DCT and turbo lag - noticeable?

[kerm1t]

Originally Posted by nathanm4

I meant turbo lag (maybe i was talking about full boost.). After a short moment, the turbos kick in.

Edit: It’s what I’m experiencing and the car has no problem.

If you're off throttle and you smash it, you will get a slight lag. Obviously turbos needs to spoil. However if your on throttle lightly and push into it, you will feel less of a spool time

On another note, the spool time is more noticeable once you're tuned

[drkeng]

Originally Posted by CanAutM3

Where did you get that BMW recommends Comfort for the steering setting ?

I gather they recommend the Sport setting since that is what they have set as the default

I think it was someone who has posted on this thread, but I'm not sure and don't want to misquote. Using the "search" function didn't let me find it. I was surprised, too.

I haven't done a comparison yet, but I have been driving in Sport, since one of reasons I got my first BMW was the tighter steering feel; I should probably try S+.

I recently drove a friend's X3 that's a few years old and the steering was super tight/stiff--couldn't believe it.

[SenorFunkyPants]

Originally Posted by CanAutM3

Where did you get that BMW recommends Comfort for the steering setting ?

I gather they recommend the Sport setting since that is what they have set as the default

Surely the default settings are chosen for maximum economy (or at least a compromise of settings) for when the car is put through the European drive cycle test, rather than any other reason.

I think the idea that BMW recommends "Comfort" steering comes from some BMW sponsored F8x M driving events where instructors have suggested it.

Myself I prefer comfort steering...Sport and above seems a bit too heavy and dull for my tastes.
But then, no matter much I try to like Sport and Sport+ throttle, I always end up going back the Efficient throttle - its just so much more predictable (and counter intuitively feels faster).....so what do I know!

[Wills2]

I don't notice any lag with mine in sport+ of course you'll have to wait for boost threshold to be reached if you're in a high gear at low revs but that's not lag.

[CanAutM3]

Originally Posted by SenorFunkyPants

But then, no matter much I try to like Sport and Sport+ throttle, I always end up going back the Efficient throttle - its just so much more predictable (and counter intuitively feels faster).....so what do I know!

I guess it boils down to what one has been accustomed to. I find the Efficient throttle setting to be very artificially damped, making it sluggish and less predictable. There is an inherent delay between foot movement and engine response. Sport is better but still feels artificially damped. Sport+ is the setting that feels the most natural to me and reminds me of the modded carburated NA engine I used to track earlier in life. I also prefer Sport or Sport+ when driving in the snow, the faster throttle response, including on lift-off, makes it easier to control how much the car slides. I do use the Efficient setting for the DD as the damping makes for smoother puttering around.

[CanAutM3]

Originally Posted by Wills2

I don't notice any lag with mine in sport+ of course you'll have to wait for boost threshold to be reached if you're in a high gear at low revs but that's not lag.

Looking at the S55 power and torque ratings, boost threshold is at 1850RPM. Mashing the throttle in Sport+ at 2000RPM, which is above the boost threshold, there is a non negligible delay before full power comes on. That is turbo lag. It is normal. At those low RPM, there are little exhaust gases available to spool up the turbos. When the throttle is opened, more air is fed to the engine which results into more exhaust gases to spool up the turbo a little more but not sufficiently to get to full boost. That additional boost does provide more air to the engine and so on until max boost is achieved. That is lag.

Try the same at 5000RPM where there is much more exhaust mass flow available at WOT and the turbos will spool up very quickly.

[Wills2]

Originally Posted by CanAutM3

Looking at the S55 power and torque ratings, boost threshold is at 1850RPM. Mashing the throttle in Sport+ at 2000RPM, which is above the boost threshold, there is a non negligible delay before full power comes on. That is turbo lag. It is normal. At those low RPM, there are little exhaust gases available to spool up the turbos. When the throttle is opened, more air is fed to the engine which results into more exhaust gases to spool up the turbo a little more but not sufficiently to get to full boost. That additional boost does provide more air to the engine and so on until max boost is achieved. That is lag.

