BMW B46

The B46 is the United States emissions-certified version of BMW’s 2.0-litre turbocharged
four-cylinder. Mechanically it is the B48; on the certification
record it is a different engine code, and it appears on more American BMWs than the B48 itself
does. If you have looked up your 330i and found an engine code you did not expect, this is
why.

What the B46 is

A 2.0-litre turbocharged inline-four with direct injection, Valvetronic and a twin-scroll
turbocharger — the four-cylinder member of BMW’s modular B-family, sharing roughly 500 cc
per cylinder with the three-cylinder B38 and the six-cylinder
B58.

The difference from the B48 is emissions certification rather than architecture. The B46
carries the hardware and calibration needed for the stricter United States standards, and the
factory code in the certification filing changes accordingly: our records hold codes such as
B4620O1-G20-S against cars whose B48 equivalents read B48A20M2F65S. Same displacement, same
1,998 cc, different certification family.

Where it is fitted

Seventy-five specification pages in our records carry a B46, drawn
from 130 EPA certification entries.

It also appears in a car with a different badge on the nose: the certification records list
the Toyota Supra 2.0 with a B46 code, in the same way the six-cylinder Supra carries a
B58.

B46 or B48: how to tell, and why it is confusing

Both codes appear on the same model in overlapping years. Our records hold 330i sedans
certified as B46 and 330i sedans certified as B48; the same is true of the 430i, the 530i and
the X1 and X2 in 28i form. Model name and badge cannot separate them, and neither can
displacement or output — a 2020 530i is rated at 248 hp whichever code it carries.

What does separate them is the certification record for that exact model year, which is
where our specification pages get the code from. For a specific car,
start with the VIN decoder: the vehicle database returns the engine
model for the car in question rather than for the model line.

The practical answer for most owners is that it does not matter much. This is one engine
family certified two ways, not two designs. Where it does matter is parts catalogues and
service documentation, which are indexed by the code — and there, guessing costs money.

What we do not publish

No reliability rating. The NHTSA complaint database records faults against a
vehicle, not an engine, and here the problem is sharper than usual: a 2021 330i in
that database may carry a B46 or a B48 and the record does not say which, so even a
complaint count that correctly isolated the model could not be split between the two codes.
Anything presented as “B46 reliability versus B48” was produced by assuming.

Common questions

What is the difference between the B46 and the B48?

Emissions certification. They are the same 2.0-litre modular four-cylinder; the B46 is the
version certified to the stricter United States standards, and it carries its own factory code
in EPA filings. Displacement, layout and rated output are the same for equivalent cars.

How much horsepower does the B46 have?

Between 225 and 255 hp in our records, depending on the car: 228 hp in the X1, X2 and 228i
Gran Coupe, 248 in the 530i, X3 and X4, and 255 in the 330i, 430i and later Z4.

Which BMWs have the B46?

On the certification records we hold: the Z4 sDrive30i, 228i Gran Coupe, 330i, 430i, 530i,
X1 and X2 28i, X3 30i and X4 xDrive30i, in the model years listed above. The Toyota Supra 2.0
uses it too.

Is my 330i a B46 or a B48?

It depends on the model year and, for some years, on the individual car. Check the
specification page for that model year, or decode the
VIN for the car itself.

Is the B46 a good engine?

It is the B48, so anything true of one is true of the other. What we can say from the data
is that it is the most widely certified BMW engine in the United States over its years and that
its output is consistent across applications — we do not publish durability verdicts, for
the reason given above.

Sources

Model lists, factory engine codes, outputs and model years from EPA annual certification
test data, with the source named on every specification page. The
architecture of the B family is described in the 2014 4
Series brochure in this archive, quoted on the B48 page.