Brand new at this please help !

[taper41]

  I should send you a beer for this 

[fastman614]

Larry, Larry, Larry, Larry.... lol!!!!!

And you, pretty much like me, "need" to know the why of that..... my man, I am going to leave that to you to figure out as the math has gotten, for me, to the point of "I now have to write it all out and slowly work through it with a paper and a pen!".... so.... I honestly hope you post any findings of the apparent "discrepancies" as I too am interested!

[fastman614]

I should send you a beer for this 

Larry.... LOOK AT THIS OFFER!!.... I honestly think that taper DOES OWE YOU A BEER  for this!.... so, isf you go to the Ohio Mile, he really needs to show up and make good!.... and for probably several others at that venue as well... If at Speedweek, Larry, just look up the Canadians!.....and then somewhere in the cosmos, taper is going to owe me/us that body design I alluded to a while ago!

[fastman614]

Seriously though, for a person who is studying engineering of any sort and for taper here who is into the aerodynamics etc. of automotive design, I would highly recommend that taper and all other engineering students in this field, get to places where high speed runs take place and for them to seriously observe.... and get information (possibly not at the site - but contact information of the competitors) and, during "lull" periods, get the real information.... stuff like horsepower, frontal area, gear ratios .... everything!.... and do any and/or all of us a huge favor..... help us out with the results of processing that information through your schools'(?) computers ....

It could also result in, if nothing else, better grades for taking it as seriously as this sounds....

[taper41]

Ill make good on the round for you fellas, and maybe a few more if he figures this out whether there is a slight advantalge with aero drag or if tere exactly equal .......either way

[hotrod]

I think I have figured it out:

The difference is an artifact of the percent of change in the ratios between the original and the modified power or drag.
At 25% change in drag or power, the difference is 2.17%, at 50% or 2x change the difference is .00000000.
It is because you are dealing with fractions in the ratios of original drag or power and final drag or power.

If the change in power or drag can be expressed as an exact integer change ie 2x rather than some decimal fraction like 1.25 or 1.33, the difference goes away. Too tired to go beyond that and what it tells us, but here are some other changes that show it is not due to the magnitude of the speed or even the size of the change but rather the fractional change from the original value to the final value.


==========================

(400 * 1100) / (.002373 * .30 * 25) = 24722573.4
cube root(24 722 573.4) = 291.316148 ft/sec = 291.316148 / 1.466667 = 198.624601 mph

(400 * 1100) / (.002373 * .30 * 20) = 30903216.7
cube root(30903216.7) = 313.810807 ft/sec = 313.810807 / 1.466667 = 213.961865 mph

(300 * 1100) / (.002373 * .30 * 20) = 23177412.6
cube root(23 177 412.6) = 285.11604 ft/sec = 285.11604 / 1.466667 = 194.397256 mph

198.624601 / 194.397256 = 1.02174591

=========================


(400 * 1100) / (.002373 * .30 * 40) = 15451608.4
cube root(15 451 608.4) = 249.071803 ft/sec = 249.071803 / 1.466667 = 169.821645 mph

(200 * 1100) / (.002373 * .30 * 20) = 15451608.4
cube root(15451608.4) = 249.071803 = 249.071803 / 1.466667 = 169.821645 mph

169.821645/169.821645 = 1.00000000

========================

(800 * 1100) / (.002373 * .30 * 80) = 15451608.4
cube root(15451608.4) = 249.071803 = 249.071803 / 1.466667 = 169.821645 mph

(800 * 1100) / (.002373 * .30 * 40) = 30903216.7
cube root(30903216.7) = 313.810807 = 313.810807 / 1.466667 = 213.961865 mph

(1600 * 1100) / (.002373 * .30 * 80) = 30903216.7
cube root(30903216.7) = 313.810807 = 313.810807 / 1.466667 = 213.961865 mph

213.961865/213.961865 = 1.0000000

Larry

[fastman614]

Larry, Too late for me as well...

I am going to look at it tomorrow...

