1 1 Nabeel Ali 2014-Me-116 (nabeelali1416@gmail.com) 2 Muhammad Ali Hassaan 2014-Me-117 (hassaan204571@gmail.com) 3 Mohib Rafique 2014-Me-114 (mohiblhr@hotmail.com) 4 Muhammad Usman 2014-Me-112 (usmaniqbal15@gmail.com) Abstract Engineers are always thinking about an advanced type of engine which is superior in thermal efficiency and has green emissions. This review paper revolves about the introduction of a new technology in the journey of development of IC engines. This advancement is done on the basis of idea of generating expansion ratio significantly higher than compression ratio. So, a Belgium Engineer name Gerhard Schmitz presented Five Stroke Engine which has better characteristic features than its predecessors and can add up to technological advancements in the field. Its prototype was manufactured by Ilmor Engineering and this concept gained momentum because of extracting more work using extended expansion stroke which is carried out in a low pressure cylinder which has larger volume compared to the two high pressure cylinders and decreased structural weight. This technology also has positive impact as an additional exhaust gas energy recovery which is very interesting and require in future development of IC engine. Keywords Thermal Efficiency, Five Stroke Engine, Back Pressure, Load, Engine Speed, Exhaust. I. INTRODUCTION Racing has for decades led the way in improvements in automobile technology and a new engine seems to be a logical step. That race is really about thermodynamic efficiency. The IC engine works on different principles and various configurations only for getting enhanced power density and reduced consumption of fuel. In past Turbo and supercharger concepts with the four stroke cycle which has identical expansion and compression ratio increased the power density of the engine but due to geometrical factor and requirement of higher expansion ratios and lower compression ratios to limit the mechanical and thermal stresses for getting a better and efficient IC engine, a fifth stroke in the existing four stroke cycle has been introduced. It is a concept to increase the expansion stroke without shortening the compression stroke.[1] A more compact combustion chamber designed for high pressure (HP) cylinders and different and new materials are used in building of Low pressure (LP) cylinder. However, some problems may raise with 5 stroke engine, e.g. power regulation, cooling system and engine balance. Hence, there is birth of a new engine, called a ‘Five Stroke Internal Combustion Engine’.[2] II. HISTORY OF FIVE STROKE ENGINE The idea of an extended expansion is not new and was already in existence more than fifty years ago. In 2003, Belgium engineer Gerhard Schmitz patented the five stroke engine technology.[3] In 2007 the English company Ilmor Engineering Ltd., built a 1,478 cc test bed engine operating on this 5-stroke concept On the test bed a power output of 130hp was measured at 7000 rpm, as was a torque of 166 Nm at 5000 rpm, and a fuel consumption of 226 g/kWh.[4] From mid-2008, a German car manufacturer has also been developing a test bed engine based on the 5-stroke concept. This manufacturer calls this concept “extended exhaust gas expansion”. The GT-Power simulation predicts a consumption of just 204 g/kWh.[5] A. Keromnes in 2013 design an engine based on an in-line, three-cylinder, turbo-charged, port-injection spark ignition engine. This engine has been designed to be used as a range extender with a maximum power of 40 kW. The engine has been tested over a wide range of conditions and the best BSFC is 226.4 g/kWh, which corresponds an engine speed of 4000 rpm and a brake power of 32.8 kW.[6] In the years 2012-2014 at the Cracow University of Technology (CUT) designed an engine of 4 in‐line cylinder, 2 fired and 2 additional Expansion of power 100 KW. The maximum torque is obtained 160 Nm at 3800 rpm. The minimum value of BSFC is 240 g/KWh at 3000 rpm corresponding 123 Nm torque.[7] Review of Development and Validation of Concept of Five Stroke Engine Nabeel Ali 1 , Muhammad Ali Hassaan 2 , Mohib Rafique 3 , and M. Usman 4 , Students, Mechanical Engineering