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We will break the B48 FAQ guide into the following subjects:
- B48 General Info
- B48 Standard Maintenance
- Common B48 Problems & Reliability
- B48 Tuning & Mods
BMW B48 General Info FAQ's
What is the BMW B48?
The B48 is a 2.0L single turbo engine that is part of the BMW B series modular engines. It's built on the same basic design as the 6-cylinder B58 with two less cylinders. BMW's B48 engine is also the successor to the 2.0L turbo N20 engine. Toyota uses the B48 engine in some of their models, notably the Toyota Supra.
What BMW's use the B48 Engine?
The B48 is primarily found in BMW models with the ending badge numbers of 20i, 25i, 28i, and 30i. A higher output version of the B48 is in some 2019+ 35i models. It's also in some Mini models along with the Toyota Supra.
- 2016-2019 120i
- 2019-present M35i
- 2016-present 220i / 230i
- 2019-present M235i
- 2016-present 320i / 330i / 330e
- 2016-present 420i / 430i
- 2017-present 520i / 530i
- 2017-present 630i
- 2016-present X1 20i / 25i / 28i / 30i
- 2017-present X2 20i / 25i / 28i / 30i / M35i
- 2018-present X3 20i / 30i / 30e
- 2018-present Z3 20i / 30i
- 2019-present Toyota Supra
How Much Horsepower (HP) Does the B48 Have?
B48 engines range from 181 to 302 horsepower in stock form. 20i models generally receive the lower output B48 engines. Most 30i models come in at 252-258 horsepower. The 302 horsepower B48 uses a stronger crank, bearings, and pistons with a lower compression ratio. Torque ranges from 214 to 332 lb-ft.
Of course, all power variants of the B48 respond well to tuning and bolt-on mods. We'll touch on this topic in the tuning & mods section.
Does the B48 Have Forged Internals?
Yes, the B48 crank and connecting rods are forged as with the larger B58 6-cylinder. Cranks are forged steel. The B48 also has drop-forged cracked connecting rods. BMW B48 rods are formed in one piece before the rod eye is cracked in two. This ensures a precise, strong fit. B48 pistons are cast, but remain fairly strong.
How Many Miles Will the B48 Last?
Longevity is a tough topic to discuss, and that includes the B48. Some of it simply comes down to the luck of the draw, maintenance, etc. Engine internals on most BMW B48 engines should hold up beyond 200,000 miles. The same can be said for the timing chain, cylinder head, etc. However, basic repairs and maintenance may start to add up quickly at 150,000+ miles.
What is the B48 Compression Ratio?
11.0:1 compression ratio. This is a decent increase over the lower 10.2 compression ratio on the BMW N20 engine. However, the higher horsepower B48 in BMW 35i models sees a drop to 9.5:1 compression. This helps the engine support the additional boost and power.
What is the B48 Bore x Stroke?
82.0 mm bore x 94.6mm stroke (3.23" x 3.72"). The B series engines saw a move to an even further undersquare design. A longer stroke helps the B48 make a lot of low-end and mid-range torque.
How Fast is the BMW B48?
Most B48 models are limited to around 130mph or 155mph. Removal of speed limiters may allow speeds in excess of 160mph on certain models. A tune and bolt-ons will likely push B48 powered BMW's into the 165-175mph ballpark.
How Many Turbos Does the B48 Have?
The B48 uses a single twin-scroll turbo. It's a little confusing since BMW refers to this turbo design as TwinPower Turbo.
B48 Standard Maintenance FAQ's
*This article is in reference to the B48 engine itself. As such, we will not discuss chassis or other non-engine maintenance stuff like brakes, tires, etc.
What Are the Common B48 Standard Maintenance Items?
A few common standard maintenance items for the BMW B48 include:
- Fluids (oil + coolant)
- Walnut blasting
- Spark plugs & ignition coils
These are the primary standard maintenance items on the B48 engine. Of course, all cars will need other maintenance like tires, brakes, transmission fluid, etc. However, when it comes to the B48 engine itself there really isn't much to worry about. In this section, we'll break down the above maintenance.
How Much Oil Does the B48 Hold? What is the B48 Oil Capacity?
B48 oil capacity is 5.25 liters (5.55 quarts).
What Oil Weights Are Approved on the B48?
BMW recommends running LL-14 or LL-17 oils on the BMW B48 engine. The standard oil weight is 0W-20. Newer LL-14+ oils are designed with fuel economy and emissions in mind. LL-01 oils follow older standards, but it's still some of the best oil in our opinion. Ultimately, anything LL01 and above will work well on the B48 engine.
As far as weights, 0W-20, 0W-30, 5W-20, and 5W-30 all work well on the B48. Some B48 and B58 owners even go for thicker 0W-40 and 5W-40 oils.
What is the Best Oil for the BMW B48?
We've always run Liqui Moly oils on our BMW's with great success. They're quality oils for a reasonable price. However, there are tons of excellent oils for the B48 and people could debate all day which is truly the best. Stick with known, quality oils.
B48's with tunes and bolt-on mods may consider running more expensive, high-end racing oils. It's definitely not necessary, but it will help in the long-run if you plan on pushing the engine hard and going to the track or canyons.
