In 1991, BMW Motorsport redesigned the S38 to improve performance. The bore and stroke were increased again, and the displacement grew to 3795cc. The compression ratio was increased to 10.5:1. The intake and exhaust ports increased in size also, and each spark plug got it's own high-voltage coil, eliminating the distributor rotor and the high-voltage wiring. A smaller and lighter Emitec metallic catalytic converter replaced the ceramic catalytic converter. The main advantage of the Emitec metallic converter is that it increases the flow of the exhaust gasses. The Bosch Motronic 1.2 fuel management system was replaced with the Motronic 3.3 system. The new system includes a resonance flap control. This feature is the same as that used on the S38B36, but with an extra switch-point at 2480 rpm.
The S38B38 was the last evolution within the S38 engine family. It delivered 347 hp @ 6900 rpm and 409 nm torque at 4750 rpm. These changes stretched the S38 to its limits (the 5.4 mm web spacing between two cylinders is very narrow. This is 0.6 mm less than the M49/3 racing engine.)
Der stod det vel svar på det meste Tatt fra BMWworld.com