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TEKNOLOGI OTOMOTIF DASAR

(2 sks TEORI)

* Motor 2 & 4 Tak (Diagram P-V & Diagram Kerja)

BENI SETYA NUGRAHA, M.Pd.

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Topik Minggu LaluProses Pembakaran (Normal, Knocking,

Detonasi)Engine Operating CycleSiklus 2 & 4 Tak (Pendahuluan)

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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

Stroke

Exhaust

Stroke

A

I

R

Combustion

Products

Ignition

Intake

Stroke

FUEL

Fuel/Air

Mixture

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Animasi Motor 4 Tak

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Diagram PV (Pressure-Volume Graph) 4-stroke SI engine

One power stroke for every two crank shaft revolutions

1 atm

Spark

TC

Cylinder volume

BC

Pressure

Exhaust valve

opens

Intake valve

closes

Exhaust

valve

closes

Intake

valve

opens

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IVO - intake valve opens, IVC – intake valve closes

EVO – exhaust valve opens, EVC – exhaust valve opens

Xb – burned gas mole fraction

Motored Four-Stroke Engine

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Pressure (bar)

100

Intake Exhaust

TC

BC

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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

Valve overlap

Exhaust gas

residual

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Pressure (bar)

100

Intake Exhaust

OVERLAPPING

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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

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Two Stroke Spark Ignition Engine

Intake (“Scavenging”)

Compression Ignition

ExhaustExpansion

Fuel-air-oil

mixture

Fuel-air-oil

mixture

Crank

shaft

Reed

valve

Exhaust

Port*

Transfer

Port*

*No valves and

thus no camshaft

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Animasi Motor 2 Tak

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EPO – exhaust port open

EPC – exhaust port closed

IPO – intake port open

IPC – intake port closed

Two-Stroke CI Engine

scavenging

Ai

Ae

Intake area (Ai)

Exhaust area (Ae)

PiPe

Exhaust Press (Pe)

Intake Press (Pi)

Cylinder Press (P)

110 CA

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Cross Loop Uniflow

Pembilasan pada Motor 2 Tak

(Scavenging in Two-Stroke Engine)

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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

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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

(TDC)

540 CA

(BDC)

360 CA

(TDC)

4-stroke

2-stroke

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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

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DIAGRAM PROSES KERJAMenghitung:Panjang Proses (=Langkah): Jumlah Derajat Putaran 1 Siklus

Jml Proses (=Langkah)Jarak Proses (=Langkah): Jumlah Derajat Putaran 1 Siklus

Jml Silinder MotorContoh:Motor 4 Tak 4 Silinder FO (Firing Order): 1-3-4-2

Gambarlah:Diagram EngkolDiagram Proses Kerja

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DIAGRAM PROSES KERJAPanjang Proses (=Langkah) = 2 x 360 CA

4= 720 CA 4= 180 CA

Jarak Proses (=Langkah) = 2 x 360 CA4= 720 CA 4= 180 CA

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DIAGRAM PROSES KERJAFO: 1-3-4-2Diagram Engkol:

Cyl: 1 , 4

CA: 0 , 720

(TDC)

Cyl: 2 , 3

CA: 180 , 540

(BDC)

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DIAGRAM PROSES KERJA

CYL/CA 0 180 360 540 720

1 INTAKE COMPRESSION POWER EXHAUST

2 COMPRESSION POWER EXHAUST INTAKE

3 EXHAUST INTAKE COMPRESSION POWER

4 POWER EXHAUST INTAKE COMPRESSION

1

2

3

4

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TUGASGambarlah Diagram Engkol & Diagram

Proses KerjaMotor 4 Tak 6 Silinder, FO: 1-5-3-6-2-4Motor 4 Tak 6 Silinder, FO: 1-3-5-6-4-2

Lengkap dengan perhitungannya!Kumpulkan pada TM y.a.d!

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Minggu depan belajar durasi katup & panjang langkah efektif

See U Next Week,

Wassalaam...