S mode on twisty roads

[johnatg]

This is a follow up to a brief comment I made recently about S mode being useful on winding roads. The problem is that the box doesn't know what's coming, so it holds 6 as you slow say from 60 to 40, then realises a couple of downchanges are needed as you accelerate away after the bend. This gets somewhat tiresome on a twisty road.

It's long, so if you can't be bothered reading, skip to the end for a brief summary!

OK - yesterday we drove way up north to our holiday haunt in the highlands. The route includes a section on the A93 from Blairgowrie to Braemar (about 38 miles) - it's one of my favourite roads as it is a nearly continuous series of bends with a very few straight sections. I thought I would run a little experiment - as we left Blairgowrie I selected S mode and held 4. The road has a 60 limit except for a short 30 section through Bridge of Cally. We encountered just one other vehicle travelling north - a motorhome, fortunstely on a rare straight section so easily disposed of. The box held 4 through almost all the bends - speed on this raod is limited more by passengers' stomachs than anything else  - not only does it have lots of substantial G corners, it also has a lot of gut-wrenching ups and downs, often coinciding with a corner - the full 3D experience!

After the Glenshee ski centre, the road changes character and becomes a glorious series of interlinked fast (er...about 60 mph) open bends so I flipped to 5 for the long but gentle (~1800 ft in 8 miles) descent to Braemar.
 
The result - 1 - yes one - downshift to 3 on one tight right hander in the 30 mile stint before the ski centre and one downshift from 5 to 4  on a tighter than average (on that section) bend after.

4 is good for a wide range of speed from 40 ish to over 100mph. 5 is better if the bends are OK for 50 - 60 mph. And progress is so smooth (except for the G forces!). We averaged ~51 mph over the section of our route (which is about 350 miles altogether).

Summary - A93, 38 miles in 45 minutes, over 100 bends, one easy overtake, 2 gearchanges (4 if you count the subsequent upshifts), one not-quite-sick wife!

Driving can still be fun - it's just that most of us have to go a long way to find the right roads! And S mode is brilliant in the circumstances - smooth pick up out of the bends.

 

 

 

 

[NemesisUK]

Drive a hybrid, always in the right gear at the right time 

[Linas.P]

5 hours ago, NemesisUK said:

Drive a hybrid, always in the right gear at the right time 

And only provides differentiation of annoying rattle-whinge on twisty roads, never-mind it never has right power regardless of the ratio... no thank you. As lovely as it is... RC interior, driving position and road holding... doesn't cover for god awful rattle can 300h engine is...  

@johnatg S-mode literally only changes throttle response and keeps gears for longer before changing. As you mentioned - it doesn't decrease shifting times (especially on downshifts), so kind of makes no sense on twisty roads. However, I got used to paddle-shifters now and using them quite a lot - it requires little bit of planning ahead (of ~0.5s), but it does provide some engine breaking into the corners and allows to be in "right" gear out of the corners nearly as good as manual.

[johnatg]

That's Power mode. I was talking S mode which locks the gear range to eg 1-4.
The point of my experiment was to see if by using the range 1-4 only on a road
with lots of bends but where you can keep to a fairly tight speed range eg 45-60 you can avoid gear changes altogether and still make decent and smooth progress . The answer was largely yes.

It's because you avoid the bogging down effect you get in D when exiting a corner which you've entered in 6.

I didn't use the paddles at all - they are mainly useful for overtaking on busy roads.

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[Linas.P]

ok sorry, misunderstood that - so are you just basically pull the gear leaver into S-mode which limits range to 4th gear (or 5th) by default. I think that is very limited use of S-mode, not criticising - just saying there is much more in it.

Quote

S-mode literally only changes throttle response and keeps gears for longer before changing

Just to correct myself, S-mode - doesn't change anything at all in terms of throttle response, nor gear changes. It is literally just "range limiter". There is one condition - you cannot select too low range to "shift-lock" or over-rev, apart from that you have full range of 1-6 to select. 1 and 2 gears are fully manual in pre-2010 models (generally pre-facelift), meaning it won't up-shift in those gears and you will hit rev-limiter, on other gears it will "blip rev-limiter" and then up-shift to prevent damage (overrides the range limiter). Regardless of the limit you selected it would downshift to select what it deems more suitable gear i.e. you stop at traffic lights - put it in S and it says 4th, but it will start from 1st from the lights. However, if you limit it to 4th on twisty roads it literally makes no difference, apart from it not shifting to 5th or 6th.

I use this limiter to mimic sequential all the time. If you get off the motorway into the slip road @~70 it will actually default to 5th. Because IS250 has relatively long gear ranges and engine breaking is somewhat limited due to torque converter, I don't think 4th is very useful on British twistiest (i.e. rather tight ones). I would only use 4th for 60MPH+, 3rd for 40MPH+ and most of the other time 2nd.

So imagine standard A-road bend, you doing presumably 60MPH but you want to have 40MPH into the bend and be in 3rd out of the bend. What I would do - I would put-it into S, then flip paddles twice into second (~2s before I actually need to brake for the bend), by the time it shifts into 2nd it already ideal time for some engine breaking (it is not phenomenal, but does work), by mid corner I would be ~40MPH, flip 1 one up to 3rd (by the time I shifts you already on the exit) and your right on the power for exit ~40MPH in 3rd. On the tighter turns/slower speeds I would probably leave it in second, but as mentioned - if you forgot to up-shift from 2nd you will hit limiter hard. 

On face-lifted models you can actually use paddle shifters straight from D, however it is kind of lottery - sometimes it decides to go back to D in mid corner and it does up-shift in any gear regardless of what you have selected.

[Fishboy]

I've done that route on two wheels a number of times, a fantastic road challenging for both drivers and riders, just watch out for the deer!

[johnatg]

Indeed - I came across a large herd of them on the road one foggy night around midnight about 20 years ago on the descent towards Braemar - unnerving!

I once hit a deer about 40 years ago on the Lang Whang - it wasn't pretty, either for the deer nor the car.

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