Excel Dyno - V2.2
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
Gear Ratio Chart - other charts include, traction,
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.
Well you can, and it's free*. All I ask is you email me and tell me what you
thought of it.
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.
Where do I get it?
Right here (only
about 300kB) - remember to say yes to macros.
If your having problems downloading the file from
the location above, I have put a copy of the file in the new yahoo group so try
to download it from there. You will probably need to join the group first
The program is currently in it's early stage of life, so it may have
bugs. If you find any bugs or can think of any way to make the program better,
then email me baja @ offroadvw.net
* Requires excel 2000 (or better)
Now did all that sound like a late night info-mercial or what?
New Excel Dyno Users Group!
To make it easy to keep up to date with the latest version / news, I
have set-up a yahoo group dedicated to the Excel Dyno!
It is an email group, so when you register I can send you an email when
the excel program is updated! Users can also email the group with any
problems, queries, or suggestions for improvements! Please join the group!
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;
- 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.
- Put tyre sizes in with vehicle type, as generally they go
- Added toggle buttons to toggle kph/mph units, metric/ imperial tyre
sizes, HP/kW power units, etc.
- 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.
- Added chart resize buttons, to automatically set the chart limits to
suit the vehicle
- Added a rollout time field for the serious racers.
- Changed the rpm range from 2-10K to 1-20K
- 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
- 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.
- I changed how the shift time was effecting the calculations, as it
wasn't quite right.
- I added more decimal places to the measured times (so they can be
compared to a time card).
- 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.
- 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
- 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
- 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
- b1.4 - started the build version history
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