Quote:
Originally Posted by swamp2
Excellent work, right in line with my predictions. However, I'm reasonably confident it will not offer an overboost feature.
As many of us have discussed prior, the numbers of 395 ft lb, approximately 415 hp and anywhere from a 7500-8000 rpm redline just are not consistent and possible together. Also BMW seems to have a decent track record (335i, 1M, F10 M5, etc.) of underrating. This M4 will be one and the same in that regard. I think they may rate the car around 425 hp but the likely actual crank hp will be in the range of 440-460. If these rumors on redline are true, and they do sound reasonable (and I always have a pretty high degree of trust in claims backed by southlight), I would guess a 7700-7800 rpm redline. It surely will not be ≥8000 rpm.
No doubt about it, the car will feel a bit flat above 6000 rpm compared to the current engine. However, flat with 10% more hp is not so terrible. Sure I'd prefer to not have this engine characteristic given such a choice.
Lastly I am 100% confident that this car despite the shape of its torque and power curves when above about 6000 rpm the former is falling fast and latter table top flat, will still only achieve maximum acceleration when shifted precisely at redline. Generally speaking, as long as the power curve does not actually fall and as long as the gear choices are reasonable, shifting at redline is required for maximum acceleration. If anyone want to continue to doubt this I would be willing to prove it either with a detailed Excel chart showing wheel force vs. speed in all gears or with a physics based acceleration simulation. Both require a resonable assumption on the torque or power curve vs. rpm and I would use something right along the lines of the one from HMR.
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Agree. I also believe that this engine will require shifting at redline in most gears.
What will be interresting is that, with such a flat power band, there should not be any drop in acceleration when shifting from one gear to another. Essentially having "450hp" available at any road speed. Further enhanced by the seamless shifts of DCT, the acceleration curve should be very smooth, progressively decreasing with road speed. As a comparison, with the peakier power curve of the S65, the wheel torque significantly drops with each gear change, yielding a "staircase" acceleration curve.