Emissions

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

Fuel is primarily made up of : s HC

Perfect combustion = s HC, O 2, N 2 in s Heat, H 2 O, CO 2 and N 2 out

Imperfect combustion s Adds HC, CO, NOx and O 2 to exhaust

Stoichiometric s Much of our emissions are related directly to A/F mixtures s Theoretical best a/f ratio for emissions, economy, performance is 14.7:1 s 14.7 pounds of air to 1 pound of fuel

Think about it s Gasoline weighs 6 pounds per gallon s Air weighs 1 pound per 100 gallons s 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 s Unburned fuel s Currently measured in parts per million (ppm)

Common causes of high HC s Misfiring will cause HCs –Ignition –Mechanical –Lean s A/f ratios off either way s Timing too advanced

Not so common causes of HC s Quench areas in combustion chamber –Carbon –Poor combustion chamber design s Cam profiles too aggressive

CO - Carbon monoxide s Currently measured in % s EXTREMELY deadly gas!!! s Partially burned fuel s Too much fuel or too little O 2 –Combustion process ran out of air s CO directly related to a/f ratios

Causes of high CO s Rich AFR - (Over fueling) s Lack of O 2 s Inverse to level of O 2

O 2 - Oxygen s Currently measured in % s Unused air in exhaust s O 2 directly related to A/F s Can also come from dilution –Air pump, exhaust leaks s Misfires will raise O 2

CO 2 - Carbon dioxide s Currently measured in % s Byproduct of complete combustion s Peak indicates good A/F s Any problems pull CO 2 away from peak

NOx - Oxides of nitrogen s Created when peak combustion temps. exceed 2500F

Causes of high NOx s Advanced timing s Inoperative EGR s Carbon build up s Anything that overheats combustion chamber s TAC stuck in ‘hot’ position

Emission Controls

PCV systems

Purpose of PCV s Control of blow by gasses (HC) s Reducing moisture and acids extending oil life

PCV system problems s Plugged system causes: –High CO at idle s Stuck open PCV causes: – lean fuel – high idle speed

Evaporative emissions system

Evap system purpose s To control HC during fuel evaporation

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

Evap system operation (purging) s Purges stored fuel vapors in canister s Typical purge warm engine at cruise s Some systems purge at idle & cruise, cold & hot engine s Computer controls s OBDII diagnostics

Early fuel evaporation systems

EFE system purpose s Helps a/f mixture vaporize on cold engine s Provide good cold driveability (cold air too dense and leans out mixture) s Improve cold emissions

EFE system purpose s Warms intake to prevent condensation of fuel s Prevents icing in carbs (temps can drop 66°f when fuel vaporizes)

Four types of EFE s 1. T.A.C. (thermostatic air cleaner) s 2. EFE grid s 3. Coolant heated intakes and throttle bodies s 4. Heat riser valve

T.A.C. components s Mode door –Cold air position for warm eng. –Warm air position for cold eng. s Uses manifold vacuum and vacuum motor to move mode door s Heat stove and pipe –Primary failure of emission tests

T.A.C. problems s Stuck in hot air position will cause ping / NOx –Often caused by a plugged bleed off hole s Any missing piece can cause cold driveability problems

EFE grid components s Electrical heater –Usually only, on carburetors and only on primary bore(s) s Commonly ceramic

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

EFE grid problems s Grids melt s Switches stick on s Heater element opens

Coolant passages s Primarily icing controls s Also helps warm intakes

Heat riser valve purpose s Directs exhaust to underside of intake manifold s Prevents condensation s Improves vaporization s Not necessary on PFI engines

Heat riser valve components s Vacuum with rod –Uses TVS s Bimetal spring s On V engines valve will plug off one side of exhaust when cold

Heat riser problems s Binding on shaft s Stuck in cold mode causing ping and NOx by overheating incoming a/f mixture s Valve disintegrating

Air pump system

Air systems purpose s 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 s Belt driven vane and rotor pump s Some use electric air pumps s Some means of filtered air intake –Often using a centrifugal filter s 1/2 Hp draw on engine

Diverter and gulp valves s Purpose: divert AIR away from exhaust on decel to prevent backfire s Gulp dumps AIR to intake –Similar to a decel valve / mixture control valve s Vacuum or electric controlled

Check valve s Purpose: to prevent exhaust from coming up into AIR system s Failed valves can cause melted hoses and diverter valves

Air manifolds and pipes s Rotting out causing backfire / exhaust leaks

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

Pulseair system problems s Back firing on decel if reed valves leak s Melted stuff is melted if valves leak s Can stick upstream

EGR systems

Purpose : flows exhaust gas into intake to lower combustion temps which lowers NOx

EGR details s Exhaust supports no combustion s Dilutes a/f mix and slows combustion slightly s First used on Buicks in 1972, common in 1973 s Does not affect a/f ratios

Three methods to obtain EGR s Floor jets –Egr at all times s Cam grinds –Egr at all times s Egr valves s VCT –variable cam timing

Control of EGR needed for three reasons s Idle; can not support dilution and little NOx s Cold; poor driveability, no NOx, not all engines s WOT; limits power and less NOx due to richer a/f

Backpressure Transducer s Limits with exhaust pressures s Exhaust pressures good load indicator s Can modulate valve s Many valves have built in transducers –Positive valves vs. Negative valves

Electronic controls s Can use vsv’s to control EGR via ECU s Electric valves –Using solenoids to control operation s Sensors –Position (EVP) –Exhaust pressure (PFE) –Temperature switch

Problems s Inop valves cause high combustion temps = pinging =NOx s Plugged EGR passages common s Too much EGR = lack of power, surge s Stuck open at idle causes rough idle due to excessive dilution

EGR testing s Egr movement under load –Some need to see VSS input s Vacuum present at valve s Lift up at idle to check passages

Catalytic converters

Two types of converters s Oxidizing s Reducing

Oxidizing s Converts HC and CO to H 2 O, CO 2 and heat

Monolith construction (honeycomb) s Ceramic coated with p&p s Lots of surface area

Pellet construction s Aluminum oxide pellets coated with p&p s Not as much surface area

Oxidizing operation s Needs O 2 to convert HC and CO to H 2 O AND CO 2 –Gets O2 from lean a/f ratios, AIR systems, missfires s Light off at 500°f, average temps 1400°f inside, 700°f outside

Reducing cat s Converts NOX into N 2, CO 2, O 2 s Needs lack of oxygen and some CO to work –Likes richer mix s Uses rhodium

Three way or dual bed

First part (bed) reducing s Gives off O 2 to help second bed s Needs CO which second bed eliminates

Second part oxidizing bed s Uses O 2 from first part s Can use air into cat behind first bed

Needs to be close to stoichiometric to work s TWC is Only found on cars with closed loop fuel

Problems s Plugging –Abuse –If not abuse must find cause before replacing u Rich u Leaded fuel u Misfire u Air system

Symptoms of plugging: s Lack of power s No start in extreme cases

Testing backpressure s Vacuum test not always accurate s Back pressure reading of > 3psi is excessive s Test at back pressure transducer, O 2 sensor, AIR fitting, EGR

Efficiency loss s Loss can be due to lead, coolant, oil, miles s Aftermarket not as effective

Symptoms: s Excessive HC or CO or both

OBDII efficiency monitor

Efficiency testing s Temps °f increase across cat s Intrusive method –Egr, AIR pipes (must seal), drilling hole –Need thin probe –Rivet holes up –Not at O 2 sensor

Using the underhood decal to ID major components