so you failed emmision testing

grumpyvette

Administrator
Staff member
you'll quickly find that one of the key factors in getting a clean burn, and low emissions is a strong ignition spark that's correctly timed, which requires a tune up in many cases and a strong battery voltage,and a decent ignition, (check your coil,cap,rotor,wires and timing advance) and a fuel / air ratio thats stays close to 14:1-15:1 during the lower idle-5000rpm power band,(IF its a carburetor equipped engine ,verify your float levels and fuel pressure) some modifications to the stock engine that usually help is a non-restrictive air filter and a multi strike ignition, and maintaining the correct engine temperature, and making sure theres no vacuum leaks and fresh spark plugs and it sure helps if the engines rings and valve seals are not worn.
naturally the fuel you use and the engines general condition effect results, one old trick to clean out combustion chamber fouling and reduce emissions, is to get the engine up to operating temps then to slowly dribble about a quart of a 50%/50% mix of water and ethanol alcohol thru the carb, while blipping the throttle as the steam produced in the combustion chamber tends to loosen and clean out carbon and combustion chamber deposits, do this a couple hours before the emission test, if you have a fuel injected engine run a can of fuel injection cleaner thru the engine and install a new fuel filter if the injectors get a bit sluggish from fuel contaminates the spray droplets are larger and burn slower causing higher emissions, the newer injector designs tend to FOG fuel in a cloud vs a STREAM like first design injectors

Spray-pattern.jpg

partly clogged injectors, or injectors running at over 80% duty cycle tend to reduce power and increase emissions
a really strong ignition spark helps reduce emissions so install new spark plugs gaped at about .045-.050 and if its a HEI, new cap and rotor and spark plug wires might be a good is a as will verifying your ignition advance curve and spark at the plugs, you'll generally want this curve below for an ignition advance curve, as a start point, obviously you need to verify timing so check your timing per the fsm (factory shop manual)
a leaking intake gasket or leaky head gasket will fairly frequently suck oil mist from the lifter gallery., or allow coolant to seep into the combustion chamber only after the engine heats up and parts expand, and oil thins, and/ or coolant pressure increases and if the intake sucking oil mist will usually burn to ash during combustion, leaving that residue , now obviously if the amount of oil mist or coolant entering the cylinder is minimal the smoke or lack of smoke due to complete or almost complete combustion will be minimal
chart3e.jpg


READING THROUGH these LINKS AND SUB LINKS may help

http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-43477

http://garage.grumpysperformance.com/index.php?threads/what-kills-o2-sensors.3049/#post-51701


http://garage.grumpysperformance.com/index.php?threads/failed-emissions.11501/#post-52995

viewtopic.php?f=70&t=202

viewtopic.php?f=50&t=268&p=18428#p18428

viewtopic.php?f=55&t=109

http://garage.grumpysperformance.co...cleaning-dirty-fuel-injectors.1906/#post-5032

Ive had good results adding a can of either one of these, on particularly dirty or suspect injectors Ive added a can of both but one on one fill-up and the other product on the next full tank of fuel.


related info

http://www.smogtips.com/failed-emissions-test.cfm

http://www.smogtips.com/trouble-codes.cfm

http://garage.grumpysperformance.com/index.php?threads/failed-emissions.11501/#post-52995

http://www.aa1car.com/library/tr1196.htm

http://www.aa1car.com/library/2000/ic60032.htm

http://www.automotiveu.com/zack5gas.htm

http://www.auto-repair-help.com/auto_di ... ailure.php


A. WHAT CAUSES HIGH HYDROCARBON (HC
)?
Below are common failures which are likely to produce high Hydrocarbon HC. Hydrocarbons are basically raw fuel, otherwise known as un-burnt Gasoline. High Hydrocarbon (HC) emissions are almost always a sign of poor fuel ignition. However, it's not always that the engine's ignition system is responsible for high Hydrocarbon emissions. Read on.

