What am I experencing here? 5000 rpm is when my motor comes alive. Ex. 3rd gear, floor it from about 3000 rpm, when the tach hits 5000 rpm the tires break loose and the motor comes alive & pulls hard til 7000 when it's rev limited. Is this torque or horspower that is breaking the tires loose & pushing me back in the seat? Also, I have never dynod the motor, but it feels like the curve would be anear verticle climb at this point. When I raced motorcycles, I would have said that this is where the motor comes "on the pipe" Oh yeah it is nat. aspirated. thanx

385 sbc

 

Sounds like you've got quite a screamer on your hands.

Torque is the thing that turns the tires(a measure of how much force is being applied). Horsepower is the thing that says how fast you can change the rate of accelleration(a mathematical calculation of work done over time).

You can't exactly separate the two in discussion since they're not mutually exclusive when it comes to internal combustion engines and cars.

There are no right or wrong answers on this type of question. You'll get a lot of opinion and that's fine. But in the Grand Scheme of Things, it doesn't matter except in the scientific and engineering realms.

 

I would put it this way;
Torque is the ability to do work.
HP is the ability to get work done

Torque is the ability to pull the revs to the redline.
H.P is the level of performance (or what's happening) when it gets there!

 

another way to put it...torque gets you there, horsepower keeps you there

 

Horsepower is just torque times a constant, in fact on any engine, ft-lbs of torque=HP at around 5800 rpm. You gotta have a killer motor to if it comes on at 5000 rpm. Many guys build motors on purpose not to have a torque peak too early, to avoid going up in tire smoke, that's why a lot of guys use carb spacers, to raise the torque peak, which also raises the peak HP rpm. I'm guessing you're running a big single plane intake manifold, like a victor jr, but I can only guess at what cam, or rear end you're running. Probably one with a lot of overlap, on some big valve heads. 2000 rpm is a small window for peak power, and you'll have to have a close ratio 5 or speed or better tranny to "stay on the pipe". Sounds like a fun motor, but not for any everyday driver.

 

Please correct me if I'm wrong. At 5252 rpm you have the same amount of horsepower and torque and above 5252rpm you have more horsepower than torque so if you have the engine coming alive above 5000 rpm it's probably not torque. My best suggestion to you is to have your car dyno tested as it is inexpensive and very helpful.

 

I got 3 pulls for $60 last Saturday...very useful info. to be gotten.

 

Neither a case of torque or HP. This is a classic case of lead foot

 

I always thought of horsepower as the measure of how fast you could get torque to the wheels...

 

HP = Torque x RPM / 5252 therefore at 5252 the torque will equal HP. I expect that after 5000 RPM your engine is getting into a harmonic state where the pressure waves of the compressions are building on each other and creating a tuned state that you can feel. Sounds like a great race engine.

 

Picture a car running into a brick wall....

Torque is what busts you through it, horsepower is how far you bust through it afterwards.

The above was told to me by an old 60's drag racer.

 

That can be an awfully expensive method to measure hp and torque.

I think I'll be satisfied with a chassis dyno.

 

It is the coefficient of friction that causes the tires to break loose.

Power is just torque x RPM.

You can use a constant to convert the ft-Lbs-RPM's to HP.

Not that this is usefull for much of anything.

The question asked is kind of like "do you walk to school or carry your lunch"?

By definition, "Torque" does not move, it is static.

Think about this way, If you hang a 10 LB weight on the end of a 10 ft long stick and hold the stick out paralell to the ground without moving, you will feel the torque of 100 Ft-Lbs trying to rotate your hand. This is not power yet.

Once you start things moving, you are making "power".

Clear as peanut butter, right?

 

True. And torque is what's being used to overcome that coefficient of friction.

True. Torque only measures force being applied, not work being done over time. Electric motors are torque rated at zero rpm. Force is being applied but no work is being done. Energy is being consumed but the only work it's doing is creating heat. Technically, this is power but not horsepower. This is because horsepower is a mathematical calculation (done many times above) that requires an RPM factor. Well, the RPM factor is zero so you can have this motor making 1,000 measured ft/lb or torque but the horsepower will be zero. We normally have issues with this since we're thinking in terms of a piston engine that must rotate to make torque and it's a difficult concept to come to grips with. Steam engines are the same...doesn't have to rotate to create torque. The pressure of the steam on the piston, whether it actually moves the piston or not, makes the torque.

Kind of true and kind of not. But this is where you hit the peanut butter since it depends on how you use the word "power." It is in fact power since energy is being expended in that your muscles are creating heat. But it isn't power in the sense of a measure of work being done...other than creating heat. It makes perfect sense if you take into account the formula for calculating horsepower and the above edification. I know you probably understand this pretty well but someone not as versed as you may come into conflict with it.

 

Thanks guys, but, whew, it will take me a while to digest the good info.

Yes it is a single plane manifold & good sized cam

 

73C34ME I have a quick question before I say anything lol. when you leave from a dead stop hard do your tires break loose then plant and the car falls on its face till the RPM's get up to about 5000 RPM then the tires break loose again?

If this is the case your cam is too big for the gears in the rear.

 

I have always looked at it drag racing terms. THe torque gets you off the line and moving and the horsepower is needed at the end of the track to keep the car accelerating. This is the reason high horsepower is more desirable than high torque in drag racing circles. Now before anyone starts on this, this is just a simplified analogy

 

Torque is force
Horse Power is the rate of doing work

If two engine have equal torque and one is at 3000rpm and the other at 6000rpm, the one at 6000rpm will have twice the horsepower. In other words it will be doing twice as much work. If someone swings a hand sledge to break rocks while another person using the same force to break rocks but is swinging twice as fast, its quite obvious who will finsh his rock pile first. The more times the same forced is applied the more work(horsepower) is done.

What gears are in that thing that it breaks loose at 5000rpms+ in 3rd gear?

 

MUCH better than my explanation. Vs.


-Mark.

 

torque is inertia (mass of your car) multiplied by acceleration, so, torque is what accelerates your car. higher torque, higher acceleration, quicker car. but then we have to consider gears. high torque, high acceleration, but eventually you red-line the engine; plenty of torque left, but engine has reached it's mechanical limits and will fly apart. so we shift gears. rpm goes down. engine is safe (for now). but we keep the pedal to the floor, so the torque is still high, so we still accelerate. this continues until we either run out of engine, torque, or gear. run out of engine: it blows. run out of torque or gear: in the top gear, you can no longer accelerate. why???? the air resistance and mechanical friction of your car overcome the torque produced by your engine, and you top out.

horsepower is then the abiltiy to use torque in order to cause motion. gears allow you to manipulate this. but evnetually the counter forces of friction and air resistance will overcome your torque.

a high horsepower engine means you can maintain a torque value for a long time (high rpm). you shift gears to lower rpm; if you have enough torque to move the new gear (mechanical advantange) and overcome air resistanc, you will still accelerate. if not, you are done.