Engine induction system and method

An engine induction system for reducing engine pumping losses provides for a minimum of two intake valves per cylinder, a primary and secondary, with valve port activation means associated with the secondary valves to control air flow to them so that at light loads only air flows through the primary intake valves, the secondary valves providing air flow at heavier loads, the primary intake valve openings being controlled so that no more than one primary valve is open at any one time; i.e., there is no overlap in openings between primary intake valves, which produces pumping losses at light loads when intake manifold vacuum is high.

This invention relates in general to an automotive type internal combustion 
engine, and more particularly, to a system and method for inducting an 
air/fuel charge into the engine cylinders in a manner to prevent or 
minimize engine pumping losses. 
In the conventional engine, if more than one intake valve is opened at any 
one particular time, the cylinder of the later opening valve must overcome 
the high suction, 15 inches Hg., for example, of the cylinder containing 
the first opened intake valve during the intake charge to the other 
cylinder. This results in an inefficient pumping loss and a lowering of 
the fuel economy. 
This invention provides a system and method of inducting air to the engine 
that reduces or minimizes the engine pumping losses during light load 
operation when the losses are the greatest, and yet provides for greater 
power output at heavier engine loads. 
The invention consists of an induction system for an engine having a 
plurality of cylinders each of which contains at least one primary and one 
secondary intake valve, along with the necessary exhaust valving. A single 
plenum is provided for the main intake of air, with a main throttle valve 
controlling the flow to the plenum. The outflow of air from the plenum is 
made to each individual cylinder intake valve by individual manifold 
runners. The primary runner to each primary intake valve is open at all 
times, whereas to the plenum secondary runner contains a throttle valve 
for variably closing or opening the runner and thereby variably 
controlling the flow of air to the secondary intake valve. The timing of 
opening of the intake valves of different cylinders is such that only one 
primary intake valve is open at any one time, with no overlap between 
primary intake valves, so that no cylinder is forced to overcome the high 
suction prevalent in another cylinder at that time. At light engine loads, 
only the primary intake valves receive air flow; whereas at heavier loads, 
the throttle valve for the secondary runners is progressively opened to 
supply air to the secondary valve to obtain greater power output to the 
engine. 
Constructions to minimize engine pumping losses are known. For example, 
Hall, U.S. Pat. No. 1,212,478, shows an eight-cylinder engine construction 
divided into two banks to in effect constitute two plenums, each providing 
four cylinders. Hall states that there is no overlapping of the valves in 
the four-cylinder engine. Therefore, the assumption is that only one 
cylinder draws at one time on one side of the dividing wall, which 
prevents any one cylinder from robbing another cylinder of a proper supply 
of gas. 
Goodrich, U.S. Pat. No 1,285,129, Funderburk, U.S. Pat. No. 2,119,707, 
Ricardo, U.S. Pat. No. 1,512,311, Anderson, U.S. Pat. No. 1,761,958, and 
Bruderlin, U.S. Pat. No. 3,800,752, all show the use of dual plenums in 
which succeeding cylinders are not adjacent one another; i.e., the 
cylinders in the engine firing order alternate between plenums so that not 
more than one intake valve of one plenum is open at any one particular 
time. 
It should be noted that the above constructions all are for 
one-intake-valve-per-cylinder constructions and that the total charge 
taken into each intake valve, therefore, is a maximum as a function of the 
main throttle valve controlling the flow of air to the manifold. There is 
no secondary intake valve providing a greater power output to the engine 
when such a demand is called for, as in the case in the invention. 
None of the references shows a multi-intake valve per cylinder construction 
wherein light loads are controlled by inducting air only through the 
primary intake valve with no overlap of openings between intake valves, 
and wherein, for heavier loads, air to secondary intake valves is provided 
concurrently to supply more air to the engine to provide the power called 
for. 
It is a primary object of the invention, therefore, to provide an internal 
combustion engine construction that minimizes engine pumping losses while 
providing for the supply of extra air to the engine when necessary to 
provide additional power. 
It is another object of the invention to provide an engine construction 
having a plurality of intake valves per cylinder with individual manifold 
runners connecting each of the intake valves to a central plenum into 
which air is inducted past a main throttle valve controlled by the vehicle 
operator, and in which secondary runners contain additional throttle 
valves for variably controlling the flow of air to the secondary intake 
valves as a function of load demand to minimize engine pumping losses at 
light load operation while supplying additional air to the cylinders for 
heavier load operation. 
It is a still further object of the invention to provide a method of 
inducting air into the engine and a system for inducting such air that 
provides a more efficiently operating engine.

