Reinforced exhaust valves BMW B38B15

BMW engines covered

The B38B15 is the turbocharged three-cylinder of BMW's modular family, sharing valves, springs, retainers, collets and rocker arms with the B48 and the B58. On the BMW side it powers, among others, the 116i and 118i F20 / F21, the 218i F22 / F23, the 318i F30 / F31 and the 418i F32.

Its cylinder head has 12 valves, 6 of them on the exhaust side, operated by roller rocker arms with hydraulic adjusters (Valvetronic on the inlet side). The BMW exhaust valve 11 34 8 621 264 has a 28.5 mm head, a 6 mm stem and a length of 99.8 mm; it is held by 3-groove collets. On this small turbocharged engine, a remap quickly raises the temperature of the gases flowing past it.

SUPERTECH reinforced exhaust valves

Between the chamber and the turbine, the head of a turbo engine's exhaust valve exceeds 1,000 °C, against 760 to 870 °C on a naturally aspirated engine. To cool down it passes about 75 % of its heat to the seat and about 20 % to the guide. For the original steel, the EV8 family values are used: 550 MPa at 600 °C, barely 300 MPa at 800 °C; beyond that the head overheats, fatigues and distorts until it leaks on its seat.

The MCEVI-1400S-HS is made of Inconel, a nickel-based superalloy that keeps 860 MPa at 732 °C and 554 MPa at 816 °C, nearly 85 % more than EV8 steel around 800 °C. Its hollow stem is sodium filled: liquid from 97.8 °C, the sodium carries heat from the head to the stem, then to the guide.

Exhaust valve technical specifications

The MCEVI-1400S-HS is fitted with KPR-6S/7 collets, which keep the original retainers and springs; VSI-BM60-E exhaust valve stem seals.

Valve fitting

The BMW valve has 3 grooves, the MCEVI-1400S-HS a single one: the original collets are therefore replaced by the KPR-6S/7, without changing retainers or springs.

The head stays at 28.5 mm, the BMW size: the exhaust seats are checked during the rebuild, with no cutting to another size.

For stem sealing, this installation takes the VSI-BM60-E exhaust seals.

Technical guide

Our brand

SUPERTECH Performance has been making valvetrain parts for racing in California for more than thirty years. For the B38 three-cylinder, its set of 6 uses the sodium filled Inconel exhaust valve of its B38 / B48 / B58 range, at BMW size.

How to choose

There is only one version for the B38; here is what it changes compared with the BMW part:

When reinforced valves become necessary

• Remap with higher boost pressure (Inconel version, the only one offered)
• Larger or hybrid turbo
• Modified camshafts or valve springs
• Track days
• Cylinder head rebuild with marked exhaust valves

Vehicle compatibility

OEM part number (exhaust valve): 11 34 8 621 264

Don't forget the inlet valves

A dismantled B38 cylinder head is the moment to check the inlet valves and valve stem seals as well.