Another question about cruise control

[Zathras]

On Mon, 25 Jun 2012 12:27:59 +0100, David <me@home.org> wrote:

>On the six cylinder BMW diesels of the era of yours, you have cruise
>control with brake function.

Indeed.

>Going down a steep hill with cruise enabled, the car will 'brake' itself
>if the speed increases an amount above the set point. How much above the
>set point the speed has reaches before the car brakes, I'm not sure as I
>cannot see the brake lights come on from the driver's seat....

Same here. It feels as though it brakes quite a lot for me though.
When the economy meter end-stops and there is more braking effect
after that point makes me think it's actually braking. I believe the
car has quite a tight control of over-speed but I've never really
tested it personally.

--
Z

[Zathras]

On Mon, 25 Jun 2012 19:14:50 +0100, "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:

>In article
><1558397481362317685.703409%steve%-malloc.co.uk@news.eternal-september.org>,
> Steve Firth <%steve%@malloc.co.uk> wrote:
>> > Ooops. I'd forgotten about that. Spoilt by the torque in my 3 litre
>> > diesel BMW, it's not something I've ever had to do.
>
>> That's more, I suspect, to do with where you drive than the torque of
>> the 3.0 diseasel. I've driven cars with more torque than yours around
>> the UK. There are motorway sections where the box will drop a gear to
>> maintain the set speed.
>
>Indeed. If it can climb any hill in top gear, it's under geared.

I know what you're saying but, I'm not sure I'd want to run much lower
rpm at high speed in a car. It's already under 2000 rpm at legal
speeds. The problem would be that the manufacturer would have to add
strength (weight) to the moving parts of the engine. This would impact
other areas of its performance.

Also, I fully agree with you in the case where an economy gear is
fitted to a car which allows it to cruise below its peak torque rpm,
but to do this in my car means going below 1300 rpm. I think this is
too low in a car diesel. Fine in a lorry.

--
Z

[Zathras]

On Tue, 26 Jun 2012 20:39:22 +0100, Tim <timdownie2003...........uk>
wrote:

>On a manual though, for the CC to stay engaged when changing down and
>slowing (for a roundabout say) makes no sense.

Yet in stating the above you haven't considered that your own driving
technique may need polish and that the car is fine?

Changing down to promote slowing down is a seriously out of date
technique practiced by many that don't know about modern driving in a
modern road car. In the case of a roundabout, changing down (if
required) should take place *after* the correct speed for the
roundabout has been reached.

Because I drive my car properly (as a direct result of recent
training), CC does not stay engaged if I'm slowing down for a
roundabout (even though it isn't automatically disengaged by the
clutch pedal).

--
Z

[Zathras]

On Thu, 28 Jun 2012 18:36:42 +0100, David <me@home.org> wrote:

>You may have seen it listed from 1,300 rpm, but this is incomplete
>information.

It's all you get from BMW in their specifications for the car. I'm
guessing they have some idea what comes off their production lines and
aren't just lying?

>On this engine (http://www.superchips.co.uk/curves/325d197ps.pdf) which
>is the same spec as yours, the actual peak is around 3.000 rpm.

While that may be true, the car tested is likely to have been one
supplied for performance enhancement - i.e. the owner wasn't happy
with what he had for some reason.

--
Z

[Zathras]

On Thu, 28 Jun 2012 17:46:20 +0000 (UTC), Tim
<timdownie2003...........uk> wrote:

>>> On a manual though, for the CC to stay engaged when changing down and
>>> slowing (for a roundabout say) makes no sense.


>I know it's not the "modern" way but frankly, I don't give a f*ck.

Perhaps this is why driving a modern car like it's an old fashioned
car "makes no sense" to you then?

I too am a mature driver and was brought up in the old ways when most
cars were a bit rubbish. Embarrassingly, it was a retired gent who
told me my driving technique was out of date and would benefit from
improvement. That shocked me into re-learning to drive properly. The
knock-on is that my driving technique now makes complete sense where
it didn't before.

--
Z

[Zathras]

On Fri, 29 Jun 2012 10:08:55 +0100, David <me@home.org> wrote:

>On 28/06/2012 22:27, Zathras wrote:
>> On Thu, 28 Jun 2012 18:36:42 +0100, David <me@home.org> wrote:
>>
>>> You may have seen it listed from 1,300 rpm, but this is incomplete
>>> information.
>>
>> It's all you get from BMW in their specifications for the car. I'm
>> guessing they have some idea what comes off their production lines and
>> aren't just lying?
>>
>
>If you dig deep enough in the archives, you find a bit more.
>
>Here is a list of M57 engines and their outputs:
>
>Engine code; Power; Torque@rpm; Year
>
>M57D25; 163 PS (120 kW; 161 hp)@4000; 350 N·m (260 lb·ft)@2000-2500; 2000
>
>M57TUD25; 177 PS (130 kW; 175 hp)@4000; 400 N·m (300 lb·ft)@2000-2750; 2004
>
>M57D30; 184 PS (135 kW; 181 hp)@4000; 390 N·m (290 lb·ft)@1750-3200; 1998
>
> 184 PS (135 kW; 181 hp)@4000; 410 N·m (300
>lb·ft)@2000-3000; 1998
>
> 193 PS (142 kW; 190 hp)@4000; 410 N·m (300
>lb·ft)@1750-3000; 2000
>
>M57TUD30; 204 PS (150 kW; 201 hp)@4000; 410 N·m (300 lb·ft)@1500-3250;
>2003
>
>^ I believe this one is from your car^
>
> 218 PS (160 kW; 215 hp)@4000; 500 N·m (370
>lb·ft)@2000-2750; 2002
>
> 245 PS (180 kW; 242 hp)@4000; 500 N·m (370
>lb·ft)@2000-2250; 2008
>
> 272 PS (200 kW; 268 hp)@4000; 560 N·m (410
>lb·ft)@2000-2250; 2004
>
>M57TU2D30; 231 PS (170 kW; 228 hp)@4000; 500 N·m (370 lb·ft)@2000-2750;
>2005
>
> 286 PS (210 kW; 282 hp)@4400; 580 N·m (428
>lb·ft)@2000-2250 ; 2004
>

I don't think my 197PS engine is in that list. However, it is likely
just to be a mapping difference away from one of the ones above.

>As you can see, these engines that have the same origins as yours, all
>have a range of rpm where the peak torque will occur.

Agreed.

> It does mean not
>that the peak is from X rpm to Y rpm.

I never claimed differently. I just repeated what the BMW spec was as
a reason for the lack of a need to change down out of top on the
motorway to maintain speed.

>
> >> On this engine (http://www.superchips.co.uk/curves/325d197ps.pdf) which
> >> is the same spec as yours, the actual peak is around 3.000 rpm.
> >
> > While that may be true, the car tested is likely to have been one
> > supplied for performance enhancement - i.e. the owner wasn't happy
> > with what he had for some reason.
> >
>
>Some people always want more than they already have.
>
>The other chart from Hartge.de helps to demonstrate that similar
>engines do not perform exactly the same as eachother. That engine had a
>peak torque at just over 2,000 rpm, hence that the peak torque will
>occur somewhere in the range of rpm quoted.

I used to have an Alfa..I know all about factory output tolerances on
a grand scale! ;-)

--
Z