FIG. 1 portrays a portion 10 of an internal combustion engine having an 
induction passage 12 opened at one end 14 to ambient air from, for 
example, a conventional engine air cleaner, not shown. The lower portion 
of passage 12 opens out into a plenum or intake manifold 16, the flow into 
it being controlled by a main throttle valve 18. The latter is fixed on a 
shaft 20 that is rotatably mounted in the walls of the passage 12 to 
control the flow of air through passage 12 by movement between the closed 
or engine idle speed position shown through a part throttle opening 
position to a wide open essentially horizontal position. 
The engine in this case would contain a number of similar cylinders, only 
one being indicated for clarity. A cylinder head 22 defines with the 
piston, not indicated, a combustion chamber 24 into which a charge of fuel 
and air is supplied. In this case, each cylinder head has a pair of inlet 
valve port openings 26, 28 into which are fitted a primary intake valve 30 
and a secondary intake valve 32. The port openings 26, 28 are connected by 
individual intake manifold runners 34, 36 to the plenum 16, as shown. The 
primary runner 34 is open at all times to communication with plenum 16, 
whereas, in this case, the secondary runner 36 contains a secondary 
throttle valve 38. The latter is fixed to a shaft 40 rotatably mounted in 
the walls of the runner for variably opening and closing the runner to 
variably control the flow of air to the secondary intake port 28. 
As thus far described, it will be seen that upon opening of main throttle 
valve 18, air will be inducted into plenum 16 by the downward motion of 
the piston in the engine cylinders so that air also is inducted into the 
main or primary runner 34 and through an open primary intake valve 30 into 
the cylinder combustion chamber. Although the secondary intake valve 32 
also will be open at this time, air will be inducted into secondary intake 
port 28 only as a function of the opening of the secondary throttle valve 
38. With valve 38 closed, all of the air inducted will be through the 
primary runner 34. 
FIG. 1 illustrates operation of the engine during light loads. At this time 
the engine pumping losses are the greatest since the vacuum level in the 
manifold generally is highest at this time. In accordance with the 
invention, as stated previously, therefore, it is desired that only one 
intake valve be opened at a time to prevent the engine pumping losses 
described previously. FIG. 1A illustrates the induction system during 
heavier load operation wherein main throttle valve 18 is opened to beyond 
its light load position. At this point, the secondary throttle valve 38 is 
opened to permit air flow into the secondary intake port 28 to supply 
additional air necessary at this time for greater power output. At the 
heavier engine loads, the vacuum in the intake manifold is approaching 
atmospheric pressure conditions; therefore, the pumping losses at this 
time are essentially minimal and several intake valves of different 
cylinder can be opened at the same time, incurring only minimal pumping 
losses. That is, an overlap could occur between the opening of the intake 
valve of one cylinder and the intake valve of another cylinder because the 
manifold vacuum has decayed and, therefore, the pumping losses would be 
low. 
FIG. 2 illustrates an essentially conventional loop operating diagram of an 
engine as compared with one representative of the engine operating as 
constructed by this invention. That is, the conventional engine with 
normally overlapping intake port openings begins its operation at top dead 
center position of the piston at point 42, proceeds downwardly during its 
intake stroke along the curve 44 towards bottom dead center position of 
the piston at point 46, with the pressure slightly below atmospheric. At 
this point, the piston starts rising during its compression stroke raising 
the pressure as indicated in FIG. 2 above atmospheric or ambient until it 
reaches a maximum at point 48 whereupon ignition occurs and the charge in 
the engine cylinder is ignited. The piston then continues down during its 
expansion stroke toward the bottom dead center position again to the point 
50 wherein atmospheric pressure level is reached and the exhaust valve 
opens. At this point, the piston continues back up towards the top dead 
center position during the exhaust stroke with essentially atmospheric or 
ambient pressure conditions prevailing to return to the starting point 42. 
As stated previously, in a conventional engine with more than one intake 
valve open at any one time, the later opening intake valve cylinder must 
work against the suction of the previously opened intake valve cylinder 
indicated by the curve 44. In the invention of this application, at light 
loads, when only the primary intake valve passage is open for one 
cylinder, and no overlap between primary intake valves of other cylinders, 
the pressure will be very close to ambient or atmospheric as indicated by 
the dotted line curve 52 starting at the point 42. As the induction 
increases during the downward stroke of the piston toward the maximum 
volume position 46, the intake manifold vacuum also gradually increases. 
The graph clearly illustrates in the crosshatched section between curves 
44 and 52, the amount of pumping losses saved by the invention by reducing 
the intake manifold vacuum normally prevalent at the beginning of the 
intake stroke. 
