For the current trend of altitude simulation of combustion engines Sierra-CP has two standard offerings but can also customise to suit your specific requirements. A medium altitude unit that uses traditional blower technology and a high altitude unit which uses specialist extraction units and couples the intake and exhaust sides.

Medium Altitude Simulation (MAS)
800mBar – 80kPa – 1,850m – 6,100 feet

High Altitude Simulation (HAS)
600mBar – 60kPa – 4,400M – 13,000 feet


Sierra CP have responded to the requirements of Euro 6 regulations on the engine intake and exhaust by adapting the standard CAHU.

  • Euro 6 regulations require the engine intake air supply, as well as the exhaust flow, to be controlled at 82.5kPa.
  • Engine intake flow and exhaust flow must match precisely.

Sierra CP have designed and built three add on module options for the intake and exhaust side of the standard CAHU.

The intake solution consists of a control valve and a buffer tank with sensors, effectively restricting the intake to the engine by a controlled amount and using the engine itself as a pump.

If reduced pressure is required from start up or the test engine is relatively small capacity then an additional extraction fan can be incorporated to provide the additional pressure reduction.

On the exhaust side of the engine a twin high pressure blower system with heat exchanger and sensors if provided, this reduces the pressure in the exhaust system to match the level required.


For high altitude simulation Sierra CP’s high altitude simulator is required. This enables pressure regulation down to 600mBar on the intake and the exhaust side of the engine representing up to 4,400m (13,000 feet)  for both engine & vehicle applications. Additionally a temperature conditioning unit can be integrated to condition temperatures down to -30°C and up to 50°C. 

The design uses a single specialist extraction device, which is ATEX rated, to evacuate the air from both the intake and exhaust side of the engine. A small bypass across the engine provides better transient control of the pressure setpoint. 

For sub-zero temperatures we use a chemical dryer to reduce the dew point of the air before it is passed through the chill down coil.