[ZPrime]

Originally Posted by stren

I also noticed some weird throttle things going on - seemingly cutting power after up shifting (6mt) when pulling reasonably hard on a corner (possibly lag or dsc - didnt' have enough time to investigate) and occasional random throttle blips when in sport+ with the clutch in when coasting to a light.

That behavior is apparently somewhat expected, because of the revmatch tech in the 6MT. As long as you don't have DSC / traction control fully off, the auto revmatch is still happening. It manages throttle for you on both down and upshift, if what I've been reading is correct. So if you're too deep into the long pedal and upshift it without lifting, it will purposefully cut power so you aren't eating the clutch up. I'm not sure if it will manage the RPMs on an upshift if you lift completely, I didn't have a long enough test drive in a 6MT car (I was in an M340ix that had a stick, I believe it behaves identically to the M2) to mess around with it much.

Your random throttle blips while coasting to a light were probably the stick being close to other gates (were you wiggling it around with your left foot down?), which would be the revmatch trying to blip for downshifts that you weren't actually making.

[atomic837]

Originally Posted by ZPrime

Note that to most people who actually want to drive the car for performance, progressive build of power is more desirable than "boom instant torque." It's hard to control a car that has near-instant high torque, like trying to balance on a razor blade. Racecar drivers want a linear powerband, not one with big fat lumps of pull that are hard to predict.

If you want insta-torque, go look at N/A American V8 stuff...

This all comes through in the better reviews of the M2 as well - they tend to mention that the car seems to want to be wrung out and shifted more - to keep it up higher in the rev range. This is atypical compared to the small single turbo 4cyl ~2L mills so common on most of the cheaper small hot cars today - WRX/STI, Focus RS, GoRf, etc. Those cars tend to hit peak torque pretty early and plateau there, but then begin to gasp and wheeze at the top of the powerband. I can state from experience that the Mk2 TTRS is the same way - the torque comes in very early, but it's out of steam by 5800 or so. Redline is at 6800 but there's not much reason to spin it all the way out there, which makes the car a bit less exciting. (Supposedly the motor/valvetrain is actually OK to rev to more like 7200, but there's zero reason to take it that high since it's way outside compressor efficiency.)

While I can appreciate that philosophy, I don't believe that BMW intentionally added turbo lag in order to provide a smoother build up of power. Peak torque is available at 1400 RPM - assuming the turbo has spooled up.

I agree that being able to rev the car to redline and still get appreciable power throughout the RPM range is great; I drove a high revving 4-banger in my earlier days... But I'm not fond of the half second hesitation that the N55 seems to suffer between pedal input and turbo response.

If the N54 I also drive wasn't appreciably more responsive, I wouldn't have any qualms.... But being able to drive them side-by-side.... Well, once you see it, you can't unsee it.

Hoping that my perception changes after break-in.

[Bluenose-2er]

Originally Posted by atomic837

While I can appreciate that philosophy, I don't believe that BMW intentionally added turbo lag in order to provide a smoother build up of power. Peak torque is available at 1400 RPM - assuming the turbo has spooled up.

I agree that being able to rev the car to redline and still get appreciable power throughout the RPM range is great; I drove a high revving 4-banger in my earlier days... But I'm not fond of the half second hesitation that the N55 seems to suffer between pedal input and turbo response.

If the N54 I also drive wasn't appreciably more responsive, I wouldn't have any qualms.... But being able to drive them side-by-side.... Well, once you see it, you can't unsee it.

Hoping that my perception changes after break-in.

I agree they did not "intentionally add turbo lag". What was done was to design the turbo engagement to provide a smoother boost and a power curve that is more accessible for driving use. If you like the kick in the pants sudden boost of turbos of old, yeah it isn't there. It is replaced with something that (in my opinion) is more drive able and enjoyable.

Throttle response is not the same as turbo lag. Throttle response is how quickly the engine responds to throttle input. Turbo lag is the delay between engine response and the power boost from the turbo kicking in. If you are using Sport+ setting that is strange you see that delay in throttle response.

[atomic837]

Originally Posted by Bluenose-2er

I agree they "intentionally added turbo lag". What was done was to design the turbo engagement to provide a smoother boost and a power curve that is more accessible for driving use. If you like the kick in the pants sudden boost of turbos of old, yeah it isn't there. It is replaced with something that (in my opinion) is more drive able and enjoyable.

Throttle response is not the same as turbo lag. Throttle response is how quickly the engine responds to throttle input. Turbo lag is the delay between engine response and the power boost from the turbo kicking in. If you are using Sport+ setting that is strange you see that delay in throttle response.

I'll withhold further opinions on the subject until break-in maintenance is complete and I can judge the car uninhibited (this weekend).

And I agree with the definition regarding throttle response and turbo lag. Throttle response isn't the problem with this car (especially in Sport+).

[stren]

Originally Posted by ZPrime

Note that to most people who actually want to drive the car for performance, progressive build of power is more desirable than "boom instant torque." It's hard to control a car that has near-instant high torque, like trying to balance on a razor blade. Racecar drivers want a linear powerband, not one with big fat lumps of pull that are hard to predict.

If you want insta-torque, go look at N/A American V8 stuff...

