terms of miles per hour.

These two questions are really one and the same, aren't they? You want to know the top speed (w/o limiter). You also want to know what speed 6th @ 7500 rpm would be. Well, the car only has 6 gears (MT), and 7500 rpm is the redline. So that would be the top speed, right? Or am I misunderstanding something?

Yes you are correct I apologize for being redundant.

275mm X 35 aspect ratio X 19 inch rim: 791.029 revolutions per mile (80.098in Circumference)
(275/35R19)

So, now calculate how many RPMS your axle is at with the motor spinning 7500RPM.

Final gear = 3.69
Sixth gear = 0.79

Math: 7500 / 0.79 / 3.69 = ~ 2572.811

Now figure out how many miles per minute you're going:

2572.811 / 791.029 = ~ 3.253

Now multiply by 60 to make 1 hour: ~ 195.18MPH.

OK... Now we have our max speed in 6th if you got enough power to push it there!


EDIT: For those that don't know, the "~" means "approximate".

Found this too: http://www.pszweb.com/car/gears.htm which output this:

According to this, my math is off, but I'm still not sure that it's totally correct. But it does say that it will hit 200+MPH.

RPM 1st 2nd 3rd 4th 5th 6th
500 3 5 7 8 11 14
600 3 6 8 10 13 16
700 4 6 9 12 15 19
800 5 7 11 13 17 22
900 5 8 12 15 19 24
1000 6 9 13 17 21 27
1100 6 10 15 19 24 30
1200 7 11 16 20 26 33
1300 7 12 17 22 28 35
1400 8 13 19 24 30 38
1500 8 14 20 25 32 41
1600 9 15 21 27 34 43
1700 10 16 22 29 36 46
1800 10 17 24 30 39 49
1900 11 18 25 32 41 52
2000 11 18 26 34 43 54
2100 12 19 28 35 45 57
2200 12 20 29 37 47 60
2300 13 21 30 39 49 62
2400 14 22 32 40 51 65
2500 14 23 33 42 54 68
2600 15 24 34 44 56 71
2700 15 25 36 46 58 73
2800 16 26 37 47 60 76
2900 16 27 38 49 62 79
3000 17 28 40 51 64 81
3100 18 29 41 52 66 84
3200 18 30 42 54 69 87
3300 19 30 44 56 71 89
3400 19 31 45 57 73 92
3500 20 32 46 59 75 95
3600 20 33 48 61 77 98
3700 21 34 49 62 79 100
3800 21 35 50 64 81 103
3900 22 36 52 66 84 106
4000 23 37 53 67 86 108
4100 23 38 54 69 88 111
4200 24 39 56 71 90 114
4300 24 40 57 73 92 117
4400 25 41 58 74 94 119
4500 25 42 60 76 96 122
4600 26 42 61 78 99 125
4700 27 43 62 79 101 127
4800 27 44 63 81 103 130
4900 28 45 65 83 105 133
5000 28 46 66 84 107 136
5100 29 47 67 86 109 138
5200 29 48 69 88 111 141
5300 30 49 70 89 114 144
5400 31 50 71 91 116 146
5500 31 51 73 93 118 149
5600 32 52 74 94 120 152
5700 32 53 75 96 122 155
5800 33 54 77 98 124 157
5900 33 54 78 100 126 160
6000 34 55 79 101 129 163
6100 34 56 81 103 131 165
6200 35 57 82 105 133 168
6300 36 58 83 106 135 171
6400 36 59 85 108 137 174
6500 37 60 86 110 139 176
6600 37 61 87 111 141 179
6700 38 62 89 113 144 182
6800 38 63 90 115 146 184
6900 39 64 91 116 148 187
7000 40 65 93 118 150 190
7100 40 66 94 120 152 193
7200 41 66 95 121 154 195
7300 41 67 97 123 156 198
7400 42 68 98 125 159 201
7500 42 69 99 127 161 203

Whether your math is off or not, I'm impressed that you were able to lead us through it. I would go with your estimate, but as you point out, you've got to have enough power to get you there. Wind resistance can be a b**tch sometimes.

Really????? They geared the Z for 200mph??? Oh lord theres gonna be some spectacular accidents.

Wind resistance is a fourth power of velocity...I doubt a $30,000 car will pack enough power to push into the 200mph range. Rolling resistance is a field of engineering I can't help with. Great job with the calculations, it's nice to see a forum where people are actually on topic and not just spitting profanities.

in theory yes the 370z can hit 195MPH but is it in practice do the same thing:rolleyes:

but maybe if it have more power ;)

and thanks crash for the information

wow.. surprised... is the Z geared different than the G37?

Actually, I can tell you how much power is required to defeat the rolling resistance and drag (assuming that the wind-speed is 0MPH!):

NOTE: I couldn't find the frontal surface area on the 370z, so I'm GUESSING it's around 1.9m^2. It could be less.

