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N55 vs B58 (M135i vs M140i)

Dyno data from both engines compared.

We often get asked what differences there are between the N55 and B58 units. On a technical level, the differences are wide ranging, N55 is open deck, B58 is closed deck. N55 is air-air intercooled, B58 is water-air charge-cooled. Despite both engines being 3.0 single turbo 6 cylinder units, very few parts are shared between them. 

Ulitmately though, what most end users really want to know is the difference in terms of power, torque and power delivery throughout the rev range.

We have had hundreds of customers with both engines, and have a lot of dyno data for both. One thing that you rarely see is dyno data for both engines overlaid, so we thought it would make an interesting case study.

We exported data first for the M135i, getting the raw values from this dyno graph:

N55 M135i Dyno Graph

We then exported the values from this dyno graph for the B58:

B58 M140i Dyno Graph

Both cars are absolutely stock (other than on the tuned runs running our Pro Tuning Box) This gives us a fair comparison between both engines.

With the values exported we can then compare power as standard for both engines:

N55 vs B58 Stock Power Dyno

As you can see, from very early on the B58 has big gains over the N55 which it holds right through the rev range.

The engines also inevitably have big differences in their torque output, right through the rev range. The B58 makes more torque everywhere and gets there ever so slightly sooner in the rev range. The boost threshold on both engines is pretty much identical, and before achieving boost pressure make very similar torque outputs:

N55 vs B58 Stock Torque Dyno

There are several good reasons for this. Other than fundamental hardware differences, one of the big changes between the two engines is the level of boost pressure that they run. Here you can see an export of manifold pressure logged from both vehicles as standard:

N55 vs B58 Stock MAP Dyno log

As you can see, the B58 has a very similar boost curve, but makes around 4PSI more than the N55 across virtually the whole rev range.

This is an interesting comparison, but again, what most end users really want to know is, "can I make my N55 M135i perform as well as a B58 M140i?"

In a word, yes. The following graph shows torque with our Pro Petrol Tuning Box fitted: 

N55 vs B58 Bluespark Torque Dyno

It makes significantly more torque than the B58 everywhere in the rev range.

The story is the same with power output:

N55 vs B58 Bluespark Power Dyno

Power gains right to redline are better than the B58 at every point, making the M135i a very capable car.

The final results are very close to those offered by many Stage 1 flash tunes, but with the advantage that our unit can be tracelessly removed in under 5 minutes.

If you are interested in what we could do for your BMW, please take a look at the relevant link below or our BMW Tuning page: 

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ID Make Model Fuel System Engine Size (cc) KW Power (PS/HP) Nm
64584 BMW BMW M135i 320PS Petrol Turbo 2979 240 326 450 Select Vehicle
65935 BMW BMW M140i 340PS Petrol Turbo 2998 250 340 500 Select Vehicle