B25 to B30 swap guide

Bali · Jan 6, 2023

I get PMs from members asking about this topic as I have done many swaps and advised others on here. This thread lists the differences and things that need to be changed when swapping engines from M54B25 to M54B30. It is only for B25 to B30 swap, and not for M52TU cars (323/328).

Below are the important things to know and do:

Get a complete B30 engine with all its attached parts, including intake system
You can keep the transmission, brakes, exhaust, DME, EWS, keys, locks, wiring harnesses in the car. Leave all your 325 components in place except the engine and intake system
Acquire a 330 airbox, MAF sensor, intake boots (B30 is larger diameter)
Any differing peripheral parts such as valve cover, coils, O2 sensors, SAP system, intake air temperature sensor, etc., should be swapped over to the donor engine
The B30 engine will start and run using the existing DME and its B25 software
Later on, after all swap-related issues are resolved, flash the DME to B30 software for optimum performance and efficiency
The DME changed from MS43 to MS45.1 on non-XI cars starting on 03/2003
See the table below for part differences. Note that XI models only got MS43 DME
The valve cover and coils changed from the large top style to pencil style on 09/2002

The two DME families and the part differences:

MS43	MS45.1
standard (narrow band) pre-cat O2 sensors	wide band pre-cat O2 sensors
vacuum-based SAP system	MAF-based SAP system
discrete intake air temperature sensor mounted on intake manifold	intake air temperature sensor built into MAF sensor, plug where the MS43 IAT sensor would go
3-wire MAF sensor	5-wire MAF sensor with intake air temperature sensor

2003 Changeover for valve cover, coils

Up to 09/2002	From 09/2002
large top coils	pencil style coils
valve cover: 11121432928	valve cover: 11127512839

Archbid · Jan 7, 2023

Don't forget the transmission
If you have standard you should get the appropriate clutch for the 330
I wrote a piece on the differences between the ZF 5 speed auto for the 325 v 330. If you put a 330 in, be mindful that you will need some modification to the transmission.

DIY: Differences between 325 and 330 ZF 5HP19 Transmissions

While not the subject of torrid debate (like sensors on M56 SULEV radiators ;) ), there is a decent amount of misinformation and confusion about the differences among the variants of the ZF 5HP19 5-speed automatics. These transmissions are found from around 1995 to 2003 on a range of BMW...

www.e46fanatics.com

And if you are particular, get the muffler, the lens from a 330 cluster and the headlight bezels

mega_stihl · Jan 7, 2023

Clutch: B30 is the only M54 (and M52) engine that uses a larger clutch, 240m instead of 228mm. Your old clutch will fit fine but will probably not last very long. Flywheels are the same.
5 speed gearbox: 330i uses a stronger ZF compared to the Getrag. Getrags will bolt up just fine and I'm running a B30 with a Getrag behind which still holds up so far. So not a necessity to get the ZF. The ZF uses a larger guibo and therefore another driveshaft. Keep in mind that if you buy a driveshaft from a 330i, you might have to change the input flange of the diff since the diff usese 4 bolts with the exception of the 330i which uses 6 bolts. If you swap over a B30 engine into your E46 and want to run the ZF gearbox, you're best off with a 328i driveshaft since it also came with the ZF (larger flector) but still has 4 holes to bolt up onto the diff.

EXCEPTION: iirc there is a 325i from 2004 if I'm not mistaken, where the Getrag uses a different input spline aswell as a different clutch.

B25 to B30 swap guide

DIY: Differences between 325 and 330 ZF 5HP19 Transmissions

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