Engine Braking
Discussion
Just a question on the liabilities involved.
My car is RWD. When I approach roundabouts and such like, if I have no immediate need to brake, i.e. the roundabout being clear, I will approach in the normal manner. On my apporach, instead of braking to slow the car down, I dip the clutch, rev the engine to the required speed whilst selecting a lower gear, let the clutch up and let the engine do the accelerating down for me. I often do this going from 5th to 3rd and then down to 2nd gear.
Since I have been driving, I have always atempted to try and successfully match engine speed to raod speed whilst doing this and would say I am very capable of doing now due to the amount of practice I have had.
My question is this, if I keep doing this, what are the consequences for my car (gearbox, clutch, engine etc)?
Also, is this a genuinely safe alternative to putting the anchors on and change down when you need to, i.e. when the change down will have a minimal impact on revs?
My car is RWD. When I approach roundabouts and such like, if I have no immediate need to brake, i.e. the roundabout being clear, I will approach in the normal manner. On my apporach, instead of braking to slow the car down, I dip the clutch, rev the engine to the required speed whilst selecting a lower gear, let the clutch up and let the engine do the accelerating down for me. I often do this going from 5th to 3rd and then down to 2nd gear.
Since I have been driving, I have always atempted to try and successfully match engine speed to raod speed whilst doing this and would say I am very capable of doing now due to the amount of practice I have had.
My question is this, if I keep doing this, what are the consequences for my car (gearbox, clutch, engine etc)?
Also, is this a genuinely safe alternative to putting the anchors on and change down when you need to, i.e. when the change down will have a minimal impact on revs?
Edited by combover on Sunday 17th September 08:40
Dear Combover - there are only two scenarios here (I think).
You either have to reduce your road speed, or you don't.
If you don't, then no braking or acceleration sense is required, so just select the appropriate gear, using the right foot to match the engine revs to the new gear.
If you DO have to slow the car down, then use the brakes. They are designed to do just that, and not only are they very efficient, they are also balanced to give the correct amount of braking force to the front and back wheels. Using the engine to slow the car down doesn't do that. It is also harder to fully balance the car by using the engine.
So on approach, use the brakes to slow the car to the correct speed, then select the gear (giving it increased revs as usual), then go. It will be better balanced, kinder to the engine, more controlled and smooth, and more efficient.
Regards
Sally
P.S. the above only relates to normal road driving, and is assuming I understood you correctly, that you are wondering whether to use the engine to slow the car down.
You either have to reduce your road speed, or you don't.
If you don't, then no braking or acceleration sense is required, so just select the appropriate gear, using the right foot to match the engine revs to the new gear.
If you DO have to slow the car down, then use the brakes. They are designed to do just that, and not only are they very efficient, they are also balanced to give the correct amount of braking force to the front and back wheels. Using the engine to slow the car down doesn't do that. It is also harder to fully balance the car by using the engine.
So on approach, use the brakes to slow the car to the correct speed, then select the gear (giving it increased revs as usual), then go. It will be better balanced, kinder to the engine, more controlled and smooth, and more efficient.
Regards
Sally
P.S. the above only relates to normal road driving, and is assuming I understood you correctly, that you are wondering whether to use the engine to slow the car down.
Edited by Lady Godiva on Sunday 17th September 11:04
Thank you for the reply.
I am talking of such things so your response was helpful.
I am saying that instead of using brakes, I merely use the gears and the natural deceleration effects of the engine when my foot is removed from the throttle pedal, to slow the car down in time for the roundabout/corner/bend.
Having done it so many times over many years, it is now almost natural to do it. I was just wondering if I was getting myself too far into a 'bad habit'.
Kind regards.
I am talking of such things so your response was helpful.
I am saying that instead of using brakes, I merely use the gears and the natural deceleration effects of the engine when my foot is removed from the throttle pedal, to slow the car down in time for the roundabout/corner/bend.
Having done it so many times over many years, it is now almost natural to do it. I was just wondering if I was getting myself too far into a 'bad habit'.
Kind regards.
Dear Combover - if you are using aceleration sense to slow down, this is certainly acceptable, and Advanced, and will do no harm.
As I'm sure you know, this is where you use gentle control of the acelerator pedal to control the speed smoothly, rather than use the brakes. The advantage is an almost imperceptible slow down, very smooth control, etc. However, one word of warning. Don't discount how much those behind sometimes need your brake lights as a guide. I will sometimes touch the brake pedal to show I am slowing down, even though I am not braking as such. I did a 30 mile journey the other day, mainly A and B roads, and just about the only time I touched the brakes was to warn those behind. One definite time for this is when you are coming out of a NSL into a 30mph zone. If you don't get the brake lights on, you can suddenly have the following driver parked in your boot, as they miss all the signs, relying on your speed and brakes to tell them what to do.
