5.
AIR INTAKE SYSTEM
CONTENTS
1. GENERAL ..... 5-1
2. AIR CLEANER ..... 5-1
3. REQUIRED AIR VOLUME ..... 5-4
4. INTAKE RESISTANCE ..... 5-4
5. TURBOCHARGER ..... 5-5
[1] GENERAL ...... 5-5
[2] COMPONENTS OF TURBOCHARGER ...... 5-5
KUBOTA APPLICATION MANUAL
AIR INTAKE SYSTEM
1. GENERAL 2. AIR CLEANER
The intake and exhaust system is very important for (1) General
engines. The air cleaner, of which purpose is to purify intake air,
In order to operate an engine smoothly, the intake and has two types, ; the dry type and wet type. The dry-type
exhaust system must be efficient enough for maximizing air cleaner, which is generally used in most cases, uses
the functions of highly reliable valve mechanism. It is a filter paper element and therefore dust removing
best to feed clean, low temperature (i.e. high density) air efficiency is very high regardless of the engine speed.
to the engine intake. (99.5-99.8%)
The intake system supplies the air required for In KUBOTA diesel engines, the dry-type air cleaner are
combustion. Insufficient air intake decreases engine employed as standard part for all models.
output. If air is not clean, wear increases on the piston,
rings and cylinder and lubricating oil smear will tend to (2) Structure of dry type air cleaner
shorten engine life. Dust or air containing moisture will infiltrate into air
cleaner through the inlet installed perpendicularly on the
Crossflow system bodies outer circumference and direct vortex flow along
Intake air temperature tends to rise if exhaust gas the guide is created inside the body.
passages are near the intake passage ; this leads to After this, the air passes through the element and will
decreased output. To prevent this, KUBOTA engines further be purified.
use a crossflow system. The element is made of high-quality paper filter and can
As shown in the diagram, the KUBOTA engine employs inhibit infiltration of very fine dust (20 ). Dust separated
the crossflow system which separates the intake and by the vortex flow will be collected into the rear-side and
exhaust systems in opposite side of the cylinder head. cover and then passed into the evacuator valve.
This arrangement effectively prevents heating of intake
air by exhaust heat which would result in decreased This evacuator valve will open and close automatically in
output. The crossflow type cylinder head provides better accordance with pulsation of suction air and discharge
volumetric efficiency of the intake, alternately placed the dust.
intake and exhaust ports minimize cylinder head
distortion due to exhaust gas heat. The following
sections cover important elements of the intake and
exhaust systems.
(1) Inlet manifold (4) Exhaust port Fig. 5-2 Structure of air cleaner
(2) Combustion chamber (5) Exhaust manifold
(3) Intake port
Fig. 5-1 Crossflow type cylinder head
[5-1]
KUBOTA APPLICATION MANUAL
1) Structure of single element air cleaner (3) Selection of air cleaner
This air cleaner is the most popularly used type for the 1) Conditions for selection
small-size general purpose diesel engine and is a ) Amount of suction air
composed of the air cleaner body, outer element, rear- b ) Environmental conditions of dust
side end cover, dust-evacuator valves, etc. The outline Small-amount dust conditions :
of the structure is shown in the Fig. 5-3. Generator, forklift, carrier, etc.
Large-amount dust conditions :
Agricultural machinery, construction machinery
c ) Mounting conditions
Mounting to engine, or mounting to machine
d ) Destination
Use in advanced countries, or to developing countries
e ) Use conditions
Operating hours and quality of maintenance
f ) Cost
Initial cost and maintenance cost
2) Selection of air cleaner and the cautionary
items
a ) Cautionary items for environment
In case that an air cleaner is used in high dust
concentration areas (high-temperature or high-
humidity area), a model of sufficient capacity should
Fig. 5-3 Structure of singleelement air cleaner be used. (It is required to use the air cleaner of one
size higher capacity than those to be used in ordinary
areas.)
2) Structure of doubleelement air cleaner
The air cleaner should be the doubleelement type.
The air cleaner of doubleelement structure is used for the
Reduction in the life of the air cleanerelement
engine to be used in more severe environmental
(clogging) is often caused by comparatively small-
conditions such as the case of construction machinery
sized dust. However, in the case that there is a
and sweeper where the amount of dust is large. This
possibility that the suction port (air intake) of air
type is made by adding the inner element to the
cleaner may be clogged by large-size dust (such as
previously-described singleelement air cleaner and the
fallen leaves and straw dust), it is required to move
structure is shown in the following figure.
the suction port to a location with less dust or to install
a pre-filter to remove such large-size dust.
In the case that there is a possibility that the air
cleaner may suck in water, a water drain hole or
water-separating device should be installed. Be very
careful to prevent the water entering engine when
washing the machine.
b ) Caution items when mounting to engines
Vibration of air cleaner should not exceed the rated
value verified in the field operation of the actual
machinery.
Large vibration will cause damage to various parts or
allow dust leakage of the element (including the
element gasket section).
