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

On the B38 three-cylinder, the exhaust valve opens into gases that carry on all the way to the turbine. There, its head exceeds 1,000 °C, while a naturally aspirated engine holds it between 760 and 870 °C. The seat takes about 75 % of this heat, the guide nearly 20 %. The original steel, referred to EV8 family values, offers only 300 MPa at 800 °C after 550 MPa at 600 °C: with more boost pressure, the head heats up, tires, warps and no longer seats tightly.

SUPERTECH makes the MCEVI-1400S-HS in Inconel: this nickel superalloy still shows 860 MPa close to 730 °C and 554 MPa close to 815 °C, roughly 85 % above EV8 in the 800 °C zone. Its hollow stem holds sodium which, molten from 97.8 °C, moves with each opening and carries heat downward, out of the head and to the guide.

It stays at the BMW size, with a 28.5 mm head and 100.1 mm overall length: the 6 exhaust valve seats of the B38 are checked at rebuild without any machining. Its single groove does, however, call for KPR-6S-7 collets in place of the 3 groove BMW parts.

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 designed motorsport valves and everything around them, springs, guides, titanium retainers, for over 30 years, out of Silicon Valley in California. Stainless steel, titanium, Inconel: each valve targets one engine and is fine-tuned with known circuit, rally and drag strip tuners.

How to choose

For the B38B15, SUPERTECH offers a single exhaust valve: the MCEVI-1400S-HS, in sodium filled Inconel, with the 28.5 mm BMW head and one groove. What is left is to pick the use and plan the matching collets:

When reinforced valves become necessary

• Remap and higher boost pressure (sodium filled Inconel version, sole version available)
• Hybrid or larger turbo
• Reworked camshafts or harder valve springs
• Track driving in a 118i or 218i
• Exhaust valves marked or burnt at a rebuild

Vehicle compatibility

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

Don't forget the inlet valves

If the B38 cylinder head is removed, fit new inlet valves to this three-cylinder engine at the same time. Here is the reference suited to this engine: