BannedCR500Riders.com

What do you guys make of this......

http://www.thumpertalk.com/forum/showth ... 887&page=3




Ive never seen a dyno graph where the HP and TQ never cross

H/P and Tq always cross at 5250. This graph starts at 5500.

Mad Dog wrote:H/P and Tq always cross at 5250. This graph starts at 5500.

Good catch I dint notice the graph started so high.

Mad Dog wrote:H/P and Tq always cross at 5250. This graph starts at 5500.

I think every dyno I did with the truck crossed at around 4200.

Edit :- Just checked, you guys are right

chew on this for a while! dont shoot me. just the messenger

Formula for horsepower is HP = Tq X rpm divided by 5250.

So Tq and Hp will always cross at 5250.

Look at every dyno sheet. Right from idle there is always a Tq number and a low Hp number. As the RPM rises, the TQ rises a little but the HP goes up alot till it crosses at 5250 and keeps going.

My unofficial opinon and observation of this is Tq is what the dyno measures, then converts the number to Hp.
Conclusion, Hp is a by product of Tq and RPM.

Torque is real force.

RPM is real rotation

Mathmaticaly, Horsepower exists as a function of the two.

Thats what he said.

Mad Dog wrote:

is Tq is what the dyno measures, then converts the number to Hp.
Conclusion, Hp is a by product of Tq and RPM.

No, he said it was a product.

A product is real.

A function is not.

I knew what he meant.....

AlisoBob wrote:No, he said it was a product.

A product is real.

A function is not.

???

In math terms...

A "Product" is the result of multiplication.

A "Function" is a relational expression.


It is indeed a function. But we're gettin a bit nitpicky here.

correct me if I'm wrong, but I always thought the main difference between torque and horse power was time. I seem to remember the early calculations of horse power being how much it can move and how quickly.
if horse power was only torque x rpm / 5252 than wouldn't EVERYTHING have the same torque to HP curve?? how do you explain a motor with 60 lbft of torque and 90 hp vs a motor with 460lbft or torque and 300 hp and that would be time, the latter is a slow turning big v-8, so even though it has tons of torque is isn't tuned to to crank up rpms at all.
maybe I'm just going crazy.

Danny, this horsepower / torque stuff use to baffle me.
I always told that torque is the rotational movement and hosrspower is the figure used to move a certain distance.
Webster's defines horsepower as lifting 33,000 lbs one foot per minute.
Waas up wit dat.

I don't know where the formula came from, but it's what's used in the automotive world.

Torque is always more than Hp below 5250 and less than above.

Your two examples denotes one engine spinning at 7875 and the other at 3224.

Notice how diesels are rated for their torque?
It's because they don't go past 5250. Horsepower looks wimpy but the torque is off the chart.

Ok I got a question that always baffled me, I used to be into tractors bigtime (laugh all you want) why are tractors always rated HP???

I had a 4.2l 4cyl diesel that was rated at 45 Hp (midsize), and another turbo diesel that was rated 82hp (bigtime power).... In the tractor world a 100 horse motor is a big ole monster 6 cyl turbo diesel, why are the ratings so low?

Why do they do it like that?

Because the rpm is low.
At what rpm did it make that power?

I.E. 100 Hp at 1800 rpm is 291 lbs ft. of torque.

Mad Dog wrote:Because the rpm is low.
At what rpm did it make that power?

I.E. 100 Hp at 1800 rpm is 291 lbs ft. of torque.

Most of 'em maxed out at around 2800 RPM, your 100hp example doesnt make sense to me tho, a 6cyl BIG turbo diesel should have a ton more than 291 TQ

Well, at 2800 rpm and 100 Hp, the Tq is only 188 lbs ft.

I don't much about tractor motors, but where is the sweet spot?
I'm guessing somewhere around 1800 - 2000 rpm.
That's where it is making it's peek Tq and is probably higher than the 188.
I also figure they have a HUGE flywheel for inertia. That coupled with adequate Tq alows them to get he job done.

Mad Dog wrote:
I don't much about tractor motors, but where is the sweet spot?
I also figure they have a HUGE flywheel for inertia. That coupled with adequate Tq alows them to get he job done.

Yea the "sweet spot" is normally around 2200, and they do have really heavy flywheels.

It just always puzzled me as a kid how a YZ490 had more HP than a 4.2l diesel lol

Your question is a good one. These things used to bother me too.
The difference is in the torque, the real measurement.
Horsepower is just s product / function of rpm and Tq.

The YZ 490 has what 45-50 lbs ft. for Tq, where as the tractor has 200 + and comes on hard from 0 with a very linear spread.
The YZ probably couldn't even spin the flywheel.