N55 VRSF DP / FBO review, vs. N54
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So I finally got around to installing my VRSF downpipe that's been sitting in my garage for 5 months. I had to take it to Kummrow because for whatever reason, in manufacturing, VRSF welded one of the O2 sensor bungs in upside down, and the bottom side of the bung is crescent shaped so needed to be machined flat so the o2 sensor could sit flush. On top of that, fitment was not exact and shifted the exhaust, so one of the support brackets for the midpipes had to be altered in order to reposition the exhaust so it doesn't rattle/push up against my rear bumper.
with that out of the way, I can now speak to an FBO N54 vs FBO N55, same mods, same tune. My N54 was a 2008 6MT, and my N55 is a 2011 6MT.
everyone always talks about how much better the N54 platform is for power due to forged internals (truth) and the fact that the N55 has a single, smaller snail and can't flow as much air through the turbo (also truth).
I'm finding that down low, they both feel the same when you aren't running meth/E85. Stage 2 fbo provides an incredible throttle response increase on both engines. Both N5x engines were designed to be low-midrange motors, and they definitely die up top. But it's been 8 months since I drove my N54 and I can safely say that it holds more boost longer by far than the N55 and you can definitely feel that up top. I can readily feel the N55 drop off and run out of breath on the stock turbo as early as 4500 rpm. I could feel the same type of wall in the N54 above 5500 rpm. The gas pedal is to the floor but the boost just tapers a LOT sooner on the stock N55. It cannot hold as much boost for as long a period of time. Peak target was still 19.4 PSI but by 5500 or so, I could hear the diverter valves releasing pressure significantly.
In pure performance, my conclusion is that if you don't want to get serious about mods and are interested in just the basic FBO setup, then either engine is more or less on equal ground. N54 will almost surely dyno a bit higher ( I will confirm this when I am on another dynojet on the 18th ), but not so drastic that it wouldn't be a driver/traction race between the two. The reason to go N54 are really when you start talking meth/E85 because then you can start raising the boost, and the stock N54 turbos just support more boost, plain and simple. If the PURE Stage 2 N55 turbo pans out as not blowing up the bottom end at 500 whp, then I would argue in most cases (for most enthusiasts) it will in the future become a wash as to whether you get an N54 or N55, and unless you want 700 whp (which requires an N54 if you want to run stock internals), then I would recommend either engine.
Subjectively, the N55 sounds a hell of a lot better than N54 in terms of engine/exhaust note when fully bolted on. by "better", i mean less raspy, much deeper tone. If you like the rasp, then N54 is for you.
All things considered against the stock N55 snail, I'll definitely be looking at the PURE Stage 2 over the next year. I have no desire to maximize boost on an aftermarket turbo like that, however, I would feel better with a turbo running 21 PSI that I know isn't being strained at its efficiency limit. 425-450 whp would be sufficient. In the immediate I am probably going to pick up a bms meth kit to get more warm fuzzies about the higher boost levels I'm running, as well as help mitigate the heat soak issues of these engines.
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
Peak target was still 19.4 PSI but by 5500 or so, I could hear the diverter valves releasing pressure significantly.
The waste gate should be taking care of this. The diverter valves should not bleed off boost when you are on the throttle.
Has anyone ran a twin turbo setup on the n55? Or only a larger single.
Edit:Unless the n5x has some crazy system going on?
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I'm excited to see this on a dyno!
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The waste gate should be taking care of this. The diverter valves should not bleed off boost when you are on the throttle.
Has anyone ran a twin turbo setup on the n55? Or only a larger single.
Edit:Unless the n5x has some crazy system going on?
The problem is that the diverter valve on n5x are shitty plastic. This was not remedied for the N55. I have an aftermarket charge pipe, but until I do some data logging I won't be able to see if my stock diverter is shot. It does happen under high boost, albeit not a guarantee. I blew both of them on my N54 within doing 4 WOT pulls after I was Stage 2 FBO, lol. Needless to say I immediately went to buy forge DVs. If it ever stops being wet outside, I will be taking the car out for some more WOT to log and see if it's all in my head. I could just be paranoid due to my past experience with N54.
nobody is running twins on an N55.
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
iirc the n55 diverter valve is on the turbo correct? and a bog warner turbo. i haven't heard of too many failures with it.
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yea it's attached the outer housing in front of the turbo. It's not directly attached/mounted to the turbo itself because it would melt to lava instantly
here is a diagram for reference:
http://www.1addicts.com/forums/attachment.php?attachmentid=621288&stc=1&d=1324300903
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
Just like the newer vw turbos. Theu have issues with the diaphragms tearing.
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i need a new car.
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
mines a 2007, and now killed with bad cam bearing ledges . be happy lol
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noooooo the dreaded cam issue. FIx that shit. Car season is upon us.
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
Indeed. Too busy to fix.. it will remain fubar till i acquire time and monies..
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whoa whoa, a car enthusiast without enough time and money? well now I've just heard it all......as I sit here crying myself to sleep every night knowing how much a Stage 2 turbo + clutch + LPFP + meth will cost me.
we'll get there someday
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
Ive been relabled as community bmw mechanic. Lol. Dont have time to fix my stuff and Work has me pinned down horribly. Looking desperately to aquire a new welding/fab job. But i dont wanna derail your thread. How was the installation of the dp? Easier than the n54?
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my threads exist purely for mindless bantering. we're all good here. IMO easier install given only 1 clamp to deal with. Getting the clamps off those turbos is a pain in the ass. But at the same time, I like having a lot of clearance to work with and if you just remove the transmission bracket that's attached to the stock downpipe, it's certainly easier but still not as much as I'd like. When I do the turbo (assuming all goes well and I can actually buy it next year), I will probably remove the engine mount as well because that would make it extremely spacious and easy to work in, especially in terms of getting the O2 sensors off.
I personally would not recommend anyone ever doing DP installs on n5x without a lift. Having to reach up to the turbo clamp from laying on your back is just a fucking pain in the ass.
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
im 6 ft tall with long arms. Having done dp installs on the lift and on the floor i prefer thw floor lay a blanket down and i just lay on my back the whole time lol
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Jordan's Dyno Pull
@DrLeadFoot
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I personally would not recommend anyone ever doing DP installs on n5x without a lift. Having to reach up to the turbo clamp from laying on your back is just a fucking pain in the ass.
Ha, I can't tell if it would be worse or better with a lift. Helped Spence do his, was a real pain, especially without all of the tools I am used to having at my disposal!
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about what you'd expect from a stupid N55.
335/380. I'm gonna go back after I get my protune and hope for 345/400. I think a Cobb with Protune will put it more in line with a JB4 which are putting out higher FBO numbers on N55s than OTS cobb maps, but that's because JB4 is mostly just a boost controller with very aggressive targets. I am 100% sure the limits of the N55 stock turbo even with the best tune is around 350 whp. Needs meth/e85 to push closer to 400.
I'm now officially saving my pennies for a bigger turbo. I won't be satisfied till I'm blowing kids out of the water north of 500 hp. If my daughter didn't just have an estimate for braces come in at $4700, I'd already have a turbo ordered.
Edit: at least I got my lowering springs installed Friday evening and they look pretty good, so at least one thing makes me not want to sell my car -
2011 E92 M3 6MT ZCP - ESS 625 supercharged
2007 Z4MR
2003 E39 M5
2002 E46 M3
2021 X5 40i -
Regardless of your dyno numbers, your car is still one of my absolute favorite looking BMW's on the road right now.
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