Catalytic Converter Considerations

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Catalytic Converter Considerations

Part No Applications: NME1004, NME1104, NME9004, NME6024, NME1105

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Mini Mania, Inc. Service Bulletin

Subject: Catalytic Converter Considerations – NME1004, NME1104 & NME9004 units

Issue

While the off-road use type exhaust header & integral high flow catalytic converter provides excellent performance, some customers have experienced failure of the Catalytic Converter Element. Typical of this occurrence is for the EML light to trigger. Underlying OBD II codes may include P0108, P0420 and others, indicating low catalyst efficiency has been detected.Several failure modes are common to all catalytic converters in all applications. This document is intended to assist in the understanding catalytic converter failures and the underlying causes.

Considerations

Lamba (O²) sensorAn O² sensor (lambda sensor) has an expected life span of about 30,000 to 50,000 miles. Sensors may fail prematurely if clogged with carbon, or contaminated by lead from leaded gas or silicone from an antifreeze leak or from silicone sealant used elswhere in the engine.O² sensors become sluggish as they age. Eventually the signal does not change at all. When this happens, the EML and/or check engine light may come on, and the engine may experience drivability problems or damage caused by an overly rich fuel condition. High fuel consumption, high CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.If the average voltage from the O²sensor is running high (more than 0.50V), it indicates a rich condition, possibly due to a bad MAP sensor, leaky injector or excessive fuel rail pressure. If the average voltage reading is running low (less than 0.45V), the mixture is running lean possibly due to a vacuum leak or because the sensor itself is bad.If the O²sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. This can cause lean misfire, hesitation, stumbling, poor idle, high hydrocarbon emissions (from misfiring) and engine damage.

If the O²sensor continually reads low (lean), it will cause the engine computer to enrichen the fuel mixture. Injector pulse width will be increased causing fuel consumption and carbon monoxide emissions to go up. Especially in a performance tuned vehicle, a constantly rich fuel mixture can cause the catalytic converter to overheat and it may be melted.

Converter Meltdown

In cases of an overheated Catalytic Converter the element deteriorates or melts, becomes dislodged and partially or fully plugs the exhaust outlet. Catalytic Meltdown occurs when the converter is super-heated due to a raw fuel condition in the exhaust flow. The excess unburned fuel ignites when it strikes the hot catalyst, burns inside the converter and drives the temperature far above the normal operating condition of the converter. The deteriorated element can then either break apart or dislodge completely and clog the exhaust system. This conditions results in poor performance high backpressure and correspondingly high compressor (supercharger) boost pressure. A converter glowing red hot or showing signs of heat discoloration are indicative of this condition.

Carbon DepositsCarbon deposits are an indication of too rich a mixture, or of oil or antifreeze entering the exhaust system. Heat backs up into the engine bay causing other heat related problems.

Catalyst Fracture

Ceramic catalytic elements can become loose, break down and deteriorate. This failure mode can be cause by road debris striking the casing, or by the packing material blowing out from around the element. Fracturing can also be caused when the element deteriorates due to overheating from raw fuel entering the exhaust system (see above).

Testing

Check OBD II codes periodically with an appropriate code reader (NME4020 or similar). Codes should be acted upon to preclude irreversible damage or a dangerous situation.

Note: A qualified technician observing proper safety procedures should perform testing.With the car safely on a lift, inspect the exhaust system and particularly the catalytic converter housing for evidence of damage by road debris.With the car still safely on a lift, separate the CAT back exhaust system from the header at the flange. With aid of a flashlight, perform a visual inspection to verify the catalytic element is intact and complete. Inspect for signs of catalytic converter overheating, such as a discolored housing. Reassemble if OK.Verify the proper operation of the upstream and downstream O² sensors.Using a 4 or 5 gas exhaust analyzer, verify that tailpipe emissions are within specifications.With ECU diagnostic equipment (such as the GT1) check fuel trims to verify proper ECU control of the engine operating parameters. The properly tuned engine will exhibit near neutral trims. Significant fuel trims should be addressed and corrected.An important step in diagnosing a the cause of a catastrophically failed catalytic converter is for a properly equipped shop to view your Mini Cooper’s long and short term “fuel trims”. Short term fuel trim is the real-time mechanism by which the fuel injection system is adjusted to provide the programmed performance and emissions. Long term fuel trims accumulate and are compiled within the ECU, and form a longer term moving average type database that follows the car’s overall fuel adjustment requirements. This reading is useful as a tell-tale to look at overall tuning of the vehicle.

An improper ECU map for the engine (due to inappropriate remapping, or the addition of performance parts without appropriate mapping), will cause long term fuel trim numbers more than a few percent.

Additional causes of converter meltdown damage include activation of the ECU's engine protection routine when the air intake charge becomes too hot. When the ECU detects that the air temperature in the intake manifold is too high, it causes the fuel injectors to deliver more gasoline than is needed in order to cool the intake charge. While the internal combustion components are cooled as intended, the excess fuel passes through the hot catalytic converter resulting in the possibility of converter meltdown as described above. This condition can be induced in tuned vehicles lacking improvements to the Intercooler. Superchargers run with inappropriately small supercharger pulleys (greater than 15% reduction) generates a great deal of excess heat, which must be dealt with via improved intercooling.

Remedy

Indications of a deposits or an overheated catalytic converter MUST be addressed before installing any replacement unit, or that unit may be damaged too.

Contact Mini Mania for price and availability of a header refurbished with a new high flow metallic catalytic converter (NME9004). These off road use only refurbished units require the return of a rebuildable core header.
Obtain a replacement catalytic converter independently and have a competent muffler shop replace the damaged catalytic converter by welding it in place of the original unit for your off-road use header. Be sure to check State and Federal regulations before proceeding.
Reinstall your original stock manifold with integral catalytic converter & reset computer.
Purchase a new replacement performance off-road header with catalytic converter.

Always reset the ECU when replacing the catalytic converter.

Warranty Considerations:Warranty covers header materials and workmanship. Heat discoloration of the stainless steel tubing is considered normal (not a materials or workmanship related issue) and is not covered by warranty. Catalytic converters destroyed from overheating, deposits or impact damage, regardless of cause, are not eligible for warranty coverage.

Mini Mania
Article Date: May 18, 2005
Car Accociations: NEW_MINI
Hits: 2418

Catalytic Converter Considerations

Mini Mania, Inc. Service Bulletin

Subject: Catalytic Converter Considerations – NME1004, NME1104 & NME9004 units

Issue

Considerations

Testing

Remedy

Indications of a deposits or an overheated catalytic converter MUST be addressed before installing any replacement unit, or that unit may be damaged too.

Contact Mini Mania for price and availability of a header refurbished with a new high flow metallic catalytic converter (NME9004). These off road use only refurbished units require the return of a rebuildable core header.

Obtain a replacement catalytic converter independently and have a competent muffler shop replace the damaged catalytic converter by welding it in place of the original unit for your off-road use header. Be sure to check State and Federal regulations before proceeding.

Reinstall your original stock manifold with integral catalytic converter & reset computer.

Purchase a new replacement performance off-road header with catalytic converter.

Always reset the ECU when replacing the catalytic converter.