Try the same at 5000RPM where there is much more exhaust mass flow available at WOT and the turbos will spool up very quickly.

The terms ‘turbo lag’ and ‘boost threshold’ are often confused, but they are two separate things

As I said I experience zero lag in sport+

[CanAutM3]

Originally Posted by Wills2

The terms ‘turbo lag’ and ‘boost threshold’ are often confused, but they are two separate things

As I said I experience zero lag in sport+

I understand the difference between the two quite well and have explained it myself on multiple occasions.

Lag is very obvious to me at lower RPM above the boost threshold. But it does not really bother me at all. You just need to be in the right gear if you want prompt acceleration. When the engine is kept in the power band, there is barely any perceptible lag, and that is what matters to me.

[Kimeran]

I drive my car all the time in the Sport+ setting for the throttle.
I don't notice any notable turbo lag, but the spool up time is quite ridiculous with mine.
if I mash on the throttle in manual mode at 1500rpm, I just have to sit patiently and wait... Once it gets close to 2800rpm or so, then it shoots off or breaks into wheelspin.
i do live around 5000ft above sea level, so that is definitely a factor.

[SenorFunkyPants]

Originally Posted by CanAutM3

I guess it boils down to what one has been accustomed to. I find the Efficient throttle setting to be very artificially damped, making it sluggish and less predictable. There is an inherent delay between foot movement and engine response. Sport is better but still feels artificially damped. Sport+ is the setting that feels the most natural to me and reminds me of the modded carburated NA engine I used to track earlier in life. I also prefer Sport or Sport+ when driving in the snow, the faster throttle response, including on lift-off, makes it easier to control how much the car slides. I do use the Efficient setting for the DD as the damping makes for smoother puttering around.

I would say that in Efficient, the throttle response is exactly as you would expect in a turbo boosted car (without the anti lag that you get in Sport and Sport +), not damped but a power output relative to the amount of boost.
Once above ~3k rpm it doesn't seem that any throttle mode produces more actual BHP/Torque.
However in Efficient you do get the surge in power when the engines gets full boost around 3k rpm that (at least to me) make the car feel faster...reminds me of my old 930 turbo which I loved.
It may well be that the software level you have in your car is different to mine which may account for different thoughts on the throttle response....I find the anti lag system for producing boost at lower rpms to be inconsistent, while it does give a better throttle response, the actual power output can vary with spikes of power/torque that upsets traction.
But you are right that its a personal preference...and its never going to be as good as the E9x M3s throttle response.

[MN2///M]

The BMW Performance Schools stress rolling onto the throttle to get maximum acceleration....in fact, they joke about people mashing the throttle and complaining about lag in the acceleration when what is actually happening is the computer nannies are retarding throttle input to maintain traction.

Turn the nannies off and then mash the accelerator and the tires will light up...

I agree with CanAutM3, this car drives best and is most predictable in Sport+ throttle and D3/S3 modes for the DCT. I suspect, but have no evidence, that all the other modes just dampen the natural output of the car through software programing.

[MN2///M]

Originally Posted by Kimeran

i do live around 5000ft above sea level, so that is definitely a factor.

I've driven my car thousands of miles at low elevations and I live at 6500 feet elevation and frequently take the car up to 9 to 11,000 feet; the computers in this car adjust so well for elevation that you won't be able to perceive any difference in the performance.

[GrussGott]

Originally Posted by CanAutM3

I understand the difference between the two quite well and have explained it myself on multiple occasions.

Lag is very obvious to me at lower RPM above the boost threshold. But it does not really bother me at all. You just need to be in the right gear if you want prompt acceleration. When the engine is kept in the power band, there is barely any perceptible lag, and that is what matters to me.

I can't describe it all fancy-like, but this

[SenorFunkyPants]

Originally Posted by MN2///M

I suspect, but have no evidence, that all the other modes just dampen the natural output of the car through software programing.