1. Improper Ignition Timing - Engine ignition timing is measured in degrees before or after Top Dead Center (TDC). Example of an ignition timing failure would be in the case where an engine's ignition timing is required to be set at 10 degrees Before Top Dead Center (BTDC) and instead is set to 15 degrees BTDC. This fault will not only cause a smog check "functional failure", but will increase Hyrdocarbon (HC) emissions as well. California allows 3 degrees +/- off of the manufacturer's required setting. Note: Late model vehicle's may not have a distributor, and therefore no timing adjustment will be needed. On these engines timing is electronically controlled by the ECU (Engine Control Unit).

2. Defective Ignition Components Your vehicle's ignition system consists of the ignition coil/s, distributor*, distributor cap*, distributor rotor*, ignition wires, and spark plugs. If any of these components are defective the engine will produce high hydrocarbons. A common reason ignition components perform poorly is due to carbon build-up. High ignition voltage traveling through the air pockets within these components form carbon. Carbon acts as an insulator between paths of electricity, decreasing the energy required at the spark plug to ignite the air/fuel in the combustion chambers properly. *Distributor-less engines do not have these components.

3. Lean Fuel Mixture - Any condition which will cause unmetered air to enter the intake manifold, and ultimately the combustion chambers, will cause high hydrocarbons (HC). This condition is called a lean miss-fire. Such faults as vacuum leaks and gasket leaks will cause lean fuel/air mixtures. Broken, disconnected or misrouted vacuum hoses will do the same. It is also important to note that many engine components rely on engine vacuum for proper operation. If any of these components are defective, externally or internally, they may cause large vacuum leaks as well. A good example of such a component is your vehicle's power brake boost

4. Defective Catalytic Converter - A defective catalytic converter (CAT) may be responsible for high HC, CO, and NOx emissions. The Catalytic Converter, commonly referred to as the CAT is a component designed to continue the combustion process within itself and emit a more thoroughly burned and less harmful emissions containing exhaust. The most accurate way to find out if your vehicle's CAT is working efficiently is by using an exhaust gas analyzer. Unfortunately this tool is fairly expensive. Testing the CAT should be conducted at a smog check repair station.

Some obvious symptoms of a bad CAT could be any of the following:

a. Major loss of power over 15-25 mph. This may be an indication that the catalytic converter is plugged up and restricting exhaust flow.

b. Strong sulfer or rotten egg smell emitting from the exhaust on an otherwise good running vehicle. This may be an indication that the Catalytic Converter isn't burning fuel completely, instead storing it, then releasing it as hydrogen sulfide.

c. Loud rattle being heard from inside the CAT. This may indicate a broken Catalytic Converter substrate. You may want to insure this sound is not due to loose exhaust components, i.e. broken muffler flanges, loose exhaust pipes, loose or cracked exhaust manifold.

5. Defective Air Injection Components - Faulty smog pump and related emissions system components will cause high HC. The air injection system is designed to introduce additional oxygen, after the metering system, to the engine exhaust as it exits the exhaust manifold, or directly before it enters the Catalytic Converter; thus burning whatever remaining fuel (HC) in the exhaust completely.

6. Low Cylinder Compression - This fault is one of the less common high HC causing problems we encounter. Reasons an engine may have low or no compression in one or more of its cylinders may include things such as burned intake or exhaust valve/s, defective valve guides and/or seals, defective piston rings, and burned head gasket/s. A wet/dry cylinder compression test will diagnose this fault. More then often if such a problem exists it will be very apparent. You should notice rough idle.

B. WHAT CAUSES HIGH CARBON MONOXIDE (CO)?

Below are common faults which are likely to produce high Carbon Monoxides (CO). Carbon Monoxide is a by-product of incomplete combustion. Carbon Monoxide exceeding maximum limits, can be due to a number of emission failures ranging from inadequate air intake to defective engine computer sensors.

1. Dirty Air Filter - The number one overlooked emissions component, yes, "emissions" component is the engine air filter. A dirty air filter will absolutely restrict air flow, thus disturbing the proper 14.7:1 air/fuel ratio required for optimum fuel combustion.

We recommend replacing the air filter at the manufacturer's required intervals; usually every 15,000 miles, or at least before your vehicle's smog check.

