BMW N63B44 engine code explained
N63B44 is the full code for BMW's twin-turbo 4.4-litre V8 with the turbos in the valley between the cylinder banks, the hot-V layout that has been in every 550i, 650i, 750i, M550i, M850i, X5 and X6 50i and M50i / M60i since 2008. The suffix matters more here than on any other BMW engine: O0 is the original N63 with the oil-consumption and coolant-pipe history, O1 the N63TU, O2 the N63TU2, and M3 / T3 the current N63TU3 that fixed most of it.
Quick answer
The N63B44 is the 4.4-litre V8 twin-turbo petrol of the BMW N63 family, built 2008-present. Bimmer.AI scores the family 5 / 10: buyable with evidence of the major preventative work, otherwise a negotiation. The tables below give every output tier and sticker letter BMW used on this stem and which cars got them; the failure table is the same one that powers the N63 family guide.
How to read N63B44
| Part of the code | Meaning |
|---|---|
| N | N-series engine generation (2001 to about 2015) |
| 63 | engine family number within the N-series |
| B | petrol, longitudinal (rear-drive platform: 1 to 8 Series, X3 to X7, Z4) |
| 44 | displacement in tenths of a litre: 4.4 litres |
| K / U / M / O / T / S + digit | output tier and revision, appended in BMW's internal naming (for example N63B44O1) |
| A / B / C / D | parts-catalogue engine version printed on the engine cover sticker (for example N63B44A) |
N63B44 output tiers and which cars have them
| Code | Output | Cars | Notes |
|---|---|---|---|
| N63B44O0 | 402 bhp (original N63) | 550i (F10 2010-2013), 650i (F12 / F13 2011-2012), 750i (F01 / F02 2008-2012), X5 xDrive50i (E70 2010-2013), X6 xDrive50i (E71 2008-2013) | Original: oil consumption, coolant transfer pipe, timing chain, injectors |
| N63B44O1 | 444 bhp (N63TU) | 550i (F10 LCI 2013-2017), 650i (F06 / F12 / F13 2012-2018), 750i (F01 LCI 2012-2015), X5 xDrive50i (F15 2013-2018), X6 xDrive50i (F16 2014-2019) | Valvetronic added; oil consumption largely fixed; coolant pipe remains |
| N63B44O2 | 444 to 456 bhp (N63TU2) | 750i (G11 / G12 2015-2019), M550i xDrive (G30 2017-2019), X5 xDrive50i (G05 2018-2019, US) | Revised cooling and injection |
| N63B44M3 / T3 | 523 bhp (N63TU3) | M550i xDrive (G30 LCI 2020-2023), M850i (G14 / G15 / G16 2018 on), 750i (G11 LCI 2020-2022), X5 M50i and M60i (G05 2020 on), X6 M50i / M60i, X7 M50i / M60i, X5 xDrive50i (G05 2019-2020) | Current generation; 48V mild hybrid on M60i cars |
N63B44 sticker letters: N63B44A, N63B44B, N63B44C, N63B44D
Here the letters and the suffixes both track the generation, which is exactly what a buyer needs. An A / O0 car needs the full original-N63 conversation: BMW's Customer Care Package (injectors, valve stem seals, crankcase vent, battery), oil consumption, timing-chain guides and the coolant transfer pipe. A B / O1 car keeps the coolant pipe and hot-V battery wear but drops most of the rest. C and D cars are Phase 1 records with little documented beyond the coolant pipe design and battery cycling.
| Sticker code | What it denotes |
|---|---|
| N63B44A | Original N63 (2008 to 2012). |
| N63B44B | N63TU (2012 to 2018). |
| N63B44C | N63TU2 (2016 to 2019). |
| N63B44D | N63TU3 (2018 onwards). |
Known problems on every N63B44
Failure data is held once, per engine family, so this table is identical to the BMW N63 guide. Cost ranges are indicative UK figures.
| Failure mode | Severity | Frequency | Typical onset | UK repair range |
|---|---|---|---|---|
| Coolant transfer pipe failure | Serious | Very common | 70 to 130k mi | £2,000 to £3,500 |
| Battery wear from hot-V heat soak | Mild | Very common | 20 to 70k mi | £200 to £350 |
| Vacuum pump failure | Moderate | Common | 60 to 130k mi | £350 to £600 |
| Oil consumption (early N63 builds) | Moderate | Common | 40 to 130k mi | Free (recall) or up to £5,000 |
| Injector and intake-valve carbon buildup | Moderate | Common | 70 to 130k mi | £400 to £1,500 |
Long-term verdict
Big twin-turbo V8 with serious long-tail. The hot-V layout (turbos in the engine valley) creates heat-soak issues that don't exist on conventional V8s. THE N63 issue is the coolant transfer pipe: plastic pipe under the intake manifold ages and leaks, £2,500-£3,500 fix. BMW issued a Customer Care Package extending warranty on this part for some US-market cars. Later N63TU2 / TU3 revisions are improved but the pipe pattern persists. Used N63 cars look cheap because of this; budget accordingly.
