Originally Posted by NISFAN
I disagree, to most enthusiasts Lag is the revs at which the Turbo is capable of producing boost. Technically known as Boost threshold.
Lag technically is the delay between throttle application and power delivery when the engine is in the boost threshold region.
The fact that the new M3 has at least 2 turbo's sequentially set up, and a very short plumbing through an water/air intercooler, to me means that it will be significantly better than a 335i in both boost threshold and Lag terms.
The major plus with a Turbo is you have a massive torque band.
When you undertand the real term of LAG, an NA engine has LAG ALL THE WAY TO REDLINE, at it never has that boosted torque increase.
Unfortunately you always seem to get NA or Turbo enthusiasts. It is usually one or the other as a preference.
No, I think most people think of lag as the time between pressing the pedal and reaching full boost. Boost threshold is a different issue and I have seen some people talk about that when they use the term lag, but I think we can all agree that, since BMW's current turbo engines can hit full boost by like 1,500RPM, this is a non-issue. I like to stay in really high gears, if I am about to stop at a red light and it changes to green when I'm rolling at about 5mph, I'll probably stick it in 3rd or even 4th gear and the N55 has absolutely no problem pulling cleanly from way down low.
Both my N55 and the N54 have perceptible lag, they're more responsive than almost any other turbocharged engine ever produced but they are still miles away from the responsiveness of a naturally aspirated motor. This isn't such a huge deal, but on an M car I expect very granular throttle control mid-corner and my 135i is seriously lacking in this department compared to the E90 M3 my brother used to have.