What Determines Highway Passing Power?

[Finch204]

As the title states, I am curious as to what determines highway passing power? By this I mean, when I'm trying to pass someone on the highway, what would allow me to pass them the quickest? Is it horsepower? Is it torque? Or both?

I guess another way to ask this question is, what determines your 60mph to 90mph time? Horsepower? Torque? Both?

 

[djohns]

I've had it explained to me like this, horsepower is how fast you're going when you hit the wall, torque is how far you take the wall after you hit it. Someone correct me
If I'm wrong. So to answer your question, horsepower.

 

[EdgeAutosport.com]

Horsepower is a function of torque.

HP= (Trq x RPM) / 5252

Here are a couple of terms to know.

Work is the result of a force acting over a distance, and its measured in foot-pounds. If I understand it correctly, this could refer to the combustion acting over the distance of the rod length.

Torque is the force created by the crankshaft. The Work done by the combustion is converted to torque via the connection of the rods (which go up and down) and the crankshaft (which goes round and round). This is measured in pound-feet (or newton-meters)

Power is how quickly work is being done. i.e. One horsepower is the power required to lift 33,000 lbs one foot in one minute.

Therefore, torque is going to be your accelerating force (passing power) and horsepower is a representation of the amount of power happening in a given time. That is why horsepower equals torque multiplied by the revs per minute. The constant (5252) is the specific revs per minute where torque and horsepower are equal. You will see this on a dyno plot where the curves will always cross at 5,252 rpm.

The short answer is that torque is going to be your passing/accelerating force. Also, don't try to pass people without downshifting to an appropriate gear (6th gear is not an appropriate gear).

 

[Finch204]

Horsepower is a function of torque.

HP= (Trq x RPM) / 5252

Here are a couple of terms to know.

Work is the result of a force acting over a distance, and its measured in foot-pounds. If I understand it correctly, this could refer to the combustion acting over the distance of the rod length.

Torque is the force created by the crankshaft. The Work done by the combustion is converted to torque via the connection of the rods (which go up and down) and the crankshaft (which goes round and round). This is measured in pound-feet (or newton-meters)

Power is how quickly work is being done. i.e. One horsepower is the power required to lift 33,000 lbs one foot in one minute.

Therefore, torque is going to be your accelerating force (passing power) and horsepower is a representation of the amount of power happening in a given time. That is why horsepower equals torque multiplied by the revs per minute. The constant (5252) is the specific revs per minute where torque and horsepower are equal. You will see this on a dyno plot where the curves will always cross at 5,252 rpm.

The short answer is that torque is going to be your passing/accelerating force. Also, don't try to pass people without downshifting to an appropriate gear (6th gear is not an appropriate gear).

Great info!

Yes sir I do drop to 4th when passing on the highway.

 

[SharksInSpace]

Knowledge bombs dropped by Edge, blowin' up our misconceived notions.

 

[mangosmoothie]

If power (HP) is how quickly work is being done, why would that NOT determine how quickly you pass the car?

 

[Finch204]

If power (HP) is how quickly work is being done, why would that NOT determine how quickly you pass the car?

Based on Edge's answer awhile ago, I would say the answer to your question is that horsepower is derived from torque, so torque still determines your acceleration force/passing power.

 

[EdgeAutosport.com]

Power is how quickly work is being done, not necessarily how fast you are accelerating. Acceleration is a result of torque acting through the transmission.

 

[Finch204]

This thread also indirectly answers why the S2000 can have over 200 horsepower but with low torque. It's because Honda compensates for the low torque with a very high redline. Same thing for the RX-8.

 

[EdgeAutosport.com]

This thread also indirectly answers why the S2000 can have over 200 horsepower but with low torque. It's because Honda compensates for the low torque with a very high redline. Same thing for the RX-8.

Exactly. Let me see if I can make a clever analogy...

Torque would be like saying how many 1lb bricks you can lift at a time while horsepower would be like saying how fast you can move them.

So if you can lift 10 bricks at a time and move them at 2 trips per minute, in one minute, you can move 20 bricks. But if you can only lift 5 bricks at a time (less torque), but you can move them at 4 trips per minute (higher rpm), you are still moving 20 bricks per minute.