GEAR RATIO - it is the ratio between the driver shaft angular speed and the driven shaft angular speed from the gearbox. In other words the ratio between the number of teeth of the driven sprocket that is on the driven shaft in the gearbox and the number of teeth of the driver sprocket that is on the in shaft coupled to the engine with the clutch. Example: 3.17:1 which means 3.17 rotations of the motor shaft at 1 rotation of the driven shaft. In this case we input 3.17 in the calculator. You can find these ratios here.
FINAL DRIVE RATIO - has the same definition with the gear ratio with the specification that the drive it refers to is between the driven shaft and the shaft that transmits the movement to the wheels.
Pmax/RPM - indicates the maximum energy rate (power) developed by the engine and the rotation speed at which it occurs. It's measured in KW or KJ/s.
See the difference between HP & HF (Horse Force). Tmax/RPM - indicates the maximum torque developed by the engine and the rotation speed at which it occurs. It's measured in Nm.
Wighted average power - is the division of total energy converted to force by the total time needed to accelerate on all the RPM range. It's measured in J/s.
Wighted average torque - indicates the average torque developed by the engine on all its RPM range. It's measured in Nm and is the second clearest (after Equivalent constant engine torque) characteristic of an engine (if it is mentioned alone without other information/characteristics). Details... Equivalent constant engine torque - is the torque with which a car's engine with one gear ratio can accelerate over the same distance in the same time, providing a single value as a characteristic for that engine on all its rpm range. It's measured in Nm and is the clearest characteristic of an engine (if it is mentioned alone without other information/characteristics). Details...
Car Transmission Calculator and Comparator
Fill in at least the mandatory fields marked with *
OBSERVATIONS:
a. Changing the tyres/wheels dimensions influences only the real speed (Attention, not the one indicated by the gauge!) and the force applied at the circumference of the traction wheels:
- by lowering the diameter, the force applied at the circumference of the traction wheels will rise and the real speed will drop,
- by rising the diameter, the force applied at the circumference of the traction wheels will drop and the real speed will rise.
- this force applied at the circumference of the traction wheels is influenced also by their mass => their inertia.
b. The torque at the traction wheels changes only by changing gear, not by changing the diameter or mass of the wheels.
c. The power at the traction wheels is equal with the power at the flywheel minus the losses through friction in the transmission (in general 15% for 2wd and 25% for 4wd that includes the losses generated by the mass /inertia of the wheels). So, the power at the traction wheels does not vary by their diameter (it varies by their mass/inertia). Therefore results that for the same power at the traction wheels there are multiple values for the force (that is influenced by the wheels' mass so we are discussing about equal masses and equal distribution of the mass for different diameters) applied at their circumference and so, a different behaviour of the car.
Results
1st gear:
The rotation speed at which the engine resumes the traction if the previous gear is changed at RPM:
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Speed at RPM (KM/H):
vs
Speed at RPM (KM/H):
vs
Torque at RPM at the traction wheels (Nm):
vs
Acceleration imposed to the vehicle at RPM (m/s2):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
2nd gear:
The rotation speed at which the engine resumes the traction if the previous gear is changed at RPM:
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Speed at RPM (KM/H):
vs
Speed at RPM (KM/H):
vs
Torque at RPM at the traction wheels (Nm):
vs
Acceleration imposed to the vehicle at RPM (m/s2):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
3rd gear:
The rotation speed at which the engine resumes the traction if the previous gear is changed at RPM:
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Speed at RPM (KM/H):
vs
Speed at RPM (KM/H):
vs
Torque at RPM at the traction wheels (Nm):
vs
Acceleration imposed to the vehicle at RPM (m/s2):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
4th gear:
The rotation speed at which the engine resumes the traction if the previous gear is changed at RPM:
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Speed at RPM (KM/H):
vs
Speed at RPM (KM/H):
vs
Torque at RPM at the traction wheels (Nm):
vs
Acceleration imposed to the vehicle at RPM (m/s2):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
5th gear:
The rotation speed at which the engine resumes the traction if the previous gear is changed at RPM:
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Speed at RPM (KM/H):
vs
Speed at RPM (KM/H):
vs
Torque at RPM at the traction wheels (Nm):
vs
Acceleration imposed to the vehicle at RPM (m/s2):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
6th gear:
The rotation speed at which the engine resumes the traction if the previous gear is changed at RPM:
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Speed at RPM (KM/H):
vs
Speed at RPM (KM/H):
vs
Torque at RPM at the traction wheels (Nm):
vs
Acceleration imposed to the vehicle at RPM (m/s2):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
Force at RPM applied at the traction wheels' circumference (N):
vs
The transmission will generate the force applied to the circumference of the traction wheels / R , equivalent with the force generated on the circumference of the initial traction wheels / R by:
OBS. 1.The torque at the traction wheels doesn't change if the tyres are changed. By changing the radius of the wheels, the only thing that changes is the force applied to the circumference of the wheels.
