N54 vs N55

[Timberwolf]

I just found out from my tech that the N55's cast iron crank shaft is 3kgs lighter thank the N54 forged unit. (bmw tech manual) So I guess each has an advantage. Lighter is nice ultimately, but it wont have the resilience the forged one will...

[Frustration]

Going from 335 to 135-54 to 135-55...


The exhaust note is absolutely deeper. Stock, it's similar to the performance ex.


On performance, after break in / learning, there is very small amount of initial lag, but the dct and your gearing choice mean that it just doesnt exist much. Press the sport button and it's just not there.

The lower mid range is more punchy in the 55.

The 54 is still pulling a bit harder above 6000.


I'm getting 2-3 more mpg, but that will change over time I would guess.



I understand how fragile ego's are around here, but I would not hesitate to call either engine bad. They're both fantastic and frankly it's a wash. Any one suggesting night and day difs or anything but incidental advantages (in either direction) are, IMO just full of themselves (no short supply round here).

[new2the3]

Originally Posted by 1SerieStud

let's cut cost and make a more modern engine combining valvetronic and twin scroll turbo technology which exhibits full torque 200 rpm's sooner than the n54. Doesn't sound like a cost cut to me

FYI - internals are still forged.

some dynos show less low end tq. I an find some dynos if you want, I think edmunds.

[UdubBadger]

Originally Posted by Frustration

I understand how fragile ego's are around here, but I would not hesitate to call either engine bad. They're both fantastic and frankly it's a wash. Any one suggesting night and day difs or anything but incidental advantages (in either direction) are, IMO just full of themselves (no short supply round here).

This is one of the smartest things I've read on these forums in 3 years.

[Frustration]

Except I meant to say either engine "great"... Meaning it's also one of the dumbest posts ever too

[UdubBadger]

we knew what you meant...

[scs]

Originally Posted by Timberwolf

I just found out from my tech that the N55's cast iron crank shaft is 3kgs lighter thank the N54 forged unit. (bmw tech manual) So I guess each has an advantage. Lighter is nice ultimately, but it wont have the resilience the forged one will...

forged vs cast, that's a huge cost savings for the n55 vs n54. not to mention forged is hell of a lot stronger. the lighter crank in the n55 would explain better perceived throttle response some have noticed compared to the n54. 7lbs or so less rotating mass is enough to notice on an engine of this size.

[NYC6]

I for one would like to see something in writing(reliable source) regarding crankshafts as opposed to some tech at a dealers word. He might be very well right but there are always alot of erroneous 'facts' that come from these types of informants.

[scs]

Originally Posted by NYC6

I for one would like to see something in writing(reliable source) regarding crankshafts as opposed to some tech at a dealers word. He might be very well right but there are always alot of erroneous 'facts' that come from these types of informants.

part numbers are different between the n54 and n55 crankshafts. pistons and rods are the same part number as far as i could tell. i'd be interested in seeing that true specs of the n55 crank.

[NYC6]

Originally Posted by scs

part numbers are different between the n54 and n55 crankshafts. pistons and rods are the same part number as far as i could tell. i'd be interested in seeing that true specs of the n55 crank.

Thanks. Thats a bit of info that might point to a non forged crank in the N55.
Does anyone know if the pistons and rods in the engines are forged?

[RPM90]

Originally Posted by scs

forged vs cast, that's a huge cost savings for the n55 vs n54. not to mention forged is hell of a lot stronger. the lighter crank in the n55 would explain better perceived throttle response some have noticed compared to the n54. 7lbs or so less rotating mass is enough to notice on an engine of this size.

"huge" cost savings?
How huge do you thing it is?

The N55 has a much more advanced and costlier valvetronic system, compared to the now old tech throttle plate design.
TS exhaust manifold takes greater design and build effort to create optimal airflow for the TS turbo. The more efficient, better design TS turbo may cost as much as the 2 smaller traditional turbos

Weight reduction is no small thing, as most people complain of ever increasing weight. A cast crank saves weight and improves engine response. That's bad? Plus, less turbo plumbing.
Sure, a forged crank is stronger, but we'll have to see if the cast unit actually posses any real problems.

People are kidding themselves if they believe that a more advanced engine, which might actually cost less overall to produce, falls in the negative notion of "cost cutting". Reducing manufacturing costs while delivering a highly advanced engine is not "cost cutting" in the negative sense.
It's pretty smart business.

