Questions and Answers

• Q: What is perfect shifting
• Q: What is influencing those RPM shifting points?
• Q: What is influencing those RPM shifting points?
• Q: How the Gear Shifting Point graph should be interpreted?
• Q: What is the structure the application tabs?

Q: What is perfect shifting?

A: If you have a car with a manual transmission the RPM at which you change each particular gear will affect the way your car is accelerating. To obtain the maxim acceleration possible you will have to change your gears at some specific RPM points, if you do that you have a perfect shifting.

Q: What is influencing those RPM shifting points?

A: Those points are influenced by a number of factors:

• the torque curve for your engine ( major influence ).
• the gear ratios for your car.
• the type size.
• the weight of the car

Q: How those RPM shifting points are calculated.

A: Basically to maximize the acceleration you have to maximize to power that the engine is producing while accelerating. To do this you have to make sure that at any time during the acceleration the engine is generating the maximum possible power for that speed.

For example ( for an hypothetical torque curve and gear ratios ) if you are doing 40 KM/H you could be in :

1st gear and you would have 6010 RPM and 92.4 HP

2nd gear and you would have4633 RPMand 91.7 HP

3rd gear and you would have 3073 RPM and 58.1 HP

4th gear and you would have 1514 RPM and 23.0 HP

You have the maximum acceleration in the gear where you have the maximum power ( in this case this is the first gear ). As your speed is increasing the gear where you have the maxim engine power ( compared with the power that the engine would deliver in other gear at the same speed ) will change. In our previous example starting with 47 KM/H the engine would deliver more power in the2nd gear than in the 1st and that is the moment when you should change gear ( perfect shift point ).

IMPORTANT:

• The shifting points are dependent on the speed for which are calculated. For example if you want to minimize the time required to reach 40 MPH you would have different shifting points then when you would want to minimize the time required to reach 100 MPH. The difference would be very small but would exists.
• The precision of the current algorithm is 1 MPH and between 100 and 500 RPM depending on the gear.

Q: How the Gear Shifting Point graph should be interpreted?

A: Basically each diagonal line represents a gear and from the position on the graph the RPM/Speed at which you have to change gear can be deduced.
For example for the graph in the image below you would have to change from the 1st gear to the second gear at around 4800 RPM and 22 MPH.

Q: What is the structure the application tabs?

• General Settings General car informations that can be set. The current car settings that can be modified are:

  • Final Drive:
  • Gear ratios for each gear:
  • Number of gear: The number of gear that a car has. The maximum number is 7, based on this attribute that gear ratio text boxes will be grayed.
  • Weight: The weight of the car in Kg or Lb
  • Cx: This is a coefficient that is measuring how aerodynamic is a particular object. Is strictly related with the shape of the object and not it size. For more informations visit http://en.wikipedia.org/wiki/Drag_coefficient
  • Frontal Area: The frontal area of the car.
  • Max RPM: The maximum RPM that the engine can support.
  • Max Torque: The maximum torque for the car. This attribute is only used to scale the graph where the torque of the car can be drawn using the mouse.
  • Transmission loss: The amount of power that is lost by the transmission.
  • Shift Time: The time that is required by the driver to shift gears.
  • Tyre settings: The dimension of the car tyres.
• Torque Settings Using the mouse you can set the engine torque curve. The precision is 500 RPM and the graph is interpolated linearly.
• Speed Rpm/Gear Here you can find informations about the speed that the cars has based on the gear and the rpm of the engine. The information is displayed in MPH and KPH.
• Acceleration Graph The approximated acceleration graph of the car. Here you can see how has the car can reach a particular speed and also the top speed. The approximated top speed is right where the graph line drop suddenly.
• Gear Shifting Point The graph with the shifting point for maximum acceleration to top speed. To accelerate to some other speed the shifting points can be different.

Disclaimer: The author is not responsible in any way for the informations that this site provides. You use them on your own risk.

For any questions or bugs found you can send a mail to admin@perfectshifting.com
Last update: 30 may 2009