Sifofin shigarwa da fitarwa na injin ƙarfafawa. Akwai wurin juyawa a kan kowane lanƙwasa wanda ya yi daidai da digiri daban-daban na injin a cikin hoton, wanda ake kira matsakaicin wurin taimakon wutar lantarki, wato, wurin da bambancin matsin lamba da ke aiki akan diaphragm na servo ya kai matsakaicinsa yayin da ƙarfin shigarwa ke ƙaruwa. Daga wannan lokacin, ƙaruwar ƙarfin fitarwa daidai yake da ƙaruwar ƙarfin shigarwa.
A cewar QC/T307-1999 "Yanayin Fasaha don Mai Bugawa ta Vacuum", matakin injinan ...