To install place the files in the correct folder and replace motor lines in the sound xml with the following:
<motor template="engineLarge" file="sounds/cat_C15_6NZ_loop.gls" volumeScale="2.2" linkNodeOffset="0 0 0.0"/>
<motor template="indoorCabinRumble" />
<retarder file="sounds/turbo_loop.gls" linkNode="0>" innerRadius="23.0" outerRadius="90.0" pitchScale="1">>
<volume indoor="0.5" outdoor="0.8" >
</volume>
<loopSynthesisRpm>
<modifier type="MOTOR_LOAD" value="-0.00" modifiedValue="0.0" />
<modifier type="MOTOR_LOAD" value="0.00" modifiedValue="0.0" />
<modifier type="MOTOR_LOAD" value="0.25" modifiedValue="0.1" />
<modifier type="MOTOR_LOAD" value="0.70" modifiedValue="0.25" />
<modifier type="MOTOR_LOAD" value="1.00" modifiedValue="0.65" />
<modifier type="MOTOR_RPM_REAL" value="500" modifiedValue="0.50" />
<modifier type="MOTOR_RPM_REAL" value="1000" modifiedValue="1.0" />
</loopSynthesisRpm>
<lowpassGain indoor="0.5" outdoor="1"/>
</retarder>