OT - 4x4 automatic car.

[The Natural Philosopher]

that's a rev limiter surely?

Lossa cars have THAT.

But the last mechanical injection diesel I worked on didn't (old tractor) have that at all,.

[John Rumm]

Don't know if you saw the episode of Fifth Gear where they sent Tiff out to some small remote Sweedish village where they have extensive frozen lakes and auto testing facilities. All the big manufacturers collect there every winter to do R&D in harsh conditions.

They did a few demos that were quite interesting on stability control and modern traction control systems. There is excerpt here:

rover also developed things like decent control, which lets you get down steep hills safely. Again it does it using techniques not available to a driver like individual breaking control on the wheels, variation of the torque splits on active diffs, along with closed loop throttle control. BMW pinched it for some of their SUVs when they owned Rover (although they don't have the low range capability to get back up the hill after!)

[The Natural Philosopher]

when there is 6" of snow, the road and the fields are pretty similar.

To he point where I have driven of the one and onto the other without realising it.

I.e. to me snow is off road conditions, whether there is tarmac underneath or not.

The lovely thing about a real off roader is it just doesn't care. Faced with a huge tailback of people blocking a roundabout queuing up to get petrol, I shamefully admit I drove straight over it to the exit road I wanted. On the basis that no police car had the same capabilities.

[John Rumm]

The studded rally ice tyres really are astoundingly narrow - almost like a motorbike tyre. I think even on ice they still lose a few studs in the course of a stage though.

[Edgar Iredale]

The LR speed limit governor looks pretty much like the rev governor with the quadrant control lever bits removed so I suppose it would be natural for them to call it a governor.

I've thought of a speed limiter as something that cuts off the ignition rather than throttles down the fuel. But now I'll accept the words can be interchangeable in some circumstances. I don't know what is technically correct in this context. I suppose elsewhere I'd agree with you that governor meant it maintained a preset speed while limiter meant it prevented speed beyond a set limit.

I too wondered about the 35 mph setting but I suppose it would be a little disconcerting to have the thing cut out at the speed limit. It was supposed to be set for "approximately 35mph (55kph) in top gear on level ground".

Hasn't this lady started something?

Edgar (going back to sleep)

[Edgar Iredale]

8>>

1948 - 1958

Mines 1957.

Edgar

[damduck-egg]

I had got to the stage of wondering if she was a real person, if she is it's no wonder her OH does nothing,probably whatever he has ever done is wrong so he has been browbeaten into submission. One thing she hasn't specified for a vehicle but should consider is how good a view the wing mirrors have. With the chip on her shoulder turning her head must be awkward.

G.Harman

[Scott M]

Now them's fighting words....

Look, ma, another one. Pass me the shotgun!

I'm not sure what that was all in aid of. I certainly didn't need a precis of different types of tyre, how they work or what conditions one might want to use them in.

My point, which seems to be eluding people here, is "the hype for selling people winter tyres on the principle summer ones are demonstrably worse in ordinary (ie DRY, COLD) wintry conditions is really rather overstated."

I'm not talking in snow, slush, ice, mud, race tracks or anything else, just what constitutes a typical British winter from November to January.

(I'm not even going to bother saying that I managed to get about perfectly well on snow covered rural roads round here on boggo 225/50 16 summer rear tyres on a RWD car in Jan/Feb.)

[ARWadsworth]

As it was you that mentioned it in your OP then you are, by your own definition, crass.

[Dave Plowman (News)]

Don't assume everyone is as incompetent as you.

Seems to me those who don't 'approve' of left foot brake on an auto either don't drive an auto or haven't learned to control their actions.

>

[Roger Chapman]

So there is at least the possibility that the 35 mph limiter was intended to stop too great a breach of the 30 limit rather than to prevent the 40 limit being attained.

Yes indeed.

ZZZZZZZZZZZ. I don't usually post very much these days either. However arguments about driving can usually get me going.

[Roger Chapman]

1948 - 1958.

[Scott M]

My problem is trying to square:

With:

That's a pretty definite case you're trying to make for it being mandatory.

Maybe it was the cars I had but I never found a slope steep enough to cause that to happen (BMW 325, 3.0 S-Type.) They always started off in first tho rather than 2nd as some modern ones do which would make a difference.

Fair enough but on the open road, even when hammering away, I never really saw the need. Similar to heel-and-toe in a manual. I rev-match my down changes in a manual but am more than happy to not overlap them with braking in that way. If I really need that continuous level of braking where my right foot couldn't be spared for a second then I really shouldn't be on the road (and I do drive enthusiastically[1], rather than just being a potter to the shops type.)

That's one of the few times I did do it just to try it out. Tho I never held the revs as high as the stall speed would have allowed!

[1] I wish I could come up with a better phrase. Kev says this and everyone mentally nods and goes "yeah, right"!

[Chris Bartram]

[snip]

DSG works rather well. It will still unexpectedly drop 2 gears if you're clumsy with the throttle in D, but in tiptronic mode it won't go up or down until you reach the limit in either direction.

[Dave Plowman (News)]

Same as Steptronic on my ZF torque converter auto. You can use kickdown to select a lower gear, though.

I'd actually prefer it to stay in the gear I've selected regardless. Don't see why it has to change up when you hit the red line. A manual doesn't. But more to the point it would allow 3rd or 4th gear starts from rest - ideal in very slippery conditions. My last car - with the same box but no Steptronic - did allow you to lock it in gear regardless.

[The Natural Philosopher]

I wansn't aware anyone did THAT.

we have snow almost every year, sufficient to cause 'Traffic chaos' or in hour case a nice emptyroad covered in snow until we get near a town..

Yep I used to get around nicely on my Sptfires in snow.

Not in the jagwar tho. Couldn't even handle wet grass.

[The Natural Philosopher]

No it isn't.

Sebastian Vettel is more capable than me, it is not mandatory that I drive like he does. Or learn how to take a 4g corner on the ragged edge with every bump requiring minute corrections to avoid a 'moment'

Mmm. on 5 speed, first tends to be 'moitain slope only' stuff.

Well that's down to driving style. One is taught to brake, change down, then turn in, then accelerate. Some people prefer to brake change gear early and then turn in to unsettle the rear a little and once its all balanced, boot it. It's almost an axiom that the fastest way is to either as hard on the brakes as you can or hard on the throttle. With not much gap for gear changes n between..

Stall speed? it aint an aircraft.

about half throttle or less seems right to me.

It just removes the torque convertor lag.

[Chris Bartram]

On 28/11/10 18:36, Roger Chapman wrote: feel you need it.

[snip] IME, by the time you're that high up the revs, you'd be better in the next gear anyway, as the torque just drops off. The one exception I've any experience of is an Audi S4, which just kept on pulling from tickover to 8K rpm...

[Chris Bartram]

Hmm....yes, but I have to say, if you're pressing on to the point of the upshift unbalancing the car, you really should be in 'manual' mode and not letting the box decide. Mind you, how bad this behaviour is varies wildly. The worst I've experienced? MKIV Escort with a 3-speed.

[The Natural Philosopher]

peak bhp is always at peak RPM. peak torque may or may not be. In a cooking class engine its certainly not, but the nearer to a race engine it is, the more the torque stays there up he rev band.

The only reason for torque to drop off with RPM is breathing ability. With a turbo or supercharger and VVT, that can be made to be a non issue.

Otherwise torque should be more or less constant from quite low down to engine disintegration RPM.