2.The above values don't take into account the tyres' pressure or wear, the air friction force or other resistive forces that appear in real situations, this being theoretical values. 3.The calculated torque at the traction wheels takes no account of the transmission's losses. 4.The calculated force applied at the traction wheels' circumference refers to the sum of forces applied at the traction wheels' circumference and takes no account of the transmission's losses (losses that include also the masses/inertias of the wheels or the differences between the masses/inertias of the different diameter wheels) Ex: F=7000N; 2WD = > 3500N at each wheel's circumference.
The alert will be visible ONLY for other authenticated users.
Torque [Nm], rotational speed [RPM] and work rate [J/s]
The air drag IS NOT taken into consideration in the actual calculation.
The start speed for this actual estimation is 0 km/h and the top speed is ~ 0 km/h.
Graph 1
For a better interpretation of these values you need the torque chart from the engine [You can find here or here that kind of charts and you can transform them in table data here].
The air drag IS NOT taken into consideration in the actual calculation.
The start speed for this actual estimation is 0 km/h and the top speed is ~ 0 km/h.
Graph 2^^
The above graph is useful only if rotational speed values and respectively torque values of the engine from the torque chart were inputted and it refers, especially, to / R wheels, / R wheels having displayed only the graph of total force at their circumference depending on the rotational speed of the engine, in 1st gear (for keeping the graph readable).
For a clearer view of the differences that appear when changing the wheels, print in pdf this report, then change the dimensions of the tyres in the fields from the beginning of the calculator and compare the graphs.
If the rotational speed values and respectively torque values are deduced by measuring the force at the traction wheels' circumference, in a certain gear, without adding the losses (or the power loss), the curve from the above graph that coresponds to the same gear in which the measurement was made has REAL ~ VALUES!
For maximum performance, the gold colored lines "Shift _-_" from the above graph must be ~HORIZONTAL !
Graph 3^^
The above graph is useful only if rotational speed values and respectively torque values of the engine from the torque chart were inputted and it refers only to / R wheels.
For a clearer view of the differences that appear when changing the wheels, click on compare button, then change the dimensions of the tyres in the fields from the beginning of the calculator and compare the graphs.
This graph shows forces and accelerations generated by the engine+transmission unit at the traction wheels' circumference, without taking into account the transmission loses. If the rotational speed values and respectively torque values are deduced by measuring the force at the traction wheels' circumference, in a certain gear, without adding the losses (or the power loss), the curve from the above graph that coresponds to the same gear in which the measurement was made has ~ real values but ATTENTION! These forces are NOT the RESULTANT FORCES that act upon the vehicle because the air friction force or other resistive forces are NOT included! The possible tyre skating is not taken into account!
For maximum performance, the gold colored lines "Shift _-_" from the above graph must NOT be visible !
Graph 3^^^ (air resistance included)
This graph appears only if values for air resistance calculation (drag coefficient, reference area and air's density) were inputted.
For example, the first two can be found here.
The air resistance alters the gears' graph lines in a nonlinear whay. It can be observed especially when the torque:RPM pairs of data points are far apart from each other.
That is why, in those cases, the fill areas in higher gears are not matching 100% with the gears' graph lines.
Long story short: you don't have to compose the response by hand.
Acceleration time [s`]
[s`] The shifting time is NOT included.
The air drag IS NOT taken into consideration in the actual calculation.
The start speed for this actual estimation is 0 km/h and the top speed is ~ 0 km/h.
In the actual calculation, the total force used to estimate the acceleration time in last gear is ... N.
That is why, in some cases, if the the gear's graph line has a small slope, the accelerating time in that gear appears to be big (incorrect).