Enjoy your driving.
Regards
Sally
As I'm sure you know, this is where you use gentle control of the acelerator pedal to control the speed smoothly, rather than use the brakes. The advantage is an almost imperceptible slow down, very smooth control, etc. However, one word of warning. Don't discount how much those behind sometimes need your brake lights as a guide. I will sometimes touch the brake pedal to show I am slowing down, even though I am not braking as such. I did a 30 mile journey the other day, mainly A and B roads, and just about the only time I touched the brakes was to warn those behind. One definite time for this is when you are coming out of a NSL into a 30mph zone. If you don't get the brake lights on, you can suddenly have the following driver parked in your boot, as they miss all the signs, relying on your speed and brakes to tell them what to do.
Enjoy your driving.
Regards
Sally
combover said:
Thank you for the reply.
I am talking of such things so your response was helpful.
I am saying that instead of using brakes, I merely use the gears and the natural deceleration effects of the engine when my foot is removed from the throttle pedal, to slow the car down in time for the roundabout/corner/bend.
Having done it so many times over many years, it is now almost natural to do it. I was just wondering if I was getting myself too far into a 'bad habit'.
Kind regards.
I am talking of such things so your response was helpful.
I am saying that instead of using brakes, I merely use the gears and the natural deceleration effects of the engine when my foot is removed from the throttle pedal, to slow the car down in time for the roundabout/corner/bend.
Having done it so many times over many years, it is now almost natural to do it. I was just wondering if I was getting myself too far into a 'bad habit'.
Kind regards.
If you're applying mechanical sympathy when using your lower gears for engine braking, I can't see that you're doing any harm. As for balancing the car better by using the brakes to slow down, I suspect this is of little significance in a normal, fairly gentle, road driving style. If things are getting a bit hectic then it probably does make sense to pay more attention to balancing the car.
Best wishes all,
Dave.
If you have a rwd car then you need to be aware of the effects of engine braking on the car's stability. If you're only using a small part of the available grip then the effects will be negligeable. But as your 'grip reserve' drops the effects will be more pronounced. For example if you're cornering hard then closing the throttle may be enough to produce a significant amount of oversteer. Similarly in very slippery conditions even in a modest amount of engine braking may be enough to make the car unstable. When I'm driving the TVR in snow then in the lower gears I have to declutch when I slow down, otherwise the engine just drops to idle leaving the back wheels sliding. Even if the effect isn't that severe it will tend to make the car unstable. But if you're talking about normal sensible driving well within the limits of grip then there's nothing particularly harmful about it; the only danger is that if you do it automatically and aren't familiar with the effect on the car's handling around the limit of grip then you may be caught out if you misjudge the conditions.
GreenV8S said:
If you have a rwd car then you need to be aware of the effects of engine braking on the car's stability. If you're only using a small part of the available grip then the effects will be negligeable. But as your 'grip reserve' drops the effects will be more pronounced. For example if you're cornering hard then closing the throttle may be enough to produce a significant amount of oversteer. Similarly in very slippery conditions even in a modest amount of engine braking may be enough to make the car unstable. When I'm driving the TVR in snow then in the lower gears I have to declutch when I slow down, otherwise the engine just drops to idle leaving the back wheels sliding. Even if the effect isn't that severe it will tend to make the car unstable. But if you're talking about normal sensible driving well within the limits of grip then there's nothing particularly harmful about it; the only danger is that if you do it automatically and aren't familiar with the effect on the car's handling around the limit of grip then you may be caught out if you misjudge the conditions.
I first got the car at the start of summer...right when it rained for about two weeks solid. The roads were very slipperry, so I had a baptism of fire there and then. I'm used to oversteering the car when I want to and controlling it when I don't. I did take it to a roundabout travelling just inside the limits of grip and then shut the throttle off just as an experiment (on a deserted road naturally). However, it's not something I do normally as I know the effects it can have.
I am merely wondering whether it's poor form to not use the brakes when others do.
As for the brake light problem, I slow down to appropraite speeds when not using the brakes, but when I have somebody intent on inspecting the first aid kit in my boot, I tend to drive very defensively, knowing that I should help reduce the impacts (potential or actual) that their driving techniques (or lack of) have.
In terms of mechanical sympathy, I always aim to make my decelration as smooth as it can possibly be...mainly through matching engine, gear and road speed together. I have even trained the girlfriend to tell me when she can feel a downchange regardless of knowing when it happened. Any lack of mechanical sympathy is like running nails down a blackboard for me.
