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Why do you need to rebalance a CHRA ?

In exactly the same way in which a wheel needs balancing after changing the tyre, the CHRA also needs balancing after it has been dismantled and rebuilt.

It is important to understand, all objects which rotate around a centre axis have a certain amount of unbalance and this unbalance will create a resonant frequency – or vibration – at specific rpm. The speed and strength of the vibration is directly related to the amount of unbalance within the CHRA.
To compare this to the car wheel, the vibration would be felt in the steering wheel. However, if the wheel is balanced more accurately, the resonant frequency is both reduced and moves to a higher rpm – which is above the fastest speed of the vehicle therefore solving the problem.
The turbo CHRA is a complex piece of machinery which has been designed to operate at temperatures up to 800C whilst reaching rotational speeds in excess of 230,000rpm (that’s over 3,800 revolutions per second.)
To operate under such extreme conditions each component in the turbocharger, which make up the main rotor in the CHRA, is manufactured to some of the tightest tolerances in the automotive industry. The turbine and compressor wheels are also precision engineered and balanced on specialist equipment as part of the manufacturing process. However, when the rotor is assembled, the accumulation of the remaining tiny imbalance in all the parts can create a rotor, which is out of balance, and will vibrate at critical speeds within the CHRA operating range.
To ensure CHRA do not vibrate excessively during operation, it must be balanced on a high speed balancing machine which is capable of accelerating the CHRA through its full operating speed and measuring the vibrations as the rotor passes through resonant frequencies. In over 99% of tests, the unbalanced CHRA has vibrations outside acceptable limits and must be further balanced to ensure the turbo will operate correctly.
We proudly operate Turbotechnics™ VSR300 high-speed balancing machine, which is one of the most trusted models amongs turbocharger repair companies.