If the N55 actually sucked, then sure, it would be "cost cutting" gone wrong. But, that didn't happen. So, the negative comments are pointless.

[scs]

Originally Posted by RPM90

"huge" cost savings?
How huge do you thing it is?

a several hundred dollar cost reduction on a single part, multiplied by tens of thousands of units, multiplied by years upon years of model ranges equals a huge cost savings.
that was my point, nothing more.

my only other point was i thought it was interesting that the part changed from motor to motor. a forged crank was a point of interest in the n54 press release in '06/'07, which obviously was something bmw thought the motor needed then.

"Crankshaft
The cast iron crankshaft is retained for the N52KP and N51. To accommodate the
increased power output of the N54, the crankshaft is forged steel."

[JB135MDCT]

Originally Posted by scs

part numbers are different between the n54 and n55 crankshafts. pistons and rods are the same part number as far as i could tell. i'd be interested in seeing that true specs of the n55 crank.

How did you get the part numbers as of March 2010 build?

Still no one has provided hard facts that the N55 crank is not forged.

[HellaFlush]

I wasn't trying to start a war, I just wanted to see what were some of the members thoughts and opinions.

[Frustration]

You're good to go.

This was such an obvious mine field that folks saw it and gently walked to the middle

[Andrew@ET]

I like he n55 better personally.. stock vs stock but if i wanted a 450 race car i would choose the n54 its definitely proven itself.


my n55 makes some pretty sick sounds for a tune only car

[scs]

Originally Posted by HellaFlush

I wasn't trying to start a war, I just wanted to see what were some of the members thoughts and opinions.

no worries man, i wasn't intending on getting attacked either. i was just responding to the different crank between the two motors.

[HellaFlush]

Originally Posted by scs

no worries man, i wasn't intending on getting attacked either. i was just responding to the different crank between the two motors.

My friend up north told me that in 2012 the N54 will be back, I don't know if that's true or not. Either way both engines seem good.

[MarkR171]

Originally Posted by HellaFlush

My friend up north told me that in 2012 the N54 will be back, I don't know if that's true or not. Either way both engines seem good.

Your friend is wrong.

[GtiGyver]

N55 sounds deeper and throatier than the N54 due primarely to the midpipe exhaust not having cats as found on the N54, and only has one cat on the downpipe instead of two as on the N54 (for obvious reasons).

As engines go, with full catle$$ exhausts on both, I doubt they would sound all that different.

As for valvetronic vs twin turbo, I'm pretty sure that two turbos cost more than a single unit mated to valvetronic.

[1SerieStud]

Originally Posted by GtiGyver

N55 sounds deeper and throatier than the N54 due primarely to the midpipe exhaust not having cats as found on the N54, and only has one cat on the downpipe instead of two as on the N54 (for obvious reasons).

As engines go, with full catle$$ exhausts on both, I doubt they would sound all that different.

As for valvetronic vs twin turbo, I'm pretty sure that two turbos cost more than a single unit mated to valvetronic.

Don't be so sure:

1) Turbochargers date all the way to many decades back, valvetronic is fairly new technology when compared to a turbocharger.

2) The single turbocharger has yet more innovative technology built into the system (twin scroll), which I am quite positive makes the turbocharger more expensive than a regular one.

So, mate a twin scroll turbocharger to valvetronic, and I can guarantee that due to newer technologies combined, you're looking at a more expensive setup. Regular twin turbo setups have been around for a while.

[RPM90]

Originally Posted by scs

no worries man, i wasn't intending on getting attacked either. i was just responding to the different crank between the two motors.

There was no "attack" as you puti, nor was there intent to attack.
You made a statement of fact, and I asked how much the difference would be.

The statements I made after asking you to clarify your comment, was intended towards the general topic and not specifically at you.
I should have been more clear.

To your point again; I know that a forged piece costs more than a cast piece. But, BWM choose to save money in one area for a reason, and then choose to spend it somewhere else for a reason.
Saving costs on manufacturing, while still delivering a great product, simply doesn't add up to "cost cutting", as I stated.

Going with a cast piece may prove to be a mistake in the long run, or BMW has since discovered a costlier forged piece wasn't necessary for the N55. Cost savings on any one item shouldn't be made outside of the whole, imo.
BMW still have to produce this engine at a price point, so they spend less on one thing and more on another.

No attack intended, just discussion.