TC.md

##Torque Converter Model

The torque converter is defined as (virtual) separate gear. Independent of the chosen AT gearbox type (serial or power split), Vecto uses a powertrain architecture with a serial torque converter. The mechanical gear ratios and gears with torque converter are created by Vecto depending on the gearbox type and gear configuration.

While the torque converter is active engine torque and speed are computed based on TC characteristic. 

 ![](pics/GBX-TC.svg)


###Torque converter characteristics file (.vtcc)

The file is described [here](#torque-converter-characteristics-.vtcc).

This file defines the torque converter characteristics as described in VDI 2153:

-   **Speed Ratio** (ν) = Output Speed / Input Speed
-   **Torque Ratio** (μ) = Output Torque / Input Torque
-   **Input Torque** (T~ref(ν)~) is the input torque (over ν) for a specific reference engine speed (see below).

The Input Torque at  reference engine speed is needed to calculate the actual engine torque using this formula:

$T_{in} = T_{ref}(v) \cdot ( \frac{n_{in}}{n_{ref}} )^{2}$

$μ(ν) = \frac{T_{out}}{T_{in}}$

with:

-   T~in~ = engine torque \[Nm\]
-   T~ref(ν)~ = reference torque at reference rpm (from .vtcc file) \[Nm\]
-   n~in~ = engine speed \[1/min\]
-   n~ref~ = reference rpm \[1/min\] (see below)

The torque converter characteristics must also be defined for speed ratios of greater than one (ν>1) in order to calculate overrun conditions or engine drag (torque<0).

The torque converter has a separate [Shift Polygon](#shift-polygon-file-.vgbs) which defines the conditions for switching from torque converter gear to locked gear.