I guess its possible...but you'd think if that what the case then they would have done something to smooth out the dramatic power surge you get in Efficient when the engine goes from low boost to full boost at >3k rpm.
Myself I like the jekyll and hyde feel that Efficient mode provides...good drivability in the lower range going to full bonkers above 3.5k rpm.

[CanAutM3]

Originally Posted by SenorFunkyPants

I guess its possible...but you'd think if that what the case then they would have done something to smooth out the dramatic power surge you get in Efficient when the engine goes from low boost to full boost at >3k rpm.
Myself I like the jekyll and hyde feel that Efficient mode provides...good drivability in the lower range going to full bonkers above 3.5k rpm.

Throttle response is still damped all the way to redline in Efficient...

[SenorFunkyPants]

Originally Posted by CanAutM3

Throttle response is still damped all the way to redline in Efficient...

Is there anything online from BMW about this?
I'd also quite like to see an rpm/boost/torque/power graph for Efficient against Sport+...that ought to be interesting.

[CanAutM3]

Originally Posted by SenorFunkyPants

Is there anything online from BMW about this?

I'd also quite like to see an rpm/boost/torque/power graph for Efficient against Sport+...that ought to be interesting.

It is mostly based on my own experience on street and track with my M4 doodling with the driving modes. It would difficult to depict this on a standard dyno graph. At WOT, all driving modes will ultimately provide the same power level. The driving modes differ in how they respond to transitions in throttle position.

The best I could find when researching this is in this excerpt from the S55 deep dive and interview, where it mentions that all filters are deactivated in Sport+, which implies that there are filters in Efficient and Sport.

There are three driving modes: EFFICIENT, SPORT and SPORT PLUS. In terms of engine activity, do these simply alter the accelerator curve?

No. With an M automobile, racetrack use is always an essential factor. Here it is necessary in all cases to be able to control very high power outputs with great precision using the accelerator pedal. For us, this means that we would not even consider a mode in which a small pedal movement would produce a great leap in power. In such a case it would not be possible to produce a measured power output. Which is why we prefer to create a largely linear torque curve controlled by the travel distance of the accelerator pedal.

So what are the differences between the EFFICIENT, SPORT and SPORT PLUS modes?

In the SPORT and SPORT PLUS modes, the waste gates remain closed under partial load and the mass flow is routed through the turbines, to ensure that the turbo chargers are already rotating at a higher base speed even in standby. Moreover, certain special engine control functions are brought into play that accelerate activation of the turbo chargers. This means that the car responds more closely to the accelerator in SPORT and SPORT PLUS modes.

The rigid drive train of the new BMW M3 and BMW M4 is, however, optimised for a fast build-up of momentum, similar to a racing car, with a carbon fibre drive shaft, rear axle rigidly bolted to the body, suitably dimensioned drive shafts, etc. This means that the rigid drive train is also an important factor of the spontaneous entrance of the new BMW M3 and BMW M4. In EFFICIENT mode, everything is more levelled out, with a high orientation towards comfort. In stark contrast is the SPORT PLUS mode, which pays absolutely no attention to any comfort factors. In SPORT PLUS, all filter functions are deactivated and the engine responds directly to movements of the accelerator pedal – but this also requires someone behind the wheel who really knows what he is doing. In SPORT PLUS, everything is transmitted as sharply as a knife, in terms of what the engineering can do to facilitate fast lap times – whether in the engine, transmission, chassis or control systems.

If you switch off DSC and activate SPORT PLUS, you can feel the outstanding response very clearly, and, for instance, make good use of it on the racetrack to influence driving dynamics using the accelerator pedal.

[Ben Overlake]

I find sport+ to be too sensitive akin to the E46 M3 with the sport button on (worthless).

My m1 setting is sport throttle, sport steering and 2 on the dct. sus is always on comfort.

