BMW M3/M4 S55
Catted Downpipe Set
Installation Instructions
Skill Level
2 - Moderate
Some Experience
Recommended
Proper service and repair procedures are vital to the safe, reliable operation of all motor vehicles as well as the personal safety of those performing the repairs. Standard safety procedures and precautions (including
use of safety goggles and proper tools and equipment) should be followed at all times to eliminate the possibility of personal injury or improper service which could damage the vehicle or compromise its safety.
BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INTRODUCTION
Turner Motorsport S55 Catted Downpipe Set
Our S55 Catted Downpipe Set offers the following features:
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OE-style fitment
Less restriction than OE downpipes
Lower boost threshold and improved turbo response
TIG welded 304 stainless steel construction
Brushed finish
200 cell 4.3” OD metallic high flow catalytic converters
TABLE OF CONTENTS
Kit Components..................................................................................................pg.3
Installation and Safety Information.............................................................pg.4
Removing the Stock Downpipes..................................................................pg.5
Installing the New Turner Catted Downpipes..........................................pg.23
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1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
KIT CONTENTS
Front Downpipe: Cylinders 1-3 (QTY 1)
Long Downpipe Flange (QTY 1)
© 2019 TURNER MOTORSPORT
Rear Downpipe: Cylinders 4-6 (QTY 1)
O2 Sensor Port Plug (QTY 4)
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Installation Hardware
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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INSTALLATION NOTES
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RH refers to the passenger side of the vehicle.
LH refers to the driver side of the vehicle.
Always use the proper torque specifications.
If applicable to this installation, torque specifications will be listed throughout the document and at the end as well.
Please read all of these instructions and familiarize yourself with the complete process BEFORE you begin.
GENERAL PREPARATION AND SAFETY INFORMATION
Turner Motorsport cares about your health and safety, please read the following safety information. This information pertains to automotive
service in general, and while it may not pertain to every job you do, please remember and share these important safety tips.
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Park your car in a safe, well lit, level area.
Shut the engine off and remove the key from the ignition switch.
Make sure any remote start devices are properly disabled.
ALWAYS wear safety glasses.
Make sure the parking brake is applied until the vehicle is safely lifted and supported.
Whether lifting a vehicle using an automotive lift or a hydraulic jack, be sure and utilize the factory specified lift points.
Lifting a vehicle in an incorrect location can cause damage to the suspension/running gear.
ALWAYS support the vehicle with jack stands.
ALWAYS read and follow all safety information and warnings for the equipment you are using.
NEVER get underneath a vehicle that is supported only by a jack, and
ALWAYS make sure that the vehicle is securely supported on jack stands.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 1:
10mm Socket & Ratchet
Remove the battery cover in the trunk, then disconnect the negative
(–) battery cable.
Negative (-) battery
terminal
Step 2:
Grasp the engine cover and pull it upwards to release it from its
mounting grommets.
Lift
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16 HUNT RD SOUTH AMESBURY, MA 01913
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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REMOVING THE STOCK DOWNPIPES
Step 3:
10mm Socket & Ratchet
Turn the three 10mm plastic nuts 90 º counter clockwise to release
them. Pull the core upwards out of the plastic expansion rivet to
release it. Lift the rain tray cover out of the vehicle (LH rain tray cover
show in the photo).
Repeat this process to remove the other rain tray cover.
Turn 90º counter clockwise
to release
Pull the core upwards
to release
Step 4:
10mm & 13mm Sockets, Ratchet
Remove all of the bolts from the carbon fiber strut brace. Release the
plastic expansion rivets which secure the rubber weather strip from
the LH strut tower (YELLOW
YELLOW arrows). Carefully lift the carbon fiber
strut brace out of the engine compartment and set it aside where it
won’t be damaged.
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Bolts
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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REMOVING THE STOCK DOWNPIPES
Step 5:
Loosen the hose clamp on the RH air box, then release the MAF
sensor connector. Lift the air box straight upward to release it from
its mounting grommets.
Loosen
Release
Step 6:
Remove the bolt which secures the rear turbo inlet pipe to the
turbocharger, then lift it straight upward to release it from the
turbocharger and remove it from the vehicle.
Shop towel
Place a clean shop towel over the turbocharger inlet to prevent any
debris from falling in.
Mounting bolt
Securing the towel over the turbocharger inlet
with a zip tie can be helpful to keep it in place.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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REMOVING THE STOCK DOWNPIPES
Step 7:
Loosen the hose clamps between the two charge pipes and the
charge air cooler.