[taper41]

I think I have figured it out:

The difference is an artifact of the percent of change in the ratios between the original and the modified power or drag.
At 25% change in drag or power, the difference is 2.17%, at 50% or 2x change the difference is .00000000.
It is because you are dealing with fractions in the ratios of original drag or power and final drag or power.

If the change in power or drag can be expressed as an exact integer change ie 2x rather than some decimal fraction like 1.25 or 1.33, the difference goes away. Too tired to go beyond that and what it tells us, but here are some other changes that show it is not due to the magnitude of the speed or even the size of the change but rather the fractional change from the original value to the final value.


==========================

(400 * 1100) / (.002373 * .30 * 25) = 24722573.4
cube root(24 722 573.4) = 291.316148 ft/sec = 291.316148 / 1.466667 = 198.624601 mph

(400 * 1100) / (.002373 * .30 * 20) = 30903216.7
cube root(30903216.7) = 313.810807 ft/sec = 313.810807 / 1.466667 = 213.961865 mph

(300 * 1100) / (.002373 * .30 * 20) = 23177412.6
cube root(23 177 412.6) = 285.11604 ft/sec = 285.11604 / 1.466667 = 194.397256 mph

198.624601 / 194.397256 = 1.02174591

=========================


(400 * 1100) / (.002373 * .30 * 40) = 15451608.4
cube root(15 451 608.4) = 249.071803 ft/sec = 249.071803 / 1.466667 = 169.821645 mph

(200 * 1100) / (.002373 * .30 * 20) = 15451608.4
cube root(15451608.4) = 249.071803 = 249.071803 / 1.466667 = 169.821645 mph

169.821645/169.821645 = 1.00000000

========================

(800 * 1100) / (.002373 * .30 * 80) = 15451608.4
cube root(15451608.4) = 249.071803 = 249.071803 / 1.466667 = 169.821645 mph

(800 * 1100) / (.002373 * .30 * 40) = 30903216.7
cube root(30903216.7) = 313.810807 = 313.810807 / 1.466667 = 213.961865 mph

(1600 * 1100) / (.002373 * .30 * 80) = 30903216.7
cube root(30903216.7) = 313.810807 = 313.810807 / 1.466667 = 213.961865 mph

213.961865/213.961865 = 1.0000000

Larry

So no matter how you cut it, power and aero drag are of equal importance for max speed ?

[tortoise]

I think I have figured it out:
 . . . at 50% or 2x change the difference is .00000000.

Larry

if  you decrease the aerodynamic drag by 25% 50% or add power by 25% 50% would the result differ or be the same, if it was on the same vehicle?

The vehicle with the reduced drag is now 10% faster than the other one.

[tortoise]

So no matter how you cut it, power and aero drag are of equal importance for max speed ?

Yes

[McRat]

...
So no matter how you cut it, power and aero drag are of equal importance for max speed ?

SCTA-BNI LSR records are based on a ruleset that dictates limitations.  Most limits are to the car body.

Hence, pragmatically, if you want to go faster legally, you need to add HP.  There are no HP limits.

And ...  You can make brick go supersonic with enough HP.  This is why they have truck classes and roadster classes.

[tortoise]

SCTA-BNI LSR records are based on a ruleset that dictates limitations.  Most limits are to the car body.

Hence, pragmatically, if you want to go faster legally, you need to add HP.

Tighten up the body gaps. Get the stance right. Big difference. Cheaper than horsepower.

[taper41]

So no matter how you cut it, power and aero drag are of equal importance for max speed ?

Yes

so decreasing the aero drag on one car by 50%,  then reseting all values back to original, then adding 50% power , you reach the same 10% increase in speed.

Wait so you are actually agreeing with hotrod, tortoise that power and drag are of equal value for maximum speed ?

[McRat]

Naw, just pump 75psig boost into the engine, and hope the body panels don't tear off.  

[tortoise]

Wait so you are actually agreeing with hotrod, tortoise that power and drag are of equal value for maximum speed ?

What part of "yes" don't you understand?

Note: my reply #233 is still correct.