BMW B58 vs S55 Testing

B58 vs S55 Dyno Comparison


We often see discussions about the relative merits of the B58 engine (found in the BMW M140i, M240i, 3/440i and more) vs the S55 found in the F8X M3/M4 as well as the new M2 competition.

Whilst you often see dyno graphs of both, we don’t often see direct comparisons. Armed with dyno data from several B58’s tested on our dyno as well as results from my own M4 Competition I thought we could produce some interesting comparisons.

For the basis of these comparisons I exported the run files of these B58’s:

The first is a bone stock M240i with and without our box fitted:

The second is another M240i with VRSF Decat, again with and without our box fitted.



We then have a stock run from our M4 Competition Pack, and then tuned with our new 3 channel tuning module for the S55:


We exported all the data from all of these runs as .csv files so that they could be re-plotted all on the same graph. Starting with the stock M4 Comp vs the Stock B58:


It is worth noting that the M4 Comp tested does have a little more power quoted than the regular M4 (450PS vs 431PS) and a lump more than the M2 competition at 410PS. Still, it beats the B58 hands down from 3000RPM onwards.



Next we compare the stock M240i with the addition of our Bluespark Pro Petrol tuning box vs the same S55 engine:


As you can see, the B58 engine is now making more power than the Stock S55 right up until 5500RPM. After this point the S55 climbs away and goes on to a higher redline, but the tuned B58 has definitely started to close the gap. 

Next we can add the decat to the B58 and again compare the results:


As you can see, now the B58 is really getting somewhere. It is making significantly more power than the S55 right up to 5800RPM, and over 100HP extra at 2500RPM. The only point at which the S55 is now beating the B58 is in a narrow band between 6000 and 6600RPM, and still only by a maximum of 17hp. The gains down low far more than make up for this.

The gains here make this package a performance bargain. With the Bluespark tuning box alone, the B58 has around the same area under the curve as the S55. Add the decat and for under £500.00 you have a package that in a straight line will out drag a stock M3/M4.

 As with any tuned vs stock debate, inevitably the next question is “what if the S55 was tuned?” Fortunately, we have already done this, and with our new multi-channel tuning system (check it out here) for the S55, the gap is inevitably significantly widened:


This takes nothing away from the B58, though it does strike me that any customers who have gone from a tuned Mx40i to the new M2 Competition might be sorely tempted to look our way for a warranty friendly tuning solution…

If you are interested in what we could do for your B58 or S55, please take a look at the relevant link below or our BMW Tuning page: 

We can't find products matching the selection.