This is a retrospective post, I already replaced my turbos, replaced my sump gasket and installed VAC sump baffle last November 2018.
At the time I had a coolant leak from the rear turbo coolant upper line, the leak wasn’t major, and I could usually go a week or so before needing a coolant top up.
But this meant that I couldn’t enjoy the car the way I like it, it would be too risky to take it to the track with any kind of coolant leaks, even a minor one.
To change the busted coolant line, I needed to drop the front subframe, and support the engine from the top. I thought if I am already there, might as well replace my turbos, change my leaking sump gasket and install a sump baffle.
Unfortunately I faced a very annoying hurdle, one of the turbo manifold studs was seized on the engine head. The Torx head of the stud broke upon removal, and there was no way to put a tool on it to turn it. Those studs are made of carbon steel, which is pretty soft and malleable to protect the threads on the engine head from getting cross-threaded or stripped by over-torquing the studs. As it’ll be a much more costly repair damaging the threads on the engine head. The downside, if the stud is done too tight, or seized on the head, it’ll most certainly shear on removal.
That’s the seized stud, couldn’t be in a worse location
I spent hours and hours trying to use different sizes and types locking pliers, I tried putting two nuts against one another and spin the inside nut, I dremelled a small section on the stud to fit a screwdriver onto it, and absolutely nothing worked. Eventually, I had to call all the local welders within 10km radius, and see if someone can come to weld a nut on the stud, and then I can put a spanner on it. A mobile welder came within two hours and welded a nut on it, which broke upon attempting to turn it. We then welded a stronger brass nut (old exhaust nut), and heated the surrounding engine head with a torch. This caused the engine head to expand, and slowly the stud started turning. It was an absolute nightmare getting it off.
Finally the bastard is out, I threw away all the old hardware, but I’ll be keeping this one for memory
The rest of the job went smooth, the steering rack is a bit of a pain to slide back on the steering column, but eventually got there after a few trial and error attempts.
Also, DO NOT torque new turbo manifold studs when inserting them into the head, there is a lot of wrong advice going around online saying that these should be torqued to 10Nm or 15Nm. ISTA/D doesn't mention anything about this. The right way to bolt these studs, is to treat them like standard head studs, basically spin them until they bottom out in the head, and that's it. Then slip the turbos on, and torque the flange nut to 20Nm. The flange nuts are what actually provides the fastening force for the turbos to the head, not the head studs themselves. So there's no point doing the studs too tight, it increases the chances of seizing them on the head and breaking the torx bit on removal in the future.
Car drove fantastic on the first test drive
, turbo rattle is completely gone now, not existent on cold-starts either. I forgot how great these cars sounded without that dreaded rattling noise (this alone is worth replacing the turbos for haha
).
From a predominantly performance perspective, the new turbos only seemed to increase peak performance by 10-15%, full throttle feels a tad stronger, BUT it improved the response time massively, reduced the lag and significantly sped up the initial spooling. I also noticed that the car pulls stronger at partial throttle applications, that’s probably because the wastegates are more closed at partial throttle on the new turbos, due to the firmer wastegates’ arms’ bushings. My old turbos had wastegate arm free-play and the dreaded rattle, which meant that the wastegates are less shut at partial throttle due to them playing around more freely.
Moving on to next task
While I was there, I also installed a baffled sump, I’ve been planning this for a while. A few months ago, I bought a spare N54 sump from the UK, and I bought a VAC Motorsport baffle from the US. I got the sump sandblasted, and took it to Rev Speed Auto for welding based on recommendation from mates.
Ray’s welds are very clean, and I definitely only want top notch work on my car
Old pan vs new pan
The concept of a baffle is very simple, it has two small gates that are free to open and close, based on the g-forces the engine is getting subjected to.
Under hard cornering and acceleration, the gates are closed to prevent the oil from slushing around everywhere inside the engine sump. This ensures that the oil pump pickup constantly has oil to suck, and reduces the chances of sucking in air bubbles or having an inconsistent supply of oil to the rest of engine components.
I also fitted the oil filter from the S55 engine in the F8x M2 Competition/M3/M4, been running it for just over 20k kms now.
Realoem entry for the S55 filter part no.:
Lastly, I got my outlets modified, this is a very common mod, just makes life easier for the rear turbo to puff air through. The stock rear outlet is squished on RHD cars for some reason. Some people reckon it’s to clear the steering rack, but I doubt it, since even if you straighten the pipe like I did, it still clears the rack fine. Unless BMW just wanted to be more cautious.
Stock outlets
After about 33-36 hours of labour, she's back hauling ass on Melbourne's roads again 