Loosen
Step 8:
Pull the charge pipes off of the intercooler, then lift them straight
upwards to release them from the turbochargers. Use clean shop
towels to prevent any debris from falling into the turbocharger
outlets.
Shop towels
Securing the towels over the turbocharger outlets
with a zip tie can be helpful to keep them in place.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 9:
Familiarize yourself with
the wiring harness routing
for the upstream O2 sensor
on the FRONT downpipe
(cylinders 1-3, highlighted
in GREEN).
Disconnect this O2 sensor
connector, then release the
harness from all retaining
clips.
Retaining
clips
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16 HUNT RD SOUTH AMESBURY, MA 01913
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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REMOVING THE STOCK DOWNPIPES
Step 10:
Familiarize yourself with
the wiring harness routing
for the upstream O2 sensor
on the REAR downpipe
(cylinders 4-6, highlighted
in RED).
Disconnect this O2 sensor
connector, then release the
harness from all retaining
clips.
Retaining
clip
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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REMOVING THE STOCK DOWNPIPES
Step 11:
8mm & 16mm Sockets, Ratchet
8mm screws
16mmbolts
bolts
16mm
Safely lift and support the vehicle in the air. Remove the steel
reinforcement plate.
Step 12:
Soak all of the downpipe nuts with penetrating oil. We highly
recommend letting the oil soak in for at least one hour before
attempting to remove them. This will further reduce the risk of
breaking or rounding them off.
Oil
Oil
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 13:
Locate the electrical connectors for the downstream O2 sensor
wiring harnesses. They are held by spring clips beneath where the
engine and transmission meet.
Step 14:
Disconnect the downstream O2 sensor connectors.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 15:
Retaining
clips
Familiarize yourself with
the wiring harness routing
for the downstream O2
sensors on the downpipes
(FRONT downpipe
downstream sensor harness
shown in YELLOW
YELLOW, REAR
downpipe downstream
sensor harness shown in
RED).
© 2019 TURNER MOTORSPORT
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 16:
Disconnect both downstream O2 sensor connectors, then release
the harnesses from all retaining clips. Let the harnesses hang down
for now.
Step 17:
12mm Socket & Ratchet
Remove the downpipe nuts.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
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REMOVING THE STOCK DOWNPIPES
Step 18:
At this point you have a choice to make. This install can be done with the exhaust system still on the vehicle, but it severely limits your
space to work. The entire exhaust system can be removed with very minimal effort by removing the hangers and hardware as noted in the
photo below.
13mm nuts
13mm nut
Pull the rubber
exhaust hanger off
of the rod HERE
Disconnect the
wiring harness from
each exhaust valve
13mm nuts
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8mm screw
& 13mm nut
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 19:
T30 Torx
Remove the two remaining bolts (highlighted in GREEN in the
photo) from the downpipe flange assembly.
Step 20:
Remove the downpipe gaskets and the remaining pieces from the
downpipe flange assembly.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 21:
O2 Sensor Wrench - or - Socket & Ratchet
Loosen the downstream O2 sensor on the FRONT downpipe
(cylinders 1-3).
Step 22:
O2 Sensor Wrench - or - Socket & Ratchet
Loosen the upstream O2 sensor on the FRONT downpipe (cylinders
1-3).
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 23:
13mm Socket, Swivel Joint & Ratchet
Completely remove the bolt from the V-band clamp on the FRONT
downpipe (cylinders 1-3).
Step 24:
Flat Blade Screwdriver
Release the V-band clamp from the FRONT downpipe (cylinders 1-3)
by gently prying the ears apart with a screwdriver as shown.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 25:
10mm Socket & Ratchet
Release the FRONT downpipe (cylinders 1-3) from the rear hanger.
Step 26:
Completely remove the upstream O2 sensor from the FRONT
downpipe (cylinders 1-3).
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16 HUNT RD SOUTH AMESBURY, MA 01913
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 27:
Remove the FRONT
downpipe (cylinders 1-3)
from the vehicle.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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Table of Contents
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 28:
O2 Sensor Wrench - or - Socket & Ratchet
Completely remove the downstream O2 sensor on the REAR
downpipe (cylinders 4-6).
Step 29:
13mm Socket, Swivel Joint & Ratchet
Completely remove the bolt from the V-band clamp on the FRONT
downpipe (cylinders 1-3). Release the V-band clamp by gently prying
the ears apart with a screwdriver as shown.
