N55 X1 Build Thread - Pics and Story Time!

[wheela]

I think that wgdc looks pretty appropriate for the boost level

[imBlasted]

Nice documentation of the work you have done. I have the same intercooler it was only listed to fit the Z4 E89.

[fnp93]

So for the next chapter in this car’s life were new tires. After a year of driving back and forth to work I ventured out one rainy day and hydroplaned the rear tires. All staying on road of course. I went home and didn’t even need a tire gauge to see, the rears were bald but the fronts were maybe 50% left. So it’s safe to say xdrive is definitely rear bias.

So it’s off to the races for some tires. I spent a little extra and went for PS4’s they look quite handsome on the car I must say

However this is when a new problem began to rear its very ugly head. Transfer case isssues *suspenseful music cue*

[fnp93]

So to recap, the car is xdrive and has a factory Msport staggered rear wheels. This is my first AWD vehicle and having owned several staggered RWD vehicles through the years didn’t think it’d be an issue. Though I had read and research online always replace all 4 tires, which really stinks due to the fact I can’t rotate the tires.

Oh well I said when I clicked purchase. I had them all mounted and balanced at Costco and went with Michelin PS4’s. VERY grippy tires I’ve found.

That said immediately I started having issues studding in the drivetrain when starting from a stop and only occurred when going straight. I would have TC randomly kick in and cut power. The car’s transmission also felt like it kind of was fighting itself. I never once had a CEL and no shadow codes

I removed my spacers to see if that was the issue, no luck. I removed the tune to see if that would help, no luck. I measured the overall width and tire height of front vs rear. The front were slightly taller than the rear however the exact same tire size was used that was on the vehicle and we’re within the 1% difference that Xdrive allows. Also, the rears were actually closer in diameter than before replacement.

I chased this problem on forums for months and even spoke with my local mechanic about this. My mechanic was convinced it wasn’t transfer case since it only happened when starting and going straight.

So after research and going off the history of it starting when I took a chance and decided to change the transfer case oil, recode the VTG, and reset adaptations.

[fnp93]

The TC oil change seems simple however having a N55 model complicated things with the mid pipe being in the way.

If you decide to do this job take it from me just unbolt it or you’ll spend over and hour getting out the transfer case mount bolt. I unbolted my exhaust from the rear resonator and unbolted the frame brace in the rear of the car and exhaust support just in front of the transfer case. I left it bolted in the header and had enough wiggle to get the bolt out.

I’ll link a video I used as reference.

A drive afterward to test and I’d say this fixed the problem by 80%.

The real fix came with a recalibration of the VTG. I used a launch xt431 to achieve this task.

*Important to note, when recalibrating the VTG I could not achieve it with the car off for whatever reason. With the car running, I was able successfully recalibrate*

With recalibration completed and 8 months of chasing this problem. The studder has disappeared!

Disclaimer do at your own risk and if you feel uncomfortable stop immediately and have a mechanic complete

[fnp93]

Bonus notes. You will need to have the car elevated but level. I didn’t feel comfortable having the car on Jack stands as this truly took me a solid 2.5 hours under the car.

I’ve used race ramps for my usual oil changes and simple under car tasks.

To keep the car level, I purchased a set of race ramp 2 piece wheel cribs and felt VERY safe under the vehicle. It gives 6 inches of lift when utilizing all 4 wheels and since the x1 sits higher than my e90 did, it gave plenty of room to work with. Side note you will need a few blocks of wood to stack on your Jack to get the car high enough.

Another disclaimer lift your car at your own risk, this is not a how to, to lift your car. Simply what worked best for me!