[C ///M]

Yes, I know I'm in the N55 forum and that the bias will generally lean that way, but that's completely fine. I'll get input from the N54 side as well.

Quick rundown- I've decided on either an N54 or N55 transplant into my N52 powered E83 X3. Initially I left it open to a lot of options, even going back to my trusty S52 (as I'm most familiar with) or trying an S54 with SMGII (I had an accident a couple years back that paralyzed most of my left leg, so I can no longer operate a clutch pedal). I even thought about going wild with an S65 or an S62, but I started wondering about transmission options. Honestly, the N55 or N54 seemed the most logical and easiest option. Whatever I went with, I'd probably want to eventually grab a turbo kit, so why not start with one...

So that being said, I'm leaning towards the N55 over the N54 for the following reasons:
-Slightly better gas mileage (supposedly)
-Better tech (newer, valvetronic, based on new system vs. M54, etc)
-Better reliability
-Lower Maintenance cost (having to rebuild 1 turbo -albeit twinscroll- down the line vs. 2 turbos

What do you guys think? End goal is a ~400 crank HP vehicle.

Thanks in advance.

Quick Disclaimer since I know you guys see enough pipe dreams on here, but no need to say that I can't do a motor swap. I'm not an amateur, this isn't my first BMW swap, and I have the means to accomplish this (with some help of course). But this project is officially a go. I plan on sourcing the motor between now and the fall so I can start the swap after the race season.

[Blk07335i]

If you can source both and the price is close I would go for the N54 all the way. I've owned the N54, S65 and N55 and the N54 is my favorite engine for a DD. N55 is close but doesn't have the same tuning potential as the N54. S65 is a great engine for the track and sounds fantastic but you have to use the entire power band to get the best from it. Just not as practical on a daily basis.

[eyim1988]

if 400 at the crank is your goal.. either or will achieve that fairly easily..

[Sam335ix]

n54.. but then again you will find an older car with higher miles. Go for the 2011 335is which still has the n54 engine in it.

[Beemw335]

N54, no questions asked.
Tune
Downpipe
Intake
And you have 420ish crank horsepower and a setup that has been proven to be reliable for thousands and thousands of miles!

[C ///M]

Wow, didn't expect that reply from this section, but it's definitely good to know. Typically I wouldn't be the kind of person to buy an engine off of ebay, but right now, there is a COMPLETE (without tranny) N54 with 38k miles for only $3,400. I figure I can knock off a couple hundred dollars maybe and it came from a 335xi. I have to check whether automatic but right there that would be the perfect motor to go into my X3. It would make the electrical the absolute easiest it could be (obviously there's still some extra work involved vs. plug in and go, but not horrible).

I'm seriously thinking about pulling the trigger.

My dream would be to find a 35is motor with DCT and happily pay extra for it, but I'm fairly certain DCT and X-Drive don't play nice and I'm not interested in removing X-drive from my X3, even if it would be totally awesome, this is still my daily.

[benzy89]

Which ever you can find -- I don't know if BMW NA sells the N54 or N55 motors to individuals (not like Mopar where you can order a crate Hemi), so you're prob looking at cars that are totalled & ripping the engine out.

The N54 has a lot more power potential, but also can be more a maintenance headache than the N55. I don't know how it'd work out when you try to upgrade things like the downpipes, intercooler & charge pipe, but I would imagine that using an N55 would be easier (1 turbo, single downpipe to single exhaust all equals less piping/headaches).

But like I started with, it really comes down to availability + if you can find either motor at a reasonable price.

[mashimarho]

The N54 has more in the aftermarket without a doubt. I'm not going to lie... I love my n55.... It sound beautiful, it's quick, and I'm different.
Not really. haha But, get the n55 if you can.

[gustnyc]

I had both motors.. Not at the same time.. I love the toys for the n54 but the fuel pump was a pain.. The n55 I think is a more solid engine.. They were both my daily drivers... The torque on the n55 is amazing, but the mid range on the n54 will eventually catch up to us and pull away..if your goal is 400hp to the crank you can achieve it wit the n54 faster.. If u want close to 400 and a more reliable engine I say go n55... Either way you win..

