United States Patent [19] [11] Patent Number: 4,731,995 McFarland, Jr. [45] Date of Patent: Mar. 22, 1988 [54] EXHAUST MANIFOLD AND AN IMPROVED [56] References Cited EXHAUST MANIFOLD, INTAKE MANIFOLD AND ENGINE COMBINATION U'S' PATENT DOCUMENTS 3,845,746 11/1974 Elsbett‘ ......................... .. 123/52 MB 4,461,248 7/1984 McFarland ..... .. 123/52 MV [75] Inventor: James D. McFarland, Jr., Torrance, 4,510,896 4/1985 Rutschmann ............... .. 123/52 MV Cahf‘ - - Primary Examiner-Douglas Hart Attorney, Agent, or Firm-Christie, Parker & Hale [731 Assignee‘ Edelbrock Corporation, El Segundo, [57] ABSTRACT Calif. An exhaust manifold for an engine has sets of branches tuned to the fundamental frequency of exhaust products [21] Appl. No.: 927,342 but with the branch length of the sets different so that the engine speed at which resonance occurs in each set is different. An inlet manifold has runner sets with each [22] Filed: No" 5’ 1986 set being paired with an exhaust manifold branch set serving the same cylinders and tuned to effect reso [511 Ilt. C1.‘ ...................... .. F02B 27/02; F0213 75/20 nance of combustion air in the runners at the same en [52] U.S. Cl. .............................. .. 60/313; 123/52 MB; gine speed that resonance occurs in its associated ex 123/52 MV haust branches. [53] Field of Search .......... .. 60/313, 312; 123/52 MB, 123/65 E, 52 MV 21 Claims, 10 Drawing Figures Zé Z4 2” /4’ /Z //4 //Q .i I_.._- \_//4 22 US. Patent Mar. 1988 Sheet 1 0f 6 4,731,995 us. Patent Mar.2_2,198‘8- sheet 2 0“ 4,731,995 US. Patent Mar. 22, 1988 Sheet 3 of6 4,731,995 US. Patent Mar. 22, l‘988 ‘ Sheet 4 of6 4,731,995 US. Patent ' Mar. 22, 1988 Sheet 5 of 6 4,731,995 4,731,995 1 2 mixture charged into the cylinders and an increase in EXHAUST MANIFOLD AND AN IIWPROVED - volumetric efficiency compared with a charge from EXHAUST MANIFOLD, INTAKE MANIFOLD AND slower air. More speci?cally, increasing the velocity of ENGINE COMBINATION the mixture at relatively low engine speeds enhances torque. (At high engine speeds, induction losses can BACKGROUND OF THE INVENTION more than offset gains from gas inertia.) . The present invention relates to exhaust and intake Piston speed directly measures the pumping charac manifolds for reciprocating internal combustion en teristics of an engine. The higher the piston speed, the gines. More in particular, the present invention relates more mixture the pistons induct into the engine in a to unique exhaust and intake manifolds that produce a given time period. Piston speed also generates pressure wide band of relatively high engine torque. pulses that affect movement of the mixture in the intake An intake manifold of an internal combustion engine manifold. As the‘ piston descends, a negative pressure conducts combustion air to the cylinders of the engine signal results and this signal travels upstream in the where it burns with fuel. In a fuel injected engine, the manifold. It is this negative pressure that produces in manifold conducts only air; in a carbureted engine, a duction. As the piston ascends, it produces a positive manifold also conducts fuel with the air. In a carbureted pressure signal that travels upstream from the manifold engine, the carburetor typically mounts on a plenum of and opposes induction. The magnitude of the signals is the manifold. The fuel and air mixture enters the ple~ ‘a direct function of piston speed, which varies even at I num from the carburetor, and from the plenum travels. 20 constant engine speed. The pressure signals travel at the to the cylinders through ducts called runners. The run speed of sound; the mixture travels much slower. The ners exit into inlet ports in the cylinder head of the engine. These ports lead to the cylinders through inlet pressure signals can be used to enhance volumetric valves. efficiency by resonance. Generally, a vacuum in each cylinder created by My US. Pat. No. 4,461,248 describes one way to use downward piston movement during an inlet stroke pressure signals in an intake manifold to enhance an draws the fuel and air mixturev into the cylinder. A engine’s performance. This patent builds on the long supercharger or a turbocharger can augment this driv recognized fact that pressure pulses traveling up and ing force. down runners can affect the ?ow of air through run The burning of the fuel-air mixture in the cylinders ners. As a positive pressure pulse, positive with respect generates high pressure products of combustion that to mean inlet manifold pressure, travels up a runner and expand against the pistons during an expansion stroke to reaches atmosphere, which may be in the plenum of the produce the engine’s power. Exhaust valves from the manifold, the