Reinforced inlet valves BMW B38A15 B38B15

BMW engines covered

The B38 is BMW's 1.5 litre turbocharged three-cylinder, with roller finger followers, hydraulic lash adjustment and Valvetronic variable lift on the inlet side. Fitted lengthways (B38B15) or transversely (B38A15), it has powered the 1 to 4 Series, the Active Tourer and Gran Tourer, the X1 and X2 since 2014, from 102 to 326 hp depending on version, hybrids included.

Its 6 inlet valves are BMW 11 34 7 633 699: 30.1 mm head, 5 mm stem, held by 11 34 1 438 142 collets. A remap that raises boost pressure exposes them to more heat and harder impacts.

SUPERTECH reinforced inlet valves

The inlet valve opens the way for the air compressed by the turbo, strikes its seat on every closing and slides constantly in its guide. It runs at 400 to 550 °C; at these temperatures the original chrome-silicon steel drops from 500 MPa at 500 °C to 250 MPa at 600 °C, 50 % of its strength lost.

SUPERTECH machines them from a racing stainless steel of the EV8 family, which keeps 650 MPa at 500 °C, 30 % more than the original steel, and 550 MPa at 600 °C, 120 % more. Black nitriding hardens and smooths the surface, so the stem wears less in its guide.

The original size is kept, 30.1 mm head and 5 mm stem, with a single groove: the seats do not need cutting to a new size.

Inlet valve technical specification

MCIVN-1400S-6: dished head, to be fitted with KPR-5.0-7S collets.

Fitting details

The SUPERTECH valve has a single groove: it is fitted only with KPR-5.0-7S collets, never with the original ones.

The original size is kept: the inlet seats are checked and refreshed as usual during the cylinder head rebuild.

Clearance is taken up hydraulically: no adjustment is needed after replacing the valves.

Technical guide

The brand offered

SUPERTECH, based in San Jose, California, has been designing valves, springs, retainers and guides for racing for more than 30 years. Each valve is drawn for a specific engine, checked by ultrasound, X-ray and laser measurement, then proven with engine builders from circuit racing to drag racing.

When reinforced valves become necessary

• Sharper camshafts or firmer springs
• Raised rev limit
• Higher boost or a larger turbocharger
• Cylinder head rebuilt for circuit or track use
• Original valves marked or worn

Compatible vehicles

OEM part number (inlet valve): 11 34 7 633 699

Related products

A rebuilt B38 cylinder head also gets new exhaust valves. They are available here: