tpaxadpom

I would want to see long term reliability data when making 507hps, matching stock S85s. But the fact someone measured 850hps on the dyne doesn't give you a full picture. I am talking long term reliability when you vary temperature, humidity, load, vibration over time. It is possible that pushing that engine to 850hps took 90% of its lifespan. It may not be big concern to modded but it is to BMW.
I don't own S85 nor N54 engine so I cannot speak from my personal experience. My opinion was formed based on information I have found online.
Here is my opinion on S85s. It is top of the line engine for E60 chassis.
1) If N54 was such a monster why not simply improve upon N54 design and be done with it? 2) Why did they replace N54 with N55?
3) Why BMW is so conservative with their SE version of N55?
I understand the need for extra cylinders required to sell at premium prices, the sound and all. 4) If N54 was such a monster why waste money on R&D developing new platforms instead of fine tuning what they've got?
5) You think BMW didn't know what N54 was capable of or they lack the engineering talent?
M cars are provocative, especially M5 E60 with crazy gear shifts around 8400rpm. You just cannot drive that car normally unlike 535i. That's is why I've asked how you drive your modded 535i.
I am glad to see you guys enjoy N54 and they've been reliable for you. At the time when I had to pick the car I skipped N54 mostly due to failure rate. After I've read numerous horror stories it was out of the question. Perhaps there is a serious sample to sample variation or BMW finally worked the bugs out.

JWMich

Wow - I love my 535i, but it looks like I'm the odd man out on this one. I'd be there all day for a low mileage E39 M5. That's a "greatest ever", whole different ball game vehicle, no way I'd pass that up.

zach1328

1) It doesn't have as much potential as V8's which is what they want their M cars to feature.
2) The n55 is almost exactly the same as the n54. I'm guessing they put very little R&D into it. The reason is has a new engine code is because it uses their new twin-scroll turbo technology rather than single scroll twin turbos. The F10 M5 uses twin-scroll twin turbos and a 4.4L v8.
4) BMW knew and still does know what it is capable of. Why do you think they used it in the 1M when the n55 had already been released? They don't want to fine tune it because then it would kill the market for M3's. Thats why they underrated the n54's power too. It came out in 2007 so if they claimed it had 330hp and 330tq, who would buy an e46 m3 with only 3 more hp and less torque?
5) As I mentioned they know its capabilities. They didn't forge the internals for shits & giggles.

I would say the main reason they left behind the n54 is for their newer twin-scroll turbo technology. If they hadn't developed twin-scrolls then I would imagine they'd still be producing the n54.
You can imagine how much more potential a twin-scroll twin turbo set up has over small twin turbos.

In case some people don't understand the difference between twin-scroll and single scroll I'll do my best:
Twin-scroll turbo's use 2 turbines inside the housing of 1 turbocharger. 1 turbine is small and spools at low RPM's to prevent turbo lag. As exhaust gasses increase the valves for the smaller turbine begin closing and allow the larger turbine to start spooling. The larger the turbine - the more power. The smaller the turbine - the less power, but also less lag.

To reduce lag with the n54 they used 2 tiny turbos. That's great for minimal turbo lag but they aren't as capable in the higher range since the turbine's aren't very large.

Notheld

In case some people don't understand the difference between twin-scroll and single scroll I'll do my best:
Twin-scroll turbo's use 2 turbines inside the housing of 1 turbocharger. 1 turbine is small and spools at low RPM's to prevent turbo lag. As exhaust gasses increase the valves for the smaller turbine begin closing and allow the larger turbine to start spooling. The larger the turbine - the more power. The smaller the turbine - the less power, but also less lag.

To reduce lag with the n54 they used 2 tiny turbos. That's great for minimal turbo lag but they aren't as capable in the higher range since the turbine's aren't very large.[/QUOTE


The single most important feature of a TwinScroll Turbo is the 2 separate exhausts manifolds. Most if not all of the boost and efficiency gain in a TS setup is extracted from exhaust scavenging.

zach1328

Yes I agree in lower gears like 1-3, but once you get into higher gears at higher RPM's the exhaust manifolds aren't changing so there is less of a loss in efficiency.
That's all stuff that will be minimized if not completely eliminated after enough R&D and innovation.

Might not be for 10 years down the road, but the point is BMW believes the twin-scrolls have more potential.

Notheld

Im not sure were talking about the same technology.

Twin Scroll Turbo separates individual manifolds for each firing cylinder and points it to one inlet in the turbo housing. BMW pretty much invented or perfected the use of bigger veins for high rpm backpressure and smaller veins for low rpm's. This isnt my opinion.

Thedohboy

My opinion, I'd get neither. :/

Here's what I've dealt with in 3 years: flooded injectors twice, bad HPFP twice, failing turbo wastegates, high carbon buildup, and more misfires as of last week; injectors + plugs again. I'm tempted to walk away from BMW altogether considering I also had issues with my last BMW.

Note: E60 535i @ 62K miles, always chevron highest octane, oil changes <10K miles, and I drive like a grandma. I've just had really bad service advisors and terrible service techs. Beware of BMW of Mountain View.

timmay77

I have both, well, E61 535xiT and an E39 M5, but it's not really fair for my E61......

Booyaazaa

First step is don't go to Mt VW BMW. I have yet to hear anything good about them from the local BMW groups I run in. You'd have better service at Concord, Fremont and Stevens Creek BMW. If you want I believe my old advisor works at Stevens Creek and i can check to get you connected. Second is 10k is too long of a interval for oil changes, especially if you still run BMW synthetic oil, 7-8k is ideal. I've had my share of problems but nothing reoccurring. I'm at 86k miles right now and got the car 3.5 yrs ago with 26k miles. The last 20k miles, after my turbos got replaced, cars been trouble free and I drive it like I stole it everyday.

That is a very nice setup and must be a beast. How much boost are you running?

timmay77

Thank you. Running 10.5lbs, it's pretty fun to drive......