The I-163-1 (initially simply the I-163) was prepared as a production standard in 1937. Externally, it resembled the standard Type 5, but was equipped with an M-25E high-altitude engine (710 hp at an altitude of 5000 m), landing flaps, a modified landing gear design, increased rudder area, and a mast antenna (a radio was supposed to be installed). In a lighter version with two wing-mounted ShKAS machine guns, the I-163's flight weight was about 1,600 kg. The required speed of 490 km/h at an altitude of 6,800 m was not achieved due to unstable engine performance. The improvements introduced on the I-163-1 could not be applied to the serial I-16 type 5.
The I-163-2 was equipped with larger landing flaps and an oil-pneumatic landing gear retraction system. Due to multiple defects, it never flew.
I-164-1 (the first with M-25V) — also known as I-16s (s="escort"), was equipped with two additional fuel tanks in the wings, which increased the fuel capacity to 500 kg and the range to 2,000 km. Initially, the I-164 was rejected due to poor manufacturing quality - serious improvement were necessary. Further tests were discontinued due to leaks in the fuel tanks built into the wing. Repairing the tanks without completely dismantling them proved impossible.
The I-164-2 was initially intended for installation of the M-62, then the M-88. The aircraft was not built.
The I-165-1 with the M-62 engine was also called the I-16bis (not the first with this designation), had additional wing tanks, a new wing with rigid skin (I am not sure, whether it was stressed skin), a modified fuselage shape and engine cowling, and oil-pneumatic retraction of the landing gear. After three flights, the engine had to be replaced. It was planned to install a new wing with a more modern profile and rigid (playwood) skin. Due to a large number of assembly defects, the aircraft was not allowed for further testing.
The I-165-2 was originally designed for the M-62, but assembly was halted in early 1938 when Polikarpov decided to redesign the aircraft for the M-88. This required too much time, so further development was discontinued - the modernization lost its relevance, since the I-180 was already ready.
The I-166 with the M-25V was built on the orders of TsAGI. The main difference from other I-16s was the engine cowling with adjustable cooling flaps, an exhaust manifold, and a front ring oil cooler. The flight weight was reduced to 1,383 kg.
Source:
It is clear that the low technological level of production did not allow for any improvements to be implemented. It is also worth noting the factory's lack of interest in manufacturing prototypes.
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