Part 1
As some of you know, I installed the European e46 M3 (not CSL) headers on my Z4MC a couple of weeks ago. I just installed the pre-cat O2 sensors on the headers and the 2 post-cat O2s and EGT sensor were not initially installed as there were no bungs for those.
I drove the car around for about 300-400 miles this way and could feel the power gains from a seat of the pants through the rev range. The power gains could be felt in the low end and mid-ramge during part throttle driving which was/is really great esp for the S54 which can use all it can get in this section of the power band.
Since the car was running perfectly fine without the 3 sensors mentioned (there is a check engine light/SES light), I brought the car to a dyno on Monday morning. The results compared to stock are VERY impressive.
Part 2
I brought the car to RRT in Dulles, VA to create a modular wiring harness that would allow relocating the post-cat O2 and EGT sensor connectors to under the car (under the black plastic cowl that hides the fuel filter, TPMS module etc.) or have them in their original location (on top of the valve colver). They used MIL spec wires, OEM black wire tubing, Deutsche connectors and gold pins to do this. James@RRT was meticulous and created an OEM style wiring harness.
He also installed an EGT sensor bung I had a friend make for me onto the secondary cats where the Euro Z4Ms and M3s have it.
Exhaust Gas Temp Sensor Discussion
The other task was to possibly install the post cat O2 bungs onto the secondary cats similar to the European spec Z4M, but we were not sure if the heat shield on the OEM section 2 would get compromised during the install so that part is yet to happen.
Part 3 - Still researching this ....
I want the car to be emission compliant (no SES light) without a flash, if possible. So here are my thoughts/options so far
(1) Find a used Z4M secondary cat section and test that out with the bungs - if someone wants to sell me one, please PM me. The research will help us all at my expense :thumbup:
(2) Find how to source a Euro cat section from a Z4M. North Haven and Tischer dont even list that part #. This will be the easiest and should be plug and play now.
(3) Find a Euro M3 cat section with all the bungs and have the flange that connects to the X-pipe correctly oriented to match the Z4M.
(4) Talk to Fabspeed to see if they will match the flange for our cars.
(5) Find hi-flow OBD2 cats and get a custom section 2 made.
Your thoughts and opinions are very welcome.
Enough words ...
The Euro headers from an e46 M3 race car-
Removed this heat shield and the secondary air pump valve and black plastic tubing.
Under body shield removed
Stock headers exposed
I made sure which O2 sensor connector goes where though BMW has done a good job of labeling as well. 1- post cat O2 for the front bank and 2 - post cat O2 for rear bank. These two connectors were relocated yesterday to under the car along with the EGT one.
Next I broke loose the EGT and O2 sensors and unscrewed them by hand and removed them from the headers.
Pre-cat O2s and EGT out and labeled. Post cat O2s are better removed from under the car.
All out ...
The flanges under the car use an E12 bolt head. I loosened these 4 but did not remove them just yet.
Next I took off the 18 11mm nuts that hold the header to the head. I found a 3" wobble head extension and a 1/4" ratchet to be the close to perfect tool for this task.
Half way there
Headers loose ... now I got under the car and removed the 4 flange bolts and guided the headers out from under the car. I could not take any pictures of this step as I had my hands full with humpty and dumpty.
Comparison picture ... the Euro headers look like athletes compared to the US spec ones.
View from the top. There is tons of space to remove these headers, but I found the easiest is to do it from under the car. F360C pointed me that way ahead of time so it saved me the aggravation of trying to do it from the top.
Install is reverse of removal. I slid the headers up from under the car and lined them up on the studs. Then loosely fitted the 4 E12 bolts on the flanges. Back on the top now to get the 6 new triangular gaskets in place (shiny side goes towards the cyl head) and the 18 nuts snugged up.
Pre-Cat sensors go in. All bolts and nuts checked and rechecked for tightness.
I disconnected the 2 post cat O2s and the EGT and labeled the connectors on the car that go to the DME.
I will post up pics of the EGT relocation and wiring harness extension later ... still not pulled them off the camera. Thanks to James@RRT for being patient and letting me take pictures and ask him a thousand questions.
tnsbruce stopped by to check on progress and bought me lunch at this great Kabob place ... and I got to ride in his awesomely quick 530i.
Dyno Plots
These are the 2 clean runs. The dip in the first run was due to the car moving on the dyno in the low RPMs. Once the strapped were snugged up that dip went away so ignore that.
The car dyno'd 313.26 whp/245.26 w tq on Monday morning as the air was nice and cold with low humidity. The SAE corrected numbers were 295.93 whp/232.07 wtq.
For comparison, SAE numbers from a Dynojet are super consistent from run to run and even on different days. Below is my stock plot done on the same Dynojet compared to the one with headers. The gains are consistent with the butt-dyno ... headers are def THE exhaust modification on these cars for a solid improvement all around.
Discuss away.