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M52TUB25 Tuning
Let's tune the BMW M52TUB25 engine from 170hp to M54B25 level (192hp).
Basic difference is that the M52TU engines use cable throttle with MS42 and M54s use drive-by-wire with MS43.
Here are both engine compared in known data:
Engine | Displacement | Bore x Stroke | Compression ratio | Power | Torque | RPM limit |
---|---|---|---|---|---|---|
M52TUB25 | 2494cm³ | 84mm x 75mm | 10.5:1 | 170hp @ 5500rpm | 245Nm @ 3500rpm | 6500rpm |
M54B25 | 2494cm³ | 84mm x 75mm | 10.5:1 | 192hp @ 6000rpm | 245Nm @ 3500rpm | 6500rpm |
They are exactly the same, except for the 22hp difference in power.
Intake manifold runners have the same inner diameter and also the throttlebody is equal in size. Partnumbers differ only because of cable vs. DBW.
Let's find out what limits the older M52TU in software
DISA
This one is easy, there is only one small part load and an even smaller full load table to compare.
You can see, that exactly where the M52TU produces its peak power, the DISA valve shuts the path between the two differential runners, leading to less air inside the cylinder.
This actively prevents the engine from producing more power from 5500rpm upwards. By the way the 2.8L brother of this engine does the same.