[SenorFunkyPants]

Originally Posted by CanAutM3

The best I could find when researching this is in this excerpt from the S55 deep dive and interview, where it mentions that all filters are deactivated in Sport+, which implies that there are filters in Efficient and Sport.

Yeah I've read that Deep dive (more of a quick paddle) interview before....and to be honest I thought it lost a lot of credibility with the sentence:
"we would not even consider a mode in which a small pedal movement would produce a great leap in power."
Which is patently not true wrt Sport+ mode.

Anyway on reconsideration there does seem to be at least one considerable difference between Efficient and Sport+ and that is the rpm at which peak boost appears to be achieved.
Looking at the torque graph, peak boost is at ~1850 rpm in Sport+.
Sport+ also benefits from some (as yet undescribed) engine mode strategies to create extra boost at low rpms and closed throttle overrun...which is sometimes inconsistent and can be felt as a spikey throttle response.
Without a graph for Efficient mode, I can only go on my own driving experience (in my 2017 Euro CP car) which is that peak boost arrives somewhere around 3000 rpm in this throttle setting...while at lower rpms you get a linear non boosted throttle response.
Above 3000 rpm there is little/nothing to choose between the two throttle settings as regards performance and throttle response....except perhaps that in Efficient the throttle response is more linear and less off/on compared to Sport+.

[CanAutM3]

Originally Posted by SenorFunkyPants

Yeah I've read that Deep dive (more of a quick paddle) interview before....and to be honest I thought it lost a lot of credibility with the sentence:
"we would not even consider a mode in which a small pedal movement would produce a great leap in power."
Which is patently not true wrt Sport+ mode.

Anyway on reconsideration there does seem to be at least one considerable difference between Efficient and Sport+ and that is the rpm at which peak boost appears to be achieved.
Looking at the torque graph, peak boost is at ~1850 rpm in Sport+.
Sport+ also benefits from some (as yet undescribed) engine mode strategies to create extra boost at low rpms and closed throttle overrun...which is sometimes inconsistent and can be felt as a spikey throttle response.
Without a graph for Efficient mode, I can only go on my own driving experience (in my 2017 Euro CP car) which is that peak boost arrives somewhere around 3000 rpm in this throttle setting...while at lower rpms you get a linear non boosted throttle response.
Above 3000 rpm there is little/nothing to choose between the two throttle settings as regards performance and throttle response....except perhaps that in Efficient the throttle response is more linear and less off/on compared to Sport+.

What you are saying does not make sense. You are essentially saying that Sport+ is a mode designed to make the car un-driveable at low RPM but makes no difference at high RPM, which defeats the purpose of the Sport+ setting.

You are entitled to your opinion, but it makes no sense to me.

[SenorFunkyPants]

Well you have Efficient mode which gives the best mpg for the official fuel economy test figures and best drivability.
And you have Sport+ which gives best low rpm throttle response and a flat torque curve from 1850 rpm.
With Sport as a sort of half way setting.
But in all cases once on full boost the torque/power ought to be the same.

[CanAutM3]

Originally Posted by SenorFunkyPants

Well you have Efficient mode which gives the best mpg for the official fuel economy test figures and best drivability.
And you have Sport+ which gives best low rpm throttle response and a flat torque curve from 1850 rpm.
With Sport as a sort of half way setting.
But in all cases once on full boost the torque/power ought to be the same.

Following our discussion, I was curious, so I did an experiment driving to work this morning. Accelerating from 4000 RPM in 3rd gear at 70~80% throttle for moderate acceleration and then abruptly flooring the throttle.

In Sport+, the added power came almost instantly when I floored the throttle.

In Efficient, the added power came on very gradually, taking a good second before full power was achieved, in the same way as if I would have slowly rolled onto the throttle.

I did a few runs in each setting with always the same result. It is clear to me that Efficient mode is not linear and has considerable damping in the higher RPM range. Try it, you’ll see for yourself .