vehicle acceleration calculation.xls
 

Description:

Cool Excel Dyno / Acceleration Program Spreadsheet type thingy. Want a cool spreadsheet that calculates your car's acceleration, 1/8 & 1/4 mile times and top speed? Or do you want to plot your gear ratio charts (rpm vs speed)? Or maybe figure out the effect of using stickier tyres to reduce wheel spin?

Main Screen - Gear Ratio Chart - other charts include, traction, acceleration, distance

New Feature!!! - I changed the traction chart to show acceleration in each gear against vehicle speed, this lets you see when to change gears for the best results. These shift points are also calculated on the main page.

How does it work? -  During my spare time I decided to make a free program that calculates acceleration times. Excel is the perfect platform because it is so easy to use. The spreadsheet uses visual basic and user forms to make the spreadsheet very user friendly and powerful. By entering all the correct vehicle data, and applying a few basic engineering principals, it is easy to calculate the acceleration of a car.

How accurate is it? - It's as accurate as the information you give it. So the hardest part is finding accurate info. High powered cars will be sensitive to % weight on the driven wheel, and tyre coefficient of friction, both are used to figured out if the car will suffer from wheelspin or not. Slower cars are more sensitive to coefficient of drag and frontal area, both are used to figure out the wind resistance of the car which limits it's top speed and slows the acceleration. A friend ran 11.99 down the 1/4 mile and the Excel Dyno calculated he ran 11.99, so if accurate data is entered it can be very accurate.

What happens if I don't know my cars details? - Well you have to find it. The program contains a database of tyres / gearboxes / cars / engines, and allows the user to add their own. At the moment the database is quite small, but will grow if people send me their info.

Build Version History

    * V2.2 and 2.1 - check out the Yahoo group, I'll summarise it some other day.
    * V2.0 - Quite a big redesign of the entire worksheet. Tweaked the math here and there to improve the accuracy and fixed small bugs. Main changes are;
          o Changed main sheet layout, added user defined fields for 0-X kph times, similar with distance. So you can calculate exactly what you want to more easily.
          o Put tyre sizes in with vehicle type, as generally they go together.
          o Added toggle buttons to toggle kph/mph units, metric/ imperial tyre sizes, HP/kW power units, etc.
          o Changed the way new engines, vehicles or transmissions are saved to the list. Also made the lists accessible so people can add, delete and modify the sheet directly. Just don't change the format of these sheets or you will stuff things up.
          o Added chart resize buttons, to automatically set the chart limits to suit the vehicle
          o Added a rollout time field for the serious racers.
          o Changed the rpm range from 2-10K to 1-20K
          o The new rev range also makes the worksheet motorcycle friendly. Most fast bikes will have the acceleration limited by tyre friction rather than flipping over from wheelstanding. I found some good data on a Hayabusa and the worksheet seems to be very accurate, but maybe a little optimistic on the 1/4 mile time (although I have seen high 9s time slips for stock Busa's). Of course the Excel Dyno is assuming a perfect rider getting an absolutely perfect launch. Reducing the tyre friction from 1.0 to 0.9 would possibly more accurately reflect the point at which wheelstanding would be a problem and gives more conservative 1/4 mile times.
    * V1.1 - A new gradient graph has been added. It lets you figure out what hills you can go up in each gear, it's good for picking a ratio for freeway cruising like I did with my 4th gear.
    * V1.0 - I got a lot of feed back from a friend with a 11second 1/4 Mile Nissan Skyline. He had dyno plots and time cards for the car, and I'm glad to say the excel dyno matches reality extremely well. The only way to get more accurate is to model the effect of the flywheel and drive-train inertia but it's very difficult for such a small gain. 
          o I changed how the shift time was effecting the calculations, as it wasn't quite right.
          o I added more decimal places to the measured times (so they can be compared to a time card).
          o I added a "flywheel" or "wheels" option for the engine power measurements. This suits most people that have dyno plots from their cars, and means the tricky gearbox efficiency value is not needed for the calculations.
          o I changed the traction chart to show acceleration for each gear against "kph" instead of "rpm". This allows you to easily see when is the best time to change gears. I then took this further and added a list of "best gear shift points" to the main page. You will see these actually work. 
    * b1.9 - Protected the "maximum power" cell on the input page. This was intended as an information cell, to tell you what the max power of the current engine is, not to input what the max power is.
    * b1.8 - Corrected Mazda KL V6 curves, I think the dyno chart I used for it had too many mods, and must not have been stock. It had too much midrange torque. Also added a Jap Spec EJ20T, since it has slightly more HP than the Australian spec model (higher compression and a few other things).
    * b1.7 - Someone actually reported a bug! fixed a problem that would only allow 3 digit vehicle weights in the new car form. Also added 1.8 turbo New Beetle specs. Added some more comments boxes with info about certain inputs.
    * b1.6 - Added a feature to work out what RPM you will do in any gear at any speed.
    * b1.5 - Added Subaru WRX car, gearbox and engine specs.
    * b1.4 - started the build version history

Version History
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Submitted On:

07 Sep 2009

Submitted By:

pneumatic

File Date:

07 Sep 2009

File Version:

2.2

File Size:

2,797.00 Kb

File Type:

xls

Downloads:

41

Rating:

Total Votes:6

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Comments  

 

#3 vino 2010-02-17 16:24

Thanks.

 

 

#2 DL12345 2009-09-20 17:40

Holy cow this is ridiculously cool! Looking forward to updates with more cars. Thanks very much for sharing it!

 

 

#1 JohnDoyle 2009-09-07 04:11

This must have taken weeks of your time. Thank you for sharing this impressive spreadsheet with us.

 

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