When including the air's resistance, if the top speed would be the value at which the total force or acceleration is 0,
then the time needed for the car to reach that speed increases very much, to over tens of minutes, even hours.
Graph 4^^
The colored areas below each graph line represent the acceleration time. The time needed for shifting gears is considered to be 0.
This graph displays the inverse of acceleration that is generated by the engine+transmission depending on the speed, without taking into consideration the transmission losses.
Graph 4^^^ (air resistance included)
This graph appears only if values for air resistance calculation (drag coefficient, reference area and air's density) were inputted.
For example, the first two can be found here.
The air drag IS NOT taken into consideration in the actual calculation.
The start speed for this actual estimation is 0 km/h and the top speed is ~ 0 km/h.
Graph 5^^
The colored areas below each graph line represent the distance covered. The time needed for shifting gears is considered to be 0.
This graph displays the speed depending on time, without taking into consideration the transmission losses.
Graph 5^^^ (air resistance included)
This graph appears only if values for air resistance calculation (drag coefficient, reference area and air's density) were inputted.
For example, the first two can be found here.
The air drag IS NOT taken into consideration in the actual calculation.
The start speed for this actual estimation is 0 km/h and the top speed is ~ 0 km/h.
Graph 6^^
The time needed for shifting gears is considered to be 0.
This graph displays the distance covered depending on time, without taking into consideration the transmission losses.
Graph 6^^^ (air resistance included)
This graph appears only if values for air resistance calculation (drag coefficient, reference area and air's density) were inputted.
For example, the first two can be found here.
Energy [J] transformed into force [N] depending on distance [m]
The air drag IS NOT taken into consideration in the actual calculation.
The start speed for this actual estimation is 0 km/h and the top speed is ~ 0 km/h.
Graph 7^^
This graph displays the energy transformed in force depending on the distance covered, without taking into consideration the transmission losses.
The energy transformed in force is calculated as the surface under the force's graph depending on distance covered.
Because the torque graph contains only 15 points, errors occur when calculating the time, distance and energy.
The total energy transformed in force between 0.00 and 0.00 km/h
is equal with the difference between the kinetic energies for these two speeds: 0.000 KJ.
Graph 7^^^ (air resistance included)
This graph appears only if values for air resistance calculation (drag coefficient, reference area and air's density) were inputted.
For example, the first two can be found here.
The air velocity relative to the ground is considered 0.
In the case of air friction, the energy transformed into force is calculated as the area under the
force's graph (WITHOUT including air resistance) depending on distance covered (WITH air resistance included).
Because the torque graph contains only 15 points, errors occur when calculating the time, distance and energy.
The total energy transformed in force between 0.00 si 0.00 km/h
is BIGGER than the difference between the kinetic energies for these two speeds: 0.000 KJ because of the energy absorbed by the air friction: KJ.
*IF the shifting RPMs are autocompleted for MAXIMIZING THE TRANSMISSION'S PERFORMANCES and the inputed torque graph is measured with the acceleration pedal PUSHED 100%!
WARNING! STAY SAFE AND OBEY THE SPEED LIMITS!
ONLY in OPTIMUM visibility and adherence conditions, keep the engine's rpm range* on the green rpm range from below:
OBS. If the downshifting (with 1 step) is made from the green rpm range from above (respectively for each gear) and the electronical limitation of the RPM is equal to the last RPM value from the torque graph, then the engine brake will be activated!
Graph 3 Comparison
Graph 4 Comparison
Graph 5 Comparison
Graph 6 Comparison
Maximum distance: m / Maximum time: s
Minimum distance: m / Minimum time: s
Refined Graph 6 Comparison
Obs. These graphs are generated from a torque curve made by straight lines between 15 points. That is why, when comparing the distance over time graphs generated by very small changes between calculations, errors can occur especially if the car’s friction with air is included.
Graph 7 Comparison
Maximum energy: KJ / Maximum distance: s
Minimum energy: KJ / Minimum distance: s
Refined Graph 7 Comparison
Obs. These graphs are generated from a torque curve made by straight lines between 15 points. That is why, when comparing the graphs of energy transformed into force depending on distance covered generated by very small changes between calculations, errors can occur especially if the car’s friction with air is included.
