This program can take basic data on a car (especially an old one) that has a manual transmission and use this data to predict how the car would perform under ideal conditions at the Newport Hill Climb (the first Sunday of every October in Newport, IN, www.newporthillclimb.com). This program can also make predictions on the performance of the car such as 0-60 and quarter mile times.
This is where you enter the information you have on a car. The items with a " * " next to them are required. Everything else is optional but the more info you can supply, the better the program will be able to model the car.
This is the description of the car you are entering. If you click SAVE CAR ABOVE, the description will appear at the bottom of the screen in the picker area. Descriptions must be unique. If you attempt to save a car with the same description as one already saved, the program will ask you to confirm before overwriting the previously saved car with the one you are trying to save.
This is the maximum horsepower of your car's engine.
This is the RPM (Revolutions Per Minute) that the engine is turning when it delivers its maximum Horsepower.
This is the peak torque of the car's engine expressed in pound-feet.
This is the RPM of the engine when it delivers its Torque Peak.
This is the number of cylinders that the car's engine has. It is required for sound effects purposes.
This is the RPM of the engine when it idles. It helps the program with sound effects and determining the minimum RPM the engine can run at. If you do not supply a value, the program will estimate it by taking the RPM @ Torque Peak divided by 5 as the value of Idle RPM.
If there is a maximum RPM that you do not want the engine to exceed, put it here. The program will not simulate the engine running above this value of RPM. Be careful that this number is not the same or below RPM @ HP Peak. Sometimes putting a value here helps the accuracy of the model because it is set close to the rpm where a tester shifted.
This is not to be confused with Rev. Limit. This is the theoretical RPM where the engine no longer produces any useable torque (i.e. all of its torque is used just to turn itself). Thought of another way, it is the RPM where the engine's torque curve crosses the X (or RPM) axis. The program calculates a value for Max RPM to achieve a best fit of the car to its performance data. In order for the car's peak Horsepower to occur at the value specified for RPM @ HP Peak, the value of Max RPM must be less than or equal to twice the value of RPM @ HP Peak. Small changes can have a big effect. Max RPM is often much higher than the Rev. Limit of the engine.
This is the displacement of the engine in cubic inches. It is used for calculating the score of the car on Newport Hill for those classes where the score is the displacement in cubic inches times the elapsed time.
This is the ratio of first gear for the car's transmission. It is expressed as the number of revolutions of the engine for each revolution of the transmission's output shaft.
Similar to 1st. These are for any additional gears your car may have.
This is the amount of time in seconds that it takes to shift from the gear above and left of the value to that below and left of the value. If no value is supplied, 0.3 seconds is entered as a default. If only one value is supplied, it will be used as the time to shift between all the gears. If a value is not supplied between two gears, the first non-zero value above will be used.
This is gear ratio of the rear (differential) of the car. It is expressed as the number of turns of the transmission output shaft/drive shaft for ever single revolution of the drive wheels. Typical values range from about 3.0 to 4.0 but higher or lower values are possible.
This is the car's weight in pounds. It is the TOTAL weight of the car including all fluids, accessories, the driver, and all the stuff in the driver's pockets.
This is the diameter of the car's drive wheels in inches.
This is the force in pounds required to just get the car to move when its in neutral on a perfectly flat surface. This value is typically between 50 and 80 pounds. Heavier cars tend to have higher values.
How I measure: I place the car in neutral in the garage. I take a ratcheting tie-down strap and attach it to a firm point on the garage wall in front of the car. The other end of the strap is attached to a game weighing scale. The hook of the scale is hooked onto the front bumper of the car. I then ratchet the tie down strap tighter until the weight on the scale reaches a maximum value just before the car starts to move. This maximum scale value is what I use for Drive Drag.
This is the top speed of the car in miles-per-hour. To get best results, you may have to tweak this number a bit. It tends to be the least accurate measured parameter of any car.
This is a number that the program calculates such that when the car is in its top gear and traveling at its Top Speed, the sum of the force the engine delivers to the wheels minus the Drive Drag, and minus the Aero Coefficient times the square of the Top Speed, is equal to zero. You can change this value but it is best not to. Small changes make big changes to the results.
This is a percentage of the engine's Torque Peak delivered via the clutch when the speed and gear of the car are such that the engine's RPM would otherwise be below the Idle RPM. The program will calculate a value for this parameter to get a best fit to the car's performance data. Typical values are around 20% but sometimes go as high as 80%. Theoretically, a value of 50% should always be possible. Experimenting with this value can lead to widely varying results.
This is the class of the car for the Newport Hill Climb. For example Model T's are in class F-1. Postwar Studebakers with 6 cylinder engines and standard transmissions are in Class H-1. This entry is only needed to set the default value of class when going to the EXPLORE RESULTS screen.
