Emissions Air is made up of : s 21%O 2 s 78%N s 1% other gasses (mostly argon)

Emissions

Air is made up of :

21%O2

78%N 1% other gasses (mostly argon)

Fuel is primarily made up of :

HC

Perfect combustion =

HC, O2, N2 in

Heat, H2O, CO2 and N2 out

Imperfect combustion

Adds HC, CO, NOx and O2 to exhaust

Stoichiometric

Much of our emissions are related directly to A/F mixtures

Theoretical best a/f ratio for emissions, economy, performance is 14.7:1

14.7 pounds of air to 1 pound of fuel

Think about it

Gasoline weighs 6 pounds per gallon Air weighs 1 pound per 100 gallons At 15:1 it takes 9000 gallons of air to

burn 1 gallon of fuel– 9000 Gallons of air is equal to a single

car garage

HC - Hydrocarbons

Unburned fuel Currently measured in parts per

million (ppm)

Common causes of high HC

Misfiring will cause HCs– Ignition –Mechanical – Lean

A/f ratios off either way Timing too advanced

Not so common causes of HC

Quench areas in combustion chamber– Carbon – Poor combustion chamber design

Cam profiles too aggressive

CO - Carbon monoxide

Currently measured in % EXTREMELY deadly gas!!! Partially burned fuel Too much fuel or too little O2

– Combustion process ran out of air CO directly related to a/f ratios

Causes of high CO

Rich AFR - (Over fueling) Lack of O2

Inverse to level of O2

O2 - Oxygen

Currently measured in % Unused air in exhaust O2 directly related to A/F Can also come from dilution– Air pump, exhaust leaks

Misfires will raise O2

CO2 - Carbon dioxide

Currently measured in % Byproduct of complete combustion Peak indicates good A/F Any problems pull CO2 away from

peak

NOx - Oxides of nitrogen

Created when peak combustion temps. exceed 2500F

Causes of high NOx

Advanced timing Inoperative EGR Carbon build up Anything that overheats combustion

chamber TAC stuck in ‘hot’ position

Emission Controls

PCV systems

Purpose of PCV

Control of blow by gasses (HC) Reducing moisture and acids

extending oil life

PCV system problems

Plugged system causes:– High CO at idle

Stuck open PCV causes:– lean fuel– high idle speed

Evaporative emissions system

Evap system purpose To control HC during fuel

evaporation

Evap system components

Gas cap Vapor liquid separator Canister Vapor line(s) from tank(s)– Electronic solenoids– Switching with purge valve– Pressure or flow sensor/switch

Evap system operation (purging)

Purges stored fuel vapors in canister Typical purge warm engine at cruise Some systems purge at idle & cruise,

cold & hot engine Computer controls OBDII diagnostics

Early fuel evaporation systems

EFE system purpose

Helps a/f mixture vaporize on cold engine

Provide good cold driveability (cold air too dense and leans out mixture)

Improve cold emissions

EFE system purpose

Warms intake to prevent condensation of fuel

Prevents icing in carbs (temps can drop 66°f when fuel vaporizes)

Four types of EFE

1. T.A.C. (thermostatic air cleaner) 2. EFE grid 3. Coolant heated intakes and

throttle bodies 4. Heat riser valve

T.A.C. components

Mode door– Cold air position for warm eng.–Warm air position for cold eng.

Uses manifold vacuum and vacuum motor to move mode door

Heat stove and pipe– Primary failure of emission tests

T.A.C. problems

Stuck in hot air position will cause ping / NOx– Often caused by a plugged bleed off

hole Any missing piece can cause cold

driveability problems

EFE grid components

Electrical heater – Usually only, on carburetors and only

on primary bore(s) Commonly ceramic

EFE grid operation

Heats and mixes a/f mixture Controlled by switches or relay– Usually powered up cold only

EFE grid problems

Grids melt Switches stick on Heater element opens

Coolant passages

Primarily icing controls Also helps warm intakes

Heat riser valve purpose

Directs exhaust to underside of intake manifold

Prevents condensation Improves vaporization Not necessary on PFI engines

Heat riser valve components

Vacuum with rod– Uses TVS

Bimetal spring On V engines valve will plug off one

side of exhaust when cold

Heat riser problems

Binding on shaft Stuck in cold mode causing ping and

NOx by overheating incoming a/f mixture

Valve disintegrating

Air pump system

Air systems purpose

To pump or allow air to be sucked into exhaust system– Completes combustion– Dilutes exhaust gasses– Gives O2 to cats– Heats O2 sensor

