Variable Exhaust Gas Paths for Motorcycle Noise and Torque
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Solution Overview
Problem
High-performance motorcycles face challenges in meeting legal noise restrictions without compromising engine performance and torque, as existing exhaust systems either restrict exhaust gas flow excessively or experience turbulence due to flaps, leading to inadequate performance at high speeds and noise levels.
Innovation Solution
An exhaust system with two fluidically separated flow paths, where a controllable flap directs exhaust gas through one or both paths based on speed, ensuring optimal flow and noise control by prioritizing an acoustically optimized path at low speeds and a power-optimized path at high speeds, with the first flow path being larger in diameter for high performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a single flow path with a controllable flap is used to limit exhaust gas stream, then noise level is reduced, but the entire exhaust gas stream experiences strong turbulence and performance is significantly reduced
Solution Approach 1:
The exhaust system is divided into two separate flow paths (first and second flow paths) that are fluidically separated from each other. Each path can be independently controlled, allowing the system to route exhaust gas through different paths based on operating conditions. This segmentation eliminates turbulence in the restricted path since the flap only affects one path while the other remains open for high-performance operation.
2Object-affected harmful factors
If the exhaust gas stream is limited to meet future noise level limits, then noise is reduced, but the desired performance is no longer achieved
Solution Approach 1:
The system dynamically switches between different flow path configurations based on engine speed and load conditions. At low speeds, the flap closes the first flow path and directs exhaust through the second flow path for noise reduction. At high speeds, the flap opens to allow exhaust through the first flow path for maximum performance. This dynamic adaptation allows the system to meet noise limits across all operating ranges without sacrificing high-speed performance.
3Object-affected harmful factors
If a flap is arranged in the flow path to limit exhaust gas stream as a function of speed, then noise is controlled, but strong turbulence occurs and torque curve is negatively impacted
Solution Approach 1:
By segmenting the exhaust system into two separate flow paths, the turbulence caused by the flap is confined only to the first flow path when it is closed. The second flow path remains completely open and turbulence-free, allowing optimal exhaust flow and torque generation. This segmentation isolates the noise-control mechanism from the high-performance flow path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution maintains sufficient power and torque across all speed ranges while meeting legal noise requirements by optimizing flow paths, allowing for direct noise control and ensuring unlimited flow through the second path at high speeds.
Implementation Method 1
a controllable flap directs exhaust gas through one or both paths based on speed
Implementation Method 2
the acoustics of which meets the legal requirements
Data Source
AI summary
An exhaust system for internal combustion engines has an exhaust tract, which has at least one first flow path and a second flow path for an exhaust gas stream. The first and the second flow path extend fluidically separated from each other from a pre-silencer to at least one end silencer. Depending on the rotational speed of the engine, the first flow path can be continuously closed by way of a controllable flap, wherein the exhaust gas stream is guided through the second flow path when the flap is closed.