2. Faulty Oxygen Sensor (O2 Sensor) The Oxygen Sensor is responsibly for delivering information to the ECU (engine control unit) or ECM (engine control module) relating to the oxygen content in the exhaust stream after it has left the combustion chambers.

The engine control computer will determine how much fuel to inject into the combustion chambers based on this data. The more oxygen in the stream, the more fuel the computer will deliver, and visa-versa. A defective O2 sensor will cause increased carbon monoxide emissions. More about oxygen sensors.

3. Defective Manifold Absolute Pressure (MAP) Sensor - The MAP sensor determines the level of vacuum created during an engine's intake stroke, and sends this information to the ECU. During low vacuum the MAP sensor assumes the engine's throttle is in some degree open, meaning you've stepped on the pedal. It relays this information to the ECU. The ECU, in turn, sends commands to the fuel injectors, or carburetor, to increase fuel delivery.

A defective MAP sensor will not report the correct information to the ECU, thus disturbing air/fuel ratio. Usually when the ECU senses a defective MAP sensor it will learn to ignore its data, and rely on preset values, and other sensors such as the Throttle Position Sensor (TPS), and Engine Coolant Temperature (ECT) Sensor; Fuel delivery will not be as accurate and high CO may result.

4. Defective Throttle Position Sensor (TPS) - Obviously a very important emissions sensor; the TPS relays information regarding the position of the air intake system's throttle plate. The throttle plate, located after the engine air filter and before the intake manifold controls the amount of air entering the combustion chambers. It is usually manipulated by the gas pedal via a cable. On late model vehicles the throttle plate may be controlled electronically. A defective throttle position sensor will confuse the ECU into thinking the vehicle's operator is demanding more or less fuel, when neither is really neccessary. Most often a faulty TPS will cause high CO, as an engine's ECU always prefers to send more fuel rather then less, in an effort to avoid a lean fuel mixture and subsequently higher engine temperatures.

5. Defective Engine Coolant Temperature (ECT) Sensor - Low engine temperature requires more fuel. When the ECU is unable to determine what the engine's accurate temperature is, it will not adjust fuel delivery properly; resulting in high CO. As explained above, the Engine Control Computer prefers to send more fuel rather then less to avoid a lean fuel mixture.


C. WHAT CAUSES HIGH NITROUS OXIDE (NOx)?
Nitrous Oxide or NOx is created when an engine's combustion chamber temperature reaches over 2500F. Vehicle manufacturers have designed several systems, which when working properly, lower nitrous oxide emissions. Below are common failures which may cause your car, truck, van, suv, or motorhome to produce high high nitrous oxide.

1. Lean Fuel Mixture - Lean fuel mixtures cause high NOx. A lean fuel mixture exists when less fuel then required is delivered to the combustion chambers or when more air then necessary is added to the fuel. In either case the lack of gasoline needed to cool the combustion chambers down is not present. Combustion temperatures increase causing high nitrous oxide emissions. A lean fuel condition may be due to a vacuum leak/s and/or defective fuel control components, such as the Air Flow Meter, Engine Coolant Temperature Sensor, and O2 sensors.
Read more about the Oxygen Sensor

2. Defective EGR System - The Exhaust Gas Recirculation system is designed to reduce NOx. The EGR system consists of an EGR valve, EGR pressure sensor, vacuum hoses, and one or more vacuum switching valves or solenoids. Later model vehicles may be equipped with electronically controlled EGR valves, which do not require vacuum lines or switching solenoids. Electronic EGR systems will have these components built in.

The EGR system's job is to re-route a small amount of exhaust gas back into the intake manifold to help reduce combustion chamber temperatures. As mentioned above NOx is created when combustion chamber temperatures reach above 2500F.

By recirculating exhaust gas back into the intake, a small amount of the air/fuel mixture is replaced with inert gas, reducing combustion temperatures.

Read more about the EGR System

3. Defective Catalytic Converter (CAT) Some vehicle manufactures have designed their cars to operate without EGR valves. Non-EGR equipped vehicles rely heavily on the Catalytic Converter to assist in the reduction of NOx. These vehicles have tendencies to develop CAT problems sooner then those which are equipped. If you own a non-EGR equipped vehicle, and have failed the emissions test for high NOx, pay close attention to the Catalytic Converter.