Two types - air pump and air suction (pulseair)

Air pump

Belt driven vane and rotor pump Some use electric air pumps Some means of filtered air intake– Often using a centrifugal filter

1/2 Hp draw on engine

Diverter and gulp valves

Purpose: divert AIR away from exhaust on decel to prevent backfire

Gulp dumps AIR to intake– Similar to a decel valve / mixture control

valve Vacuum or electric controlled

Check valve

Purpose: to prevent exhaust from coming up into AIR system

Failed valves can cause melted hoses and diverter valves

Air manifolds and pipes

Rotting out causing backfire / exhaust leaks

Pulseair system

No pump Uses negative exhaust pulses Reed valves Can still divert or block off AIR Can be computer controlled Often mounted to air cleaner

Pulseair system problems

Back firing on decel if reed valves leak

Melted stuff is melted if valves leak Can stick upstream

EGR systems

Purpose : flows exhaust gas into intake to lower combustion

temps which lowers NOx

EGR details

Exhaust supports no combustion Dilutes a/f mix and slows

combustion slightly First used on Buicks in 1972,

common in 1973 Does not affect a/f ratios

Three methods to obtain EGR

Floor jets– Egr at all times

Cam grinds – Egr at all times

Egr valves VCT –variable cam timing

Control of EGR needed for three reasons

Idle; can not support dilution and little NOx

Cold; poor driveability, no NOx, not all engines

WOT; limits power and less NOx due to richer a/f

Backpressure Transducer

Limits with exhaust pressures Exhaust pressures good load

indicator Can modulate valve Many valves have built in

transducers– Positive valves vs. Negative valves

Electronic controls

Can use vsv’s to control EGR via ECU Electric valves– Using solenoids to control operation

Sensors– Position (EVP)– Exhaust pressure (PFE)– Temperature switch

Problems

Inop valves cause high combustion temps = pinging =NOx

Plugged EGR passages common Too much EGR = lack of power,

surge Stuck open at idle causes rough idle

due to excessive dilution

EGR testing

Egr movement under load– Some need to see VSS input

Vacuum present at valve Lift up at idle to check passages

Catalytic converters

Two types of converters

Oxidizing Reducing

Oxidizing

Converts HC and CO to H2O, CO2 and heat

Monolith construction (honeycomb)

Ceramic coated with p&p Lots of surface area

Pellet construction

Aluminum oxide pellets coated with p&p

Not as much surface area

Oxidizing operation

Needs O2 to convert HC and CO to H2O AND CO2

– Gets O2 from lean a/f ratios, AIR systems, missfires

Light off at 500°f, average temps 1400°f inside, 700°f outside

Reducing cat

Converts NOX into N2, CO2, O2

Needs lack of oxygen and some CO to work– Likes richer mix

Uses rhodium

Three way or dual bed

First part (bed) reducing

Gives off O2 to help second bed Needs CO which second bed

eliminates

Second part oxidizing bed

Uses O2 from first part Can use air into cat behind first bed

Needs to be close to stoichiometric to work

TWC is Only found on cars with closed loop fuel

Problems

Plugging– Abuse– If not abuse must find cause before

replacing Rich Leaded fuel Misfire Air system

Symptoms of plugging:

Lack of power No start in extreme cases

Testing backpressure

Vacuum test not always accurate Back pressure reading of > 3psi is

excessive Test at back pressure transducer, O2

sensor, AIR fitting, EGR

Efficiency loss

Loss can be due to lead, coolant, oil, miles

Aftermarket not as effective

Symptoms:

Excessive HC or CO or both

OBDII efficiency monitor

Efficiency testing

Temps 100-200°f increase across cat Intrusive method– Egr, AIR pipes (must seal), drilling hole– Need thin probe– Rivet holes up

– Not at O2 sensor

Using the underhood decal to ID major components