Great instructions by customer/member WilliamM256
Installation of the complete RoadsterSport Street Exhaust Combo with catalytic header
I just completed installing the RoadsterSport complete street exhaust combo, with catalytic header ceramic upgrade and Helmholtz midpipe, on my 2006 MX5 NC, GT, 6 spd with factory handling package (shock tower braces, suspension, sway bars, etc), and AC. It is an early 2006, built for a dealer show, so there may be some differences from later builds. Yes, it is a garage queen, 25,000 miles, never in salt. Everything fit, it was a relatively easy one person job.
Brian’s instructions were helpful, but I have added some things to it which you might find helpful.
This applies to installing the ENTIRE exhaust system (muffler, midpipe, header), Please refer to photos on Brian's original post, which are fairly close to my car.
• 3/8” metric socket set with ratchet, flex handle, standard and deep sockets, 3”, 6”, and 10” extensions
• ¼” metric socket set
• Set of metric offset ratcheting end wrenches
• 22mm or 7/8” open end wrench
• Torque wrench
• Header insulation tape (2000F, high temp, foil over fiberglass fabric) You only need about 10 inches.
• Can of Blaster or Aero Kroil penetrant
• Tube of anti-seize compound
• Spray bottle with 10% solution of dish soap & water
• Of course, small LED work light (it won’t burn your hand!), flashlight, pliers
• Box of small baggies and felt pen (to bag and tag the nuts you take off)
• Also handy to speed things up, a battery powered impact wrench
• Not required but very handy: small hands, flexible fingers, double jointed wrists
(From Brian) This install can be accomplished by a good shadetree mechanic. However, if you do NOT have a full set of metric wrenches, (see above) including extensions of different lengths and including wrenches with indexable angled heads (offset ratchet end wrenches work too) for tough to reach spots, then you should have a licensed mechanic do this installation for you. Read all instructions and examine the photos below before you begin so you know where you are going! PLEASE NOTE we do NOT guarantee that ANYBODY can do a header install on these cars, exercise some judgment after reading this thread about whether or not you should hire a professional to do this install. Also note the optional O2 extension cords, which not everybody will need...but many will find very helpful.(I strongly recommend the shorter (front) O2 extension.)
First, place the car on ramps or jack stands (NOT JUST A JACK) and remove several pieces.
• Spray penetrant on the nuts for the muffler and mid-pipe flanges, the lower header hanger bracket nuts, and all seven of the header to block nuts. Don't spray where the studs connect to header on this downstream connection...just the nuts on the end of the studs against the springs.
• Spray the soapy water on the rubber hangers for the midpipe and muffler. Wiggle them back and forth to get the soapy water into the hangers.
• While you are under the car, remove three plates, one under the mid-pipe hanger, one approximately under the mid-pipe to header joint, one under the oil pan. Bag and tag the bolts. Note that it is easy to reinstall these plates, because each one has a slotted hole at one corner. So you can just slide the plate into place and then screw in the rest of the bolts. (Don’t remove the reinforced frame brace which is also the front jacking point.)
• Disconnect the battery, remove the battery and battery box. You will need to carefully disconnect the plastic wire routing clips from the side of the box so you can reuse them.
• If equipped, remove passenger side and center portions of the strut brace.
Remove the muffler and midpipe:
• Use a 14mm deep socket to remove the two nuts at the exhaust flange.
• Remove the 4 rubber hangers from the muffler. It may help to brace up the muffler with a couple of blocks of wood, then use another small block of wood and hammer to pop the rubber hangers off the supports.
• Set the muffler aside. You will not need the stock nuts or gasket ring.
• Use a 14mm deep socket to remove the midpipe from the header. This is a spring loaded connection, which allows the midpipe to flex on the header flange. If you are lucky, the nuts will come loose and leave the studs in the header. Bag and tag the springs and the nuts. If the studs come out of the header instead, save them as well. You can take them apart later.
• Now slide the mid-pipe bracket off the rubber hanger. It is fairly well balanced, so you should be able to wiggle it back and forth to pull it off. Give it another squirt of soapy water if it is sticking.
• Set the mid-pipe aside. You will not need any of the hardware on it.
• Remove the outer chassis-mounted heatshield (one nut and two bolts) shown in the picture below in my hand. It is important to wear gloves for this install because the heatshield edges can be razor sharp! This item will be reinstalled so place it safely aside with the hardware that connects it to the vehicle. (The outer heatshield is a real pain to remove. The firewall nut is easy, you can best reach the rearward bolt from underneath with a 16” extension to your socket. The front bolt is a b***h. I found that it could be removed from the top side with an offset ratchet end wrench and a lot of finagling.) You will need to bend the heatshield a little to get it out, but it will bend back.
