[Bahooki]

Hello,

I know I’m going to be blasted for this and told to buy a 335i, but I’m going to list a few reasons why I’m not going to do that.

- My N51 has a crack in the block and is leaking oil, so the motor is toast. It goes through a quart every couple weeks. I’m not going to sell someone this car like and then go buy a 335i because that would be dirty.
- This was my first car and I’ve had it for years, I don’t want to get rid of it. My dad’s biggest regret was selling his first car, I’d like to hold on to this.
- I have a mechanic that is very excited to do this and charges extremely affordable labor rates

Now that that’s out of the way,
I have a 2010 328i. The car is fun and a fucking blast to drive. It’s a 6 speed, it’s got the 3 stage intake manifold because it’s an N51, catless MMW headers, catless midpipes, an AA Catback, and a BPC tune. It is dead even with my friend’s stock auto 335i all the way until about 80mph where the 335i pulls away. I noticed I was going through lots of oil, so I assumed the oil filter housing, or maybe valve cover gaskets. I had them checked and there wasn’t a leak to be seen. I took it to another euro mechanic, and he swore there was oil coming from this random spot in the back of the block, but could not figure it out whatsoever. He said he had never seen anything like it. Then my clutch started slipping really bad (borderline undriveable), so I went to a single mass flywheel and had a new clutch installed. My old clutch that was removed looked brand now and like it had 5,000 miles on it, but the dualmass flywheel had oil burns and marks all over it. So somehow oil was getting onto my clutch. He checked the rear main seal, and it looked absolutely fine. I then had another mechanic really go up in the back of the motor and try and figure it out, and sure enough there was a hairline crack in the back of the block where oil was coming out of.

That being said, I started looking for N51s and N52s, but then I realized that I really don’t want to spend $4000 in parts and labor to be exactly back to where I started, and maybe even in a worse spot (as N51s are surprisingly harder to find than N52s). I started looking into 2JZ swaps funny enough, because I have a fully refreshed 2JZ sitting in my garage I’ve been building for a bit to eventually put in something, but quickly realized that was just ridiculous. (Props to the guy who shoehorned one into his Z4 in this forum though, haha). I realized that BMW basically made a 2JZ themselves. I’ve been finding N54 335s on Copart with 6 speeds and 50-60,000 miles for about $2500 consistently and want to make it happen.

Here’s what I need to my knowledge
- 335i fuel system
- 335i DME
- 335i 6speed as it’s much stronger
- I’m going to swap the brakes if they’re in tact
Here’s what I’m curious about
- do the 335s have better rear ends? Would it be worth swapping as well?
- electronics. Oh man.

My electronic knowledge is hazy at best, so I apologize in advance if I sound like an idiot. To my knowledge, I’m going to just need the 335i DME which should simply replace my current 328i DME. But then I’m going to need someone to code it to work with my car. That’s really the extent of what I know in terms of electronics, and that’s what worries me. I really like to know what I’m biting off before I begin something. Will I also use the 335i engine harness?

I’d love some help on the electronics side if anyone can offer some advice/knowledge. There’s a company out by me (Seattle area) called BIM Coding. They do custom coding on BMWs, and I contacted them to see if it was something they could do or knew about.
Feel free to call me an idiot and tell me this is a mistake, I thrive on criticism.

Nash

[RocketSurgeon]

Ok, I admire what you are trying to do, but you should realize this is a VERY complicated and costly endeavor. The DME is encrypted and locked to the CAS, so you'll either need to swap the 335i CAS and keys, or pay somebody with AUTOHEX a few hundred to sync them for you.
I would swap the entire 335i front subframe/engine/transmission onto your car, along with the driveline and rear subframe/diff. You're talking about a lot of work and a lot of hours, so it's going to cost quite a bit.

[Bahooki]

Originally Posted by RocketSurgeon

Ok, I admire what you are trying to do, but you should realize this is a VERY complicated and costly endeavor. The DME is encrypted and locked to the CAS, so you'll either need to swap the 335i CAS and keys, or pay somebody with AUTOHEX a few hundred to sync them for you.
I would swap the entire 335i front subframe/engine/transmission onto your car, along with the driveline and rear subframe/diff. You're talking about a lot of work and a lot of hours, so it's going to cost quite a bit.

Thank you for the info. I’m assuming CAS is the comfort access system? Also, do you know if 335s have LSDs or if they’re open like 328s?

Edit: my thinking all along was that I was going to need to swap the keys over, but I didn’t think about the CAS. What is involved in swapping it? Would it be physically swapping the door handles and computer? Or would I just need to swap the computer that manages it?