Fig. 5-4 Structure of doubleelement air cleaner
[5-2]
KUBOTA APPLICATION MANUAL
Be careful so that the suction port of air cleaner is not When cleaning the element, it should be done by
subjected to the detrimental conditions such as the blown air or water washing. (Depending on the kind
followings : of the element, water washing is allowed, or specified
a) Air cleaner should not inhale hot air, such as the detergent can be used.) In case of blown air
hot side cooling air of radiator. remember to blow air from the inside toward the
b) Air cleaner should not inhale exhaust gas. outside.
Particularly fine carbon will cause to early When removing the element, stop the engine.
clogging. In case that there is a pin hole on the element, replace
c) Air cleaner should not inhale the material having it with new one.
viscosity such as mist of crankcase.
Cautionary items when piping to the air cleaner Installation example of air cleaners are shown :
a) Is the inner diameter, length, or bending of pipe
appropriate ?
Be careful so that the intake air resistance should
not be too great.
b) Is the dust seal of piping system complete ?
If there is even the least gap in the suction air
system, it will result in the early wear of the moving
parts of engine.
Therefore, checking of the following items is required.
1) Is clamping force of the hose clamp sufficient, and
will not the hose clamp be loosened by vibration ?
Are all hose connection “rubber to metal”.
Are all rubber hose connections tight on metal
connections.
2) Is strength of the hose sufficient ?
(Will not distortion or damage of the hose be
incurred by negative suction pressure or positive
suction air pressure ?)
3) Will dust infiltrate through the screw holes ?
c) If an extension pipe is installed to the suction port,
or the hose between air cleaner and intake Fig. 5-5 Air cleaner installations
manifold is too long, it may result in an engine
output decrease or smoke increase.
c ) Cautionary items on maintenance
Maintain the air cleaner within the time specified in the
operators manual. (In the case of the air cleaner
provided with a dust indicator, maintainance should
be performed after the warning of clogging is
indicated.)
Unnecessary maintenance will be the cause of
problems, such as the damage or deformed element.
Be careful so that dust adhered on the element
should not infiltrate to the outlet side of air cleaner
when removing the element.
Fig. 5-6 Air cleaner installations
[5-3]
KUBOTA APPLICATION MANUAL
3. REQUIRED AIR VOLUME 4. INTAKE RESISTANCE
The volume of air required during engine operation can Resistance of the intake system is caused by the air
be determined by the following formula. cleaner and intake piping. This resistance must be kept
below a certain point. To prevent decrease of engine
Q1 = Vh N C k 10-3 output, this resistance must be held within the following
limits :
where as : Q1 = Amount of intake air (m3/min)
Vh = Total displacement (liter) (1) Resistance caused by air cleaner
N = Engine speed (r/min) Dry-type air cleaner (paper cleaner)
C = Coefficient 4 cycle 0.5 Initial stage 200 mm (7.87 in.) Aq max.
= Intake efficiency 0.85 to 0.87 After use 500 mm (19.69 in.) Aq max.
k = Coefficient
Natural aspirated engine : 1.0 (2) Resistance caused by intake piping
Turbo charged engine : 1.5 100 mm (3.937 in.) Aq max.
providing that :
1 mm Hg = 13.595 mm Aq
The intake efficiency of KUBOTA diesel engines shall be 1 in. Hg = 13.595 in. Aq
as follows :
Natural aspirated engine 1 mm Aq = 0.07356 mm Hg
Engines of 3000 r/min or less : 0.87 1 in. Aq = 0.07356 in. Aq
Engines of 3600 r/min or less : 0.85
Turbo charged engine : 0.80 Note 1 : Measurement position :
At intake manifold inlet or inlet to turbocharger
The air volume required for KUBOTA diesel engine is Note 2 : Initial total resistance (resistance caused by
refered to in section. (TECHNICAL INFORMATION) cleaner and piping) should not exceed 250 mm Aq
(9.84 in. Aq)
Example Calculation The intake piping should be made of a high quality
compounded rubber with exceptional resistance to
[Engine model : V2203, Engine speed : 2800 r/min] aging, oil and cold to reduce chances of cracking
during operation.
Q1 = Vh N C k 10-3
Vh = 2.197 lit
N = 2800 r/min
C = 0.5
= 0.87
k = 1.0
Q1 = 2.197 2800 0.5 0.87 1.0 10-3
= 2.68 m3/min
Fig. 5-7 Intake resistance measurement point
[5-4]
KUBOTA APPLICATION MANUAL
5. TURBOCHARGER
[1] GENERAL
If air can be drawn in at a greater rate before it enters the
cylinder more fuel can be burned and the output will be
increased.
A turbocharger discharges the compressed air into the
cylinders by a turbine using energy of the exhaust gas as
power. Use of a turbocharger allows a small engine to
have a high output.
[2] COMPONENTS OF TURBOCHARGER
The turbocharger is a compact unit mounted on the outlet
of the exhaust manifold.
It consists of a turbine portion to convert exhaust gas
energy into a rotating force, a compressor to compress
intake air, a waste gate valve to prevent excessive
pressures at high speed operation, a lubricator to supply
engine oil to bearings and a boost compensator to adjust
the fuel injection amount at low speed and during
acceleration.
(1) Waste gate piping (4) Turbine
(2) Compressor (5) Exhaust port
(3) Lubricating piping (6) Lubricating oil return pipe
Fig. 5-8 Example of turbocharger
[5-5]
