Intake manifold with multiple stage ram induction

Details Intake manifold with multiple stage ram induction Intake manifold with multiple stage ram induction

1999-04-06

2001-04-03

Kamen, Noah P. (Department: 3747)

Internal-combustion engines

Intake manifold

For use with carburetor upstream of manifold

C123S184320

Reexamination Certificate

active

06209502

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of four-cycle internal combustion engines, and more particularly to a multiple stage ram intake manifold for a four-cycle internal combustion engine.
BACKGROUND OF THE INVENTION
Internal combustion engines generate power by igniting a mixture of fuel and air. In order to get the most power from the fuel, that is, for the most efficient operation, many parameters of the combustion process must be optimized. Much research has gone into finding ways to increase efficiency by varying these parameters. As a result, the fuel efficiency, and hence fuel economy of vehicles, has improved dramatically.
Two of the important factors affecting the efficiency of internal combustion engines are air/fuel ratio and volumetric efficiency. Volumetric efficiency is defined as the volume flow rate of air into the intake system divided by the rate at which volume is displaced by the piston. Not only is it important for these parameters to be optimized for each cylinder but it is also important to minimize variations in these parameters. Such variations can occur within a given cylinder at different times, or can occur between individual cylinders in an engine. Undesirable variations in combustion parameters will create imbalances in the engine's operation that will affect efficiency and overall performance.
One example of such an imbalance is known as “odd fire” power impulses. This occurs, for example, in two cylinder, 45-degree V-Twin motorcycle engines. In these engines there occurs an interval of 315 degrees of crankshaft rotation between a first pair of power impulses, followed by an interval of 405 degrees between the following two power impulses. The different spacing results in different air/fuel conditions occurring in the intake manifold when the charge enters the cylinder. Such differences may result from variations in factors such as temperature, pressure or turbulence inside the intake manifold.
In any event, these variations cause the cylinders to fire with different air/fuel ratios and different volumetric efficiencies depending on whether they fire after the 315-degree interval or the 405-degree interval. This affects the way the engine operates, for example it results in timing differences in back-pulse waves through the induction system before mechanical induction demand. This can adversely affect the performance of the engine, causing it to run less smoothly and with lower efficiency. Thus, it would be desirable to provide a way to minimize the variations in the air/fuel conditions between cylinders that result from “odd fire” power impulses.
SUMMARY OF THE INVENTION
An intake manifold for a four-cycle internal combustion engine with multiple stages to reduce imbalances in volumetric efficiency and air/fuel ratio. The intake manifold utilizes at least two ram stages coupled by a plenum chamber. The first stage includes a ram tube that carries the air/fuel mixture from the carburetor, or throttle body to the plenum chamber. The second stage includes at least two ram tubes that carry the air/fuel mixture from the plenum to a plurality of intake valves through cylinder head intake ports.
The plenum chamber acts as a buffer between each intake valve and the carburetor or throttle body. The air/fuel mixture enters the first stage ram tube and passes into the plenum chamber. These gases then pass into either one of the second stage ram tubes, depending on which cylinder is at its intake stroke. By drawing the air/fuel mixture from the plenum instead of directly from the first stage ram tube, differences in the air/fuel ratio and volumetric efficiency are minimized. This is because the transient differences in the conditions that exist within the first stage ram are reduced within the plenum chamber. For example, differences in the air/fuel mixture that depend on the time interval between successive power impulses, resulting from “odd fire” power pulses, are lessened within the plenum chamber. The result is that the conditions within the plenum chamber are much more stable than within the first stage ram tube so that both cylinders receive charges that are more similar and the engine runs in a more balanced manner.


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