[srey]

The 335i has an open diff. If you are swapping the 6mt gearbox, though, you might want to swap it anyway to maintain the stock final drive ratio (3.08).

[Emilime75]

Why not have the block welded? What the hell caused it to crack in the first place? What you're contemplating on doing is quite the endeavor, and if you're paying a shop to do it, will cost a fortune, regardless of how "reasonable" their rates are. When you include the cost of the donor car, replacement parts for whatever donor parts are broken, all of the "might as wells" while everything is apart, shop labor...not to mention, if the shop doing the work isn't well versed with BMW electronics and coding, you're in for a very rough, and expensive ride.

[Bahooki]

Originally Posted by Emilime75

Why not have the block welded? What the hell caused it to crack in the first place? What you're contemplating on doing is quite the endeavor, and if you're paying a shop to do it, will cost a fortune, regardless of how "reasonable" their rates are. When you include the cost of the donor car, replacement parts for whatever donor parts are broken, all of the "might as wells" while everything is apart, shop labor...not to mention, if the shop doing the work isn't well versed with BMW electronics and coding, you're in for a very rough, and expensive ride.

I wish I knew. I’ve never heard of this on a single other forum and no shop has ever seen or heard of it. I assume it must be a manufacturing defect. It doesn’t ever get very far below freezing where I live, and I park in a garage. I understand it’s not going to be cheap, but neither is an N51/N52. I can also part out the donor car. I’ve found many 335i’s selling for less than an N51 alone. I found $1200 to be very reasonable for the labor of swapping motors alone. Add in a trans, rear end and maybe even the front subframe and lets say $2500 on the further end. $2000 car. $500 to get someone to program it. Part out the interior and what I can off the car for $1000, then scrap it for $250. I’m in at $3750. An N51/N52 would be $2000 and about $1000 in labor. Adding in $1000 for unexpecteds with the N54, I’m at $4750. $1750 more for basically an OEM twin turbo motor is worth it for me. Add in a JB4 and that’s 150 horsepower over my 328i. I’ve spent far more than $2000 for far less horsepower with my 328i. I definitely see your point, but I’ve done a lot of CBA on this. I have a spreadsheet with much more detailed numbers, but the math comes out roughly the same.

Who knows, maybe this will be a huge mistake and I’ll end up regretting not just getting an N51. But I know for a fact if I just go with the N51 I’ll regret not trying to be a bit more ballsy.

[Emilime75]

I understand, it seems like a worthwhile endeavor on paper, but in reality, it never ends up being that. I've been there, have done roughly a dozen engine swaps back in the day, and they all end up costing considerably more than anticipated. This was with relatively simple VWs of the 80s/90s, which are nowhere near the complexity of more modern MBWs. If you're itching to have a project car and do some more "ballsy" things with it, start with something simpler, like that 2jz, which has aftermarket swap support.

Seriously, your will to do this is commendable, but you're in over your head. I would;

A. Pull motor, find/clean/prep crack and weld it.
B. Find a used, replacement long block.

Car-part.com currently has around 60 N51s as low as $1100. Looks like average they're running about $15-1600. There's one that claims 90k miles for $320.

http://www.car-part.com/cgi-bin/search.cgi?userSearch=int&userPID=1000&userLocatio n=All+States&userIMS=&userInterchange=D%3D%3D>BP&u serSide=&userDate=2010&userDate2=2010&dbModel=9.12 .2.2&userModel=BMW%20328i&dbPart=300.1&userPart=En gine&sessionID=12000000016240362&ref=mobileweb&use rPreference=zip&userZip=37217&userLat=36.1083000&u serLong=-86.6676000&userIntSelect=188961&userUID=0&userBrok er=&iKey=&userPage=1

Fix the car, sell it, buy a 335i. Years later, when you're a dad, you won't have any regrets selling your 328i, not when you've jumped into a 335i. Hell, just tell the kids the 335i was your first car. They won't know.

[halik008]

You might have estimated $4750.....you you end up sinking $7-8k into a car now worth $6k. Buying a wrecked car is only going to get you core engine. Unless you plan on installing it and hoping for the best you will be replacing all the components that are bitch to get to....clutch, water pump, themostate, oil gasket, and so on.

You need to swap the entire powertrain, with 335i trans your gear rations will be all messed up with 328i rear end.

[srey]

You already have a 2jz in your garage. Swap that in instead. Or start paying out the car and use the proceeds toward a car you really want.