Hi,
So...it was my turn to go the RB turbo route. I came to the conclusion that the only sane/safe method by which I can increase the power of my car is to get some larger turbos. I don't like methanol injection (although I do have a HFS-4 kit installed) and I don't like the e85 stuff because blending it and keeping count of what you have in the tank is just as messy as the methanol route. Not to mention I can't find e85 here
I have quite a bit of experience with aftermarket stuff and from my experience, the more you stray from the OEM designs, the more problems you are likely to have. Rob Beck's design in which you keep everything mostly OEM is what appealed to me the most.
My immediate goal is to increase the power on 98-100RON pump gas with no methanol compared to the max I got on stock turbos and the same fuel. I would like to have a daily driver car with significantly more kick than on stock turbos. However, this goal will change once the Spring will come, I will then pursue maximum power on 98RON + methanol.
Installation
The installation of N54 turbos (regardless of OEM or RBs) is difficult and took about 16 hours (just like BMW states). In fact, not really difficult but very time consuming, because in order to install them, you have to remove: downpipes, water pump, thermostat, cooling fan, engine cover, cabin filter and the plastic cowl, turbo oil lines, turbo water lines, drain water, drain oil. And reverse everything after install.
The RB turbos have what I consider an Achilles heel when it comes to the install: they are supplied with a threaded stud that holds the water lines in place. That stud has only 2-3 threads into the turbo, and if you tighten it a bit more than "lightly", you will strip the threads in the turbo (however, if coolant leaks because not enough tightening it can ignite and that's a really bad thing).Stripping the turbo thread is what happened in my case and I heard that it has happened several times until now. However, this is not really a problem, the installer welded the stud in place and we could resume the installation the next day. I would recommend Rob Beck to re-think this mechanism by pre-welding the stud on the turbo, or providing an aluminium or copper stud instead in order to not ruin the turbo threads but rather the stud, in case of over-tightening. I have to say that Rob Beck very kindly offered to replace the center core for free (I would only pay for shipping, of course) but being in Europe this is so much of a hassle and waste of money that I preferred to weld the stud in place.
By the way, my 11kg Wagner intercooler stripped the threads on (one of the two) holes on the plastic front part that holds the intercooler in place (problem easily solved by using a larger bolt that re-threaded the plastic hole). It was however still kept in place by the solid silicone hoses that were provided with the intercooler. Imagine what a 13kg Helix intercooler would do. I always thought that aftermarket companies do not do enough R&D. How can you hold a 11-13kg with only 2 bolts screwed in a plastic cover ? (remember, the OEM intercooler only weights 3kg).
My stock turbos, although they were not smoking at all, had both some radial and lateral play.
Road feel
I do have a ProTuningFreaks Cobb map on order but it did not arrive yet, so I tried the RBs with the Stage 2+FMIC Aggressive pump gas/no meth map which I read that it somewhat works with the RBs, because on stock turbos the load targets are too high to be hit (by my car at least) anyway. What I can tell you that you can feel a significant "lightness" of the car already. There seems to be much more power compared to stock turbos, even more than what I could get before on pump gas + methanol. I did not go past 5000RPM but you can feel that these turbos have huge potential.
The exhaust is a bit louder with the RBs, probably because the turbine opening is much larger. I am so glad I have non-droning BMW Performance exhaust
There is no smoke whatsoever coming from the exhaust. Also, the start-up wastegate rattle that I was having with my stock turbos is now absent.
Cabin feel
I hear a faint whistle in the cabin with the RBs. This was not heard on stock turbos. The turbo whine with the windows open is significantly louder than with the stock turbos, even with my closed intakes. But I really like this, it gives the car more personality. However the turbo sound is not obnoxious, it's very acceptable.
Lag
*preliminary impressions* There is quite a bit of extra lag and non-linearity with the RBs, on this map I have used. But don't get me wrong, there is huge torque at low RPMs, *maybe* even more than before, but climb 700RPM up and you get a shove in the back with even more torque I like this, in a way. However, I will update the impressions once I have the chance to test the PTF map, maybe that is more linear.
Dynos
Coming in 3-4 days, depending on when my PTF maps are ready.