[SteveC]

Originally Posted by kaishang

You don't necessarily produce more power at higher rpm. You need a certain power to travel down the road at constant speed and if you accelerate you need more power.

Power = torque * rpm * a constant number.

Thus you can have a given power with
(i) high torque and low rpm
(ii) low torque and high rpm

Cars engines don't have a fixed torque/power output for a given rpm. For a given rpm setting, the car can vary the torque (and power) by injecting more or less fuel and using more or less turbo boost. Only at 100% load, is torque/power fully dependent on rpm.

There is a particular problem IMHO with the way BMW transmissions are programmed such that when you are at low rpm (say under 1700rpm) and in D, the transmission will resist downshifts until you have applied a lot of throttle. Then, suddenly it will downshift 1 or 2 gears. The rpm jumps to around 2500, you are in the middle of the engine's powerband with your foot near the floor and the wheels break traction.

For this reason, when I'm approaching a situation at relatively low speed and light or no throttle and know I'll need to accelerate, I use DS. The same thing as has happened to OP has happened to me, but with DS the problem goes away.

Hi Kaishang,
In essence, what you're saying is that a car has a throttle

The point is that a car needs a certain amount of power to maintain a steady speed and has power reserves that vary with RPM.

The engine has far higher power reserves at 3000rpm than it does at 1200, so applying throttle at 3000rpm will apply a lot more power to the wheels than at 1200rpm for the same throttle opening.

Your strategy of changing down to avoid the lack of acceleration then sudden violent kickdown of the AT is understandable and one reason why I drive a 330d rather than the 335d. Thinking back to my test drive, I can imagine that that particular transmission behaviour could be a major problem on a damp, cold road, especially in a remapped car. A gentle downshift and steady application of throttle would indeed be preferable to no accleration followed by a rapid 2 gear kickdown and explosion of power

[grey man]

I'm old enough and was fortunate enough to be driving powerful RWD cars before traction control was available. You learned to use the controls to put down as much power/force as conditions allowed. (as you did with braking before antilock brakes)

I quite recently went on an invited day on high speed/defensive driving in a modern(ish) RWD car with ABS, traction controls etc - and on an airfield we were shown how these aids work - and what can be done with them on - and off.

There is no doubt that for drivers who are either lacking practice with high powered cars, or just not concentrating 100% these aids are very worthwhile. I would not normally turn them off, simply because they provide an excellent safety measure. However it is true that a skilled driver can do better with them turned off, but he/she has to be good, concentrating hard and know the car well.

335d is a superb car, but with the electronics off - its not what anyone would call a 'beginners car'. Things just happen too easily and too quickly for that.

[kaishang]

Originally Posted by SteveC

Hi Kaishang,
In essence, what you're saying is that a car has a throttle

The point is that a car needs a certain amount of power to maintain a steady speed and has power reserves that vary with RPM.

The engine has far higher power reserves at 3000rpm than it does at 1200, so applying throttle at 3000rpm will apply a lot more power to the wheels than at 1200rpm for the same throttle opening.

Your strategy of changing down to avoid the lack of acceleration then sudden violent kickdown of the AT is understandable and one reason why I drive a 330d rather than the 335d. Thinking back to my test drive, I can imagine that that particular transmission behaviour could be a major problem on a damp, cold road, especially in a remapped car. A gentle downshift and steady application of throttle would indeed be preferable to no accleration followed by a rapid 2 gear kickdown and explosion of power

Ha ha, yes BMWs are equipped with a throttle feature

The problem with the kickdown is that before the kickdown you might be in 4th @ 1500rpm and 80% throttle. Suddenly it's kicked down and you are in 2nd at that same 80% throttle. If you forced a downshift before the sudden kickdown either by using a more downshift-happy DS mode or using the paddles, then you would never be anywhere near 80% throttle in the first place.

[doughboy]

Originally Posted by wayne71

Its happened a few times and I'm starting to wonder if maybe the remap is too much for the car (or me), then I see some of you guys with 400+bhp 335i's and wonder how the hell you cope.

A much more delicate right foot is required! Just take it steady and apply throttle gradually, pulling out at 15mph and giving it sudden beans could just be too much for the tyres to cope with.

I probably haven't used more than half throttle for weeks, well maybe once or twice Even then I would apply throttle gradually over a second or two, never suddenly (even in the dry too TBH)

With winter tyres on which are very grippy and let go progressively in cold, wet conditions, the car still spins up in second very easily, and slides all over the place in anything other than a straight line with too much gas.

Winter tyres also give off a very strong burning smell compared to normal rubber when worked a bit!

[zltm089]

Originally Posted by wayne71

I dont understand that, I thought with DTC on and DSC on was pressing nothing (ie no driver aids switched off), DTC off was pressing once and DSC off was keeping it pressed.

