The Carnot cycle has a low mean effective pressure because of its very low work output. Hence, one of the modified forms of the cycle to produce higher mean effective pressure whilst theoretically achieving full Carnot cycle efficiency is the Stirling cycle. Please see the link: https://www.sciencedirect.com/topics/chemical-engineering/Stirling-cycle
"On the strength of the core invention (the regenerator) the Stirling cycle suffers from a reputation of having the Carnot efficiency as its ultimate limit."
Three power producing cycles have been so far known that include two isothermal processes, namely, Carnot, Stirling, and Ericsson. It is well known that the efficiency of the Carnot cycle represented by 1−𝑇𝐿/𝑇𝐻 is independent of its working fluid. Using fundamental relationships between thermodynamic properties including Maxwell's relationships, this paper shows in a closed form that the Ericsson and the Stirling cycles also possess the Carnot efficiency irrespective of the nature of the working gas.
The important aspect of the results presented in this note is that the Carnot cycle is not the only one which possesses the highest efficiency among engines operating between the same low- and high-temperature thermal reservoirs. Indeed, the idealized Ericsson and Stirling engines are as efficient as the Carnot engine. These results reveal that the class of heat engines which undergo two isothermal processes has the same efficiency irrespective of the nature of the working substance. So, the Ericsson and the Stirling cycles would deserve to be introduced in thermodynamics classrooms and textbooks; especially considering their practical importance. Article Substance Independence of Efficiency of a Class of Heat Engi...
What is missing in the question is whether it is a simply a question for a student in a class on thermodynamics or is there interest in looking at what real efficiencies are like. Some class of answers for the former are indicated by others.
If it is the latter, it can be stated that real engines always show up much less efficiency than Carnot efficiency. Making engines compact demands the heat release be performed within a certain time. This leads to broad results that reciprocating engines operating on gasoline and diesel have efficiencies between 10 to 50 % (cal value to electrical energy) depending on the size of the system -a few kWe to 50 MWe range. The smaller engines operate at high speed ~ 5000 rpm and larger high power engines operate at as low a speed as a few hundred rpm. As different from this, Stirling engines of low power have efficiencies of 2 to 5 %, larger systems are claimed to go up to 30 %, but the manufacturers of these engines seem to close down their industries over a time as has happened in Europe some times.
The Carnot Cycle, the Ericsson Cycle and the Sterling Cycle when operating between two identical constant temperatures all have the same maximum efficiency. These ideal cycles use the same ideal working fluid. The Carnot Cycle consists of two isothermal processes and two isentropic processes. The Ericisson Cycle consists of two isothermal and two constant pressure processes, and the Sterling Cycle consists of two isothermal and two constant volume processes. When building engines to operate on these cycles, I doubt if the Carnot cycle machine has ever been made to function. A little effort has been made to produce a machine to work on the Ericisson cycle and a lot of effort has been made to produce a Sterling Cycle machine. Phillips BV have produced designs for Sterling engines and have used them in reverse in the field of cryogenics. Small ones as toys have been quite successful. Stephen.
The Carnot efficiency is always more than the efficiency of other cycle. It is the maximum theoretical efficiency that can not be achieved in practical applications but we use it to compare the actual efficiency of other power cycle to see how close (optimum) their efficiency to Carnot.