Thursday, January 24, 2008

Regression analysis of 1/8 mile vs 1/4 mile trap speed

Using data collected at, a regression analysis of 1/8 mile vs 1/4 mile trap speed was performed. Chosen vehicles were Mitsubishi Lancer Evolution and Subaru Impreza WRX and STIs as they are AWD, have forced-induction, are about the same size and weight and present similar frontal areas.

Based on 100 observations, significance F is 2.3*10-114. P-value was less than 0.05 thus we are forced to reject the null hypothesis.

y = 1.32024246643736 * x - 5.40977006570778; where y is predicted 1/4 mile trap speed and x is observed 1/8 mile trap speed.

Detailed graphs found here.

Building upon the LRT formulas as put forth by Jeff Lucius, we can estimate horsepower given the equation:

hp = (mph / 215.39)3.3135 x weight (lbs)

Friday, January 18, 2008

Torque values

Why is it so difficult to get high torque values out of a 4 cylinder engine? Can't we keep increasing the boost assuming that fuel quality is not a problem?

A piston's acceleration does not follow a sinusoidal waveform. Plotting instantaneous torque with mean torque vs crank angle rotation, a 4 stroke, 4 cylinder engine would typically experience almost 4 times more than mean torque values at peak and almost 2 times below of mean torque through each cycle of rotation. On a dyno this is averaged out. On the other hand an even-fire V8 or V12 would go through lower extremes through its own cycle.

This is why I believe it will not be easy to get "torque monsters" out of 4 stroke, 4 cylinder engines as compared to V8s and V12s with similar swept displacements. It ultimately comes down to engine design and materials.

Thursday, January 17, 2008

Apple price gouging

Using current spot exchange rates of SGD 1.43 to USD 1, the MacBook Air 1.6 GHz at USD 1799 should be priced at SGD 2573. Yet it is going for SGD 2988 here, a USD 290 premium. That's 16% of the retail price! If that's not ridiculous enough, the 1.8 GHz model is USD 3098, but in Singapore it goes for SGD 5088 or USD 3558, a mind-blowing USD 460 difference!

Moral of the story: buy your Apple products elsewhere.