What are the differences between these two engines?

 

An excellent question. I think the answer has to do with emissions or associated mpg ratings. Also, it's my understanding that the B48 was first and was followed by the B46, in the US anyway. Now I'll await an answer from someone who knows something. Also, which of the two is the better one?

 

B46 is the ULEV version of the B48. Mainly the same engine with different programing but there ste some component changes like different can sensors etc.. B46 is the current US engine, B48 was only in the 2014 cars here but is still being used outside the US.

 

The B48 is being used in the 2015 JCW's in the US

 

Basically the B46M is the SULEV version of the B48M. Performance is identical on both, though there is a slight mpg difference (if I remember right, highway was higher on the B46, but city was lower?), and of course, lower emissions on the B46.

The B48O is the engine in the current F56 JCW.

The B38 engine in the Cooper models is changing to the B36 for 2016 as well - same stuff: identical performance, the B36 is the SULEV version of the same engine, and I'm sure we'll see some slight mpg differences.

 

Mini makes some odd changes with motor selections, why use the b48 in the JCW.

 

The B48 is still used in the Cooper S through Europe.

The B46, as has been said is the low emissions version for you guys in the states. The B46 also uses the same, better, turbo as the B48O JCW.

You guys are lucky!

http://www.etk.cc/bmw/EN/parts/info/...6637/appliance

 

You opened Pandora's box.
Is the new turbo larger and does it have potential for a higher state of tune?

 

I would have thought so!

 

You can get a safe 270bhp just with the Burger Tune on the b46.

 

Interesting topic and this can be useful info for peeps who are needing an engine swap. Be aware of the B46/B48 engines you find to swap into the car you have. According to RealOEM, there are specific notes saying that if you have a B46 car, then swapping into B48 needs a DME remap, and vice versa going to B46 with a B48. Mainly the programming is key. AND most importantly, the oil measuring device has to match the DME mapping or it'll measure wrong.

 

Great information.

Unrelated and noobish question: What's the difference between the JCW and the MCS engines other than the tune. I thought I read that it had stronger parts or it's more "re-enforced" (my terms, can't remember the original ones). I just wanted to know if lifespan would be an issue for uptuned engines.

 

I cross-checked the measurements to the internals of both MCS and JCW B48 engines, they are exactly the same bore, stroke, piston, and rods. However, with JCW having compression ratio of 10.0 and MCS at 11.0, the only way that can happen with same bore and stroke is if the deck height and dome volume is larger for the JCW to achieve these targets. So that there alone is a major difference I can find between the two. However, both engines use the same cast aluminum pistons, not forged; henceforth you see more blown pistons and piston rings on highly tuned JCW's. I see lots of this issue being logged in the Asia side of the tuner world on B48 engines, both BMW and Mini vehicles..

 

@Yupetc , can you clarify? If the pistons are the same, but JCW has lower compression, shouldn't it be less prone to blowing up?

 

@J_L , yes, you're correct, JCW does have lower compression and I suspect this is achieved in the dome design and deck height in the heads, not in the main engine components such as pistons, rods, and crank (The reason is because BMW's new modular engine initiative gave all of these B38 and B48 motors practically the same basal structures).

And with a lower compression, yes, JCW motors are RELATIVELY less prone to blowing up (pre-detonation is what I'm referring to). However, with the same pistons, rods, and crank, the weakest link is still going to be the pistons and those rings, it's the same for both S and the JCW. But if you tune a JCW and S with similar boost profile, the pistons on the S should crap out before the JCW does. I'm only comparing the stock S and stock JCW with similar route to modification and boost (these aren't directly apples to apples comparison because compression ratio alone is the only differentiation I'm discussing here.) I can also attest that the VVT drivers in the cams system is a further differentiation between the JCW and the S. There are 3 different type of VVT bundles, I don't have all of them, but I believe there's one for B46, B48, and B48(JCW) each. I just happened to have a B48 and a B46 engine in my garage right now. And doing this swap takes a lot of diligent work in knowing the differences and trying to make everything work without re-programming the DME. If I just want to directly swap the B48 donor engine into the B46 receiver car, then the simplest way to do this is to reflash the ECU with the B48 programming plus changing out the oil level sensor. The hard way around it is to convert B48 donor motor with as many B46 receiver parts as possible and hope the transplant won't be affected with the original B46 DME program. This is what I'm doing right now.

Also a disclaimer in regards to the JCW versus S internals, I do not have the time to dig much into this, but if I'm not mistaken, the JCW and the S shares the same internals such as crank, pistons, rings, and rods from 2015 to 2018 or 19 (in these internals, everything's forged except for the pistons which are casted). Someone can correct this, but I believe it's when they rolled out the 300bhp+ versions of the B48 in those Countryman and newer JCW's that gets the upgraded forged pistons. So unless you have one of those newer more powerful motors, upgrading the tune and boost to achieve more than 250whp without doing the pistons is a very bad idea. There are reported cases of B48 engines with irresponsible tunes in the other BMW vehicles to see piston and ring failures. Luckily we don't see rods flying through the motor casing anymore. The rods are quite strong.

 

A major difference between the B46 and the B48 motors is the SULEV equipment in emission-related components.

Also if you have a SULEV MCS, be aware if the car comes with a black radiator or an original aluminium colored radiator. Currently I come across issues finding the correct radiator for my B46. The radiator has black coating, indicating it's a (manganese or magnesium) coated radiator. This coating is constantly being checked with an EAC sensor (Environmental Air Catalyst). The sensor is there only to tell the car that a coated radiator is in place, any further programming difference beyond this point I don't know. But for those of you who ever run into the need to replace your radiator AND provided your MCS has the SULEV coated one, you need to cross reference the right part. If you have a B48 it'll be the regular aluminum radiator, then it doesn't matter because if you receive a B46 radiator, you simply won't plug that EAC sensor in and it won't make a difference to how the car runs.

 

By the way, I've successfully transplanted a B48 motor into the B46 platform MCS. The motor started right up with no issues. There's one other guy who owns a BMW X1 that also transplanted a B48 motor into the B46 platform. Motor runs strong, loving it already.

 

Good morning (over here in Germany), saw your post and i am on the way to do the same. B48 in B46 Mini (F56 2015). B46 4th cylinder no compression. Car was parked 2.5 years when we bought it.. Do you ran into major problems with the connections by changing the engine,(electric, cooler.....). Thank for your help on this.