• Remove radiator cap to relieve pressure on the system and then unbolt heater and coolant line from above exhaust manifold and disconnect both the coolant and the heater hose lines by using a pliers to pull off the clamp you can see here to the right of my hand. You will drip about a quarter cup of coolant from this high point in the engine bay, Brian used a small shallow bowl to catch this fluid when Brian opened the connection.
• Remove the vent line from the valve cover. Carefully unclip the green plastic locking tabs, then pull the line from the plastic hold down clip and move it out of the way.
• If you have air conditioning, remove and save the nut that holds the metal AC lines to the firewall. When you are removing the header, you will need to gently lift the lines off the hold down stud. This will give you a needed additional inch of clearance.
• Now that you have created some space, remove the heatshield from the factory header. It is two parts and the upper "cap" part is held on by numerous little 10mm bolts. Neither part of this shield is reused.
• Continue removal of the factory heatshield by removing the lower portion of the heatshield. You will need to bend it slightly to get it out but it will easily bend back to original position. This gives you access to the 15mm nuts that hold the header to the motor. Spray the nuts with penetrant and leave for an hour. There is a third connection point underneath, between the head and the outlet, to a bracket...spray those two 15m nuts too.
• Unplug the two O2 sensors. Note these are simple plugs that each have a release button which Brian has his finger on below. All you need to do is squeeze that button with your thumb while you grip the plug to release each plug. You do this by reaching up from below the car.
NOTE: For RoadsterSport Catted Street header you can release the plug socket from the socket bracket and stretch the upstream sensor wire to reach the location on the new header. Or get the first short extension cord we offer on the site for the first O2 sensor bracket (easier and less likely to damage the wire). Feel free to order the extension so you have it handy....and return it for refund if you don't use it.
• Remove the 15mm nuts which hold the header to the motor.
• There is another connection point about 5 inches up from the downstream connection...remove the 14mm bolts that hold the converter to the heavy steel bracket at this point and remove the bracket which will not be used again (it supports the substantial weight of the factory converter and is not needed for the much lighter header you are installing).
• While you are under the car, use a 22mm open end wrench to remove the lower sensor plug from the header. This will greatly ease removal of the header and reduce the chance of damaging the sensor wires.
• HERE IS THE KEY TO MAKING THIS PROCESS EASY. Tilt the alternator forward. You can easily do this by removing two bolts...and with the alternator tilted forward the factory header assembly will come out easy.
• The alternator has three 14mm bolts holding it to the block, one bolt on top and two on its underside. Back out (without removing) the top side bolt, and the underside bolt in the very bottom left of the picture below. Also loosen the remaining underside bolt about one turn. Then the alternator can be tilted forward.
Brian removed the factory header several times without doing this step and it was very difficult.
Now the factory header can be removed! It still won’t be easy.
• Now the header can be slide off the studs and fished out. I found that it was impossible to remove the header without removing the lower O2 sensor plug from the catalyst first.
If you have AC, you can raise the AC lines on the bulkhead 1-2 inches without bending them to give a little more clearance. Be careful not to bend the small ¼” refrigerant line that runs to the compressor.
• It will help to have a second person hold the AC lines and the coolant lines up out of the way. After that, with a lot of careful twisting, turning, and lifting, I managed to get the header out. Watch your hands. The stud for the frame mounted heatshield, and a frame projection where the heatshield weldnut is located are very sharp and right in the way.
• Leave factory header manifold gaskets on (stainless steel sheets are used on this car and used over and over, not crush gaskets).
• The factory manifold gasket for the header is reused. The factory gasket for the downstream connection is also reused...just use a very thin edge (such as on a small flat tipped screw driver) to GENTLY pry it off the factory header as shown and then slide it onto your new header.
• Before installing your new header cut the thermal tape into two pieces. Clean the black plastic protective case on the rear section of the alternator and cut the tape into two pieces. Remove the backing and apply this thermal reflective tape sections side by side to cover the portion of the rear alternator case that will face the first header primary.
NOTE: tape not supplied or needed with our ceramic coated header versions. (I added the tape just to be safe, clearance to header is very close.)
This tape is provided for the alternator rear case. Buyers of ceramic versions should chase the threads on header outlet with 10x1.25 thread chaser to clear coating from threads. (I did not find it necessary to chase the threads).
We tested the header without doing this step with a temp probe on the alternator and never found the temperatures reached levels of concern with the first primary tube a good inch (I found only ½” of clearance with mine.) above and behind the alternator but in an abundance of caution we use this tape to give the alternator's protective case some extra protection.
• Congrats, the hard part is done! Remove the upper O2 sensor from the old header, and remove the studs from the header to mid-pipe flange. Install the studs in the new header. You can install the lower O2 sensor in the new header from underneath, after the header is in place. I found that I also had to install the upper O2 sensor after the new header was in place, to get clearance to install the new header, but then it is very difficult to tighten the plug. It can be tightened with a small vise-grip pliers if you are careful.