Read more about the Catalytic Converter


4. High Engine Mileage - Over an engine's lifetime, carbon build-up develops in the engine's combustion chambers. The more miles on your engine, the more carbon build-up on the pistons, cylinder heads and valves. Carbon build-up decreases the available space for the air/fuel mixture to combust, and causes higher cylinder compression. High compression results in high temperatures and high NOx. Keep in mind this problem is usually seen in vehicles with over 150,000 miles which have been poorly maintained. The solution to this problem is called De-Carbonizing. It usually costs around two labor hours at a smog check repair station. It will remove a good amount of carbon out of an engine. This will increase combustion space, lower compression and lower NOx.

5. Engine Overheating - Inadequate engine cooling can will high NOx. If your vehicle's cooling system is not working efficiently, (i.e. bad radiator, thermostat, hoses) high NOx will be created. Remember high NOx nitrous oxide is created when an engine's combustion chamber temperatures reach over 2500F. You will want to make sure your vehicle's cooling system is working properly, and your vehicle's temperature gauge is always indicating normal.
 

grumpyvette

Administrator
Staff member
http://www.type2.com/library/exhaust/comix.htm

http://garage.grumpysperformance.com/index.php?threads/so-you-failed-emmision-testing.3522/

http://www.importtuner.com/tech/impp_11 ... ewall.html

theres lots of related answers in the links and sub links
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/

http://garage.grumpysperformance.co...s-cause-a-bad-idle-in-drive.14203/#post-72114

http://garage.grumpysperformance.com/index.php?threads/testing-1985-89-m-a-f-sensor.1475/#post-43635

http://garage.grumpysperformance.co...le-shooting-flow-chart-info.11536/#post-71845

http://garage.grumpysperformance.co...ittent-cylinder-miss-problem.9478/#post-57225

http://garage.grumpysperformance.co...g-your-tpi-maf-and-cpu-links.2825/#post-56790

http://garage.grumpysperformance.co...-you-failed-emmision-testing.3522/#post-52999

http://garage.grumpysperformance.co...and-verify-each-possibility.11219/#post-50643

http://garage.grumpysperformance.co...-idles-and-sometimes-stalls.10688/#post-46303

http://garage.grumpysperformance.com/index.php?threads/1991-c4-runs-like-crap.10616/#post-45635


http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-regulators.635/

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.co...u-need-to-know-setting-float-levels-etc.1115/
0900c1528008fca5.gif

EMISSION COMPONENT LOCATIONS
creml.png

Testing Standards
One thing to understand is that the (Washington) State standards are much more general than you might think. The Department of Ecology sent me the current standards, and they do not distinguish one type of car from another - it goes strictly by model year. Only two things are actually regulated: Hydrocarbons (HC) in parts per million (ppm) and Carbon Monoxide (CO) percent. They do measure Carbon Dioxide (CO2) but only to validate the test. The total of CO and CO2 must exceed 6% for the test to be valid. The actual standards are:
Model Year HC (ppm) CO (%)
68-74 900 6.0
75-80 600 3.0
81-93 220 1.2
94-99 100 0.5

These are the upper limits. The DOE claims that a properly running car, tuned to the manufacturer's specs, should not exceed 300 ppm HC and 1.5% CO if it is not equipped with a catalytic converter. Those figures drop to 100 ppm HC and 0.5% CO for cars with converters. Notice that the upper limits do not distinguish between cars with catalytic converters and those without.
Causes of Emissions
Where do HC and CO come from? Basically from incomplete combustion. Complete combustion of gasoline would yield CO2 and water and we wouldn't have a problem. But complete combustion isn't feasible in today's engines. So we get unburned hydrocarbons going out the tailpipe along with carbon di- and monoxide, nitrogen oxides (NOx) and various other unhealthy crap. Interestingly, the nitrogen oxides aren't measured or regulated in Washington, yet NOx is the real "baddie" when it comes to environmental effects. Nitrogen dioxide (NO2) is a major poison that causes paralysis of the central nervous system. It reacts with sunlight to produce both smog and ozone and causes irritation of the lungs and mucous membranes.

