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Discussion Starter #1
not sure if I understand this, but shouldn't torque and horsepower intersect at 5250 rpm's? From what I remember Tq is relative to Hp or vice-versus, calculated on a set formula. If it is than tonight didn't make any sense. We went to the dyno where I saw a VTEC cross at around 7K along with others all over the place. Mine is strange too, actual crossed at 4700 and SAE at 4300 rpms. what am I not getting? thanks

later,
Wes
 

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It's 5252 rpms,and that is becuase of the formula used to calculate torque.
The reason that the rpms are not crossing right is that the dyno operators are not scaling the graph the same on both sides,and that will throw off the crossing pont.
JL
 

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it's actually the value that they calulate horsepower based on torque. HP is just a mathematical value of torque.
 

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clearwaterms said:
it's actually the value that they calulate horsepower based on torque. HP is just a mathematical value of torque.
Dynos do not measure torque.I was mistaken in this assumption awhile back,and was corrected on this. HP is measured,and the torque is calculated from that. If you don't beleive me,then do a dyno pull and remove the rpm pickup during the pull...what goes away on the graph? Torque does..If Hp is calculated,then HP would go away on that graph.
JL
 

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Johnny,

I didn't know that, but i do know that HP when calulated is based off of torque, or that is always what I thought, because HP can't be put againt any thing..

Torque, is how much weight an object can move when connected to a solid rod a foot away (hence pounds/foot)
 

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That's right for torque,and it's hard to follow,but the dyno measures how fast you accelerate the drum. This is work,and HP is a unit of work.
JL
 

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JohnnyLangton said:
Dynos do not measure torque.I was mistaken in this assumption awhile back,and was corrected on this. HP is measured,and the torque is calculated from that. If you don't beleive me,then do a dyno pull and remove the rpm pickup during the pull...what goes away on the graph? Torque does..If Hp is calculated,then HP would go away on that graph.
JL
Dyno's measure torque directly. Torque is a twisting force, and thats what gets the drum rolling. An engine dyno is the only true way to measure horsepower. A chassis dyno measures torque, and makes a horsepower calculation based off of that. But, you are right, as to why they #'s don't cross at 5252 RPM on a dyno graph.
 

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Calvert2812V said:
Dyno's measure torque directly. Torque is a twisting force, and thats what gets the drum rolling. An engine dyno is the only true way to measure horsepower. A chassis dyno measures torque, and makes a horsepower calculation based off of that. But, you are right, as to why they #'s don't cross at 5252 RPM on a dyno graph.
No..that sounds all nice a correct,but it's not.

A Dynojet measures power by measuring the acceleration of two huge drum's rotation. The basic procedure involves positioning the car's driving wheels so that when power is applied to them, they turn the Dynojet drums. Rate of rotation change is then used to calculate the amount of power being applied to the drums very accurately. This process is very simple and gives very consistent measurements. It is also now very clear why the Dynojet is said to measure your car's power at the wheels which should be the actual power we will be concerned about in the first place.
JL
 

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Discussion Starter #10
so if the scaling is off it only affects the crossing points? also, why did it change from 4700 to 4300rpms corrected? just wanna make sure my numbers are on.

later,
Wes
 
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