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Old 10-11-2010, 10:17 PM   #1
TrickTizzle
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Join Date: Nov 2008
Location: Minneapolis/Milwaukee
Posts: 3,117
My Ride: 325i
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E46 325i Headers Installed - Dyno Graphs included

Ok guys, if you remember my last thread of my B25 stock dyno at 155whp, I got the car dyno'd after headers to show my 11whp gain. Not too bad for a 325i.
The installation was a breeze, the bolts on the head came off like butter without breaking any studs or such! I did not take of the motor mount, and it is definitely not needed, plenty of room to take off headers.
Disconnecting headers from cat-back was a pain in the @ss. 4 of 4 bolts snapped and then I had to punch the fvck out of it with a pneumatic impact gun, and the damn thing wouldn't budge. I ended up taking a pry bar and pry-ed it off.
I was able to install 15 out of the 16 bolts, the middle bolt on the back header was impossible. I had all sorts of extensions and such available, just not possible at all.
I went back and checked the system for any leaks and such, and it is all ok. No leaks were found.
Connecting the header to cat-back was a b1tch. We used a hydraulic jack also to move the cat-back around, to try to align them up perfectly, it just wouldn't happen. We were MM off for the bolt to catch on to threads, and then I pushed my foot down on the foot hydraulic jack to get more leverage and the whole car got up and moved literally 4 inches to the left off the lift. Now we have to get all the stuff out of the way, lower car, re align, etc. Then after hour and a half of messing around with that last bolt we just used a nut and bolt and it did the trick. Hasn't snapped yet, and no leaks were found.
Make sure you use OEM gaskets and nuts.
Here are some pictures and such below.

Ceramic Coated Header from Anthony @ BimmerBrakes




To anyone that wants to purchase headers, I definitely recommend these, I had no issues what so ever. Everything was a perfect fit, oxygen sensor bungs are actually functional. The sensors screwed right in, and they were perfectly placed.


OEM Catalytic Converters


Notice the difference


M54B25 Engine Block



And on to the dyno graphs

NET GAIN = 11 WHP/ 3TQ SAE CORRECTED

Stock Dyno




Dyno with headers


-Kind of pissed off the guy needed 12 pulls to get 3 clean ones, where as the first guy got 3 good pulls each time...My tires are pretty worn out now.


Overall I'm very happy with results. Love the new exhaust tone. Love the new smell.
No service engine soon light due to o2 sims that work perfectly which were also bought from BimmerBrakes. I got the header install done in approximately 8 hours, BUT I did have the car on the lift ft high, and a professional toolbox with all extensions, pieces, etc.
Very fun install. Not hard at all, but never again.

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