Check a specific N63B44 listing
Paste any BMW N63 listing, VIN or registration. Bimmer.AI identifies the exact engine and returns the buyer report in 30 seconds.
Run a Bimmer.AI buyer report →Bimmer.AI is designed to help you identify BMW-specific buyer risks before you travel, negotiate, or pay for an inspection. It does not replace a physical inspection by a qualified mechanic, a legal vehicle-history check (e.g. HPI Check), or independent verification of finance, stolen, or write-off status. Repair-cost ranges are indicative UK figures that vary by region, specialist, parts supply, and labour rates.
Frequently asked questions
N63B44O0 vs N63B44O1: what changed?
The O1 (N63TU, 2012 onwards) added Valvetronic, revised pistons and rings, new injectors and a revised crankcase ventilation system, which together cured most of the original N63's oil consumption. It kept the hot-V layout, so the coolant transfer pipe under the intake (£2,000 to £3,500 when it leaks) and the battery wear from underbonnet heat carry over. For a used buyer an O1 is a much safer car than an O0 at similar money.
Which N63B44 should I avoid?
The original O0 (2008 to 2012) without documentation of BMW's Customer Care Package work and a coolant pipe replacement. With both documented it is a fast, cheap V8; without them it is a £3,000 to £6,000 liability. The O1 and later are fine buys with the coolant pipe and battery history checked.
Is the N63B44T3 in the M550i and M850i reliable?
Early signs are good. The TU3 (2018 onwards) has revised turbos, cooling and injection, and most cars are still within warranty, so the failure-mode set is thin. The two things to check are the aluminium charge-pipe conversation on tuned cars and the 48V mild-hybrid system on M60i cars. The hot-V battery cycling and the coolant pipe design remain, so budget for them past 80,000 miles.
Which BMWs have the N63B44 engine?
The N63B44 went into the following cars, by output tier. N63B44O0 (402 bhp (original N63)): 550i (F10 2010-2013), 650i (F12 / F13 2011-2012), 750i (F01 / F02 2008-2012), X5 xDrive50i (E70 2010-2013), X6 xDrive50i (E71 2008-2013); N63B44O1 (444 bhp (N63TU)): 550i (F10 LCI 2013-2017), 650i (F06 / F12 / F13 2012-2018), 750i (F01 LCI 2012-2015), X5 xDrive50i (F15 2013-2018), X6 xDrive50i (F16 2014-2019); N63B44O2 (444 to 456 bhp (N63TU2)): 750i (G11 / G12 2015-2019), M550i xDrive (G30 2017-2019), X5 xDrive50i (G05 2018-2019, US); N63B44M3 / T3 (523 bhp (N63TU3)): M550i xDrive (G30 LCI 2020-2023), M850i (G14 / G15 / G16 2018 on), 750i (G11 LCI 2020-2022), X5 M50i and M60i (G05 2020 on), X6 M50i / M60i, X7 M50i / M60i, X5 xDrive50i (G05 2019-2020). The two-letter family badge is N63; any listing that quotes the family code is talking about one of these.
Is the BMW N63B44 reliable?
Bimmer.AI scores the N63 family 5 out of 10, which makes the N63B44 buyable with evidence of the major preventative work, otherwise a negotiation. Big twin-turbo V8 with serious long-tail. The hot-V layout (turbos in the engine valley) creates heat-soak issues that don't exist on conventional V8s. THE N63 issue is the coolant transfer pipe: plastic pipe under the intake manifold ages and leaks, £2,500-£3,500 fix. BMW issued a Customer Care Package extending warranty on this part for some US-market cars. Later N63TU2 / TU3 revisions are improved but the pipe pattern persists. Used N63 cars look cheap because of this; budget accordingly.
What does N63B44 mean?
N is the N-series engine generation (2001 to about 2015), 63 is the family number, B means petrol, longitudinal (rear-drive platform: 1 to 8 Series, X3 to X7, Z4), and 44 is the displacement in tenths of a litre (4.4 litres). BMW appends an output tier and revision (K, U, M, O, T or S plus a digit) in its own naming, and the parts catalogue adds a version letter (A, B, C) that is what you see on the engine cover.