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16 HUNT RD SOUTH AMESBURY, MA 01913
1.978.388.7769
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
REMOVING THE STOCK DOWNPIPES
Step 30:
Remove the REAR downpipe (cylinders 4-6) from the vehicle.
Step 31:
Inspect the downpipe gasket inside each turbocharger housing for
any signs of wear, damage, or leaks. Replace as needed.
© 2019 TURNER MOTORSPORT
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
Step 1:
O2 Sensor Wrench - or - Socket & Ratchet
Transfer the downstream O2 sensor from the stock FRONT (cylinders 1-3) downpipe to the new downpipe. There is not enough room to
install this downpipe into position with the upstream O2 sensor in place, so we will install this sensor later on.
Transfer both O2 sensors from the stock REAR (cylinders 4-6) downpipe to the new downpipe.
Torque all three of these O2 sensors to 50 Nm (37 Ft-lbs).
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
Step 2:
Guide the REAR downpipe (cylinders 4-6) into position from below.
Step 3:
13mm Socket & Ratchet
Loosely install the V-band clamp onto the REAR downpipe (cylinders
4-6).
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
Step 4:
Due to the shape and diameter of the catalytic converter on the FRONT
downpipe, there isn’t enough room to fit it between the engine and the
subframe. This is shown in the RH photo; The area shaded in RED represents
the space the downpipe needs to fit through, the YELLOW circle represents
the actual size of the converter.
This is easily remedied by removing the lower engine mount bolts (arrows in
the photo below) and lifting the RH side of the engine approximately 3/4” - 1”.
We don’t want to lift much more than this to avoid putting stress onto the
wiring harnesses and hoses. It is important to note that we’re removing the
bolts from both engine mounts, but we only want to lift on the RH side of the
engine. Once you’ve removed the engine mount bolts, proceed to Step 5
on the next page for more information.
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
#2: Guide the new
downpipe into place
Step 5:
Carefully lift the RH side of the engine upward 3/4”–1”, then guide the
FRONT downpipe (cylinders 1-3) into position.
#1: Lift the RH side of
the engine 3/4”–1”
Step 6:
13mm Socket & Ratchet, O2 Sensor Wrench
Loosely install the V-band clamp onto the FRONT downpipe
(cylinders 1-3). Loosely install the upstream O2 sensor.
#2: Loosely install
the V-band clamp
#1: Loosely install the
upstream O2 sensor
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
Step 7:
10mm Socket & Ratchet
Loosely reinstall the rear hanger into the new downpipe. Please note
the assembly order as shown in the diagram below.
Step 8:
Reconnect and re-secure the downstream O2 sensor harnesses.
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
Step 9:
Install the flange assembly and the downpipe gaskets onto the new
downpipes.
Step 10:
Reinstall or reconnect the exhaust system.
• Twist the downpipes as needed to align them with the exhaust.
Torque the downpipe bolts/nuts to 19 Nm (14 Ft-lbs).
Torque the V-band clamp bolts to 13 Nm (10 Ft-lbs).
Torque the upstream O2 sensor on the FRONT downpipe
to 50 Nm (37 Ft-lbs).
Reconnect the negative (–) battery terminal.
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BMW M3/M4 S55 CATTED DOWNPIPE SET INSTALLATION INSTRUCTIONS
T#588388
INSTALLING THE NEW TURNER CATTED DOWNPIPES
Step 11:
Reconnect and re-secure
the upstream O2 sensor
harnesses.
© 2019 TURNER MOTORSPORT
16 HUNT RD SOUTH AMESBURY, MA 01913
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Your Turner Catted Downpipe Set installation is complete!
These instructions are provided as a courtesy by Turner Motorsport
Proper service and repair procedures are vital to the safe, reliable operation of all motor vehicles
as well as the personal safety of those performing the repairs. Standard safety procedures and
precautions (including use of safety goggles and proper tools and equipment) should be followed at
all times to eliminate the possibility of personal injury or improper service which could damage the
vehicle or compromise its safety.
Although this material has been prepared with the intent to provide reliable information, no warranty
(express or implied) is made as to its accuracy or completeness. Neither is any liability assumed for loss
or damage resulting from reliance on this material. SPECIFICALLY, NO WARRANTY OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE OR ANY OTHER WARRANTY IS MADE OR TO BE IMPLIED WITH
RESPECT TO THIS MATERIAL. In no event will Turner Motorsport, Incorporated or its affiliates be liable for
any damages, direct or indirect, consequential or compensatory, arising out of the use of this material.