John Scott Posted March 4, 2006 Share Posted March 4, 2006 I’ve always enjoyed how ScottieGNZ and a few others take a car’s observed performance, run it through their supercomputers and give us tangible numbers relating to horsepower, torque, and time. Maybe Scottie is some kind of savant and can do this by counting on his fingers and toes. Regardless how calculations are made, it helps me to appreciate the relationship of power and its application to performance cars. Very Cool! Sometimes we try and go the other direction in making predictions based on dynos, magazine articles, and the most famous of all, seat-of- pants or butt dynometer.. This has many valid applications, but more likely “$h!+ that car is sooo fast it must have like 600 horspower and do 1/4s in 8 flat,” when in reality it had 290 and went 13 seconds. Depending on your ability to hear B.S. It makes for either entertaining or annoying conversations. My favorite subject of late is wheel horsepower so I throw out this question. Do your formulas account for aero drag, and can they be modified for differences in Cd and frontal area? I just wonder about an early Z with it’s notorious aerodynamics of a water buffalo in reverse, and frontal area of a sheet of plywood, pushing 130+ mph. This has to require way more hp than a say new Corvette doing the same speed, even if they were the same weight. Maybe you guys are making even more power than the formulas indicate. Just a thought. I know many disregard the Gtech, and I'm not touting all of its virtues, but I liked the idea that the instrument gives results that are affected by rolling and wind resistance, unlike a stationary wheel dynometer.. If you know your vehicle’s frontal area and Cd, I found a cool link for aero drag hp calculations. http://www.gtechprosupport.com/support/AeroDragCalc.htm In the meantime, keep the numbers coming. John Quote Link to comment Share on other sites More sharing options...
mtcookson Posted March 4, 2006 Share Posted March 4, 2006 Wouldn't happen to know how to calculator the frontal area would you? Does that include all front facing parts (windshield, hood, bumper, mirrors, etc.) or does it include something else? This definitely seems like a pretty cool calculator. Quote Link to comment Share on other sites More sharing options...
tube80z Posted March 4, 2006 Share Posted March 4, 2006 Wouldn't happen to know how to calculator the frontal area would you? Does that include all front facing parts (windshield, hood, bumper, mirrors, etc.) or does it include something else? A DIY way to do this is put paper behind the car and shine a light head on and outline the shadow on the paper. Then add up the area on the paper to see the total area. The basic idea is to see how big a hole you're trying to punch in the air. Cary Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 9, 2006 Share Posted March 9, 2006 I agree. I love auto math. In my CD book I include 7 performance calculators I created on Excell and one of them is, "Hp & Tq Loss due to Aerodynamic Drag" calculator. The input parameters are tire diameter, Engine VE%, Peak Hp, Peak Tq, Peak RPM, Axle Ratio, Cd, Frontal Area, and your choice of up to 6 transmission gear ratios. This particular calculator then offers for each gear ratio MPH for each gear ratio Flywheel Tq Driveshaft Tq Drivewheel Tq Aero-Drag ft.lbs Aero-Drag Tq Engine Hp Remaining Engine Tq Remaining It is really cool to play with the numbers for any engine-car combo for indicators as to when a particular combo runs out of steam at what rpm/speed. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted March 9, 2006 Share Posted March 9, 2006 The 1st gen Z has a frontal area of 17.45 sq.ft. To obtain the frontal area of any vehicle - an accepted practice is to sqat in front of your vehicle and measure your length x width of said car. Then multiply that by .80; and of course your final answer needs to be in sq.ft. not sq.inches. The typical formulas for calculating 1/4 mile performance was obtained emperically and I've not read anywhere that said formula included Cd or Frontal Area parameters in its calculation. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
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