You can enter data on three kinds of tests:
When you first start the program, you will see some of the spaces in the opening screen are populated with values. These values are for a 1950 Studebaker Champion without overdrive. The values for the engine, transmission, and car are taken from Studebaker factory shop manuals and from the Studebaker National Museum's monograph on the 50-51 Studebaker cars. The performance data comes from the November 1949 issue of Mechanix Illustrated. The article is by Tom McCahill- the father of instrumented auto testing for the consumer.
Clicking on GO FIGURE! causes the program to start computing a model for the car. When the program has finished, the results show that while the model matches the car's performance for 10 to 60 in 3rd gear and standing 0.5 mile, it is off by nearly a second in 0-70 and 1 tenth of a second in 0-60 time. Top speed is given at 81 mph (Tom McCahill stated top speed as 80-82) and Max RPM as 8000. If one clicks on the Freeze speed while refining (which unfreezes the Top Speed) and then clicks on REFINE FIGURE, the program recalculates. Now, the Top Speed has been reduced to 79.4 and the Max RPM to 6160. For all four performance tests, the times are spot on. The program now has a fairly good model of the car.
The program is basically trying to figure out several acceleration, time and distance problems. To calculate acceleration, it first needs the torque that the engine is supplying for any given RPM. To do this, the program first defines 4 RPM values- Low RPM, RPM @ Torque Peak, RPM @ HP Peak, and Max RPM. The middle two values must be supplied by the user while the first and last values may be calculated by the program.
Low RPM is found by looking at the following two values: Idle RPM (supplied by the user or calculated by taking RPM @ Torque Peak/5) and the RPM of the engine at the starting speed of a "X to Y mph in Z seconds using gear ratio R" speed test supplied by the user- whichever is lower.
Max RPM is set to a starting value equal to 2 times the value of RPM @ HP Peak.
Now the program can define the torque of the engine at three of the above RPM values. The torque of the engine at RPM @ Torque Peak is simply the value of Torque Peak. The engine's torque at RPM @ HP Peak is give by the formula Horsepower*5252/RPM @ HP Peak. The engine's torque at Max RPM is defined as 0. The program now uses the above RPM and Torque values to create a set of two linear approximations of engine torque for any RPM between the RPM @ Torque Peak, RPM @ HP Peak, and Max RPM.
Now the program calculates a value for Aero Coefficient (using Top Speed). With this done, the program can now start doing trials.
If "X to Y mph in Z seconds using gear ratio R" data is available, the program will adjust the torque of the engine at Low RPM until the car's time in simulation matches the value supplied. If no "X to Y using gear" data is supplied, the engine's torque at Low RPM is assumed to be 90% of the engine's Torque Peak.
Now the program will use "X mile in Z Seconds" data to run trials in order to find a value of Start Slip % that will yield the correct time. If no "X mile in Z seconds" data is available but a "0 to Y mph in Z Seconds" is, then the program uses this data to determine Start Slip %. If none of the above is available, the program will use 20% as a default value.
Finally, the program will use any "0 to Y mph in Z Seconds" data available to adjust Max RPM and Top Speed (if not frozen) until a best fit of all the data is obtained. The program may have to repeat all of the above steps several times to get the best result.
This can take some detective work. Owner's manuals, shop manuals, and sales literature for your car may contain engine and transmission data and sometimes even the car's shipping weight (i.e. weight without fluids and possibly the battery). Magazine articles tend to be the best places to get performance data. The internet is a huge help in locating sources of information but it does take patience. I've had to go pretty deep in a search engine's results listing to find what I wanted. Coker Tire's website is a good source for tire diameters for older cars.
In experiments I have done, the program does not work too well with automatic transmission equipped cars. The problem is the the effect of the torque converter. A different computer model would have to be developed for such cars.
It works somewhat on such cars but not as well as normally aspirated cars. The problem is the immense effect the turbo or supercharger has on the engine's torque output at any given RPM depending on conditions (and the algorithm of any computer controls on the engine).
The data for the hill is obtained from Google Earth by measuring elevation changes in 100 foot increments over the course from the start line to the finish line. The program then uses this information to determine the incline of the car as it climbs the hill.
This often happens when you have a car that you originally modeled using UDATE ENGINE ONLY or UPDATE FIGURE SAME ENGINE & BODY. The program calculates things in thousandths of a second while things like * Top Speed (mph) are measured in tenths (at best). GO FIGURE! recalculates everything while UDATE ENGINE ONLY and UPDATE FIGURE SAME ENGINE & BODY only recalculate certain things in the model of a car. Slight rounding differences can propagate through and lead to slight differences in results.