The two major factors that influence emissions are fuel mixture and ignition timing. The old rule of thumb has been to use an air/fuel mixture ratio of 12:1 for power and 15:1 for economy. HC emissions are lowest at about 16:1 to 16.5:1. CO emissions are fairly low and constant above 15:1 but go up rapidly below that. So a lean mixture is better as far as emissions go. But a lean mixture can be hard to ignite and an overly lean engine will tend to overheat and ping or detonate. Missing can also cause a high HC reading due to the unburned gas. Try to go as lean as you can. If you are running SU's, they are easy to adjust; other carbs require more work. Fortunately, a CO reading of 6.0% equates to an air/fuel ratio of 12.24:1, so you should be okay from that standpoint.

As for ignition timing, advance has very little effect on CO emissions, but it does increase HC output. How much it increases depends on the air/fuel ratio. At around 16:1, the HC emissions at 40o advance are more than double what they are with 20o advance. At 12:1 the increase due to the same advance is more like 50% but the overall HC is still much higher than at the leaner ratio. The bottom line is, the less advance, the less HC.
Optimizing
As we have seen, the two main factors in your engine that affect emissions that you can easily modify are mixture and ignition timing. But that's assuming the engine is running correctly to begin with. A tired engine that is sucking oil past the valve seals and guides and is blowing combustion gases past worn-out rings is going to have a tough time passing the test no matter how you tune it.

A certain amount of engine oil will be burned even in a fresh engine. The cleanliness of this oil can affect emissions readings. If the oil is really grubby, change it before you go in for the test.

There are other factors affecting the richness of the mixture besides the jetting. A dirty or plugged air filter will cause an artificially rich condition. Install a clean filter before you go in for the test. Better yet, install a low-restriction unit like a K&N filter and pick up a couple of horsepower in the bargain.

Usually an engine runs a lot richer on the idle jets than it does on the primary circuit. You might be able to get off the idle jets by raising the idle speed, but it has to be under 1000 rpm or they won't run the test.

One cause of HC emissions at idle is weak or inadequate spark. High compression and a lean mixture will make it harder to get full ignition, as will fouled spark plugs. A long-duration or multiple-spark ignition system like those made by Crane or MSD will assure more complete combustion at low rpm and clean up some of those HC problems, in addition to giving you more power and cleaner spark plugs. Make sure you have fresh plugs in the engine for the test.

A more subtle factor that affects HC emissions is cam timing. Long duration cams with lots of overlap (where the intake and exhaust valves are open at the same time) increase HC because unburned fuel flows directly from the intake to the exhaust. This is great for top-end performance because it cools the exhaust valve and helps scavenge the cylinder of the waste gases from the previous power stroke. But it can kill you at the testing station.

Can you do anything about it? Yes. High-revving engines with heavy valve springs are notoriously hard on valve seats. The valves pound away at the seats and sink into the head. This tightens up the valve lash. Since many of these cams have long ramps at the ends of the valve events, this decreased clearance will actually increase the effective cam duration and consequently the overlap increases, too. In addition to increasing HC, this can also hurt low-end performance. Make sure your valves are adjusted correctly to prevent excessive overlap.
Into the Future
The State standards have gotten tighter over time. For example, the last time I tested our 510, the HC standard was 1000 ppm; now it is 900. In 1990, the standards for our 1984 Stanza dropped from 300 HC and 2.0 CO to 220 HC and 1.2 CO. We may be faced eventually with going beyond tuning and maintenance to keep our cars on the road. Some firms like HKS are starting to produce free-flowing catalytic converters. And Haltech sells an electronic fuel injection system that can be installed on just about any car, including old Datsuns. It is programmable from a pc so you can change the tuning very easily. A number of the hot autocrossers are using it now. Knock sensors are already available that can be tied into an electronic ignition system to retard the timing. It is conceivable that we may have to resort to such modifications in the future. That seems like a high price to pay, but how much is your breath worth?

