Engine Efficiency - Community College of Philadelphia



Engine Efficiency

Thermal Efficiency

35% lost to cooling and lubrication

35% lost to exhaust gas

5% loss in engine friction

10% loss in power train friction

End result %15 of gasoline power is applied to wheels!

Volumetric Efficiency

Amount of air that fills the cylinder VS how much can it hold?

Variables include intake, exhaust, and valve timing and sizes.

Other types of engine designs;

Atkinson Cycle Engine

Uses the idea that the intake valve is left open longer - past BDC compression. When used with a variable valve timing system, it allows control over engine displacement!

Highway = 2.0 L

WOT or high load = 2.5 L

Advantage, efficient

Disadvantage requires variable valve timing and extra hardware.

Two Stroke Engines.

Every TDC stroke is a power stroke.

Advantage - more power per RPMs.

No Valves.

Disadvantage - VERY dirty engine to run.

Loud. Smoky. Poor cold running since engine runs so rich.

Wastes fuel since some of it blows out the exhaust with each stroke

No low RPM torque

Diesel Engines

Uses more fuel than air

All are injected

Needs glow plugs to pre-heat fuel when cold

Runs on compression, has no ignition system or spark

Can run on Kerosene, Corn Oil, Peanut Oil.

Uses a fuel pump to act as speed of engine

Advantages - Very efficient with the fuel it uses.

Very high torque.

Disadvantages - “soot, noise”

Water in fuel

Dirt in fuel

Vibration

Thank GM….

Modern diesels are far better at being clean, and low noise generators.

Some diesels are as fuel (MPG wise) as a Hybrid, and do so w/o the electric motor and battery! Up to 60 MPG!

Rotary Engine

Felix Wankel

Two Cycle design, however has no pistons and valves.

Uses two plugs per rotor

Very high power w/small displacement

Very high and never ending HP curve

Limited only by speed of external engine parts

Advantages - 3 total moving parts!

Disadvantages - Seems to get 20 MPG

Apex seal failure 60K miles

Fairly dirty, older ones used 4 converters, inline…!

Miller Cycle

Similar in design and idea to the Atkinson cycle engine

Uses a super charger as well as the modified intake stroke of the Atkinson cycle

Stratified Charge Engine

Uses both a rich and lean mixture in the same cylinder

More of a cylinder head design

Your Honda engines were like this.

Uses a 3rd intake valve to do this.

Motor oils

API

SAE

What it does

S/C ratings

Synthetic oils

5w30 vs 10w40?

What does that mean?

Oil Pump

Filters

Pressure Relief Valve

Bearings

Oil Level

Pressure Gauge

Water Cooling Systems

T-stats

Water Pumps

Coolant Types

Radiator

Heater Core

Hoses

Pressure Cap

190~210 deg F.

Add Ons:

Oil Pressure Gauge

Oil Temperature Gauge

Oil Cooler

Lower Temperature Thermostat

Deeper core radiator

More cooling fans

Oil Pressure Tests:

Why?

Oil Pressure warning system/gauge

Engine Knocking or noise

Check oil level

Quality

Last oil change?

Filter brand?

Grade of oil?

Locate oil grades and quantities

Locate and test oil pressure sender circuit

How they work: Switch is grounded to engine block when pressure is low, completes ckt and turns on warning light.

How to test. Jump sensor wire to ground with engine running, and check status of warning light. Check sensor resistance between sensor output and ground. Resistance should change when engine is started.

Remove sensor

Install pressure gauge

MAKE SURE THREADS ARE THE SAME!!!

Start engine

Check for leaks

Check hose

Routing around hot engine parts!!!

Warm up engine to operating temp

(Use Thermo gun, or wait until cooling fans cycle once)

Run engine at 2000 RPM.

Measure pressure at idle and 2000 rpm

Check with specs in Mitchell’s On Demand.

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