• Now drop the new header into place and finger tight the nuts that hold the header to the head using liberal amounts of anti-seize compound.
• As you likely noticed in removing the factory header, the lower connection is a spring loaded connection that uses nuts on studs. Brian: CAUTION: If you slam the nuts all the way to the top of the studs during install you may find it very difficult later to get the nuts separated from the studs...if this happens you can take that stud to your local auto parts store and get a replacement if they have the same (not likely) or a metric threaded bolt of the same spec and slightly longer (at least quarter inch longer) to make install with the spring connection easier---again use liberal amounts of anti-seize. Torque manifold nuts to 25 ft/lbs.
• You probably won’t be able to reach one of the header nuts on the underside of the tubes. You can use a ratcheting end wrench from underneath to tighten it, but you will need to guess on the torque.
• Install the lower O2 sensor from underneath, using anti-seize. Tighten with a 22mm open end wrench.
• If you were unable to install the upstream O2 sensor prior to installing the header, install it now, using anti-seize. Tighten it as much as you can by hand. Finish tightening it anyway you can. (I found that I could work my hand into place with a small vise-grip plier and grab the 22mm nut to pull it tight. The little cup shaped shield around the nut makes it miserable to get a wrench into place.)
• Plug the O2 sensors into the receptacles. The lower sensor wire will be long enough. If you purchased the short extension for the upper sensor, just plug that into place, routing the wire away from the header. Otherwise you will need to pull the existing receptacle plug out of the bracket and find a way to hold the wire off from contact with the header.
• Picture below shows the only way you are going to get the alternator back into position. You need to take the tension off the belt. Notice that the spring loaded tensioner is the pulley immediately under the alternator pulley. You need a 14mm socket on a long wrench to reach it and then apply torque clockwise (pushing wrench toward driver's side headlight) to take the tension off the belt so you can thread your alternator bolts back in. If you have removed the battery box, you can easily do this by yourself.
• Now reconnect coolant lines and attach the bracket again to engine block with original hardware, reorient the line as originally installed, including the plastic clamp that holds it organized up by the overflow bottle.
• Reconnect the breather tube to the rocker arm cover, and clip into place.
• Reinstall the firewall bracket hold down for the AC lines.
• Reinstall the battery box, and clip the plastic wiring clamps into place.
• If equipped, reinstall the center and passenger side shock tower brace.
• Install the main heatshield again which protects the brake lines from radiant heat.
Brian: Please do NOT use header wrap, it traps moisture and no header maker will warranty a header with header wrap. Instead, consider our TDR heat blankets (which don't trap moisture) or our ceramic coated versions or nothing at all (stainless material is already MUCH more thermally efficient than mild steel used in cheaper headers).
Install new mid-pipe and muffler:
• Assemble the two pieces of the mid-pipe. Lay the old mid-pipe on the floor next to the new one.
First, slide the supplied clamp over the joint. Orient it so the clamp nut faces down and to the driver’s side of the car when the pipe is installed. Then spray soapy water on the connection and slide the pipes together.
Adjust the length of the new pipe to closely match the old one. Orient the Helmholtz tube to the driver’s side of the car, using the mounting bracket on the pipe as a guide. Tighten the clamp just enough so that the pipes don’t slide easily, and position the pipe in under the car.
• Now lift up the mid-pipe and hook the mounting bracket into the rubber hanger.
• Loosely connect the flange to the header flange, placing the spring over the studs on top of the mid-pipe flange and finger tightening the nuts.
• Readjust the clocking position of the Helmholtz tube as high up toward the body as possible, but to clear all points on the underside of the car by at least ¼ inch. Do not tighten the mid-pipe connector clamp yet.
• Torque the sprung connection to the header flange (yes, you want the springs compressed) to 17ft/lbs.
• Next, install the muffler,
• Remove the two rubber muffler hangers from one side of the car, using liberal amounts of soapy water spray. Leave two mounts on the opposite side of the car in place.
• Slide the muffler hanger brackets into the mounts still on the car, and support the muffler roughly level.
• Slide the rubber muffler hangers you just removed onto the body brackets and muffler hanger brackets.
• Orient the mid-pipe flange to mate almost exactly with the muffler flange. Place the new aluminum gasket in place, install the two bolts and nuts and finger tighten them.
• Check position of the chrome outlet tubes, and reposition them in or out as necessary by adjusting the length of the mid-pipe. Then tighten the mid-pipe clamp bolt to 15 ft lbs.
• Tighten the muffler flange bolts to 25 ft lbs.
Install the cover plates back under the car
• Reinstall the three cover plates under the car and torque nuts to 18 ft/lbs.