Why doesn't torque increase linearally with horsepower?

Case in point. DD2000.

I started with 245hp and 345tq
Now I have 483hp and 497tq

Why did hp go up 238 yet tq only went up 152?

 

Are those peak numbers?

 

Yes.

 

You can't really expect a linear relationship when you're comparing values at two different points on the curves.

 

Horsepower = torque times RPM divided by 5252. If you input a cam that operates in a higher RPM band than your base engine, for instance, torque may be higher but it is also occurring at a higher RPM. So, there are two factors raising horsepower, not just one.

 

Okay. At the same point, peak useable hp, I have 483hp and 461tq. This is at 5500 RPM. My hp surpassed my tq. I wonder what the dyno test looks like on a stock 92 5.7l TPI.
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Isn't hp a byproduct of torque?

 

can you post up the torque and HP curves for your base engine and newly cammed engine?

 

HP will always surpass torque at 5252 RPM. See five7kid's equation.

HP is a product of torque and RPM. See the equation again.

 

I'll have to change all the values back to stock to get a dyno graph of the stock engine. Is there one available online somewhere?

I was only able to take pictures of the graph and table. Unfortunately dd2000 doesn't allow me to do much with it's display besides printing.

I see you are correct at the 5252 Apeiron. Interesting.

 

Here are pics of my screen.

 

Your horsepower and torque do not increase linearly with each other because horspower is a function of torque AND rpm. Were it only a function of torque then they would increase linearly together.

 

They'll also change linearly at any given RPM, but it doesn't necessarily follow that they have any particular relationship at all at different speeds.

 

If the torque curve of an engine were perfectly flat then the hp curve would increase linearly with increasing rpm. (aside: most electric motors behave that way, even at zero rpm). But a real engine doesn't have a flat torque curve because the cylinder filling isn't uniform with rpm. The choice of camshaft and the acoustics of both the intake and exhaust systems affect the cylinder-filling in an rpm-dependent way as well as in a throttle-angle-dependent way.

So the torque curve isn't flat with rpm, and therefore the graph of hp vs rpm isn't a straight line. With that said, over a moderate range of rpms the torque curve is flat within 10 to 20% (say 1600-4000 rpm) and so the hp will increase nearly linearly in that range. When the cylinder filling becomes really poor (at very low rpms when the camshaft overlap hurts, or at very high rpms when there isn't enough overlap and duration) the torque is greatly reduced, and therefore so is hp.

It's all about imperfect cylinder-filling. Percent cylinder fill is directly proportional to cylinder pressure and therefore torque. The rate that this occurs (in an rpm sense) is (horse)power. If you can follow the thought experiment starting with perfect and then imperfect cylinder filling, you can understand how it affects torque and power. HTH.

 

Thanks for the explanations. I think i've got it!
Somebody asked me this question last week and I couldn't give him an answer. I guess I just had to find out the answer.