Kind regards.
Lady Godiva said:
I did a 30 mile journey the other day, mainly A and B roads, and just about the only time I touched the brakes was to warn those behind.
Sally, I find this a bit strange. I can't conceive of how or why one would drive like this. I'm not in a great place to comment as you are an advanced driver and I am not. However, why would you not want to use your brakes? I drive a TVR, but consider myself to be a bit of a granny driver. Even so, the brakes come in for regular use. I'm a bit confused!
Hope that comes across as genuine questions rather than criticism!
GRaham
In nutshell, and keeping in policy with IAM / RoSPA ...
You can use engine braking, no problem, but you shouldn't change gear to brake, else you're not following the system of car control.
Information
Position
Speed
Gear
Accelerate
Speed and Gear should be separate (bar a few exceptions).
Nothing wrong with not changing gear to keep engine braking though, eg. twisty road, hold say third, then when you lift off you have engine braking.
Martin
You can use engine braking, no problem, but you shouldn't change gear to brake, else you're not following the system of car control.
Information
Position
Speed
Gear
Accelerate
Speed and Gear should be separate (bar a few exceptions).
Nothing wrong with not changing gear to keep engine braking though, eg. twisty road, hold say third, then when you lift off you have engine braking.
Martin
Edited by mph999 on Monday 18th September 00:01
gridgway said:
Sally, I find this a bit strange. I can't conceive of how or why one would drive like this.
Don't see anything strange about it, personally. In pootling mode I only need the brakes at junctions and other hazards that require a significant loss of speed, and even then it's only very gentle braking except for the odd occasion where a late go/no-go decision may be involved.
combover said:
I will approach in the normal manner. On my apporach, instead of braking to slow the car down, I dip the clutch, rev the engine to the required speed whilst selecting a lower gear, let the clutch up and let the engine do the accelerating down for me. I often do this going from 5th to 3rd and then down to 2nd gear.
Edited by combover on Sunday 17th September 08:40
Why do you rev the engine while the clutch is dipped when changing down?
falcemob said:
combover said:
I will approach in the normal manner. On my apporach, instead of braking to slow the car down, I dip the clutch, rev the engine to the required speed whilst selecting a lower gear, let the clutch up and let the engine do the accelerating down for me. I often do this going from 5th to 3rd and then down to 2nd gear.
Edited by combover on Sunday 17th September 08:40
Why do you rev the engine while the clutch is dipped when changing down?
To match engine revs with roadspeed for the lower gear, so that the change will be smoother.
combover said:
I will approach in the normal manner. On my apporach, instead of braking to slow the car down, I dip the clutch, rev the engine to the required speed whilst selecting a lower gear, let the clutch up and let the engine do the accelerating down for me. I often do this going from 5th to 3rd and then down to 2nd gear.
My question is this, if I keep doing this, what are the consequences for my car (gearbox, clutch, engine etc)?
Also, is this a genuinely safe alternative to putting the anchors on and change down when you need to, i.e. when the change down will have a minimal impact on revs?
My question is this, if I keep doing this, what are the consequences for my car (gearbox, clutch, engine etc)?
Also, is this a genuinely safe alternative to putting the anchors on and change down when you need to, i.e. when the change down will have a minimal impact on revs?
You are obviously an extremely focused driver, and doing what you do very well will make you a better driver than using a more conventionally approved system less well. However, I go with the 'brakes are to slow, gears are to go' mantra.
If you need two gearchanges, not only are you doing more work, and sacrificing progress by slowing earlier than necessary, but you are a little less smooth than with a single slowing action.
Meanwhile, your question was about safety and mechanical sympathy. I don't think there are any safety or mechanical sympathy issues with your approach.
By the way, you imply that you think the 'Roadraft System' requires changing down at a road speed which will have a minimal impact on revs. Not necessarily so. Under the system you would block change (avoiding intermediate gears) down to the most suitable gear for negotiating the hazard, but that gear might well be one requiring a significantly higher engine speed to match the road speed.
gridgway said:
Lady Godiva said:
I did a 30 mile journey the other day, mainly A and B roads, and just about the only time I touched the brakes was to warn those behind.
Sally, I find this a bit strange. I can't conceive of how or why one would drive like this. I'm not in a great place to comment as you are an advanced driver and I am not. However, why would you not want to use your brakes? I drive a TVR, but consider myself to be a bit of a granny driver. Even so, the brakes come in for regular use. I'm a bit confused!
Hope that comes across as genuine questions rather than criticism!
