Why the Toyota Supra Makes Less Power Than the BMW Z4
The engines are nearly equal, but not equal enough.
BY
BOZI TATAREVIC
JAN 28, 2019
The Toyota Supra shares a platform and a large majority of its components with the BMW Z4. But as we
discovered last summer and
recently confirmed, the Z4 will make 47 more horsepower than the Supra in top trim. Since ECU tuning has become so advanced with modern engines, the automatic response might be to think that it is all in the programming. A BMW parts catalog reveals that the changes go further than the code.
According to the BMW ETK catalog, the US variant of the Supra will be equipped with the B58B30C engine. It carries part number 11002463592, and seems very similar to the engine for the US-spec Z4 M40i. However, the Z4 engine is actually the B38B30B, and has part number 11002464415. What does that mean? There are internal differences. Searching the interchanges for the two part numbers shows that the US Supra engine is the same as what Europeans will see in their variant of the Z4 M40i, while the US M40i engine will be used in the new G20 M340i 3-series.
Digging into the motors reveals that the first different part is the cylinder head. The Z4 has a cylinder head part number of 11127934495 while
the unit in the Supra is marked as 11127934494. The differences are not apparent based on the catalog illustration, and instead are likely to be in the castings of the cylinder heads as both use the same exact camshafts, valves, and ancillary components.
Moving to the bottom end, both engines use the same crankshaft and bearings, but the pistons and connecting rods are different. The Z4 piston–part number 11258678934–is found in a variety of BMW products including the US M340i and European spec 7-series sedans.
The Supra piston–part number 11258681079–is found in the motor for the US spec 7-series and the X7.
Based on the catalog entries, basically every other component seems to be the same. The final difference appears to be in the turbocharger. The Z4 uses part number 11657934387, which is only shared with the M340i, while
the Supra uses part number 11657934332, which is only shared with the Euro-spec Z4 M40i. Even though the turbocharger appears to be different, all of the clamps and mounting hardware are the same between the two. Even though the unit on the Z4 might have bigger wheels in it, there is a good chance that it should bolt right up to the Supra.
The hardware for the ECU is even the same; the two cars
share the 86T0 DME. After looking at the parts, it doesn't look to be very hard to replicate the power of the M40i in the Supra.
For those that want to make an OEM equivalent, the primary components to change will be the pistons and rods as those are likely built to withstand a little more boost. Swapping the cylinder head and turbocharger would complete the package. A tune will take advantage of all of those components.
We’re likely to see tuner shops digging into these cars as soon as they hit the ground. Based on what I see here, it likely won't be very complicated for them to make even more power than the Z4 M40i.
