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 top speeds.. 
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Post Re: top speeds..
Mooneggs wrote:
Ryan wrote:
But if you have an infinitely long road, your top speed will be the same wether you poured concrete in the trunk or not.


but don't you need more HP to pull more weight?


you mean torque.

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November 25 2008, 8:51 PM
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Post Re: top speeds..
mitmaks wrote:
Ryan wrote:
No matter how much people say it, weight has nothing to do with top speed.... because weight itself is a downward force, and downward forces do not affect lateral forces.... Friction is also neglible, when talking between the bearings.


actually it does. It takes more torque to propel your fat friend, gf, mom etc.



Torque is a really complicated thing, and for the sake of argument on top speed, let's stay away from it because it's negligible at high speeds anyway. The fact of the matter is, mass has almost no effect on top speed, end of discussion.

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November 25 2008, 11:04 PM
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Post Re: top speeds..
I might die. This frusturates me, I quit, right after this.

mitmacks, people use HP and Tq without discretion. As a matter of fact, there is a rather direct relationship between them, so I wouldn't get picky about that. My most recent memory on the situation, is that dynos only measure torque and convert it to HP.(something about time related)

Here's a really good one. Note the formula says ABSOFREAKINGLUTELY NOTHING about weight, or mass, or any other downward force.

http://www.miata.net/sport/Physics/06-Speed.html

Simply layman one
http://answers.yahoo.com/question/index ... 016AAme9b3

Proof that Wiki is built by retards
http://wiki.answers.com/Q/Does_weight_effect_car_speed

Here's one for mitmaks, for the rest, scroll down to where it asks our question.
http://www.nsxprime.com/FAQ/Miscellaneo ... PSpeed.htm

Here's probably the best one so far, it explains how weight affects it
http://www.pumaracing.co.uk/TOPSPEED.htm


I think the last one here will make you all happy.

In conclusion, a vehicle, travelling on a straight, flat infinitely long road, is negligibly affected by weight. It is, but its barely a rounding error in the grand scheme of total resistance.

If you have a time or distance constraint (drag racing) or corners (require you to slow and speed up again) then yes, weight is a massive factor.

Really cool site
http://www.zerokarma.com/mx-3/mymx3.htm

Our coefficient of drag is 0.31, and top speed estimated 191kph on the stock v6.

Other cars with our coefficient
Audi A4B5
06' Civic Sedan
Lamby Diablo
RX7(all)
RX8
Nissan Versa
RAV4

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November 25 2008, 11:15 PM
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Post Re: top speeds..
Thank you once again Ryan. :D I'll still be here to argue until I get tired of it. :lol:

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November 25 2008, 11:40 PM
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Post Re: top speeds..
Its not my top speed..but its up there......for your viewing pleasure....proof an mx3 wit 260,000km can still get up to speed....
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December 02 2008, 6:57 PM
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Post Re: top speeds..
tmac4t4 wrote:
Its not my top speed..but its up there......for your viewing pleasure....proof an mx3 wit 260,000km can still get up to speed....
Image


Psh, my friend did a bit more than that in a 626 with a constant CEL that spits all kinds of smoke out the exhaust a day after crashing it into a ditch. :lol:

I gotta say though, I'm surprised how quickly that little K8 can get an mx3 up to speed, those 130 horses go a long way.

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December 02 2008, 7:29 PM
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u cant tell in the pic, but my CEL is on..been on since i bought the car..and i dont do oil changes any more..i just burn it, then top it up :lol:...i could have picked up quite a bit more speed but was running out of road

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December 02 2008, 9:29 PM
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Post Re: top speeds..
^ you car must be an auto! :lol:


December 03 2008, 4:34 AM
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Post Re: top speeds..
Top speed for cars is related to power and gears. More commonly the gears. We run out of RPMs in fifth before the wind resistance will be high enough to overcome the power with which our our engine pushes the car thru the wind.

If our cars had super long gears like say a honda civic vx (226mph @ 8k in fifth) the engine power may come into play before we reach our gear limitations.

Our gears top out in the 150-165mph range depending on which tranny you have on the car (mx3 vs mx6) I can confidently say even a stock K8 can carry an MX3 to 160 with enough road.

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December 03 2008, 12:08 PM
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Post Re: top speeds..
mx-3_4evr wrote:
^ you car must be an auto! :lol:


yup...i dont mind the auto tranny in these cars..mine needs flushed desperatley but compared to any gm cars ive had..its at least still holding up at 260k :shrug:...also ive raced 5spd mx3's and surprisingly my auto keeps up with ease..pretty much even really :shrug:

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December 03 2008, 7:03 PM
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Huh. That's cool!

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December 04 2008, 12:46 AM
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Post Re: top speeds..
Ya, i read that page with the NSX a few weeks ago, just haven't had the time to mention it

But your talking about downward forces, and I agree that they wouldn't affect the top speed.