Yes, thats my understanding Pete....

DTC off .....1 press of the button....

DSC off .....press and hold.... (on your own mode)

[zltm089]

Originally Posted by HighlandPete

What do you mean by those statements? "DTC off" is either touching nothing, (default) or holding for several seconds and having no DSC protection either.

"DTC on" is pressing the button quickly and showing the DTC image. Is that what you mean, because I don't quite follow the consequences?

HighlandPete

Sorry bit of confusion on the ON/ OFF ....

I think " DTC OFF" is pressing the button quickly and showing the DTC image.....Just because it says DTC on the dashboard doesn't mean that its "on" ....it simply warns you that DTC is actually OFF! ;-)

[HighlandPete]

Originally Posted by zltm089

Sorry bit of confusion on the ON/ OFF ....

I think " DTC OFF" is pressing the button quickly and showing the DTC image.....Just because it says DTC on the dashboard doesn't mean that its "on" ....it simply warns you that DTC is actually OFF! ;-)

I've read so many confused descriptions about DTC on here, totally wrong assumptions on how DSC and DTC are configured.

Default is DSC on, and DTC off.

YOU ACTIVATE DTC by switching it ON press switch once, for using in snow, slush, loose surfaces, etc., (when you want more traction, but at a certain cost in terms of stability). To deactivate, you press again, indicator light goes out and you are back on full DSC.

No wonder some of us have different results when using DTC, we are not all using it as intended.

For normal day to day driving we need to do nothing. It's not really intended we run with DTC activated all the time, by pushing the DTC button.

HighlandPete

[zltm089]

Pete, even for normal day to day driving, I think DTC should be activated (1 press of the button, on or off whatever we want to call it....) ....due to the shit RFT and lack of LSD, I find the car to be better with DTC activated...and plus you save on you brake pads aswell!!!....

[HighlandPete]

In the context of this very thread I do wonder, as it is only beneficial if we are pushing more to the limits.

Perhaps I'm from the old school and drive with greater safety margins. I could have my DSC flashing like crazy, but I don't see that as good driving, in fact I'd be down my self for being pretty amateurish. I'm not a hestitant or slow driver, but to me the safety aids are just that, additional stuff, if I'm impinging on them in normal road driving, I'm the one needing some skills.

BTW, I'm on original rear pads at 45k miles and still indicates about 20k to go.

HighlandPete

[Dave_3]

Originally Posted by HighlandPete

Perhaps I'm from the old school and drive with greater safety margins. I could have my DSC flashing like crazy, but I don't see that as good driving, in fact I'd be down my self for being pretty amateurish. I'm not a hestitant or slow driver, but to me the safety aids are just that, additional stuff, if I'm impinging on them in normal road driving, I'm the one needing some skills.

HighlandPete

I think exactly the same.

D.

[grey man]

Originally Posted by Dave_3

I think exactly the same.

D.

Another in full agreement

[doughboy]

Originally Posted by HighlandPete

In the context of this very thread I do wonder, as it is only beneficial if we are pushing more to the limits.

Perhaps I'm from the old school and drive with greater safety margins. I could have my DSC flashing like crazy, but I don't see that as good driving, in fact I'd be down my self for being pretty amateurish. I'm not a hestitant or slow driver, but to me the safety aids are just that, additional stuff, if I'm impinging on them in normal road driving, I'm the one needing some skills.

BTW, I'm on original rear pads at 45k miles and still indicates about 20k to go.

HighlandPete

Remember that the esp is intervening way, way, way before the little yellow light flashes.

You think you are driving 'well' and smoothly, but the car is already cutting power, dulling throttle response and applying brakes on your behalf but you don't know it.

The only way you know is by turning esp off and feeling how that car comes alive all of a sudden, no flashing lights before or after, just a more 'real' car.

If you are old school, like me, then put DTC on, it's the 'real deal', not the fluffy cushioned safety world of start up.

[MEGA]

Originally Posted by wayne71

No driver aids had been switched off and I'm driving on Michelin pilot sport RFT

This.

Get some decent tyres and it will be fine.

[ALF_E90]

Originally Posted by doughboy

Remember that the esp is intervening way, way, way before the little yellow light flashes.

You think you are driving 'well' and smoothly, but the car is already cutting power, dulling throttle response and applying brakes on your behalf but you don't know it.

The only way you know is by turning esp off and feeling how that car comes alive all of a sudden, no flashing lights before or after, just a more 'real' car.

If you are old school, like me, then put DTC on, it's the 'real deal', not the fluffy cushioned safety world of start up.

I have come to the same conclusion - especially with winter tyres on the standard ESP is too keen to cut in and I like to go for the DCT mode all the time when driving at all keenly. The result is better, smoother progress.