AP Exhaust 644178 Catalytic Converter - Front

Brand	AP Exhaust 644178
Position	Front
Body Material	Stainless steel
Inlet Gasket	Yes
Inlet Hardware	None
Inlet Type A	Welded v-band flange
O2 Sensor Ports	2
Outlet Gasket	None
Outlet Hardware	None
Outlet Type A	3.12" od
Overall Length (IN)	19
Type	Federal / epa direct-fit
Product line	Direct Fit Converter
Fits	BMW · 38 vehicles

Direct-fit design. Built to OE dimensions for straightforward replacement.

Stainless steel body. Helps resist exhaust-system corrosion in demanding conditions.

Two O2 ports. Supports sensor placement in the exhaust stream.

Cross-references 18407645241 for the same application. See all 1.

$594.36Free shipping

In stock · usually ships same day before 1pm CST

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Overview

AP Exhaust 644178 is a Federal / EPA direct-fit catalytic converter built for BMW applications that require exact OE dimensions and fitment. It uses stainless steel construction, a welded V-band inlet flange, and two O2 sensor ports for a clean replacement setup.

Compatible with BMW 535i, 535i xDrive, 640i, 740i, 740Li, 740Li xDrive, X5, and X6 front applications, this converter is engineered for direct installation on the listed vehicles. AP Exhaust 644178 is also cross-referenced to 18407645241 for the same application.

Key Features

Federal / EPA direct-fit catalytic converter
Stainless steel body for exhaust system durability
Welded V-band flange inlet for OE-style connection
Two O2 sensor ports for sensor integration
Built to exact OE dimensions and fitment

Detailed Description

AP Exhaust 644178 is part of the Direct Fit Converter line, a product line focused on OE-style replacement fitment and manufacturing consistency. The converter uses ARISTO substrate chemistry and advanced production methods to support efficient converter loading while maintaining the dimensional accuracy needed for proper installation. For BMW 535i, BMW 640i, and BMW X5 front applications, this design helps match the original exhaust layout without custom fabrication.

The stainless steel body, 19-inch overall length, and 3.12-inch OD outlet reflect a direct-fit configuration intended for the listed BMW models. AP Exhaust 644178 is a practical replacement choice when the original catalytic converter is restricted, damaged, or no longer performing as required.

What It Is Used For

Replacing a failed or inefficient catalytic converter
Restoring exhaust flow after converter restriction
Addressing emissions-related drivability concerns
Replacing a damaged OE-style exhaust component
Maintaining proper sensor placement with two O2 ports

Installation Notes

Fits 2011-2016 BMW 535i, front; 2011-2016 BMW 535i xDrive, front; 2012-2015 BMW 640i, front; 2013-2015 BMW 740i, front; 2013-2015 BMW 740Li, front; 2013-2015 BMW 740Li xDrive, front; 2011-2014 BMW X6, front; and 2011-2013 BMW X5, front. Review the emissions notes before ordering, as some applications are listed for Federal and California emissions and include state-use restrictions. Verify flange style, sensor port count, and outlet dimensions against the original part before installation.

Quality Assurance

AP Exhaust states that its manufacturing process uses automated workstations, spinner welding equipment, and high-speed production lines to maintain OE dimensions and fitment consistency. The Direct Fit Converter line is built around replacement accuracy and controlled production standards.

This part fits 38 vehicles

Always verify fitment with your vehicle's VIN if unsure. Submodel & trim restrictions may apply.

Year	Make	Model	Liters	Cylinders	Fuel Type	Position	Notes
2016	BMW	535i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2016	BMW	535i xDrive	3.0L	L6	—	Front	Direct Fit
2015	BMW	535i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2015	BMW	535i xDrive	3.0L	L6	—	Front	Direct Fit
2015	BMW	640i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2015	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740Li xDrive; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2015	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740Li; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2015	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740i; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2015	BMW	740Li	3.0L	L6	—	Front	Federal and California Emissions; Direct Fit Converter
2015	BMW	740Li xDrive	3.0L	L6	—	Front	Federal and California Emissions; Direct Fit Converter
2014	BMW	535i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2014	BMW	535i xDrive	3.0L	L6	—	Front	Direct Fit
2014	BMW	640i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2014	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740Li xDrive; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2014	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740i; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2014	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740Li; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2014	BMW	740Li	3.0L	L6	—	Front	Federal and California Emissions; Direct Fit Converter
2014	BMW	740Li xDrive	3.0L	L6	—	Front	Federal and California Emissions; Direct Fit Converter
2014	BMW	X6	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2013	BMW	535i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2013	BMW	535i xDrive	3.0L	L6	—	Front	Direct Fit
2013	BMW	640i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2013	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740Li xDrive; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2013	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740i; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2013	BMW	740i	3.0L	L6	—	Front	Direct Fit; 740Li; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2013	BMW	740Li	3.0L	L6	—	Front	Federal and California Emissions; Direct Fit Converter
2013	BMW	740Li xDrive	3.0L	L6	—	Front	Federal and California Emissions; Direct Fit Converter
2013	BMW	X5	3.0L	L6	GAS	Front	Direct Fit
2013	BMW	X6	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2012	BMW	535i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2012	BMW	535i xDrive	3.0L	L6	—	Front	Direct Fit
2012	BMW	640i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2012	BMW	X5	3.0L	L6	GAS	Front	Direct Fit
2012	BMW	X6	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2011	BMW	535i	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
2011	BMW	535i xDrive	3.0L	L6	—	Front	Direct Fit
2011	BMW	X5	3.0L	L6	GAS	Front	Direct Fit
2011	BMW	X6	3.0L	L6	—	Front	Direct Fit; Federal and California Emissions. Not For Sale or Use on vehicles licensed in the state of CA, CO, ME & NY. Restrictions may apply in other states. Check with your state authority for details.
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Directly replaces or cross-references 1 part number

Cross-reference numbers are provided for identification purposes only. Always confirm fitment before ordering.

18407645241