Top speed

[APEXistud]

Originally posted by Section 8:
<STRONG>Apexi: wheel horsepower and miles per hour should have nothing to do with each other, maybe if you figured in the weight of the car you might be able to figure out some relationship but I really doubt it. I'm sure it would take a lot less horsepower to accelerate a civic to 100mph than it would take to move a heavier car like a RX-7.

Shawn</STRONG>

Don't know where you're getting your information from, but whp has everything to do with mph/topspeed. Without horsepower and torque a car won't be able to overcome the aerodynamic wall/resistance it will begin to encounter once it gets closer to it's terminal velocity. Sure the weight of the car has a lot to do with top speed as well, but so do the width of the wheels you are using (wider tires mean more drag), a long with a pretty long list of other things: eg spoilers, front lip, under tray of a car

And of all the heavier cars you could have chosen from to mention, an RX-7 is definately the wrong car since it is one of lighter high horsepowered cars. And getting a car to 100 isn't the issue here, we're talking about TOPSPEED. The amount of horsepower needed to abtain topspeed is the issue. The greater horsepower and torque a car has, the greater the topspeed it can achieve. That is a fact.

 

[Section 8]

wheel horsepower and miles per hour should have nothing to do with each other

Apex, I'm not getting my info from anywhere, I'm just trying to figure it out in my own head, and that's why I said SHOULD. Maybe I should have made myself more clear, I understand that you need horsepower to pull or push a car up to speed and to overcome parasitic drag, I just don't believe that there could be anyway to draw a mathematical relationship between wheel horsepower and top speed, there are way too many factors such as weight of the car and the areodynamics of a car. what if you had 2 exact same cars, lets say MP3s, both stock, but on one you roll the windows down, now, that one is less areodynamic than the other, that one will not achieve the same speed as the one with the windows rolled up, I know it will only be a minute amount of difference but logically the one with the windows rolled down will travel slower. Same horspower, weight everything...all I'm trying to say is that you cannot draw a relationship between whp and top speed...
correct me if I am wrong please =)

Shawn

 

[trobbins]

All other things remaining constant(Draq, weight, etc..), more horsepower = higher top speed, and it is a direct relationship. A but in general, HP is what creates top speed. At high top speeds, weight becomes a little factor on top speed. Weight is a factor that burdens acceleration. A good example of this is a motorcycle (Crotch Rocket Style). A light weight motorcycle can accelerate rather quickly, however a motorcycle is basically an areodynamic disaster. So getting a motorcycle to top 200 MPH requires a LOT of HP. Raising the top speed from say 50 to 60 mph may require and additional 10 HP but raising it from 200 to 210 can require 5 to 10 times more horse power due to the unbelieveable effects of wind resistance.

So a long story short, for high top speeds, HP and Drag have the most affect on Top speed. Increasing HP while keeping Resistance constant will raise top speed.

Tim

 

[tritonheat1]

BS:look at it this way, and don't take it the wrong way guy's (1999-2001) pontiac Grand Am GT that i have will shutdown at 113mph uh lets see 3200lbs but have V-6 175hp 205lbs ram air engine. MP3 140hp everyone has gone over 120mph. (pontiac sunfire GT) 150hp 155lbs top speed 114mph. Chevy Monte Carlo V-6 240hp top speed 121mph. "Gee" 100hp advantage and V-6 engine and can hit only 121mph that's pathetic. To all and everyone who think's horsepower is your answer to=topspeed, (WRONG) that's part of it your horsepower and flbs give's you power to your gears and the powerband kicks in at sae@horsepower. there's nothing wrong with your horsepower being low and doesn't mean you can't have top end. Well there's other preference to like where you have bottom end to get to 0-60 or 0-100mph but don't have top end or where your 0-60mph takes a bit slower and have top end.

 

[Section 8]

Originally posted by APEXistud:
<STRONG>If we can figure out a formula that can calculate whp to mph. We can figure out what the average top speed our MP3's are excepted to have.</STRONG>

I know that horsepower is relevant when it come to top speed, but my arguement this whole time is in regard to the above quoted statement. It assumes that there is an exact mathematical relationship between top speed and wheel horsepower, which there isn't.

Shawn

 

[mp3speed]

i hit 125 racing honda delsol.our cars kill em.i bout took out a amish buggy but i went up over a ditch and in the field . lucky me

 

[APEXistud]

Originally posted by tritonheat1:
<STRONG>BS:look at it this way, and don't take it the wrong way guy's (1999-2001) pontiac Grand Am GT that i have will shutdown at 113mph uh lets see 3200lbs but have V-6 175hp 205lbs ram air engine. MP3 140hp everyone has gone over 120mph. (pontiac sunfire GT) 150hp 155lbs top speed 114mph. Chevy Monte Carlo V-6 240hp top speed 121mph. "Gee" 100hp advantage and V-6 engine and can hit only 121mph that's pathetic. To all and everyone who think's horsepower is your answer to=topspeed, (WRONG) that's part of it your horsepower and flbs give's you power to your gears and the powerband kicks in at sae@horsepower. there's nothing wrong with your horsepower being low and doesn't mean you can't have top end. Well there's other preference to like where you have bottom end to get to 0-60 or 0-100mph but don't have top end or where your 0-60mph takes a bit slower and have top end.</STRONG>

Dude, what the hell are you talking about. If the top speed is electronically controlled, it doesn't matter how much HP you have, when you hit that top speed the ECU will cut the fuel and your engine won't go any faster. All GM's that I can think of have top speed governers or some sort of RPM activated fuel cut. Sicne the MP3 (at least to my knowledge) has no speed governer, we are limited to the Aerodynamic wall and HP. Think about what you're saying before you post bro, please

 

[APEXistud]

Originally posted by Section 8:
<STRONG>I know that horsepower is relevant when it come to top speed, but my arguement this whole time is in regard to the above quoted statement. It assumes that there is an exact mathematical relationship between top speed and wheel horsepower, which there isn't.