BTW just a side note, one of my friends had an older 1989 TPI corvette that he changed the oil, and all the filters and checked the timing etc, installed new plugs, and had a local shop test his car before he did the state mandated testing, he passed emission testing,in the shop, but was a bit higher than ideal on the readings, he upgraded the ALTERNATOR to a 200 amp alternator and increased the plug gap from .035 to .047 and had the car retested at the same local shop, those two changes even with the old plugs showed a noticeable reduction in unburnt fuel "HIGH HYDROCARBONs" by over 40% so obviously a far more robust ignition spark helps reduce emissions, when he tested at the state run test facility he had very low emission levels, and his corvette has over 100K miles
catalytic converters can be tested on car, with the engine running, at operating temperature.
its a good idea to test with a vacuum gauge as described earlier, but a quick check can be done with an I.R.TEMP GUN,
Using an infrared temperature tester, like I link to below, the "gun" style with the red laser pointer, measure the inlet and outlet temps of the converter.

The temperature difference from one end to the other, should be approximately 100 deg/F.

The INLET should be 100 deg/F or so COLDER than the OUTLET end.

If the outlet is significantly colder than the inlet, converter is usually plugged.

heres the one I use and recommend
T504-4254_product.jpg

http://www.professionalequipment.com/ex ... ermometer/
this defective cat is very common on older c4 corvettes
caty3.jpg


viewtopic.php?f=56&t=495

viewtopic.php?f=56&t=3049&p=8053&hilit=catalytic#p8053

viewtopic.php?f=80&t=2813&p=7258&hilit=catalytic#p7258

viewtopic.php?f=80&t=728&p=9217&hilit=catalytic#p9217

viewtopic.php?f=32&t=1174&p=20327&hilit=catalytic#p20327

viewtopic.php?f=80&t=2813&p=13444&hilit=catalytic#p13444
 
Last edited by a moderator:

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Sensor


Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.

Sensor Locations

Sensor


Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.






https://www.autozone.com/videos/v/delphi-mafsensors-101/224995962/

you really need a scan tool of some sort to work on corvettes

http://garage.grumpysperformance.co...o-you-failed-emmision-testing.3522/#post-9307

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.com/index.php?threads/spark-plug-info.202/

http://garage.grumpysperformance.co...rough-from-a-different-site.16114/#post-97329

http://garage.grumpysperformance.com/index.php?threads/timing-tabs-and-indicators.1015/

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/

http://garage.grumpysperformance.co...ning-with-an-air-fuel-logger.6765/#post-25598

http://garage.grumpysperformance.com/index.php?threads/air-fuel-meters-and-tuning.268/#post-18435

http://garage.grumpysperformance.com/index.php?threads/odd-exhaust-temps-and-failed-smog-test.15817/

http://garage.grumpysperformance.co...atio-or-infrared-thermometer.6174/#post-19287

http://garage.grumpysperformance.co...m-with-how-your-c4-corvette-runs-badly.15212/

http://tpiparts.net/emissions



Emissions Devices

Disclaimer: The information contained within this article is intended for educational purposes only. It may be illegal to remove, modify, or tamper with any emissions device on your vehicle, depending on the state in which you live. Please check your local rules and regulations to ensure that you abide by them.

Before we discuss how these systems operate, I would like to comment on a general misconception associated with fuel injection in general. I have heard on numerous occassions that fuel injection in general is too complicated and restrictive due to emissions devices. In reality, the problem lies with people assuming that the emissions components are somehow required as part of the whole fuel injection platform, and that these devices pose a significant restriction in performance. Just because you are running a fuel injection system, does not mean you will have emissions devices. In addition, having emissions equipment does not prevent someone from running whatever engine modifications they want. The loss in power from these emission devices is quite small.

As many of you already know, Tuned Port Injection engines were factory installed on vehicles that were required to be emissions compliant. To ensure that emissions requirements were met, GM used several devices to lower emissions output. Basically, these can be broken down into three main systems : EGR, A.I.R., and EECS. None of these are absolutely necessary to run a Tuned Port Injection intake, but may be legally necessary if you want to be street legal in the state where you live.