air there moves with the disturbance cre cylinders open while the products of combustion are ating a depressed pressure or a locally rari?ed zone. still at high pressure relative to atmospheric pressure. The resulting negative pressure travels down the run This residual pressure, called blow-down pressure, and 35 ners, and it detrimentally affects the ?ow of gas in the the ascent of the pistons in the cylinders force the prod runners by reducing the pressure differential between ucts of combustion from the cylinders into an exhaust the runner and ‘the cylinder. A negative pressure pulse manifold. traveling upstream produced by a descending piston The dynamics of induction of fuel and air into an reduces the pressure in the plenum: air rushes in to fill engine and the exhaust of products of combustion from 40 the low pressure zone, generating a positive pressure an engine are very complicated, making generalizations pulse that travels down the runner toward the cylinder. difficult. Some of the factors affecting induction and If a positive pressure pulse arrives at the cylinder at exhaust include'intake and exhaust valve timing, piston the right time, say when the inlet valve is about to close, speed, gas inertia, gas friction, resonance, intercylinder the pulse can add significant quantities of mixture to the interference, and manifold geometry. 45 cylinder to increase the power of the engine by increas The intake valve timing of today's internal combus ing the volumetric efficiency of the engine. When the tion engines has an inlet valve starting to open while its length of runners is adjusted to take advantage of this companion exhaust valve is in its ?nal stages of closing phenomenon, it is known as intake manifold tuning. The and before its piston reaches top dead center. An inlet time it takes for apressure pulse to travel up and back in valve closes several crank degrees after its piston 50 reaches bottom dead center. On the exhaust side, the a runner depends on runner length. Because the time of exhaust valve opens several degrees before bottom dead the pulse’s arrival back at the inlet port must be close to center on the expansion stroke and closes after top dead the time the inlet port is about to close, the speed of the center and after the exhaust stroke. The timing of inlet engine must coincide with the pulse travel time. Tuning, and exhaust valve opening and closing accommodates in short, works in only limited speed ranges. When a the several crank degrees of engine revolution needed manifold is tuned, it is said to resonate in the engine to get them open an effect amount and to effectively speed range that the positive pressure pulse augments close and to accommodate gas inertia. cylinder charges because the pulse adds to the pressure It is quite apparent that the more mixture inducted driving the charge into the cylinders. into a cylinder with each cycle, the more power an My ’248 patent divides up the runners of an intake engine will have, the more efficient it will be. A mea manifold into sets, with each set being tuned to produce sure of engine efficiency reflecting the amount of cylin resonance at engine speed ranges. The patent also der charge is “volumetric efficiency,” which is the teaches that combustion air speed at resonance should volume of air a cylinder actually receives divided by the ’ be the same as the speed at engine speed maximum volume swept by the piston. With no induction loss, if 65 torque and to adjust runner cross-sectional area so that the air travels fast in the runners towards the end of the this happens. This produces a broader band of high induction cycle, its inertia overcomes the pressure build torque in the enginethan would be the case with all the up at this time and results in an additional amount of runners producing resonating in the same speed range. 4,731,995 3 4 As inlet manifold runner tuning was known long tion of the engine to effect resonance at substantially the before my '248 patent, so was exhaust manifold tuning. same selected two engine speed ranges as the inlet mani Exhaust manifold tuning reduces residual exhaust gas fold. Thus, the exhaust manifold enhances the effects of pressure in the cylinders in a selected engine speed the inlet manifold at a selected range of engine speeds in range so that the inlet charge sees low resistance. The producing augmented performance. idea in exhaust manifold tuning is to get a rati?ed pres In greater detail, the combination includes the inlet sure pulse in the vicinity of the exhaust valve just as manifold having a ?rst set of runners of equal effective combustion air begins to enter the cylinder and combus cross-sectional area with respect to one another.