Originally Posted by tttosrt6
why not just use pi and figure out the exact circumference of the stock pulley and the bigger pulleys and at different RPMS... distance over time= speed... I am sure if I had the right tools to measure the exact diameter of the stock pulley and the S/C pulley there wouldn't be no guessing... math + physics = exact science... no opinions no other answers!... but I forgot schools now teach how to have high self esteem and integrate... not how to calculate the circumference of a circle or know what speed is
with the data YOU gave me(155mm crank, 74mm S/C pulley) this is what is correct for STOCK pulleys... in reallity with our cars... not ratios out of diameters difference...
the circumference is the distance the belt is moved after one rotaion.
the formula is 2xpixR... we already have 2R = 155(stock)
155pi = 3.141x155 = 485.855mm
74pi = 3.141x74 = 232.434mm
485.855mm/232.434mm = 2.090
so every rotation per minute = 2.090 rotations of the S/C
5800rpm(stock)= 5800x2.090 = 12122
6175rpm(tuned ecu)= 6175x2.090 = 12905.75
you can use these formulas to know what is really going on under there
I appreciate everybody trying to calculate and get a good answer why our max is so low and our stock is so high well I don't know the max but I KNOW the stock(if of course those pulley diameters you posted are correct)
I do know math and physics and how to calculate circumference. And I know that speed is the magnitude of a velocity vector
You don't need to calculate 2*R*Pi, because we're looking at ratios.
2*R*Pi = D*Pi
Dcrank*Pi/Dsc*Pi=Dcrank/Dsc. Pi divides out. When can do the math with just the pulley diameters. Your calculated ratio of 2.090 differs from mine of 2.094 because of rounding.
I noticed you used lower RPMs for your calculations. Are those the actual RPM limits of our engines? I thought it was 6000 stock and 6200 with a tune. I was using the same values Brian used. He asked someone to check his math so I did. It was really late when I did all this, so I didn't break out a ruler and actually measure the diameters of our stock pulleys to verify Brian's numbers.
I figured Brian knew what the sizes are and went with that. Besides, I'm really interested in the new S/C pulley being developed and was wondering myself if we could use it in conjunction with the after market crank pulleys.
I enjoy doing math (yeah, I'm weird like that) and had some free time, and no one else checked Brian's numbers, so I did.