[fasteddie222]

A lot of people say to get n54 because of the mods... People never see the positive side of the n55 for example it is a lot more fuel efficient than the n54 which keeps me happy.

[benzy89]

Fuel mileage is nearly the same. I'm N54 FBO and averaging 24 MPG right now

[eyim1988]

Originally Posted by benzy89

Fuel mileage is nearly the same. I'm N54 FBO and averaging 24 MPG right now

Haha wow. I'm averaging like 19

[benzy89]

It's my DD & I'm running the COBB Stg 2+ Sport tune which is good for mid-300 WHP/low-400 WTQ (?), so it's not like I baby it around. And about 2/3 of the drive is highway, but when you're cruising at 90 that really doesn't help.

[gustnyc]

Originally Posted by eyim1988

Haha wow. I'm averaging like 19

Both u guys are lucky, I was 18.8mpg with ppk and now 17.9 with jb4.. I was 16.9 with a jb+ on my n54 and 16.0 with jb4 on my n54...mix highway and city driving..

[eyim1988]

I was ~20.2 avg stock.. But with e85 mixes im still supirsed i pull of a 18.8-19 mpg

[CPWINCH]

N54 all day

[C ///M]

I really appreciate the comments. I have a few specific questions for those familiar:

Fuel Economy. Really, I know comparisons are ridiculously difficult due to driving style, altitude, temperature, fuel type, etc... I mean the list goes on. But really, the N55, all things equal, is supposed to get better mileage, right?

What about maintenance? I'm not worried about the HPFP, because I'm certain that BMW's newest part has got to have the problem sorted, right? I'll make sure and get the newest part. However, what about other maintenance costs like when the turbos eventually need to be rebuilt? I guarantee that I'm only settling for somewhat lower mileage motors, like under 50k miles and in the 30's would be perfect. But if I do get a 50k mile motor and I'm half-way to a snail rebuild, what costs more? Two small turbos or the slightly larger twinscroll unit on the N55?

Most of the N54 comments are all about power, but maybe i wasn't clear that I'm really not interested in going much over 400 crank hp, obviously more torque would be nice. This is still an X3, so i'd like reliability, best fuel economy possible considering the type of performance, less maintenance cost if possible.

[eyim1988]

finding a used n54 will still probably be cheaper than buying a used/new n55. But you can satisfy your needs with either engine.. The n55 has more torque as well.

[MAK2008]

I've had both. I wish I would have kept my 2008 335 xdrive coupe but I wasn't into modding it when I had it. I just miss that car (color and options mostly).

I think for what you want, the N55 might be the way to go. I get slightly higher mpg witht he N55 but it's really not that much, maybe 1mpg, 2 tops... and that could be how I drive it, not sure. I think I'm right at 22.5 average since I got it.

Looking at what some of these guys are getting with their modded N55s, you should be right at 400hp at the crank. I just have a JB4 and so far I'm pretty happy with it.

I think I'll just sit and wait for a turbo upgrade to be developed some day. Hopefully in 2 years or so when this car is paid off and I'm out of warranty.

[Dark_Knight_335]

Originally Posted by eyim1988

finding a used n54 will still probably be cheaper than buying a used/new n55. But you can satisfy your needs with either engine.. The n55 has more torque as well.

So I noticed! Got an extra 101 torque out of the beast with Dinan stage 2

[F335i]

Go for N55 (less miles), if 400 crank hp is your goal, you can easily do it with a good mix of e85 and a tune, but if e85 is not close to you, then go for n54 with 93 octane or 91 with nos octane booster assuming you're not going to buy a meth kit.

[eyim1988]

Originally Posted by F335i

Go for N55 (less miles), if 400 crank hp is your goal, you can easily do it with a good mix of e85 and a tune, but if e85 is not close to you, then go for n54 with 93 octane or 91 with nos octane booster assuming you're not going to buy a meth kit.

you dont even need e85 to reach 400 to the crank. downpipes/exhaust tune is enough /w 93 octane.