Santana PS-10, Service Manual

Page: 417 / 627

ENGINE FUEL AND EMISSION CONTROL SYSTEM 6C-35
Experimental measurements
The map can be measured:
- on the injector work bench
- in the engine on the bench
In both cases an injection pressure is established and the
injectors are tested (if done on the bench, more than one injector
can be measured at the same time) with and electrical control
of duration (ET) and of fixed frequency (NG).
On the injector work bench, the measurement of the injected
amount is carried out directly, accumulating, during a specified
time, the fuel in graduated cylinders, dividing the accumulated
amount by the number of injections.
With the engine on the bench, the injected amount (QCARB) is
measured indirectly by the fuel consumption, generally measured
with a gravimeter and expressed in kg/h. The measurement is
carried out during a sufficiently long period to smooth out errors.
In any case, the engine speed and the injection pressure must
remain constant during the measurement. Moreover, all the
recyclers (pump, pressure restricters, injectors) must be replaced
in the circuit after the meter until the measurement remains
unaltered.
The injected amount for each injector for each cycle is :
6
10
8
1 1
60
1
⋅ ⋅ ⋅ ⋅ =
eNG
C Q
n c
Where:
Q
c
: amount injected in mm
2
/cycle/cylinder
C
n
: hourly consumption in kg/h
NG: regime r/min
d
: fuel density in kg/dm 3
(
d
diesel
= 0.835 kg/dm 3 )
while:
2
⋅ =
t
c
N
N
e
with:
N
c
number of cylinder
N
t
number of strokes (2 or 4)
It is plain that in the case of the bench test, the flow is measured
separately in each of the injectors, while with the engine on the
bench, the flow is measured on the number of injectors; in the
latter it is impossible to know if there is inequality between the
injectors. Therefore, it is useful to measure the temperature of
the exhaust gases in each cylinder, a safe enough index of the
torque distributed by each of the cylinders and consequently of
the amount of fuel injected in each cycle. Based on these
measurements, it can be determined if the working of the injectors
is similar. For this it is necessary to place thermocouples or
thermometers in contact with the exhaust manifold outlets, in
the zones near the fixing clamp at the cylinder head.