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johnta1 · 03-12-2014, 08:02 AM

From Larry Meaux's forum:

Quote:

paulzig wrote:
Just a quick Question:

I notice these figures around all the time and I'm a bit confused ...

If you set something up on a dyno thats 300-600RPM/sec acc rate does that mean that the dyno allows the motor to accelerate at that rate, and if it CANT do it it helps it to do so??

OR if its steady state does the motor have to accelerate the water brake??

If so, does it stand to reason that something is 'EASIER' to acclerate on a steady state dyno that it will more readily put that power down and run ET/MPH that the dyno shows when worked out on Moroso or an online calculator like ETABWIN??

I'm thinking along the lines of LESS reciprocating/rotating mass using light cranks, rods pistons etc ??

Is there anything in this, making more HP in a short space of time or am I way off??

the SF-901 Software + Electronics control the Servo Valve on the Water Brake's discharge
so that in turn sets the amount of Load on the Engine and the Rate of Load -vs- RPM if you choose an acceleration test.

Its a computer controlled acceleration rate .... the Dyno tries to maintain that RPM/SEC Rate as best it can ,
it does vary a bit, but overall 600 RPM/SEC comes out around 600 RPM/SEC on average .

it takes about 1 second to turn the Test Rate knob to your choice
its that easy on a SF Dyno

Anytime you accelerate a mass it take force
the amount of force would be relative to where the mass is distributed from the axis or centerline of rotation ( Polar Moment of Inertia = PMI or POI )
Any rotational mass thats accelerating will loose more and more HP the faster you try to accelerate it .... and that includes any objects in the Absorber or Dyno that are
geared to or accelerating with the Engine

600 HP = So lets say you Dyno your Engine at zero acceleration test rate ( Steady-State )
585 HP = 300 rpm/sec acceleration test rate
570 HP = 600 rpm/sec acceleration test rate

so i ask you.... what HP would you input into a computer program to simulate how quick you would run in 1/4 mile ?

so to be fair and accurate , you would need to input a second value to represent the HP loss to Dyno test rotational inertia

so in a 1/4 Mile DragRace Simulation Program you might input 570 HP along with 600 rpm/sec so it becomes 600 HP @ steady state
or you input 585 HP at 300 rpm/sec and it becomes 600 HP @ steady state in the program
or you input 600 HP steady-state , and it remains 600 HP in the Program
so that all 3 combinations end up or equal to 600 HP in the program

then the computer program now knows the engine puts out 600 HP @ steady-state
now when the RaceCar launches off the starting line and revs + gear changes , etc,
the rpm/sec rate is vastly different from the Dyno rate
so down the dragstrip or track, the engine typically in first gear could be as high as 5000 rpm/sec in 1st gear on a 500 cid ProStocker
the computer program has to keep track of all component rotational inertia losses every .001 second or whatever you use as your time increment or time step .

_________________
Meaux Racing Heads
MaxRace Software
ET_Analyst ( DragStrip Simulation Software )
PipeMax ( Engine Simulation Software )
http://www.maxracesoftware.com