Now, I see it this way. I do agree that maybe a small percentage of weight could be added and it neglegably affect the top speed from what I've read so far (which what doesn't explain what I've experienced myself on a few seperate occasions). But also, you'll agree that if you add quite a bit of weight, you can have the car literally have a very hard time accelerating. I'm sure you could imagine that how slow an Mx-3 would be accelerating if it weighted twice as much. Now as your accelerating, the motor is working alot harder because of the added weight. Also, as your accelerating, the air resistance is building as per usual. So how you've got the motor working harder pulling it's added weight accelerating towards it's potential top speed, but it's leaving less power to deal with the resistance of the air.

This is the way I see it, but I said before, you need to accelerate to get to top speed, and for accelerating, weight is definitely part of it, and the motor has to deal with that added weight no matter how much speed it wants to gain for the acceleration, it still needs to overcome that force. Now you've got me researching stuff now. According to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration. Your motor would be that force and it does require some force to be applied to require it to maintain it's velocity because of wind resistance. But now with the added weight, it requires more force to cause an acceleration, leaving less available power to deal with the increase in wind resistance...

I hope you see what I'm trying to explain, but I think this may be a problem for Mythbusters ;)

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December 04 2008, 8:01 PM
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Nd4SpdSe wrote:
Ya, i read that page with the NSX a few weeks ago, just haven't had the time to mention it

But your talking about downward forces, and I agree that they wouldn't affect the top speed.

Now, I see it this way. I do agree that maybe a small percentage of weight could be added and it neglegably affect the top speed from what I've read so far (which what doesn't explain what I've experienced myself on a few seperate occasions). But also, you'll agree that if you add quite a bit of weight, you can have the car literally have a very hard time accelerating. I'm sure you could imagine that how slow an Mx-3 would be accelerating if it weighted twice as much. Now as your accelerating, the motor is working alot harder because of the added weight. Also, as your accelerating, the air resistance is building as per usual. So how you've got the motor working harder pulling it's added weight accelerating towards it's potential top speed, but it's leaving less power to deal with the resistance of the air.

This is the way I see it, but I said before, you need to accelerate to get to top speed, and for accelerating, weight is definitely part of it, and the motor has to deal with that added weight no matter how much speed it wants to gain for the acceleration, it still needs to overcome that force. Now you've got me researching stuff now. According to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration. Your motor would be that force and it does require some force to be applied to require it to maintain it's velocity because of wind resistance. But now with the added weight, it requires more force to cause an acceleration, leaving less available power to deal with the increase in wind resistance...

I hope you see what I'm trying to explain, but I think this may be a problem for Mythbusters ;)


You're speaking in the practical sense, I'm speaking theoretically. Practically, mass does affect top speed because not everybody has the salt flats in their backyard, so they will run our of road. Also remember that inertia works both ways, it'll help keep your car going forward, this might cancel out the mass difference when dealing with top speed.

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December 04 2008, 10:09 PM
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I do agree with Nd4SpdSe.... But I can't figure in my head by how much. The thing is, the acceleration can still be 0.00001m/s^2, and you'll still eventually get there. Its still only a matter of how long it takes.

Whoops, I posted again.

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December 04 2008, 11:02 PM
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Post Re: top speeds..
Mad Cow wrote:
You're speaking in the practical sense, I'm speaking theoretically.


Ok, no problem. I didn't know you were speaking theoricially.

Also, back to pratical:

"The larger the inertial mass of a body, the smaller the effect of a certain force and the slower the change in speed. The body with the smallest inertia shows the highest acceleration and vice versa." "Inertia just says that something tends continue doing what it was doing."

Ryan wrote:
I do agree with Nd4SpdSe.... But I can't figure in my head by how much. The thing is, the acceleration can still be 0.00001m/s^2, and you'll still eventually get there. Its still only a matter of how long it takes.


Hmm, lol, how can you agree with me, yet argue against me? Regardless, the forces required in the acceleration is still the same no matter on how much since it all adds up no matter how small the increments, and the requirement for more force keeps going up as you add more mass to move. Also, the wind resistance at X speed is still the same, no matter no fast or slow you accelerate.

However the force required will vary depending on how fast you accelerate, so ya, you might be right if you can accelerate so slowly, but even then, that force required will increase as you increase the weight, so even if you accelerate super-slowly, there will be a point that too much weight will require more force that the motor has, and there should be in intersect point of "wind resistance vs acceleration" where the accleration speed on a graph would just go up exponentially to inifinity, technically never hitting 0. It may hit 0 for "acceleration", but I can't see that right now. I'd have to let that idea brew for a bit, but I wouldn't be surprised if the wind resistance would null out all forces, where the only variable would be weight which would in turn vary the amount of force availble for accleration, which would then directly affect the force it can apply against wind resistance.

I'm just glad you understand what I'm trying to say. I'm not trying to win, I just want to understand and appease the thoughts in my brain so even if I lose, I'll understand ;)

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December 04 2008, 11:18 PM
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