This inspection applies to
All compression ignition engined vehicles with four or more wheels
Reasons for not carrying out a smoke test
Do not carry out a smoke test if the engine is not in a safe condition
to do so. This will involve questioning the vehicle presenter and
a brief examination of the engine condition. A smoke test must not
be carried out if the oil temperature is below 60°C. The reason
for not conducting a smoke test must be clearly shown on the VT30.
(see introduction 2h)
When to do the test
The smoke test must only be completed when the engine is at normal
operating temperature.
It is not normally sufficient to run the engine with the vehicle
stationary to warm it up to temperature
The engine oil temperature measured by a probe in the oil level
dipstick tube is to be at least 80°C, or normal operating temperature
if lower (60°C minimum). Testing an engine below normal operating
temperature may affect the test result
If owing to vehicle configuration temperature measurement is impractical,
the establishment of the engines normal operating temperature may
be made by some other means, for example by the operation of the
cooling fan or the engine block temperature measured by the level
of infra-red radiation to be at least an
equivalent temperature
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A. Vehicles first used before 1 August 1979
Where possible check that:
. there is sufficient oil in the engine
. the oil pressure Is not too low
. there is no abnormal engine noise
. the governor has not been tampered
with
. the engine is at normal operating temperature
(see Information column)
Raise the engine speed to around 2500 rpm, or half the maximum engine
speed if this is lower
Hold this speed steady for 30 seconds to ensure that the inlet and
exhaust system is fully purged
Allow the engine to return to idle and the emissions to stabilise
1. Assess the smoke emitted from the
tailpipe
2. Rapidly increase the engine speed to around 2500rpm or half the
maximum engine speed if this is lower and assess the smoke emitted
from the tailpipe during acceleration
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A. Vehicles first used before 1 August 1979
1. The exhaust emits dense blue or clearly visible black smoke for
a period of 5 seconds at idle
2. The exhaust emits dense blue or clearly visible black smoke during
acceleration which would obscure the view of other road users
Note: The criterion is density and not volume of smoke. The description
'dense smoke' includes smoke or vapour which largely obscures vision
Older vehicles, particularly pre-1960, sometimes emit unavoidable
smoke due to their design. Such smoke is not a reason for rejection
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Smoke meter probe
With some types of smoke meter care must be taken to ensure that
the probe is correctly aligned to the exhaust gas flow. Reference
to meter manufacturers instruction may be necessary
Suitable smoke meters
Suitable smoke meters are those accepted by VI calibrated and maintained
in accordance with VI's instructions
Suitable engine temperature measuring devices
Suitable engine temperature measuring devices are only those accepted
by VI
Automatic transmission
When testing vehicles fitted with automatic transmission care must
be taken to avoid overheating the transmission system.
Do not carry out unnecessary engine acceleration or prolonged high
rewing of the engine. Reference to vehicle manufacturers instruction
may be necessary
Recording Emissions Test Results
Record the results of the test Via the VTS Device. (se introduction
paragraph 3 at the beginning of this inspection manual)
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B. Vehicles first used on or after 1 August 1979
Where possible check that:
. there is sufficient oil in the engine
. the oil pressure is not too low
. the camshaft belt is in a satisfactory
condition
. there is no abnormal engine noise
. the governor has not been tampered
with
. the engine is at normal operating
temperature
If appropriate, remove oil temperature probe. Raise the engine speed
to around 2500rpm, or half the maximum engine speed if this is lower
and hold for 30 seconds to fully purge the inlet and exhaust system
Raise the engine speed slowly to maximum to check the operation
of the governor. Once the engine speed has stabilised or if it becomes
clear that the governor is not working, release the pedal, return
to idle and stop the engine
Prompt the meter to carry out a zero check
Check that the smoke meter probe can be inserted into the tailpipe
1. Insert the probe fully and securely, in line with the gas flow.
Restart the engine
Fast Pass
Following the meter prompts, depress the accelerator pedal quickly
and continuously but not violently, to reach full fuel position
in less than 1 second
Hold it there until a release prompt is given, then immediately
release the pedal. Allow the engine, and any turbocharger fitted,
to return to idle speed
At the end of the 1 st acceleration read the smoke level displayed
on the meter. If it is at or below 1.50m-1 the vehicle has passed
this part of the test and a pass result will be displayed on the
meter. Go to Method of Inspection 3
2. If the 1st acceleration smoke level is greater than 1.50m-1 carry
out two further accelerations following the meter prompts
At the end of the 3rd acceleration, read the mean smoke level displayed
on the meter. If it is at or below the appropriate limit, the vehicle
has passed this part of the test and a pass result will be displayed
on the meter. Go to Method of Inspection 3
If the mean smoke level is too high, carry out further accelerations
up to a maximum of 6 in total
After each acceleration, check the mean reading. This part of the
test is complete when either:
. the mean of any 3 consecutive smoke readings is at or below the
appropriate limit, or
. six accelerations have been performed
3. Assess whether the smoke emitted from the exhaust, regardless
of measured density, is likely to obscure the vision of other road
users
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B. Vehicle first used on or after 1 August 1979
1. The emissions cannot be measured because a tailpipe accessory
is fitted or a deliberate modification has been made which prevents
insertion of the smoke meter probe
Note: There is no reason for rejection for vehicles that do not
meet the fast pass criteria
2. After 6 free accelerations, the mean of the last 3 smoke levels
is:
a. for a non-turbocharged engine, more than 2.50m-1
b. for turbocharged engines more than 3.00m-1
3. Exhaust emits excessive smoke or vapour of any colour to an
extent likely to obscure the vision of other road users
Note: The criterion is density and not volume of smoke. The description
'dense smoke' includes smoke or vapour which largely obscures vision
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