Modern gearing + BGOL
Discussion
Hi all,
I've only really been reading the Advanced Driving forum for the last few days, dragged over here by the front-page promo for Reg's e-book, which I very much enjoyed (especially the willingness to be so un-stuffy and flexible with the "rules").
I've had a good lurk and a good sift through the history, and was delighted to see all the usual arguments, I mean topics, well covered.
Here's something I've been wondering recently. It's not a new problem, but seems to be more pronounced on modern cars.
We're tanking along a DC merrily at 70mph+ in 6th in our tall-ratio TDi. We approach a busy roundabout, and we're planning to stop.
How do you all deal with the fact that, without interim downshifts, you simply cannot pull up and dip the clutch at the last minute in 6th? 6th is soooo tall, that the clutch needs dipped very early, or we're relying purely on momentum to stop it stalling.
If we come down the box on approach, we get marked down for BGOL, and having 2 braking maneuvers instead of one. If we don't come down the box, we're not in the correct gear for the engine speed, and have to dip the clutch veeeeeery early. I know that's not a bad thing as such, as you're still under control on the brakes, but it "feels" horrible to be clutch-in for so long.
So, does anyone else with a tall 6-speed TDi recognise this problem, and how do you approach it.
Cheers!
I've only really been reading the Advanced Driving forum for the last few days, dragged over here by the front-page promo for Reg's e-book, which I very much enjoyed (especially the willingness to be so un-stuffy and flexible with the "rules").
I've had a good lurk and a good sift through the history, and was delighted to see all the usual arguments, I mean topics, well covered.
Here's something I've been wondering recently. It's not a new problem, but seems to be more pronounced on modern cars.
We're tanking along a DC merrily at 70mph+ in 6th in our tall-ratio TDi. We approach a busy roundabout, and we're planning to stop.
How do you all deal with the fact that, without interim downshifts, you simply cannot pull up and dip the clutch at the last minute in 6th? 6th is soooo tall, that the clutch needs dipped very early, or we're relying purely on momentum to stop it stalling.
If we come down the box on approach, we get marked down for BGOL, and having 2 braking maneuvers instead of one. If we don't come down the box, we're not in the correct gear for the engine speed, and have to dip the clutch veeeeeery early. I know that's not a bad thing as such, as you're still under control on the brakes, but it "feels" horrible to be clutch-in for so long.
So, does anyone else with a tall 6-speed TDi recognise this problem, and how do you approach it.
Cheers!
So we're all agreed, there's no better practice taught in the books than dipping the clutch. It's definitely the advice of the advanced crowd. We don't like more than one braking move, and we don't like BGOL (except in exceptional circumstances).
Well, here's where I stick my neck out...
In my opinion, it sucks. I don't want to do 150 yards with the clutch in.
We all know that in an emergency stop you don't dip the clutch until the last possible second to stop a stall. And yet, here we are happy to do 150 yards approaching a roundabout with the clutch dipped?
I like an interim shift to 3rd around the 200 yard board, usually just in between 2 separate braking actions (very rarely H&T on the road... I don't usually feel like driving with such gusto in a TDi estate).
I'm not doing it for engine braking, I'm doing it because I think 6th gear is a stupid gear to be in at that point, and I think having the clutch dipped is a compromise in an emergency stop situation.
I'd love to know what distance from the give way line others find they have to dip the clutch (in top gear), and at what speed. If anyone happens to notice on their commute, do please chip in.
Well, here's where I stick my neck out...
In my opinion, it sucks. I don't want to do 150 yards with the clutch in.
We all know that in an emergency stop you don't dip the clutch until the last possible second to stop a stall. And yet, here we are happy to do 150 yards approaching a roundabout with the clutch dipped?
I like an interim shift to 3rd around the 200 yard board, usually just in between 2 separate braking actions (very rarely H&T on the road... I don't usually feel like driving with such gusto in a TDi estate).
I'm not doing it for engine braking, I'm doing it because I think 6th gear is a stupid gear to be in at that point, and I think having the clutch dipped is a compromise in an emergency stop situation.
I'd love to know what distance from the give way line others find they have to dip the clutch (in top gear), and at what speed. If anyone happens to notice on their commute, do please chip in.
I think we're agreeing the same points. I just wonder if anyone else feels that the point at which the engine starts to struggle has changed since the rules were made, due to the mapping of modern TDis, and the stupidly long 6th gear for economy. It's all driven by manufacturer MPG Top Trumps and emissions, but the effect is that I think one rule is now a bit out of date.
Thanks for the input.
Thanks for the input.
