TEKNOLOGI OTOMOTIF DASAR (2 sks TEORI) TEKNOLOGI OTOMOTIF DASAR (2 sks TEORI) * Motor 2 & 4 Tak (Diagram P-V & Diagram Kerja) BENI SETYA NUGRAHA, M.Pd.

Topik Minggu Lalu Proses Pembakaran (Normal, Knocking, Detonasi) Engine Operating Cycle Siklus 2 & 4 Tak (Pendahuluan)

Siklus Kerja Motor Bensin 4 Tak (Four stroke Spark Ignition (SI) Engine) Stroke 1: Fuel-air mixture introduced into cylinder through intake valve Stroke 2: Fuel-air mixture compressed Stroke 3: Combustion (roughly constant volume) occurs and product gases expand doing work Stroke 4: Product gases pushed out of the cylinder through the exhaust valve Compression Stroke Power Exhaust A I R Combustion Products Ignition Intake FUEL Fuel/Air Mixture

Animasi Motor 4 Tak

Diagram PV (Pressure-Volume Graph) 4-stroke SI engine One power stroke for every two crank shaft revolutions Pressure Spark Exhaust valve opens Exhaust valve closes 1 atm Intake valve closes Intake valve opens TC BC Cylinder volume

Motored Four-Stroke Engine Pressure (bar) 100 10 BC TC Intake Exhaust IVO - intake valve opens, IVC – intake valve closes EVO – exhaust valve opens, EVC – exhaust valve opens Xb – burned gas mole fraction

Four-Stroke SI Engine OVERLAPPING Pressure (bar) 100 Valve overlap Exhaust gas residual 10 Intake Exhaust IVO - intake valve opens, IVC – intake valve closes EVO – exhaust valve opens, EVC – exhaust valve opens Xb – burned gas mole fraction

Siklus Kerja Motor Bensin 2 Tak (Modern Two-Stroke Spark Ignition Engine) Stroke 1: Fuel-air mixture is introduced into the cylinder and is then compressed, combustion initiated at the end of the stroke Stroke 2: Combustion products expand doing work and then exhausted * Power delivered to the crankshaft on every revolution

Two Stroke Spark Ignition Engine Exhaust Port* Transfer Port* Fuel-air-oil mixture Reed valve Expansion Exhaust Intake (“Scavenging”) Crank shaft *No valves and thus no camshaft Fuel-air-oil mixture Compression Ignition

Animasi Motor 2 Tak

Two-Stroke CI Engine EPO – exhaust port open EPC – exhaust port closed IPO – intake port open IPC – intake port closed Cylinder Press (P) scavenging 110 CA Exhaust area (Ae) Ae Intake area (Ai) Ai Intake Press (Pi) Pi Pe Exhaust Press (Pe)

Pembilasan pada Motor 2 Tak (Scavenging in Two-Stroke Engine) Cross Loop Uniflow

Power to weight ratio (PWR) lebih besar dibandingkan motor 4 tak MECH 435 Kelebihan Motor 2 Tak: Power to weight ratio (PWR) lebih besar dibandingkan motor 4 tak karena menghasilkan tenaga setiap putaran poros engkol. Konstruksi sederhana, hanya ada saluran (ports) - tidak perlu mekanisme katup yang rumit Perawatan lebih mudah Banyak diaplikasikan pada motor kecil : sepeda motor, motor tempel, kompressor, pemotong rumput, gergaji mesin (chain saw), ............. Kekurangan Motor 2 Tak: Pembilasan kurang sempurna (tidak selesai/terlalu bersih)  Emisi tinggi, bahan bakar tidak ekonomis Proses pembakaran tidak bersih karena membakar oli  Emisi tinggi

Single Cylinder Engine Motor 2 Tak menghasilkan Power (Langkah Usaha) setiap 1 putaran poros engkol (360 CA). Motor 4 Tak menghasilkan Power (Langkah Usaha) setiap 2 putaran poros engkol (720 CA). Interval torsi yang dihasilkan motor cukup jauh, menyebabkan getaran pada mesin. Dimensi mesin sangat kompak sehingga motor 1 silinder umumnya diaplikasikan pada kendaraan kecil. 180 CA (BDC) 0 CA (TDC) 720 CA 540 CA 360 CA 4-stroke 2-stroke

Multi-cylinder Engines Multi-cylinder engines digunakan untuk mendistribusikan volume silinder motor pada beberapa silinder. Keuntungannya memperpendek interval torsi yang dihasilkan motor, sehingga mengurangi getaran dan menghasilkan karakter torsi yang dihasilkan lebih rata/halus. Konfigurasi yang umum digunakan: a. Inline b. V c. Boxer

DIAGRAM PROSES KERJA Menghitung: Panjang Proses (=Langkah): Jumlah Derajat Putaran 1 Siklus Jml Proses (=Langkah) Jarak Proses (=Langkah): Jumlah Derajat Putaran 1 Siklus Jml Silinder Motor Contoh: Motor 4 Tak 4 Silinder FO (Firing Order): 1-3-4-2 Gambarlah: Diagram Engkol Diagram Proses Kerja

DIAGRAM PROSES KERJA Panjang Proses (=Langkah) = 2 x 360 CA 4 = 720 CA Jarak Proses (=Langkah) = 2 x 360 CA

DIAGRAM PROSES KERJA FO: 1-3-4-2 Diagram Engkol: Cyl: 1 , 4 CA: 0 , 720 (TDC) Cyl: 2 , 3 CA: 180 , 540 (BDC)

DIAGRAM PROSES KERJA 1 4 2 3 CYL/CA 180 360 540 720 1 INTAKE 180 360 540 720 1 INTAKE COMPRESSION POWER EXHAUST 2 3 4 1 4 2 3

TUGAS Gambarlah Diagram Engkol & Diagram Proses Kerja Motor 4 Tak 6 Silinder, FO: 1-5-3-6-2-4 Motor 4 Tak 6 Silinder, FO: 1-3-5-6-4-2 Lengkap dengan perhitungannya! Kumpulkan pada TM y.a.d!

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