Motorsport Developments - How Do I Check Boost Pressure

Car image

Equipment

Accurate boost gauge, length of hose, hose connectors.

Connection

Check the manufacturer's data to establish the boost pressure limits.
On the majority of petrol engine vehicles, the boost reading is taken from the inlet manifold.
Connect the boost gauge hose into a convenient take-off pipe on the inlet manifold. Ensure that the connection is after the throttle butterfly valve (a vacuum will be present with the engine ticking over).
Do NOT connect boost gauge hose into brake servo vacuum line.
Carefully route the boost gauge hose back to the dashboard. Do not allow hose to foul throttle linkage or any other moving parts i.e., cooling fan, alternator or water pump.
Connect the boost gauge to the hose and place in a convenient position which can easily be read from the driving position.

Testing

Drive the vehicle until a normal water temperature reading is attained.
Choose a long straight empty road (preferably with a gentle incline). Steady the engine speed to around 3000 rev/min and select either third or fourth gear, depending on road speed.
Using your left foot on the brake pedal, gently increase throttle whilst applying the brakes to maintain 3000 revs/min.
When full throttle is reached at 3000 rev/min check the boost reading on the gauge.
If the boost pressure requires adjustment, consult the manufacture's recommendations.

IMPORTANT NOTES:

If, whilst taking a boost reading, pinking or detonation is audible from the engine, the test should be aborted to prevent damaging the engine.

This test will overheat the vehicle's brakes in a short time. The test procedure must be conducted within five seconds to prevent brake fade.

Only conduct testing on a private test ground or closed road.

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