Rog,
I have no agenda whatsoever. I happen to think that this rule is out of date with some modern cars, and wondered if there's a good way to adapt it. I'm not demanding anyone agrees with me. If they don't, or don't want to, or their car doesn't have this problem, then that's fine. I don't even have a better suggestion of what to do. I know the downsides of an interim gear change. I'm simply saying that the system for this scenario was created in a time when cars behaved differently, and for years I've had no problem with it. Then I bought a TDi with a tall 6th gear and for the first time it feels like the system is wrong for this car. in this scenario.
I'd have thought this was exactly the kind of fiddly off-message discussion that would get the community brains going.
Don't get me wrong, I know the system off by heart. I understand the concepts perfectly (regardless of my flawed human ability to execute them).
I don't believe for one minute that we shouldn't look critically at the system. It has to be revised and kept up to date. I left one advanced forum because they simply refused to entertain any discussion that their precious system was in any way flawed. That's why it's so refreshing to hear Reg talk about the practical differences between a test and the real world.
No agenda, total understanding of all sides of the problem, I just wanted to see if anyone else thought, "Oh yeah, my car does that too!"
EDIT: Sorry, didn't answer your question.
I feel dipping the clutch completely (to the floor) is less controlled. I feel dipping it just enough to stop a stall is slipping, and not mechanically sympathetic. I'm not saying either are right, wrong or otherwise. Just that all the possible solutions to the problem seem to have an element of compromise.
I have no agenda whatsoever. I happen to think that this rule is out of date with some modern cars, and wondered if there's a good way to adapt it. I'm not demanding anyone agrees with me. If they don't, or don't want to, or their car doesn't have this problem, then that's fine. I don't even have a better suggestion of what to do. I know the downsides of an interim gear change. I'm simply saying that the system for this scenario was created in a time when cars behaved differently, and for years I've had no problem with it. Then I bought a TDi with a tall 6th gear and for the first time it feels like the system is wrong for this car. in this scenario.
I'd have thought this was exactly the kind of fiddly off-message discussion that would get the community brains going.
Don't get me wrong, I know the system off by heart. I understand the concepts perfectly (regardless of my flawed human ability to execute them).
I don't believe for one minute that we shouldn't look critically at the system. It has to be revised and kept up to date. I left one advanced forum because they simply refused to entertain any discussion that their precious system was in any way flawed. That's why it's so refreshing to hear Reg talk about the practical differences between a test and the real world.
No agenda, total understanding of all sides of the problem, I just wanted to see if anyone else thought, "Oh yeah, my car does that too!"
EDIT: Sorry, didn't answer your question.
I feel dipping the clutch completely (to the floor) is less controlled. I feel dipping it just enough to stop a stall is slipping, and not mechanically sympathetic. I'm not saying either are right, wrong or otherwise. Just that all the possible solutions to the problem seem to have an element of compromise.
Edited by TartanPaint on Friday 14th August 09:43
R_U_LOCAL said:
We are planning to stop at the roundabout, but we're also looking to go, which is a key concept when applying the system in the circumstances you describe. So, from the beginning, lets see how we apply system to this roundabout on a dual-carriageway that we're approaching at speed in top gear. Lets go through the five phases of the system in order...
etc...
A reply from Mr Local himself. Most honour'd, I am. *doffs cap*.etc...
Thanks for the consideration given to your response too. It's exactly as expected, and a great write up of the techniques. There's a way to pass the test, and a real-world to adapt to afterwards.
I did of course deliberately leave out the "...but looking to go" in this hypothetical situation. I'm really interested in the cases where you do actually get all the way down to 0mph in 6th gear, as that's the most extreme case for this problem.
Oh, Reg, on the "swerve and return" bit in your book, your theory that it's a subconscious physical reaction to the driver's thoughts and intentions... I guess that's possible. My theory has always been that it's the same cause and effect as hazard fixation. You go where you look. I think they're simply checking their offside mirror, which causes them to steer towards the offside, and the return is them looking forwards again and correcting their course. Maybe not, maybe a bit of both. Anyway, thought I'd share.
Edited by TartanPaint on Friday 14th August 09:42
Edited by TartanPaint on Friday 14th August 09:46
Quite true about autos. Good point.
So, to increase my oily-bits understanding a little...
If you dip the clutch just a little, the friction plates will slip together until the just enough load is removed from the engine to stop the stall. The load I'm referring to is the momentum which is overrunning the engine. As revs drop, the wheel speed passed through the gearbox in a high gear results in the crank being dragged down to an RPM lower than the engine can comfortably idle at. The ECU map will probably compensate for a 100rpm or so drop below idle with more fueling and some advanced ignition, until it can't drag the revs up any longer, and then you get judder.