GRaham
Dear Graham - firstly, you are in a super place to comment, regardless of who is or isn't Advanced, as everyone on here has an interest in drving. You may be much more Advanced than I am. Trust me, I'm learning more than I'm teaching (that wasn't meant to be as patronising as it sounds!!!).
There are many reasons to use the accelerator to control the speed rather than applying the brakes. One of the IAM tips (there are many) reads as the following three paragraphs:
Fuel consumption and the environmental benefits of advanced driving techniques go hand in hand. Key to both is “acceleration sense”. One question you might ask yourself is: “What is the delay time between you lifting off the accelerator and applying the brake?”
QUOTE.
Acceleration sense is about how you vary your foot pressure on the accelerator pedal so you don’t have to brake. Surprisingly to some, one of the pillars of fuel efficient driving is accelerating briskly to a safe cruising speed. A good test for fuel efficient driving is to imagine yourself somewhere that allows you to achieve an average speed between 30mph and 50mph, where you may need to brake regularly. Then increase that delay time: the longer you can avoid braking the more you are using the momentum you’ve built up. It means thinking a bit further ahead of where you are. Most drivers tend to go straight from accelerator to brake – and that is when fuel consumption suffers.
Another example: imagine we are in town approaching a roundabout. Where do you want the vehicle ahead of you to be when you reach the next roundabout? The more skillful you become at timing, the more fuel efficient you will be. It’s much better if the vehicle ahead is moving into the roundabout when you arrive.
END QUOTE.
If someone said what are the benifits, but KISS, then I would say:
You can get a far smoother transition in speeds.
It reduces wear on the brakes.
It helps to reduce petrol consumption.
Braking, even at low speeds (e.g. 30mph), can unbalance the car.
It promotes good observation and anticipation.
The last one is extremely important. For example, you can leave braking right to the last minutes, then be reactive (you may not want to do that, but you can if you wish). However, to use accelerator sense, you HAVE to have really good forward vision, or it doesn't work. You can't leave anything to the last minute, as accelerator sense is a very smooth reduction or increase.
It's what allows you to keep moving in a line of traffic where everyone else is stop start. It's what allows you to reach the lights just as they turn green. It's what allows you to reach the roundabout exactly as the space appears. It lets you arrive at the parked car just when you can move out around it. It lets you hold the speed in a 30mph zone bang on, without drifting over.
The trouble with writing things on here is that as soon as you're off, you think of something that makes it clearer. The best thing is to search on the web for info. Also, I'm sure there are others on here far better able to explain it than me.
Remember, any change in technique may only be very marginal. But if we are truly aiming to be advanced, then the marginal differences matter, as well as the bigger ones.
Regards
Sally
P.S. give it a go, and see if it smooths out the driving. If not, lets chat again.
P.P.S. I'm sure this is obvious, but can I stress that acceleration sense doesn't mean you don't slow down. You do, just not on the brakes. The speed up to and through a hazard is the same for 2 cars, it's just that one is one the brakes and the other isn't.
Edited by Lady Godiva on Monday 18th September 17:16
combover said:
Just a question on the liabilities involved.
My question is this, if I keep doing this, what are the consequences for my car (gearbox, clutch, engine etc)?
Also, is this a genuinely safe alternative to putting the anchors on and change down when you need to, i.e. when the change down will have a minimal impact on revs?
My question is this, if I keep doing this, what are the consequences for my car (gearbox, clutch, engine etc)?
Also, is this a genuinely safe alternative to putting the anchors on and change down when you need to, i.e. when the change down will have a minimal impact on revs?
In answer to your question, if you are mathing revs when changing down, there should be no adverse effect on the car. In fact, apart from being smother, you are reducing wear on the clutch by doing so.
Personally, I use the brakes and then change, but usually use your method for the gearchange. If I'm say going to select second gear at anything above 10mph or so, I'll double de-clutch. eg. selecting 2nd at say 30 puts a hell of a strain on the syncro rings in the gearbox, double de-clutching reduces, if not eliminates this.
Why select 2nd at such I high speed I hear somebody ask - well, I may want to "balance the car" on entry to a bend and then have maximum acceleration available, perhaps for an overtake (+ it's fun
) Martin
Lady Godiva said:
gridgway said:
Lady Godiva said:
I did a 30 mile journey the other day, mainly A and B roads, and just about the only time I touched the brakes was to warn those behind.
Sally, I find this a bit strange. I can't conceive of how or why one would drive like this. I'm not in a great place to comment as you are an advanced driver and I am not. However, why would you not want to use your brakes? I drive a TVR, but consider myself to be a bit of a granny driver. Even so, the brakes come in for regular use. I'm a bit confused!
Hope that comes across as genuine questions rather than criticism!