As stated previously, the invention necessitates having no more than one 
primary intake valve open at any one time during light loads where all of 
the valves are connected to a single plenum. This is suitable for an 
engine with four or less cylinders. However, for an eight or six cylinder 
engine, a plurality of plenums would be necessary. In the latter case, as 
seen in FIG. 3, two plenums 54, 56 would be used, with each being 
connected to four cylinders of the engine. A normal firing order would be 
cylinders 1, 3, 7, 2, 6, 5, 4 and 8, which will be seen to assure that not 
more than one primary intake valve of one plenum is open at any one 
particular time. 
FIG. 4 illustrates the control timing for the intake valves of each 
cylinder with respect to each other to provide for minimal pumping losses 
at light engine loads and yet greater air flow for greater power at the 
heavier engine loads. More specifically, FIG. 4 shows a valve plot of 
cylinder number versus engine crank angle with the bar 60 indicating the 
duration of opening of the primary intake valve for the particular engine 
cylinder associated therewith, and bar 62 indicating the opening duration 
of the secondary intake valve associated with that same engine cylinder. 
The mechanism for opening and closing the engine valves in this case 
causes both primary and secondary intake valves of a particular cylinder 
to be opened at the same time, the flow of air to the secondary valve 
ports 28, however, being controlled in this case by the secondary runner 
throttle valve 38. 
The operation as exemplified by FIG. 4 is as follows. During light load 
operation, as seen in FIG. 1, secondary throttle valve 38 will be closed. 
Therefore, as the piston begins moving downwardly from its top dead center 
position seen in FIG. 4, both intake valves 30 and 32 are opened as 
indicated by the bar graph 60, 62. The flow of air to the secondary intake 
port 28, however, is prevented by the closed throttle valve 38. At light 
load conditions, therefore, to avoid opening of more than one primary 
intake valve at any one time, the primary intake valve 60 remains opened 
until the piston reaches just short of the 180.degree. crank angle 
position, at which time it closes. This occurs some degrees before the 
opening of the primary intake valve 30 of the next cylinder, in this case 
cylinder 7, in succession of firing order, as indicated by the bar graph 
64. The intake valve associated with cylinder 7 then closes just prior to 
the piston attaining the top dead center position for a 360.degree. crank 
angle rotation and prior to the opening of the intake valve for cylinder 
six, as indicated by the bar graph 68. The same opening duration and 
closing occurs again for cylinder four, as clearly indicated at FIG. 4. 
It will be seen, therefore, that only one primary intake valve of each 
plenum is open at any one particular time during light load operation with 
no overlap of openings between the primary intake valves of different 
cylinders. The secondary intake valves 32 also are open, but no air is 
supplied to that port because the secondary throttle valves 38 are closed. 
As the load increases, the main throttle valve 18 will be rotated more open 
to provide a greater supply of air to the engine cylinders. Simultaneous 
with the rotation of the main throttle valve, the secondary throttle valve 
38 also will begin to move to an open position to admit air into the open 
secondary intake valve 28. This is illustrated graphically in FIG. 4 by 
the bar graph 62. Since greater power calls for a demand for a greater 
supply of air, in this case, there is Provided an overlap of openings 
between the secondary intake valve of one cylinder and the primary intake 
valve and secondary intake valve of the next succeeding cylinder in 
succession of firing order. This is permissible because the manifold 
vacuum level is low and, therefore, the pumping losses will be low. 
The amount of air directed to the secondary intake port will of course be 
in proportion to the load and the degree of opening of the main throttle 
valve, by means not shown. By a study of FIG. 4, therefore, it will be 
seen that the secondary intake valves all may be opened earlier than 
closing of the previous primary intake valve in the firing order and stay 
open longer than their associated primary intake valve and are open when 
the next primary intake valve in succession opens, so as to provide the 
overlap necessary to supply enough air fuel charge into the cylinder to 
attain the necessary power demanded. 
From the foregoing, therefore, it will be seen that an engine induction 
system construction is provided that minimizes engine pumping losses 
during light load operation by the supply of air through primary intake 
valves alone without overlapping of intake valve openings between 
different cylinders, while at the same time providing secondary intake 
valves for each cylinder, the air flow to which is controlled as a 
function of load to supply additional air when necessary to the engine to 
provide additional power demanded for heavier load operating conditions, 
the secondary intake valve openings overlapping with those of its 
associated primary intake valve as well as the primary intake valve 
openings of the other cylinders to provide the necessary volume of air 
demanded. 
While the invention has been shown and described in its preferred 
embodiment, it will be clear to those skilled in the arts to which it 
pertains that many changes and modifications may be made thereto without 
departing from the scope of the invention.