Speed calc.

[TripleT]

Ok with the speed calc. when you get your mph or kph what does your hp have to do with it? If the only thing you put in that has to do with the engine is the rpm and how many teeth are on it.

If anyone can understand my question. I know it might seem kinda confusing.

 

[klicky96]

Okay, horsepower is the amount of torque your engine is giving off. Horsepower does not have anything to do with the number of revolutions an engine can have. Okay, lets say you have a 3HP 2-stroke running off of ethanol at 7800rpm, and then you have a 427HP V-8 running of gasoline at 2000 rpm. Which engine do you thing will be able to make a 3,000 pound vehicle move? Of course, you chose the V-8. Why?! Well, because with it's higher horsepower rating, it gives off more torque.


You see, many people think that just because you have a 'higher horsepower' engine, then the engine is faster. Well those people are wrong. The only difference between a 2HP engine and a 20HP engine is the quickness that it can accelerate a vehicle or how much torque it can give off.

 

[jman231994]

Okay, horsepower is the amount of torque your engine is giving off. Horsepower does not have anything to do with the number of revolutions an engine can have. Okay, lets say you have a 3HP 2-stroke running off of ethanol at 7800rpm, and then you have a 427HP V-8 running of gasoline at 2000 rpm. Which engine do you thing will be able to make a 3,000 pound vehicle move? Of course, you chose the V-8. Why?! Well, because with it's higher horsepower rating, it gives off more torque.


You see, many people think that just because you have a 'higher horsepower' engine, then the engine is faster. Well those people are wrong. The only difference between a 2HP engine and a 20HP engine is the quickness that it can accelerate a vehicle or how much torque it can give off.

Actually thats not true. Torque and Power are seperate things. They are linked, but they are not the same. My favourite example of this is an old truck I saw last year. It only made 160hp, my parents soft roader makes around 200hp from memory. Does that mean the car should beat the truck at towing things? Heck no. The truck would have many times more torque than the car, but the trucks useful RPM is much lower resulting in a lower horsepower rating.

I admit I dont fully understand it and my analogy could be wrong, but the way you worded it makes it sound like you are saying that HP=Torque which is not true as Power is a relation between torque and rotational speed.

http://en.wikipedia.org/wiki/Horsepower#Relationship_with_torque

 

[OzFab]

Horsepower = RPM x torque

The amount of horsepower doesn't affect your top speed, it only affects how fast you get to that top speed.

Whether you have a 6hp engine or a 16hp engine, they will both only rev to 3600rpm (stock) but a 16hp will get there a lot quicker

 

[OzFab]

Okay, horsepower is the amount of torque your engine is giving off. Horsepower does not have anything to do with the number of revolutions an engine can have. Okay, lets say you have a 3HP 2-stroke running off of ethanol at 7800rpm, and then you have a 427HP V-8 running of gasoline at 2000 rpm. Which engine do you thing will be able to make a 3,000 pound vehicle move? Of course, you chose the V-8. Why?! Well, because with it's higher horsepower rating, it gives off more torque.


You see, many people think that just because you have a 'higher horsepower' engine, then the engine is faster. Well those people are wrong. The only difference between a 2HP engine and a 20HP engine is the quickness that it can accelerate a vehicle or how much torque it can give off.

Actually thats not true. Torque and Power are seperate things. They are linked, but they are not the same. My favourite example of this is an old truck I saw last year. It only made 160hp, my parents soft roader makes around 200hp from memory. Does that mean the car should beat the truck at towing things? Heck no. The truck would have many times more torque than the car, but the trucks useful RPM is much lower resulting in a lower horsepower rating.

I admit I dont fully understand it and my analogy could be wrong, but the way you worded it makes it sound like you are saying that HP=Torque which is not true as Power is a relation between torque and rotational speed.

http://en.wikipedia.org/wiki/Horsepower#Relationship_with_torque

To get technical; neither of you are wrong but, neither of you are entirely correct either. See the first line of my other post, that says it all

 

[CAPITAL_KARTS]

I disagree, there are engines made for higher top speeds. I have seen engines with 7000 max rpm and also snowmobile engines (which I will be putting in a dune buggy) have a top rpm of (often) 10,000 rpm.

 

[OzFab]

I disagree, there are engines made for higher top speeds. I have seen engines with 7000 max rpm and also snowmobile engines (which I will be putting in a dune buggy) have a top rpm of (often) 10,000 rpm.

For the purpose of this explanation, I was referring to industrial engines, which is what the majority of our members use. Please, don't add to the confusion.