How Often to Change B48 Oil? B48 Oil Change Interval (OCI)
We recommend changing the B48 oil every 5,000 to 8,000 miles. Or once a year - whichever comes first. Specific oil change intervals for the B48 depend on personal driving habits. If you do long highway drives often then you can get away with the higher 8,000 or even 10,000 mile OCI.
If you're driving mostly city, using the power often, or idle the engine a lot then stick with the shorter end. Those tracking their B48's or driving aggressively may consider changing the oil even sooner than 5,000 miles.
BMW recommends oil changes every 10,000 miles. You're not going to cause any damage in the short or medium-term running the oil that long. However, we think a 10,000 mile OCI is too long for longevity. Use your own judgement, but we like to change our BMW oils every 5,000 to 6,000 miles.
What is the Best Coolant/Water Mix on the B48?
We recommend a 50/50 water and coolant mix for the BMW B48. Water actually offers better cooling benefits than actual coolant. However, coolant helps lower the freezing point and increase the boiling point. It also helps prevent corrosion.
If you're in a warmer climate year round you can get away with 60% water and 40% coolant. Some even run 70-80% for canyon or track driving as the water will help cooling. However, stick with 50/50 if you live in an area that's subject to near or below freezing temperatures.
Is B48 Coolant Really Lifetime?
No - we don't agree with the lifetime coolant designation. BMW does consider B48 engine coolant to be a lifetime fluid. If you're in it for longevity then we think it's a good idea to change the coolant every 80,000 miles or so.
How Often to Change B48 Spark Plugs?
Turbo engines love to burn through spark plugs. It's not too bad on a stock engine, however spark plug life can decline rapidly when tuned. We recommend the following B48 spark plug replacement intervals:
- Stock: 40,000 - 60,000 miles
- Modded: 15,000 to 30,000 miles
Some of this also depends on your driving habits. Those who often use the B48's power and boost will land on the shorter-end. A tune-only can bring spark plug life down to about 30,000 miles. Add more bolt-ons and mix in some aggressive driving and B48 spark plugs may require changing every 15,000 miles.
What B48 Spark Plugs Are Best?
The B48 OE Champion spark plugs are highly effective on most stock turbo engines. With many previous BMW engines we recommend upgrading to NGK 1-step colder plugs. However, the Champion spark plugs hold up very well for a stock turbo B48.
The NGK 97506 spark plugs are OE for the older N20 engine. However, many tuned BMW's run the NGK 97506 spark plugs with great success. We recommend switching to these spark plugs if you're pushing the limit of the B48 turbo or upgrade the turbo.
How Often to Change B48 Ignition Coils?
Ignition coils also wear pretty quickly on turbo engines like the B48. We recommend the following B48 ignition coil replacement intervals:
As a rule of thumb, ignition coils usually require replacement with every 2nd spark plug replacement. They last about twice as long. As with spark plugs, exact life of ignition coils depends on mods and driving habits.
What is B48 Walnut Blasting?
Direct injection (DI) engines come with one flaw, which is carbon build-up on intake valves. Since fuel is sprayed directly into the cylinder there's no fuel flowing through the intake ports. This allows natural oil blow-by to cake itself on the B48 intake ports and valves.
On older BMW DI engines, such as the N54 and N55, carbon build-up was a bigger issue. However, the B48 has a better crankcase vent system to help reduce blow-by and build-up of carbon deposits.
Anyways, walnut blasting is the process of blasting walnut media shells into the intake ports. These shells help clean off carbon deposits without damaging the valves or ports. It requires a shop vac and walnut media shells.
Do You Need to Walnut Blast the B48?
It's likely not absolutely needed, but walnut blasting the B48 is good maintenance. The N54 sees carbon build-up as often as every 40,000 to 60,000 miles. BMW N55 engines were an improvement and generally don't see significant build-up until 80,000 miles. Again, the B48 engine should be an even further improvement.
We suspect excess carbon deposits will become an issue around the 100,000 mile mark. Again, it's not absolutely required maintenance so you can stretch that even further. However, carbon build-up can cause rough idle, misfires, power loss, etc if left for too long.
How Expensive is B48 Maintenance?
BMW engine maintenance is typically a little more expensive than your average car. The same can be said about turbo engines in general. Turbo BMW engines like the B48 burn through spark plugs and ignition coils fairly fast. Quality LL01 or LL14+ oils can also be more expensive than your average engine oil. Point is - standard maintenance isn't the cheapest. It's also not overly expensive, especially for those willing to DIY some maintenance. Expect the following B48 maintenance costs:
- Oil & Filter: $60-100 every 5,000 to 8,000 miles
- Coolant: $30-200 every 80,000 to 100,000 miles
- Spark plugs: $79 every 15,000 to 60,000 miles
- Ignition coils: $169 every 40,000 to 90,000 miles
- Walnut blasting: $400-600 every 100,000+ miles
Costs can add up a little more if you're having all BMW B48 maintenance done at the dealer or a repair shop. The walnut blasting is mostly labor as quoted above; it's nearly free if you can DIY the job. Anyways, B48 maintenance isn't horrible as shown above.
