Comments on: The latest BMW engine: N55 – found in the BMW 5 Series GT

By: Stunning photos BMW 5 Series GT

Stunning photos BMW 5 Series GT — Sun, 18 Oct 2009 16:36:23 +0000

[...] 535i GT model will also be available in 2010 powered by the new N55 twin-scroll [...]

By: Spy Photos: BMW 3-Series Convertible Facelift

Spy Photos: BMW 3-Series Convertible Facelift — Tue, 01 Sep 2009 01:06:15 +0000

[...] Engine wise, many BMW fans and owners are looking forward to possible new engines, from the ultra efficient 2.0 liter diesel with fuel consumption ratings of 4.1 l/100km(57MPG ) to the N55 3.0 liter engine. [...]

By: pandamalone

pandamalone — Wed, 08 Jul 2009 08:56:03 +0000

Honestly I am disappointed BMW replace the two small turbochargers with one single twin-scroll turbocharger. It’ll definitely cut cost and weight, but performance-wise a single twin-scroll charger is still not as good. Not to say the twin-turbo has better potential for tune-ups. The introduction of valvetronic is good, however it won’t help as significantly as it did in the N52 which is still port injection and whose engine load is solely controlled by the amount of air-fuel mix into the cylinder. Engine response toward sudden fuel paddle kick-downs will be better, thou, with valvetronic. It provides a solution to kill dead volume in the intake manifolds, similar to the one-throttle-per-cylinder design in the E46 M3’s S54B32 but cheaper.

By: Doug

Doug — Wed, 27 May 2009 14:43:04 +0000

@tk: Great diagram! Although, it was baffling at first because it looked like the turbos were on backwards. That choice in routing particular cylinders in both banks to particular scrolls is interesting, it must have to do with the firing order?

In the link below, there’s good pictures of the 4.4L and fantastic commentary from readers regarding the engineering decisions. The article mentions that variable geometry is very expensive, and BMW is using very simple turbochargers, benefitting from short exhaust and intake length (thanks to air-water intercoolers) that minimize compressible volume and thus turbo lag. There’s no explanation for twin-versus-single turbos, though.
http://www.autoblog.com/2008/01/21/detroit-2008-bmws-twin-turbo-4-4l-v8/

I wonder if they’ll move to water intercooling on the N55, and how the performance segmentation will work (eg, NA -> T -> TT).

By: tk

tk — Wed, 27 May 2009 05:07:17 +0000

@Doug: http://www.flickr.com/photos/bimmerfile/3491324570/in/set-72157617551106180/

i can’t find a pic of the exhaust manifold for the N55, but i’m sure it’s similar to the one from the X5/6 M engine above (seriously, anyone know the engine code for this thing?). obviously, the N55’s would have 3 cylinders feed each of the inlets, instead of 2 on the X5/6 M engine.

not exactly ‘trick’ per se – just a necessary design to make the twin scroll turbos work.

By: Doug

Doug — Wed, 27 May 2009 03:09:44 +0000

Horatiu — would be really interesting to hear what they say! Who are these “right people”?

@tk: Honestly, I thought I’d read of at least one BMW that used it, so assumed they were moving to that.

What’s this trick exhaust manifold you speak of?

Another possibility is that each scroll is shaped so as to provide different benefits.

By: tk

tk — Wed, 27 May 2009 00:01:41 +0000

@Doug: good question. i’d like to know the answer also.

but i do know that they don’t have variable vane geometry like the 997 porsche turbo’s turbos. low-rpm boost is accomplished through the trick exhaust manifold and twin-scroll turbos.

By: Horatiu B.

Horatiu B. — Tue, 26 May 2009 23:09:34 +0000

@Doug: Let me find out tomorrow if we can get the right person to answer this question. I’ll send the question to the right people and see what we can get

By: Doug

Doug — Tue, 26 May 2009 23:01:39 +0000

If a single twin-scroll turbo is equivalent to the twin/sequential turbos in the N54, why did they use twin turbos to begin with? Twin scrolls aren’t that new. Why are they using twin turbos in the 4.4 if one will do? It just adds complexity to the plumbing and engine tuning.

I understood that the benefit of these turbos was not so much that they’re twin-scroll, but that they have variable geometry (do they?) and can force faster spinup with less exhaust pressure.

By: Carlos Perez

Carlos Perez — Tue, 26 May 2009 18:49:26 +0000

Isn’t supposed that the N54 was going to recibe an actualization to generate 326 hp?? because if so, it doesn’t make much sense to offer this engine with less hp that the N54.

And same question here, this engine qualifies as a turbo, twin turbo, or supercharged engine?? (The last one is the least probable, but just in case, i’m no to relationated with the turbos topic)

By: steven

steven — Tue, 26 May 2009 16:18:05 +0000

so are there 1 or 2 turbos in the new 760. i just assumed there were 2, but a quick search makes me think 1, based on the fact that they used the term “twinpower” there too…

just curious…

By: Shawn

Shawn — Tue, 26 May 2009 14:40:28 +0000

Incredible! Place this engine in the new 135Tii or 335Tii with their respective low weight and I will sign my name on the dotted line. If the massive 4000 lb + 5 GT can average nearly 32 mpg – imagine the performance and efficiency of the engine in a much lighter car (1000+ lb lighter!!!).

Once again BMW’s dominance in engine technology leads the way. Bravo.

By: Blog Auto

Blog Auto — Tue, 26 May 2009 13:44:43 +0000

@Horatiu B.: its from the 5 series GT press release, the engine in the pictures is the L6.. :=)

By: Horatiu B.

Horatiu B. — Tue, 26 May 2009 13:43:29 +0000

@Blog Auto, is that from the Press Release since I can’t find any photo of the N55?

By: Blog Auto

Blog Auto — Tue, 26 May 2009 12:09:44 +0000

you can find the picture of the N55 if i’m correct : http://blogautomobile.fr/moteur-bmw-n55/

By: Joe

Joe — Tue, 26 May 2009 08:06:45 +0000

How long do you think until we see this engine in the 335i?

By: mb81

mb81 — Tue, 26 May 2009 06:30:24 +0000

the engine is not similar to the one of X5/X6, but to the one of the new V12 in 7series. It uses a single twin scroll turbocharger, too.

By: tk

tk — Tue, 26 May 2009 05:25:38 +0000

negative. the turbo used in the N55 is made my borgwarner (you’ll have to look at the high-res press images to see the logo).

http://www.flickr.com/photos/bimmerfile/3556702522/in/set-72157618667535940/

the turbos used in the 4.4 twin-turbo (anyone know the encode for this thing?) is made by garrett.

http://www.flickr.com/photos/bimmerfile/3490510341/in/set-72157617551106180/