Z4 observations

[Asbjorn]

To get the fastest acceleration you need the shifting points to sit so that the area below the hp curve is maximized. As you know, the hp curve is just a product of torque and rpm. And on most cars, where peak hp happens close to the red-line, "maximization" is achieved by reving the engine to its red-line, especially in lower gears.

For example, if the hp curve drops equally on each side of the hp peak rpm (lets say it happens at 5000rpm), and the next gear shift will lower rpm by 1000, then you better shift at 5500rpm, no matter if the red-line is at 10.000rpm. But, of course, if red-line is at 5300rpm, then you have to shift at that point and hope the next gear only drops rpm by 600.

With the 35is the hp curve is more or less flat from 4500-6500rpm. That makes this engine rather different form NA engines as well as big turbo engines, but similar to for instance rally car engines. If you are only allowed to produce xx hp, then you will be having more fun if they are available at almost any rpm. The 35i/35is N54 is an example of that. The 30i isn't. (although still a great NA engine with a wide torque band!)

Anyway, so as long as each gear change keeps you above 4500rpm. you will actually accelerate faster than by reving to red line at 7000rpm. First gear change (M1 into M2) drops rpm around 2000 and second (M2 into M3) drops it around 1500. The following higher gears even less. So when in M2 and up there aren't many reasons to shift later than 6000-6500rpm. It will only make the DCT hotter, stress the engine, and provide a slower lap time.

And btw, even in sport+, the D and S modes will also never take you past 6500rpm AFAIK.

[nicknaz]

Really surprised that so many posters on this forum are happy to give up max hp and weight to power ratio to get low end torque.

[Asbjorn]

I stand corrected, and just learned something new about my car! My car indeed has a kickdown switch and it is activated very close to the "floor" or the gas pedal. In D mode it will kick-down even if I don't hit this switch, so I always thought it was just the carpet or something playing with my pedal. Anyway, if I hit this kickdown switch it indeed kicks down even in manual mode. I happens in all modes (DSC=off, Sport+ and Normal/Comfort).

So C&D is correct, but you can just avoid pressing past this kick-down switch if you dont like it...

On the positive side, having the switch will allow you to do multiple down-shifts even in manual mode. That is nice because our Z4 does not have the function where you can pull and hold the levers on the steering wheel to get multiple downshifts (like with an M5).

And btw if I activate the kickdown-switch and keep my pedal pressed to the floor it seems I can still upshift at low rpms in manual mode.

[R1robot]

Thanks for the info Asbjorn. I doubt the Z4 is a low-end vehicle compared to the 135i...so why does the 2010-current 135i get the N55 engine and the new Z4 still has N54?

[nicknaz]

Internet speculation I've seen is that N55 is a fuel economy play and the N54 is better for modifying.

I was playing around with the DCT on the way home and it shifts right at the 7000rpm redline

[R1robot]

i see, is your 35i manual DCT? If so, how does that even work? never driven a bmw with paddle-shifting. Every bmw i've owned was a manual gearbox

[Asbjorn]

Originally Posted by nicknaz

Internet speculation I've seen is that N55 is a fuel economy play and the N54 is better for modifying.

I was playing around with the DCT on the way home and it shifts right at the 7000rpm redline

+1
The N55 with its valvetronic is more fuel efficient, more responsive, cheaper to produce and does not have the same issues with the HPFP and carbon build-up as the N54

Given the sales numbers it is easy to speculate that there simply was no business case for updating the 35i to fit the N55 with the LCI.

On the plus side the N54 has won the international engine of the year award in its class every year since 2007, and it simply has more potential for extra horsepower.


Regarding the shift at redline I assume you mean in Manual mode?

[Asbjorn]

Originally Posted by R1robot

i see, is your 35i manual DCT? If so, how does that even work? never driven a bmw with paddle-shifting. Every bmw i've owned was a manual gearbox

http://en.wikipedia.org/wiki/Dual-clutch_transmission

Try searcing for DCT on youtube also!

[nicknaz]

Originally Posted by Asbjorn

Regarding the shift at redline I assume you mean in Manual mode?

With the car in "sport+" setting, and gearbox setting in either S or M mode the car shifts at 7000rpm when I have the throttle all the way to the floor (i.e. pressing down the kickdown switch)

@r1robot... My last bimmer was traditional 6 speed manual with clutch pedal and now I'm so sold by the dual clutch technology for cars that I'm not planning to keep for a long time. It has some flaws (i.e. upshifting automatically at redline, sometimes not downshifting if the car is sideloaded) but overall I think the fast shifts are great (better than I could do for sure, especially going through the 2nd to 3rd gear "dog leg")

[Asbjorn]

Originally Posted by nicknaz

With the car in "sport+" setting, and gearbox setting in either S or M mode the car shifts at 7000rpm when I have the throttle all the way to the floor (i.e. pressing down the kickdown switch

You sir are correct. Even with the car in normal setting, and gearbox setting in D it revs to 7000rpm when pressing down the kickdown switch. I cant believe I drove this car for almost 1 year without noticing this kickdown switch.

Anyway, without activating the kickdown switch it revs to 6500rpm (except in manual mode of course). That is, unless there is wheelspin, in which case the car might shift earlier and even double upshift (again, except in manual mode)

[CeEl]

Must admit, never "experimented" that much with it ... I probably should!

I enjoy just going to that first resistent point (not past it to kick down); I find that gives me the nicest sound (top down) & least wheel spin when driving off from a stop.

I do sometimes kickdown when the car is already in motion, eg. for overtaking. Even though it's often hardly necessary Using the flaps to quickly shift into manual mode & lower gear, and when I am done it reverts back to regular D.

[Blu Yea]

I agree. Even though i went from the Z3 3.0 to the 3.5i and knew it would be a big jump. WOW was i surprised. Man, when you go full manual and hit 4K rpm it takes off like rocket.
Getting rid of the RFT this week and can't wait to feel the Super Sports instead. If i can get rid of the broken metal sound in the back, it will be heaven. Someone mentioned the difference with the 19" wheels over the 17's, yea actually drives like a bigger car, which in a way it is.

Originally Posted by Toink

Personally, the moment I knew that there was a 35is next to the 35i, I just stopped looking for a 35i and got the 35is instead.

But even for the 35i I definitely recognize your experience. I came from an '06 3.0Si to my current sDrive35is. The 35is is way more sensational than a regular 3.0 and the twinturbo setup has lots of potential, so more power/torque is easy to obtain.