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Dear Kanjeng Pembaca sekalian,… ketika juragan membahas tentang engine All New Honda Cb150R yang mempunyai bore x stroke 57.3 x 57.8 mm … disebut overstroke banyak yang mempertanyakan …!!! Yaaagh tentu saza juragan dalam menganalisa berpatokan kepada definisi tentang apa itu square engine, apa itu oversquare dan apa itu undersquare …!!! Juragan nggak mau terjebak … tentang ‘marketing’ definition… lebih mengarah ke real technical definition …!!!

An engine is described as a square engine when it has equal bore and stroke dimensions, giving a bore/stroke value of exactly 1:1.
An engine is described as oversquare or short-stroke if its cylinders have a greater bore diameter than its stroke length – giving a ratio value of greater than 1:1. This configuration decreases the torque but allows the engines to run at higher speeds and in fact develop greater peak power. 
An engine is described as undersquare or long-stroke if its cylinders have a smaller bore (width, diameter) than its stroke (length of piston travel) – giving a ratio value of less than 1:1. This configuration increases the displacement and therefore the torque of the engine, but may reduce the peak speed at which it is safe to run.

Square, Oversquare and Undersquare are terms that describe the ratio of  it’s bore and stroke. Bore is the cylinder’s diameter, and Stroke is the piston’s travel from the very top, to the very bottom: square engine has the exact bore and stroke dimensions, undersquare is when the stroke length is longer than the bore, oversquare is when the bore is larger than the stroke length.

Dari 2 (dua) definisi diatas… terlihat kata exactly… alias persis… klop… ratio bore/stroke nya 1 : 1 …!!! So gampang melihatnya… jika bore = stroke nya sama disebut square engine… jika bore > stroke maka disebut oversquare aka overbore, dan sebaliknya jika bore < stroke maka disebut undersquare aka overstroke …!!! Pertanyaannya ada nggak konfigurasi otomotif dengan square engine …???

Di bidang otomotif,… monggo dilihat Honda J30A SOHC VTEC menggunakan konfigurasi 86 x 86 mm… jadi bisa dibilang square engine …!!! Motor Yamaha SS 125 SOHC mempunyai konfigurasi 54 x 54 mm ….!!! BMW M52 dual Vanos juga mempunyai konfigurasi 84 x 84 mm … so ini juga square engine … dan masih banyak lage contoh-contoh yang nggak bisa disebutkan …!!! So kalau sudah bicara tentang definisi yaaagh kudu hitam putih… coz ini soal technical…!!! Nggak bisa seperti marketing yang lebih ‘art’ … sehingga bisa disebut nearly square …!!! Last,… ibarat angka Rp. 1 juta kurang 1 rupiah… apa bisa disebut Rp. 1 juta …???