Shawn</STRONG>

OOops, I shouldn't have mentioned having a calculation idea. But what it comes down to is that my idea/theory/hypothesis or whatever you want to call it is correct....... Increasing HP will increase your top speed. That should be a no brainer. MP3_TIM explains it better than I could have.

 

[jayrcr]

sorry you guys but the car on the bottle wouldnt go past 125 the car went to lean.Off the bottle 120 is tops.then i ran out of road.

 

[jayrcr]

with more hp you have to acount for adding more fuel.

 

[initialRES]

The top speed debate.... There is NO SET WAY TO GET TOP SPEED. Some cars do it with high horsepower, others with low drag, it all depends on the car.
There was a test I read about talking about the NSX and the lamborghini countage (how the hell do you spell that?) The NSX lacked about 100 HP on the lamborghini but they both had the exact same top speed because the NSX had less drag.
Then there are instances with cars like the honda insight. It has very little HP but due to the design of that body, it takes half the power to maintain a speed of 60 mph than the civic SI takes.

So Horsepower does mean alot in the top speed deal, but so does drag. And yes I have heard about the really low speed limiters on GM cars. It is kinda sad. My integra can top out higher than monte carlos.

 

[tritonheat1]

boy, apex before u open your mouth and start talking crap do to the stuff u just replied when i answered your stupid ? , (you said the amount of horsepower needed to abtain topspeed is the issue)'. well i just proved your retarted part of the sentence you replied to section 8 was wrong. damn guys when u gonna learn horsepower has nothing to do with topspeed even though i posted that reply to apex cause what he said. Well horsepower just get's u to how fast you wanna go until u reach that topspeed limiter or governer.

 

[kep0ne]

if horsepower gets you to your top speed, then it has a direct relation to it (top speed)

 

[initialRES]

I don't exactly know what you just said triton, but HP does have something to do with top speed. Not all cars have a limiter. The limiter is in the ECU and only certain cars have those.

 

[APEXistud]

Originally posted by tritonheat1:
<STRONG>boy, apex before u open your mouth and start talking crap do to the stuff u just replied when i answered your stupid ? , (you said the amount of horsepower needed to abtain topspeed is the issue)'. well i just proved your retarted part of the sentence you replied to section 8 was wrong. damn guys when u gonna learn horsepower has nothing to do with topspeed even though i posted that reply to apex cause what he said. Well horsepower just get's u to how fast you wanna go until u reach that topspeed limiter or governer.</STRONG>

Bro, if you really think that you're right. Either you are playing dumb or you really are dumb. What do you drive again? Yes, DRAG and HP both determine your top speed, but mainly HP determines the topspeed more so that Drag on a stock bodied, street driven cars. Yes, the Honda Insight has less Drag, but with less HP it's not really gonna go anywhere.

Triton, do me a favor and pic up the latest issue of SCC (Sport Compact Car) and read the article on the Bonneville SI's. See how they both have the same engine, but one is Supercharged. See how the supercharged one goes faster. Hmmmm, I wonder how it's faster
Could it be because it has more HP. The end......We're all right triton and you, my friend are wrong......

 

[bluep5]

To join this fun and exciting debate initialRes is completely correct, unless of course the laws of physics don't apply to certain cars.

Physics 101

A running car will have two major forces acting on them. One is from the torque at the wheels (directly related to HP). The other is the force placed on it from drag.

Let's say Fd is the drag force. and Fw is the force at the wheels (directly related to HP). Laws of physics will state that the forces on the car are in equalibrium.

Fw - Fd = m*a

Where m is the mass and a is the acceleration. When they are equal there is no acceleration. (Fw=Fd)

The drag force is directly related to it's velocity ie Fd=k*v where v is the speed of the car and k is sort of the drag constant (related but not the one that you see in specifications).

*edit* Errr... I was incorrect Fd=k*v^2.

So we have your top speed is = the Force on the wheels divided by the drag coefficient.

And in the end a larger drag coefficient means a slower top speed. Less force at the wheels (HP) means a lower top speed.

*edit* P = F*v or Fw = P/v therefore when Fw = Fd k*v^2 = P/v or P = k*v^3. This is the power required to drive the car with a drag constant of k at a velocity v.

This was covered breifly in Physics 12 but I suppose nobody was listening (I sure wasn't)... It didn't really sink in for me till about 12th year university..

*Edit* oh yeah, one more thing.. In most cars the drag coefficient is very close. In our cars it's speced at about 0.33. I think the jetta is 0.31... The insight is 0.25. So this says for the same HP the insight will go about 30% faster (we had 120, insight would be 156)

Oh well,

BP5

[ 11-30-2001: Message edited by: Blue P5 ]

[ 12-01-2001: Message edited by: Blue P5 ]

 

[initialRES]

Blue P5, I knew there was some formula but I had no idea what it was. I think I learned more from your post than I did in all of high school hahah
By the way, what did you study in college?

 

[bluep5]

I studied electrical engineering (it wasn't 12 years it was actualy only 5 but felt like 12).

 

[kep0ne]

if the drag coefficient is higher is tha tbad? or is it better if its lower

al

 

[bluep5]

Higher drag is bad (Lower top speed, some affect on acceleration).