As you say, the clutch is our tool to remove the force of momentum from the engine and reduce the strain on it.
Now, I'm interested in the purpose of just slipping the clutch enough to remove just enough of that force to avoid a stall. Are you saying you don't completely disconnect the engine from the gearbox? I would have thought that removing just enough load to keep the engine from stalling would transfer strain (if we think of the difference in the opposing forces between engine and wheel speed as a strain) to the clutch plates. Which I would say based on no evidence at all was a bad thing. If you dip the clutch completely, the drive train is split and the two sides can run at whatever speed they like with no strain.
If you don't feel any judder, that would suggest your left pedal position is beyond the bitey point and the plates are completely disconnected. So really there's no difference between "just enough" and "all the way to the floor". Or is there?
Ta in advance.
So, to increase my oily-bits understanding a little...
If you dip the clutch just a little, the friction plates will slip together until the just enough load is removed from the engine to stop the stall. The load I'm referring to is the momentum which is overrunning the engine. As revs drop, the wheel speed passed through the gearbox in a high gear results in the crank being dragged down to an RPM lower than the engine can comfortably idle at. The ECU map will probably compensate for a 100rpm or so drop below idle with more fueling and some advanced ignition, until it can't drag the revs up any longer, and then you get judder.
As you say, the clutch is our tool to remove the force of momentum from the engine and reduce the strain on it.
Now, I'm interested in the purpose of just slipping the clutch enough to remove just enough of that force to avoid a stall. Are you saying you don't completely disconnect the engine from the gearbox? I would have thought that removing just enough load to keep the engine from stalling would transfer strain (if we think of the difference in the opposing forces between engine and wheel speed as a strain) to the clutch plates. Which I would say based on no evidence at all was a bad thing. If you dip the clutch completely, the drive train is split and the two sides can run at whatever speed they like with no strain.
If you don't feel any judder, that would suggest your left pedal position is beyond the bitey point and the plates are completely disconnected. So really there's no difference between "just enough" and "all the way to the floor". Or is there?
Ta in advance.
Edited by TartanPaint on Friday 14th August 11:53
Good discussion.
I want to throw something else into the mix as an idea.
Hypothesis: On modern manual boxes, 6th gears which are ludicrously tall have been brought about by MPG and CO2 targets, and should be seen as economy cruising gears only.
How about the concept of something like this (as an improvement or modernisation of our own planning without any alteration to the system):
6th gear on some vehicles is an economy gear which compromises control of the vehicle in exchange for reduced fuel consumption, when it is safe to do so. It should not be used when a significant reduction in speed can be anticipated.
With that in mind, the very first step of our roundabout plan could be as far away as, "I can see a cluster of streetlights in the far distance indicating a roundabout on this route, which will require me to reduce speed significantly, so I'm going to stop using my economy gear at this time, and select 5th". Assuming, 5th can get you a lot closer to your "stop/go" point with a more acceptable amount of coasting, the problem is solved long before we have even started our final IPSGA for the hazard itself.
All we've done is pick a gear which is more appropriate for the information we have.
Any takers?
I want to throw something else into the mix as an idea.
Hypothesis: On modern manual boxes, 6th gears which are ludicrously tall have been brought about by MPG and CO2 targets, and should be seen as economy cruising gears only.
How about the concept of something like this (as an improvement or modernisation of our own planning without any alteration to the system):
6th gear on some vehicles is an economy gear which compromises control of the vehicle in exchange for reduced fuel consumption, when it is safe to do so. It should not be used when a significant reduction in speed can be anticipated.
With that in mind, the very first step of our roundabout plan could be as far away as, "I can see a cluster of streetlights in the far distance indicating a roundabout on this route, which will require me to reduce speed significantly, so I'm going to stop using my economy gear at this time, and select 5th". Assuming, 5th can get you a lot closer to your "stop/go" point with a more acceptable amount of coasting, the problem is solved long before we have even started our final IPSGA for the hazard itself.
All we've done is pick a gear which is more appropriate for the information we have.
Any takers?
R_U_LOCAL said:
I wouldn't take that option if my speed was into three figures, but at more moderate speeds it's definitely an option for those who don't like staying in a high top gear whilst braking.
Good point. I've been testing this for a few days, and I really like it so far.I have not however tested it from a starting speed of 3 figures, you'll be pleased to hear.
Back in a tick, off to do some "research". 
Looking forward to the gopro vids! Most of the videos I use for educational purposes are getting on a bit, and feel very dated. I think you'll make some half-decent revenue by being the go-to channel for up-to-date driving demos.
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