Its located in folder Farming Simulator 22/data/sounds/
You should increase volume indoor/outdoor from 1 to some higher number...for me 2.5/3 is perfect...engine sound is now much louder.<!-- VEHICLES -->
<!-- Engine -->
<template name="engineDefault" >
<volume indoor="2.50" outdoor="3.00" />
</template>
<template name="engineSmall" parent="engineDefault" innerRadius="8.0" outerRadius="60">
<volume indoor="2.50" outdoor="3.00" />
<lowpassGain indoor="0.40" outdoor="1.0" />
<lowpassCutoffFrequency indoor="250.0" outdoor="20000.0" />
<lowpassResonance indoor="1.0" outdoor="1.0"/>
</template>
<template name="engineSmallVintage" parent="engineSmall" >
<volume indoor="2.50" outdoor="3.00" />
<lowpassGain indoor="0.9" outdoor="1.0" />
</template>
<template name="engineMedium" parent="engineDefault" innerRadius="8.0" outerRadius="65">
<volume indoor="2.50" outdoor="3.00" />
<lowpassGain indoor="0.45" outdoor="1.0" />
<lowpassCutoffFrequency indoor="250" outdoor="20000.0" />
<lowpassResonance indoor="1.0" outdoor="1.0"/>
</template>
<template name="engineMediumVintage" parent="engineMedium" >
<volume indoor="2.50" outdoor="3.00" />
<lowpassGain indoor="0.9" outdoor="1.0" />
</template>
<template name="engineLarge" parent="engineDefault" innerRadius="8.0" outerRadius="70">
<volume indoor="2.50" outdoor="3.00" />
<lowpassGain indoor="0.50" outdoor="1.0" />
<lowpassCutoffFrequency indoor="250.0" outdoor="20000.0" />
<lowpassResonance indoor="1.0" outdoor="1.0"/>
</template>