For Your phrase with these outsized great importance in auto society, "JDM" can be an acronym for a fairly tedious phrase: Japanese Domestic Market. It refers to products built and meant for sale and use within just Japan (i.e., not for export). This involves anything from autos like the Autozam https://elevemotors.com/product/chevrolet-camaro-ls-16-20-oem-2-0l-turbo-engine-motor/