Reg's Youtube Channel

Topics relating to Advanced Driving in cars
gannet
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Re: Reg's Youtube Channel

Postby gannet » Sat Nov 21, 2015 6:16 pm

fengpo wrote:Brake gear overlap in the given scenario could be another tool. I would like to add heel and toe to my tool box (more like lack of tools in the box) Audi don't allow it. Brain wave try it in the BMW, I'll watch the late great Senna doing h & t in the NSX first ;)

Interestingly I was driving a car just last weekend that the owner has been unable to get it to H&T...

I managed it with no trouble at all - Skoda Octavia vRS Diesel...

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Mr Cholmondeley-Warner
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Re: Reg's Youtube Channel

Postby Mr Cholmondeley-Warner » Sat Nov 21, 2015 9:45 pm

Brake gear overlap is covered in 5. above. H&T is just a specialised form of it.
Nick

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Mr Cholmondeley-Warner
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Re: Reg's Youtube Channel

Postby Mr Cholmondeley-Warner » Sat Nov 21, 2015 9:46 pm

gannet wrote:Interestingly I was driving a car just last weekend that the owner has been unable to get it to H&T...

I managed it with no trouble at all - Skoda Octavia vRS Diesel...

VAG cars are very picky about the order you touch the pedals in. Some of them will allow H&T as long as you're definitely off the throttle before you touch the brake, then don't come off the brake before you go back to the throttle (if that makes sense?).
Nick

true blue
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Re: Reg's Youtube Channel

Postby true blue » Sat Nov 21, 2015 11:40 pm

Mr Cholmondeley-Warner wrote:
true blue wrote:Before I could H&T, it was put to me that downchanging from 2k revs or so without rev matching would be acceptable.

Hardly sympathetic, though, and wearing on the clutch.


Indeed - which is why I have since learnt to H&T! Living in Cambridgeshire means that hills are a rare thing for me, so it had never really been an issue before. I'm curious though - if that weren't an option for whatever reason (let's say not having that skill), which of your 4 remaining options would you advocate? Would you prefer to sacrifice control of the vehicle for mechanical sympathy?

waremark
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Re: Reg's Youtube Channel

Postby waremark » Sun Nov 22, 2015 12:24 am

For me, partial overlap - brake down to the turn, declutching when required to prevent judder, pre-select 2nd or 1st depending on car before the turn and while still braking, let out clutch with rev matching as soon as no longer downhill.

What disadvantage would that have compared to H & T?

true blue
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Re: Reg's Youtube Channel

Postby true blue » Sun Nov 22, 2015 3:24 am

My points so far have been based on the situation where I had this discussion in the spring - one of the glorious roads in the Teesdale area, on a multi-cornered downhill section in particular. Here the choices were either:

1) Start the descent in 3rd, and stay there until the bottom. Brake as necessary, declutch if speed drops too low.

2) Start the descent in 3rd, braking as required to control speed/balance. When 3rd is no longer viable, declutch, select 2nd and re-engage clutch without using throttle to rev match. Benefit: better control than 1). Drawback: avoidable clutch wear.

3) Start the descent in 3rd, braking as required to control speed/balance. When 3rd is no longer viable, declutch, select 2nd, off brakes, rev match, engage clutch, back on brakes if needed. Benefit: mechanical sympathy. Drawback: less control than 2).


Depending on the steepness of the descent and the distance between corners, either of 2) or 3) may be reasonable choices. At the start of my afternoon I was using option 1, and it was not very satisfactory. Later in the drive I believe I used both 2) and 3). I did find 2) entirely unnatural at first, and still don't much like it, but I think it has its place in occasional circumstances.

To get back on topic, hopefully one of Reg's future offerings will give a more expert view on the matter than I can!

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R_U_LOCAL
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Re: Reg's Youtube Channel

Postby R_U_LOCAL » Sun Nov 22, 2015 11:24 am

true blue wrote:To get back on topic, hopefully one of Reg's future offerings will give a more expert view on the matter than I can!


Hopefully!

Although I'm conscious that my current offerings aren't quite at the level yet to answer some of the detailed questions asked on this site. I'm pitching the early videos at those with no or limited experience of AD as a sort of introduction to the basic principles.

For example, I'll be going out today to film a piece on the system of car control, but it'll be an introduction to system rather than an exploration of the minutae of brake/gear overlap. The problem with going into too much detail is that you get into the realms of opinion and preference, where there is no right or wrong answer, just different answers with similar outcomes.

Lets see how it goes - for now, I'll be happy if my offerings are suitable for those of you with students or associates to use tyem as a teaching aid.
Reg Local - author of "Advanced & Performance Driving" http://tinyurl.com/qbxwocx

true blue
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Re: Reg's Youtube Channel

Postby true blue » Sun Nov 22, 2015 6:21 pm

Video or otherwise Reg, I'm sure we'd all be pleased to hear your opinion...

Black Cat
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Re: Reg's Youtube Channel

Postby Black Cat » Mon Nov 23, 2015 7:53 am

true blue wrote:1) Start the descent in 3rd, and stay there until the bottom. Brake as necessary, declutch if speed drops too low.

2) Start the descent in 3rd, braking as required to control speed/balance. When 3rd is no longer viable, declutch, select 2nd and re-engage clutch without using throttle to rev match. Benefit: better control than 1). Drawback: avoidable clutch wear.

3) Start the descent in 3rd, braking as required to control speed/balance. When 3rd is no longer viable, declutch, select 2nd, off brakes, rev match, engage clutch, back on brakes if needed. Benefit: mechanical sympathy. Drawback: less control than 2).


Excuse a long time lurker interposing some thoughts.

My own experience of heel and toe sounds like Reg's in that most cars I have driven have a brake pedal too high relative to the accelerator to allow me to easily H&T under normal levels of braking for road driving. My feet (size 9) are neither unusually large or small, so am fascinated to hear how people manage to get around this problem.

It seems to me that there are a couple of useful variations on the theme that are not detailed which help if your feet don't want to H&T.

Firstly option 2 can be done more sympathetically, simply by ensuring that while the clutch is depressed you continue to brake. The effectiveness will depend on your speed, but by the sounds of it it would be good in the situation described. So in my ride 3rd would become unviable around 15mph, but then if I were to brake down to around 11-12mph while changing to 2nd you move into a mechanically nicer setting. I would be bringing the clutch up with an engine speed of around 900-1000rpm and a road speed in 2nd equivalent to maybe 1100rpm, so the speed difference across the clutch is negligible. I'm not having to have the clutch down for an unduly long time to lose the extra 3-4mph, so control isn't compromised.

Option 3 is more useful if you are a bit quicker, but want the lower gear for more control rather than because 3rd is running out. You can retain good control simply by slowing to a little below your ideal speed, to give you some time to match revs while the speed begins to rise slightly on the downhill back to your preferred speed.Say I was doing 25mph in 3rd using the brakes to maintain speed, so wanted 2nd for more control: lose a few more mph under braking down to say 20mph, release brake, raise revs (while road speed increases down the hill), release clutch in 2nd. This is one of the few cases where I prefer a blib to a sustained rev change.

I agree with Reg that this is an area where there are always likely to be compromises and tradeoffs. Personal preference and the particular characteristics of the car, as well as the prevailing road conditions are likely to have a strong bearing on the approach taken for me.

true blue
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Re: Reg's Youtube Channel

Postby true blue » Mon Nov 23, 2015 10:18 am

Thanks - useful food for thought next time I find myself in a car that I can't H&T on an interesting downhill road.


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