View Single Post
      01-18-2010, 02:18 PM   #3
gmza
Private
14
Rep
85
Posts

Drives:
Join Date: Jul 2008

iTrader: (0)

Garage List
Torque on the N55 actually comes in earlier and lasts longer when configured in 225kW 400Nm mode. The later torque is when configured in 245kW (430? Nm) setup; only reason the torque peaks later is that the engine management limits the peak at 430Nm; it'll reach 400Nm at the same revs, irrespective of config.

Personally I think that 99% of the improvements in this engine are down to integration of valvetronic. This is what is letting it breath better at the lowest and highest revs, spreading the torque and improving economy.

The choice to go from twin turbo to single twin-scroll turbo seems like nothing more than the good sense of achieving the exact some outcome at a much lower cost and greater simplicity. Well, at least from a manufacturing perspective; from engine management it is probably more complex, but software is easy to change, hardware isn't. Turbochargers are devilishly expensive items and using a single twin-scroll should have a significant impact on cutting the cost of manufacturing the engine.

In terms of driving, I would be extremely surprised if it is possible to notice the difference between the two. Their performance characteristics are virtually identical and the N54 revs quite high already.

Valvetronic's most notable influence (performance-wise) on the previous generation (non-turbo) engines was that the engines reved higher and more freely. And even then the benefits were small by comparison to a change from aluminium to magnesium for the cylinders. I had two 140kW E39 525i (pre-valvetronic) and a 160kW 325i (with valvetronic). The 160kW motor was much nicer, particularly at the top end. But the N54 already revs high, even without valvetronic... The turbo engines are unlikely to use magnesium construction any time soon as they're subjected to greater pressure.

I'm not convinced about the weight argument. 4kg just isn't noticeable on a 1560kg car. You'd get significantly more benefit simply by being judicious about your options list or driving with 10% less fuel in the tank...

As for tuning, I think it's also much of a muchness, however, the N54 is a slightly less complicated engine from a management perspective and most tuning involves changing the engine management...
Appreciate 0