What was the deal about dyno graphs crossing at 5250? I forgot.

[BlueOvalStangGT]

The other day we went to dyno my freinds Cobra(477 rwhp) and I was looking at the graph and it didnt cross at 5250. Wasnt there some deal about math equations that made every graph cross at 5250? I said something and everyone looked at me like I was high on crack, am I imagining things?

 

[mo_dingo]

The other day we went to dyno my freinds Cobra(477 rwhp) and I was looking at the graph and it didnt cross at 5250. Wasnt there some deal about math equations that made every graph cross at 5250? I said something and everyone looked at me like I was high on crack, am I imagining things?

The torque curve will always pass the HP curve at 5250 IFF the scales are kept the same. But a lot of times, they will change the start/end values so that you can get a better overall view of the graph. I.E. a boosted supra at 2 bars will definately need the graph values changed to keep the graphs on the page, because they torque spikes so dramatically at a certain RPM.
Scott

 

[bimmertech]

5250 is the constant in the equation used to measure hp, prolly why. i have never heard of this before, new food for thought.

 

[Zero Signal]

The real question is what's the deal with some dyno graphs NOT crossing there. I always suspect someone is fudging the numbers when I see those.

 

[nmcgrawj]

The real question is what's the deal with some dyno graphs NOT crossing there. I always suspect someone is fudging the numbers when I see those.

He just said above they change the end value of each axis which gives it a different scale.

 

[DARK-5.0]

On a true to true scale, they should cross at the 5250 mark. 5250 is a constant in horsepower equations. Just like when reading a compressor map for a turbo, you take the cid, the 5250, etc and it will give you the flow numbers to read a compressor map. I still don't have a solid understanding of it, but some crazy einstein figured it out. Heres some stuff from a google search.

T = Time ( seconds )
N = Velocity at load ( rpm )
Ta = Average Torque During start ( ft-lbs )
WR2 = Rotating Inertia (lbs-ft3)
W = Weight (lbs)
R = Radius of Gyration (ft2)
308 = Constant derived converting minutes to seconds, mass from weight, and radius to circumference
To = Operating or running Torque ( ft-lbs )
HP = Horsepower delivered by electric motor
N = Rotational velocity ( rpm, revolutions per minute )

5250 = Constant converting horsepower to ft-lbs/minute and work/revolution to torque

So there you go.

Jeremy