TEKNOLOGI OTOMOTIF DASAR 2 sks TEORI Motor 2

TEKNOLOGI OTOMOTIF DASAR (2 sks TEORI) * Motor 2 & 4 Tak (Diagram P-V & Diagram Kerja) BENI SETYA NUGRAHA, M. Pd. 1

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

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

Animasi Motor 4 Tak 4

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 Intake valve closes 1 atm Intake valve opens TC BC Cylinder volume 5

Motored Four-Stroke Engine Pressure (bar) 100 10 BC TC Exhaust Intake IVO - intake valve opens, IVC – intake valve closes EVO – exhaust valve opens, EVC – exhaust valve opens Xb – burned gas mole fraction 6

Four-Stroke SI Engine Pressure (bar) 100 OVERLAPPING Valve overlap Exhaust gas residual 10 Exhaust Intake IVO - intake valve opens, IVC – intake valve closes EVO – exhaust valve opens, EVC – exhaust valve opens Xb – burned gas mole fraction 7

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 8

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 9

Animasi Motor 2 Tak 10

Two-Stroke CI Engine Cylinder Press (P) EPO – exhaust port open EPC – exhaust port closed IPO – intake port open IPC – intake port closed scavenging 110 CA Exhaust area (Ae) Ae Intake area (Ai) Intake Press (Pi) Ai Pe Pi Exhaust Press (Pe) 11

Pembilasan pada Motor 2 Tak (Scavenging in Two-Stroke Engine) Cross Loop Uniflow 12

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 13

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). 2 -stroke 4 -stroke 0 CA (TDC) 180 CA (BDC) 360 CA (TDC) 540 CA (BDC) 720 CA (TDC) Interval torsi yang dihasilkan motor cukup jauh, menyebabkan getaran pada mesin. Dimensi mesin sangat kompak sehingga motor 1 silinder umumnya diaplikasikan pada kendaraan kecil. 14

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 15

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 16

DIAGRAM PROSES KERJA �Panjang Proses (=Langkah) = 2 x 360 CA 4 = 720 CA 4 = 180 CA �Jarak Proses (=Langkah) = 2 x 360 CA 4 = 720 CA 4 = 180 CA 17

DIAGRAM PROSES KERJA �FO: 1 -3 -4 -2 �Diagram Engkol: Cyl: 1 , 4 CA: 0 , 720 (TDC) Cyl: 2 , 3 CA: 180 , 540 (BDC) 18

DIAGRAM PROSES KERJA CYL/CA 0 180 360 540 720 1 1 INTAKE COMPRESSION POWER EXHAUST 2 COMPRESSION POWER EXHAUST INTAKE 3 EXHAUST INTAKE COMPRESSION POWER 4 POWER EXHAUST INTAKE COMPRESSION 2 3 4 19

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! 20

Minggu depan belajar durasi katup & panjang langkah efektif See U Next Week, Wassalaam. . . 21