First figure out how much drag force there is:
F_drag = (Drag Coefficient) * (Frontal Area-meters) * (Volocity-Km/s)^2
200MPH = 89.42Km/s
F_drag = 0.29 * 1.9 * 89.422 = 4405.76 N

Now we figure out the rolling resistance:
F_tire = (Vehicle Weight-Kg) * 9.8 * (drag_contribution)
F_tire = 1506 * 9.8 * 2.43% = 358.64 N

Now calculate how much power is needed to push against these forces:
P = F * V
P = 4764.4 * 89.42 = 426032.648 Watts = 571.32HP

So, approximately 571HP is needed to get the car to 200MPH

you sir... are brilliant. lol

Why thank you! :)

I'm curious as to where the (2.43% drag contribution) value came from. As I stated earlier rolling resistance is not a calculation I'm familiar with. I had no idea there were~745 Watts/Horsepower. I guess you learn something new everyday.

Your physics is correct, however calculus is needed to give the exact ammount of power needed to go 200 mph

^^^ I based the drag contribution on math I did earlier for as similar car. I don't have the spreadsheet on this computer with the calculations, but drag contribution is recalculated based on the speed since speed is not constant, but rather squared. Originally 35MPH was calculated at approx 1.3%, at 200MPH my calculations gave me approx. 2.43%. When I get to my other computer, I'll post up the formula I used to get that contribution.

And, yeah, I've been doing the watts/hp conversion for a while because I've been researching electric cars for a long time, and most electric motors all have specs in metric units instead of imperial. So it's all in KW and NM instead of HP and TQ.

I don't see how calculus is needed for the exact number of HP need to achieve a certain speed.

How can you factor in the resistance produced as the drivetrain's speed increases. Similarly I'm wondering what is meant by drag coefficent? What is the unit for drag
coefficent. I do not believe calculating wind resistance is as
Simple as drag coefficent * surface area* velocity. As I stated earlier wind resistance is a
Fourth power function of velocity. It gets terribly complicated from there.

You've got the formula wrong (a little). It's drag_co * surface area * velocity^2

All cars have a drag coefficient. It's the ability for air to pass around the vehicle. The only way to find this number is to have the car tested in a wind tunnel. Here is a video of this being tested:


Then you derive the force of the drag (f_drag) from the amount of area pushing against the air, by the drag_co, and by the speed at which it is hitting the air.

If you've got a better formula for figuring this out, please let me know, because this is the way I was taught how to find the force of drag. As far as I understand, the only drag quadratic equation is for fluid. Am I wrong? Here is the formula I've broken down, maybe I missed a step, but this looks right to me:
Drag equation - Wikipedia, the free encyclopedia

Laminer flow on a Pagani Zonda... I guess now I've seen it all. I may be mistaken but I'll go fetch my fluid mechanics textbook, I could have sworn wind resistance was a fourth power of velocity function. However everything I've read off google agrees with Crash. It appears in the Zonda video that there are a few Eddies coming off the rear of the vehicle... There is an enormous amount of drag created as the air spins off the back of the car. Is Pagani hiring Aeronautical Engineers?

^^^ LOL. No idea. I have no clue about aerodynamics engineering. I just took the formulas off the internet and plugged them in accordingly. My engineering isn't in physics, it's in software! :) But I figure I have a freaking awesome learning curve. I took telecommunications management and screwed the bell curve for the rest of the class. Learned how to do the math for electronics engineering in a couple years of studying electric cars, and picked up some stuff for calculating power and time. I learn what I need to know at the time, but I retain pretty much everything. :) But I do have a firm grasp on mechanical engineering.

That's cool I remember my AP Physics class back in high school...The teacher would call out the test grades in front of the class. Needless to say I wasn't very popular with the kids who were asking for a curve on their grades. I even recall having a snickers bar thrown at me in the middle of a test. My father was a software engineer... Isn't most of that work being outsourced to the middle east. Just about every time I call Microsoft I get someone in India.

Yep... Sadly, that is the case. EVERYONE hated me in math classes and a professor at my college was fired because he was teaching the math wrong and I kept arguing with him about it in class.

And yeah, again, it's sad that all of the software is being outsourced to India and China. Although, from what I hear, it's getting out-sourced to the UK now as well. I'd imagine it's a lot more pricey, but who knows. I won't outsource to India. I did before and they screwed me.

When you call Microsoft, you're not getting their software development department. You're getting their customer-care department which was ALSO out-sourced to India. (as many companies have done) although, Canada also gets a lot of the out-sourcing for customer care too.

I do SPECIAL coding. Stuff people don't want outsourced or want it done fast and under the radar. I specialize in new technology programming. Not in building the same thing over and over for different people. That's where India does well. They have vast libraries of code they've created over MANY years of development and they just snap together code like legos to create something.

I'm the opposite. I write code that has never been written before for ideas that are right out of the wood work.