Exhaust Gas Recirculation System (EGR)

The sole purpose of the EGR system is to reduce the formation of Oxides of Nitrogen (NOx). These are formed when the temperature in the combustion chamber reaches very high levels. To avoid this situation, the EGR system is used to lower combustion chamber temperatures by admitting small amounts of exhaust gas back into the combustion chamber. As you can imagine, exhaust gas does not burn, and does not help the combustion process. If the EGR system would admit exhaust gas into the combustion chamber at idle, it would cause a rough idle, or stalling. As a result, EGR does not allow exhaust gas into the chamber at idle (nor at wide open throttle, more on that later...). To accomplish this, there has to be some way of controlling EGR flow.

The way this is accomplished is actually quite simple. First of all, there is a round, flying saucer - looking part that mounts on the intake manifold. This is called the EGR valve. There is an opening in the intake manifold from the cylinder head that allows exhaust gas to move up to the valve. When vacuum is applied to the valve, it allows the exhaust gases to pass. To control when the valve receives vacuum, an EGR solenoid is used. This part mounts on the passenger side near the back of the intake manifold. It has a vacuum line which supples ported manifold vacuum, and another vacuum line running to the EGR valve. When the ECM requests EGR to be ON, it sends a signal the the EGR solenoid, which then allows vacuum to be applied to the EGR valve. When the ECM wishes EGR to be off, the solenoid will cease to apply vacuum to the EGR valve.

The ECM will turn on the EGR solenoid by grounding it. It does this via pulse width modulation (PWM). This means that the ECM will turn on and off the solenoid many times a second. Just how many times this occurs will affect the amount of vacuum applied to the EGR valve, and therefore the amount of exhaust gas admitted into the combustion chamber. During the time that EGR is requested by the ECM, fuel output and spark advance are also altered. More timing is added, and the fuel mixture is leaned a bit.

During WOT (wide open throttle), the ECM shuts down EGR. Since EGR will play no role whatsoever under WOT, it will not impede the engine's ability to generate horsepower.

How does the ECM know if there is a problem with the EGR system? Well, the answer depends on what year TPI setup you have. If you have an 85-89 setup, then there will be a single wire that goes to the base of the EGR valve. This is basically a temperature switch. When the ECM requests EGR, it will check this wire to see if there is a change in temperature. If no change is detected, the ECM will think there is a problem with the system, and will throw a code 32. Most of the time, the problem is the temperature switch that is bad. However, you should first check for vacuum leaks, check that all vacuum lines are properly routed, check the harness connector at the EGR solenoid with a voltmeter, and make sure that the EGR passages are not clogged with deposits.

The 90-92 TPI setups did not use a temperature switch on the EGR base. Instead, the ECM monitors the MAP voltage to determine if an EGR request was successful or not. When EGR is turned on, engine vacuum will lower a little. The ECM will throw a code 32 if it suspects that the EGR request was not successful.

So what would someone gain by disabling EGR? Just about the only thing would be less parts under the hood. Basically, removing EGR gives you more space (although not much). To correctly disable EGR from your vehicle, you MUST at the very least, disable it in the prom. This is done by setting the minimum temperature to enable EGR to 151 degrees Celsius (maximum allowable temperature), and setting the minimum vehicle speed to enable EGR to 255 mph (maximum allowable speed). Since the engine will never reach either of these conditions, EGR will never be requested by the ECM. Since EGR will never be requested, it does not matter if you leave the EGR system all installed in its original place, or if you remove it from the car. If you decide to remove it, you will need an EGR block off plate to cover the hole in the intake manifold.

If you simply remove the EGR system from the car, but do not disable it in the ECM, you will run into significant problems. You will likely run into detonation, the engine will run very poorly, lack power, and will probably run on the hot side as well. In addition, you will get a code 32 before running very long. If you recall from before, the ECM alters fuel and spark advance when it thinks EGR should be on. If no EGR flow is possible because you removed it, you will have a lean condition which will be further aggravated by advanced timing.

I have not had a chance to discuss A.I.R or EECS (canister purge). I will finish the article as soon as I have some spare time, but I wanted to post the EGR section for the moment atleast.
 
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