This all comes through in the better reviews of the M2 as well - they tend to mention that the car seems to want to be wrung out and shifted more - to keep it up higher in the rev range. This is atypical compared to the small single turbo 4cyl ~2L mills so common on most of the cheaper small hot cars today - WRX/STI, Focus RS, GoRf, etc. Those cars tend to hit peak torque pretty early and plateau there, but then begin to gasp and wheeze at the top of the powerband. I can state from experience that the Mk2 TTRS is the same way - the torque comes in very early, but it's out of steam by 5800 or so. Redline is at 6800 but there's not much reason to spin it all the way out there, which makes the car a bit less exciting. (Supposedly the motor/valvetrain is actually OK to rev to more like 7200, but there's zero reason to take it that high since it's way outside compressor efficiency.)

Yeah - I'm actually surprised with the S55 that they didn't lower maximum boost at lower rpm to give it a more progressive linear power feel. Some reviewers complained a a lot about how that low end torque hits so hard and catches them off guard, others however said you just needed to know how to not mash a pedal Certainly they could have at least added two or more modes - flat torque to linearly increasing torque. They could have even been linked to the modes - comfort - medium torque at low rpm, sport - high torque at the low rpm for aggressive daily driving, sport+ = race mode - lower torque at low rpm with more of a progressive NA feel.

Originally Posted by ZPrime

That behavior is apparently somewhat expected, because of the revmatch tech in the 6MT. As long as you don't have DSC / traction control fully off, the auto revmatch is still happening. It manages throttle for you on both down and upshift, if what I've been reading is correct. So if you're too deep into the long pedal and upshift it without lifting, it will purposefully cut power so you aren't eating the clutch up. I'm not sure if it will manage the RPMs on an upshift if you lift completely, I didn't have a long enough test drive in a 6MT car (I was in an M340ix that had a stick, I believe it behaves identically to the M2) to mess around with it much.

Your random throttle blips while coasting to a light were probably the stick being close to other gates (were you wiggling it around with your left foot down?), which would be the revmatch trying to blip for downshifts that you weren't actually making.

Huh - interesting - I didn't know you needed dsc completely off for revmatch to be off, I thought sport+ on it's own disabled rev matching. But then I had also thought traction control was actually off in sport+ because the light comes on the dash. Certainly the revmatch seemed to go away in sport+ but maybe it's different or it just lined up better with my style? The revmatching blip in the other modes seemed to happen quite quickly - usually very soon after going into neutral. I tend to shift quite slowly when cruising around town so it was usually out of sync with me and quite noticeable when it did happen. The blip while coasting was weird because it was much more delayed than normal after going into neutral and it didn't happen everytime. Sadly I didn't get much time to really figure things out though. I actually tried wiggling the stick in neutral and even putting the car into gear without lifting the clutch to see if it was that but it wouldn't blip either.
Does it blip as you start to lift the clutch?

[ZPrime]

The only way to fully defeat revmatch is to fully disable traction control, which requires long-holding the DSC button for 5-10 seconds until the light comes on in the dash.

Sport+ puts the traction into "M Dynamic Mode" (MDM), where it is still on but a bit more permissive than usual. AFAIK, you get the exact same thing by just short-pressing the DSC button without using Sport+. (I don't actually own a BMW yet to test all of this firsthand, just going off of what I've read.) This whole "MDM" thing is so damn confusing - Audi just calls it "Sport" traction control and it's invoked the same way (short press of the traction control button). Audi also changes nothing else when you push traction control... the manual from BWM implies that throttle response is also altered when you're in MDM / "sport DSC"... I'm not exactly sure why they do this.

This thread elsewhere on the forum (thanks Artemis!) is very informative as far as the traction control/DSC modes go along with the "Driving Dynamics Control" (DDC / "drive program") are concerned.

The revmatching presumably uses hall-effect sensors (magnetic) mounted in the gearbox or on the shift lever somewhere so it knows what gear you are about to get into, just before you actually fully slot the lever there. That's when the blip happens on downshifts - as the stick is moving, and ideally before you let the clutch out. If you keep your foot on the clutch too long and screw around, it "cancels" the revmatch and will let RPMs drop to idle like a normal car.

[No Boost]

^Tapping the DSC button puts it into MDM (traction) mode. It also nueters throttle response the same as comfort/DSC completely off. Sports+ is the way to go for me.

[Jamesembry]

I notice the lag too after shifts. I assume that since you go from full throttle to idle during a upshift, the blowoff valve lets all the pressurized air out and once you go back to full throttle it has to start over and build boost again. I haven't driven one with a dct but I assume it wouldn't be as noticable if at all. I would also assume a sport downpipe would help but due to the nature of a turbo motor, I don't think it can be eliminated.

I however am not a BMW engineer though!

[stefan]

Originally Posted by Jamesembry

I notice the lag too after shifts. I assume that since you go from full throttle to idle during a upshift, the blowoff valve lets all the pressurized air out and once you go back to full throttle it has to start over and build boost again. I haven't driven one with a dct but I assume it wouldn't be as noticable if at all. I would also assume a sport downpipe would help but due to the nature of a turbo motor, I don't think it can be eliminated.

I however am not a BMW engineer though!

This is exactly right. DCT does accelerate more smoothly thanks to fast shifts which keeps you in boost. I haven't wrung out a manual version yet but I imagine if you're high in the revs during shifts you'll maintain that boost or most of it.

[ChrisK]

I agree. With the DCT in Sport - I don't feel any lag.