Carrying Out The Measurement; Description Of The Measuring Instrument - Bosch EFAW 65 B Operating Instructions Manual

1. Method of measuring
The Bosch filter-type smokemeter works according to the paper
filter method. It belongs to the group of the indirect indicating
exhaust-gas measuring instruments.
With the aid of a proportioning pump a certain amount of exhaust
gas is taken from the exhaust pipe of the engine in question and
sucked through a filter paper. The black mark which thereby
appears on the filter paper is a measure of the soot content in the
exhaust. Evaluation of the blackened filter paper is carried out
with an evaluating scale (degree-of-grey shading scale).
2.

Description of the measuring instrument

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1. Metering pump
2. Probe
3. Clamping device
4. Hose
5. Rubber ball
6. Grip head for pump plunger
7. Pneumatic valve
8. Compressed-air supply
9. Rotary knob for filter paper
10. Seal ing cap
11. Rubber plug
The measuring instrument consists of two separate parts:
- Proportioning pump with exhaust-sample pick-up and
- evaluate scale (degree-of-gray shading scale).
2.1 Proportioning pump EFAW 65 B, 0 681 169 058
The proportioning pump is used for exhaust measurements by
means of the acceleration method. The diameter of the sooted
area for filter discs is 12 mm. The suction time is reduced to
6-8 seconds. The proportioning pump is fitted with a magazine
containing a filter-paper roll. By means of a rotating knob the filter
paper is moved along after each measurement. To facilitate the
speedy checking of a large number of vehicles the filter paper is
automatically fitted or removed during forward and rewind. In the
same way the plunger of the proportioning pump can be brought
into working position with compressed air instead of by hand. For
this purpose a compressed-air connection and an actuating valve
are fitted.
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3.

Carrying out the measurement

3.1 Measurement according to the acceleration
method with the proportioning pump EFAW 65 B
This measuring method is particularly suitable for the speedy
checking of a large number of vehicles (e.g. with the Technical
Inspection and Approval Authorities). The proportioning pump
has been designed so that it can be used by one person. The
pump is hung up on a stand and can be taken down by the test
official from within the vehicle cab.
3.1.1 Measurements on the vehicle and on the test stand
Engine operating requirements:
When measurements are made the engine must be running warm.
The cooling-water temperature must be at least 60°C.
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a) The exhaust sample sensor is fitted into the exhaust pipe and
fastened with the clamping divece.
b) The engine is accelerated from idle to maximum speed as
quickly as possible and three times in succession.
c) Approx. 1 second before the 4th. acceleration the suction
stroke should be started by pressing on the rubber ball.
d) By operating the compressed-air cock the plunger is brought
into working position again. The filter paper es moved along
to the next frame by turning the rotating knob )The filter paper
es fitted and removed automatically).
e) Repeat the measurement three times (c and d). Bring the
plunger into working position and tear off the sooted
measuring strip.
3.1.2 Evaluating the sooted filter strip
The sooted surfaces (12 mm Ø) of the filter strip are compared
with the blackened surfaces of the Bacharach scale and at the
point where the degrees of blackening are the same, the value is
read off the scale.
The surfaces of the Bacharach scale have 10 different degrees
of blackening. Degree 0 applies to soot-free exhaust. Degree 9
corresponds to exhaust with a high soot content.