BMW B48 Reliability & Common Problems
Is the B48 Reliable?
Yes, we believe the BMW B48 is a pretty reliable engine. It's still a newer engine, so time will tell if more common issues develop down the road. BMW reliability seems to be trending in the right direction, though. At least when you compare the B48 and B58 reliability to that of the earlier N54, N55, N63, S65, etc.
Toyota is also using the B48 engine in their Supra models. They did tweak the design a little bit, but it's still a testament to the reliability of the B48.
What Are the Most Common B48 Engine Problems?
*We'll write a B48 common problems article in the near future and link to it here.
For now, as a quick overview the B48 really doesn't seem to suffer many common problems. Some have issues with coolant loss. Otherwise, there isn't too much to talk about with B48 common failures. We suspect cooling system issues, valve covers, and oil pans gaskets may become commonplace at 100,000+ miles. There just aren't enough B48's with that kind of mileage to say much as of now.
How Expensive is the BMW B48 to Own?
Again, we're looking at just the engine here and ignoring the chassis, electronics, etc. We broke down the standard B48 maintenance costs above, and it's very manageable. The B48 is also a seemingly reliable engine thus far. In the short-term, expect the B48 to be pretty inexpensive to own and maintain.
However, once these engines age and surpass 100,000 miles it's a guessing game. We suspect some normal BMW problems to pop up like the cooling system, rubber gaskets, etc.
Why is My B48 Idling Rough?
Rough idle can be a frequent "issue" on many engines. Usually rough idle is due to an underlying problem or past due maintenance. If you're noticing rough idle from the B48 engine consider the following:
- Spark plugs/ignition coils
- VANOS solenoids
- Carbon build-up
- Leaking fuel injectors
Spark plugs and ignition coils are the most common cause of rough idle on the B48. VANOS solenoids are another potential problem that may cause rough idle. At higher mileage, excess carbon build-up might lead to a rough idle. Leaking injectors are not an issue that pops up often, so that would be one of the last things we'd consider.
BMW B48 Tuning & Mods FAQ's
What is the Best BMW B48 Tune?
There is no perfect answer to which tune is best for the B48. Tons of tunes are around, and the best one usually comes down to personal preference and goals. The most important aspect is sticking with a quality, trusted tune. We believe a couple of the best B48 tunes to start with include:
- bm3 (bootmod3)
These two tunes are the most common off-the-shelf (OTS) options for the B48 engine. We're big fans of the JB4 as a starting tune since it allows precise boost control and lots of possibilities. Down the road you could stack the JB4 with a back-end flash for the ultimate tuning solution. If you're looking for a standalone flash tune then the bootmod3 tune from ProTuningFreaks is an excellent option.
How Much Horsepower Can a Stock Turbo B48 Make?
~300-350whp. It's still early in the world of tuning the B48. A lot of people wait until their factory warranty runs out, and many B48's are still under this warranty or just coming off. The larger B58 engine also overshadows the B48 for tuning potential.
Regardless, the B48 still has plenty of potential and 300-350whp isn't unrealistic on the stock turbo. Low 300's is likely the more realistic ballpark. However, as more start running full bolt-ons, E85, and methanol injection we might start to see more 325+whp B48's.
How Much Torque Can a Stock Turbo B48 Make?
~325-350wtq. Again, the same concepts apply with the HP discussion above. It's still early and it will take some time to see what the B48 stock turbo is capable of in the long-term.
What Does B48 FBO Mean?
FBO B48 stands for full bolt-on. Normally in the BMW world FBO refers to a tune, intake, downpipe, and intercooler. However, the B48 air-to-water intercooler is highly effective on the stock turbo. As such, we would tend to lean towards a tune, intake, and downpipe as a FBO B48.
What is the Max Boost on the B48 Stock Turbo?
We wrote an article about the max boost the stock B48 turbo is capable of. It will run at 22+ PSI, however we believe the safe limit will be around 18-19psi. Anything over 20psi will not add much power. It will, however, add a lot of stress to the turbo and engine.
What is the Best B48 Catless Downpipe?
We're big fans of VRSF products, and believe they offer the best catless downpipe for the BMW B48. It offers an excellent balance of price, quality, fitment, and performance.
How Much Horsepower Does a B48 Catless Downpipe Add?
A catless downpipe on the B48 will offer about 15-25whp gains. The more aggressive the tune and boost the bigger gains you'll see. Check out our B48 downpipe upgrade guide for more.
What Are the Limits on B48 Stock Internals?
Engine limits are always a tough topic. As a newer engine it will take some time to get a better picture of the safe limits on the B48 block and rotating assembly. A modest tune and bolt-ons should be very safe. Of course, there's always risk in increasing power, torque, and boost.
We know the older 2.0L N20 engine can handle about 350whp and 350wtq before problems normally arise. The B48 receives a stronger closed deck block. However, it's usually the rods or pistons that let go first. As such, the limits of the B48 might fall in the same ballpark.
**Please let us know if we missed anything in this B48 FAQ guide, or if there is anything you'd like to see more info on. Otherwise, scroll down and check out some more awesome B48 content.