A new exhaust system for two stroke engines

2023

Aim of the project: A small and compact system capable of creating a variable backpressure wave based on the operating parameters of a small two-stroke engine.

Description: Having the possibility to choose my thesis topic, and having studied the propagation of waves inside ducts, I decided to cover one of my favorite topics: "Two-Stroke exhaust systems" and create a system capable of solving the typical problem of a small two-stroke road engine:

the power delivery only at a well-defined number of revolutions.

To do this I started by looking at the latest discoveries in the technical field, by combining 3 patents I managed to arrive at a solution that on the paper delete their weak points by combining them together.

This system has a rotary valve made of titanium (the weight of the guillotine alone is approximately 10 grams) which, controlled by an electric motor and a dedicated control unit, is able to self-regulate based on the operating parameters of the engine constantly providing a different response at each engine's rotation speed.

Different backpressure wave up to 13'000 RPM with a gear reduction less than 1.4.

To verify the effectiveness of this, a lambda probe has also been inserted, capable of helping the system to understand if part of the fresh charge has been wasted at the exhaust.

The system is very compact and has an external diameter of approximately 25cm (Only case, without gears and e. motor).

To extend its life span, a ceramic coating can also be applied inside and a different type of sealing for the shaft can be applied.

The second part downstream of the guillotine has the function of speeding up the exit of the exhaust gases, lengthening and shortening based on the operating conditions.

Results: A system that, at least on paper, is capable of generating a variable backpressure wave regardless the engine revolutions.

Cross-section view of the system:

Fully assembled system: