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About fm540i

  • Birthday 08/03/1959

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  • Gender

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  • From
    Chicago, Illinois
  • Porsche Club
    PCA (Porsche Club of America)
  • Present cars
    2007 997 C4S
    2007 Range Rover Sport Supercharged
  • Former cars
    BMW 750i
    BMW 540i
    BMW X5

fm540i's Achievements


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  1. The MAF sensor on the stock 3.8L airbox and the X-51 are interchangable. I've done the conversion with no problems other than adapting the X-51 inlet hose to the stock inlet plenum. No errors, car runs great with the second inlet and X-51 airbox.
  2. The airbox is around $700, the deck seal $10, the inlet hose around $50. I'm also going to add the air mass sensor wire extention as soon as it arrives from Germany. The stock airmass sensor is a direct fit but the stock wiring harness could be a little longer. The only item I have not addressed yet is the oil filler tube. I purchased the X-51 oil filler tube because it's shorter than the stock tube which does not fit up perfectly to the new airbox. The only problem is I can't figure out how to unbolt the stock oil filler tube without dropping the engine. If your hands are smaller maybe it could be accomplished but I can barely fit my hands deep enough to feel the oil filler bolts let alone actually get a socket on them. I'll take some pictures when I get a chance.
  3. I've finished the retofit and love the results. The X51 airbox is a direct drop in replacement for the stock airbox but there are a few work arounds required. First, you have to be comfortable cutting a hole in the lower metal portion of your decklid. Follow the template and be careful and it's not a problem. A good dremel tool is helpful. It will take some time to deburr the cut and fit the factory seal to the decklid properly but once done it looks stock. Just above the lower metal deck is a black plastic deck which is countored for the cutout. Once you make this cut the second air inlet breaths freely to the outside air. Beyond this the only issue is the inlet duct between the new airbox and the stock inlet manifold. I purchased a good quality silicone transition that acts as a spacer between the x-51 inlet hose and the stock manifold. Once trimmed and glued with a good high temp silicon it fits up perfect to the stock manifold/ Stock manifold has an OD of 3.25 inches. X-51 inlet hose has an ID of roughly 3.75 inches. Buy a silicone hose with roughly .25 inch walls and an ID of 3.25 inches and you have it made. It's a beautiful airbox and the engine breaths much better at higher RPM. Sound is a little louder and I find the engine is a little rougher until fully warmed up. (lot's more cold air coming in than stock)
  4. Your correct, the retrofit instructions call for the modification of the deck lid. I've ordered the kit but still need to come up with a solution on the air inlet hose. The stock MAF sensor works but the stock inlet diameter is obviously smaller than the X-51 inlet. I'll keep everyone updated.
  5. I'm about to embark into uncharted waters. The X51 airbox is a direct replacement for the stock 3.8L airbox except the air inlet tube connecting the airbox to the inlet manifold is larger ie. a wider diameter. Anyone tried the retrofit, the X51 airbox looks great and at $800 is a lot cheaper than the Champian Motorsport carbon fiber box which runs $3 grand. 2007 C4S
  6. I just completed an install of Europipes exhaust with x51 headers on my 2007 C4S and I have to say I'm impressed by this system. Great quality, fit is perfect and the sound is music to the hears. Not too loud but with an agressive bark more like a air cooled 993 or a new GT3. Classic german flat six sound. I would highly recommend the system. Install is DIY with careful planning and a few tools. I can't wait for mine to fully break-in over the next 500 miles. www.europipe.be
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