GRaham
Dear Graham - firstly, you are in a super place to comment, regardless of who is or isn't Advanced, as everyone on here has an interest in drving. You may be much more Advanced than I am. Trust me, I'm learning more than I'm teaching (that wasn't meant to be as patronising as it sounds!!!).
There are many reasons to use the accelerator to control the speed rather than applying the brakes. One of the IAM tips (there are many) reads as the following three paragraphs:
Fuel consumption and the environmental benefits of advanced driving techniques go hand in hand. Key to both is “acceleration sense”. One question you might ask yourself is: “What is the delay time between you lifting off the accelerator and applying the brake?”
QUOTE.
Acceleration sense is about how you vary your foot pressure on the accelerator pedal so you don’t have to brake. Surprisingly to some, one of the pillars of fuel efficient driving is accelerating briskly to a safe cruising speed. A good test for fuel efficient driving is to imagine yourself somewhere that allows you to achieve an average speed between 30mph and 50mph, where you may need to brake regularly. Then increase that delay time: the longer you can avoid braking the more you are using the momentum you’ve built up. It means thinking a bit further ahead of where you are. Most drivers tend to go straight from accelerator to brake – and that is when fuel consumption suffers.
Another example: imagine we are in town approaching a roundabout. Where do you want the vehicle ahead of you to be when you reach the next roundabout? The more skillful you become at timing, the more fuel efficient you will be. It’s much better if the vehicle ahead is moving into the roundabout when you arrive.
END QUOTE.
If someone said what are the benifits, but KISS, then I would say:
You can get a far smoother transition in speeds.
It reduces wear on the brakes.
It helps to reduce petrol consumption.
Braking, even at low speeds (e.g. 30mph), can unbalance the car.
It promotes good observation and anticipation.
The last one is extremely important. For example, you can leave braking right to the last minutes, then be reactive (you may not want to do that, but you can if you wish). However, to use accelerator sense, you HAVE to have really good forward vision, or it doesn't work. You can't leave anything to the last minute, as accelerator sense is a very smooth reduction or increase.
It's what allows you to keep moving in a line of traffic where everyone else is stop start. It's what allows you to reach the lights just as they turn green. It's what allows you to reach the roundabout exactly as the space appears. It lets you arrive at the parked car just when you can move out around it. It lets you hold the speed in a 30mph zone bang on, without drifting over.
The trouble with writing things on here is that as soon as you're off, you think of something that makes it clearer. The best thing is to search on the web for info. Also, I'm sure there are others on here far better able to explain it than me.
Remember, any change in technique may only be very marginal. But if we are truly aiming to be advanced, then the marginal differences matter, as well as the bigger ones.
Regards
Sally
P.S. give it a go, and see if it smooths out the driving. If not, lets chat again.
P.P.S. I'm sure this is obvious, but can I stress that acceleration sense doesn't mean you don't slow down. You do, just not on the brakes. The speed up to and through a hazard is the same for 2 cars, it's just that one is one the brakes and the other isn't.
Edited by Lady Godiva on Monday 18th September 17:16
Nicely put ...
Just to add to this, try drivng and pretend you don't have any brakes (ie. use them as little as possible, don't run into anything ...) and you'll soon develop acceleration sense.
Martin
Dear Graham - I've just got home, and I'm about to put the Tuna on for tea for the Lump of Lard who got my hand, but not my mind!!! You are probably thinking "oh no, I wish I had never asked" but assuming you are still slightly interested, I thought I would just add the following.
You probably already use acceleration sense to some degree without using it.
A Good description is in Roadcraft, as follows:"Aceeleration sense is the ability to vary vehicle speed in response to changing road and traffic conditions by accurate use of the accelerator. It is used in every driving situation: moving off, overtaking, complying with speed limits, following other vehicles and negotiating hazards. good acceleration sense requires careful observation, full anticipation, sound judgement of speed and distance, driving experience and an awareness of a particular vehicle's capabilities. A lack of acceleration sense causes many common mistakes: for example, accelerating hard away from a junction and then having to brake sharply to slow to the speed of the vehicles in fornt; or accelerating to move up behind a slower moving vehicle and then having to brake before overtaking. If you have good acceleration sense you are able to avoid unecessary braking".
I've had a quick check and acceleration sense is mentioned in Roadcraft, PYADT plus other books. It is taught on the IAM RosPa, HPC and other advanced courses. Police Class 1 drivers are taught to use it, as do other Advanced drivers (Security Personnel and other Professional drivers). It is mentioned on the Cadence commentary video amongst others.
Regards
Sally
P.S. let me know how you get on with it. I'll leave you alone now, so enjoy your driving whatever your style.
You probably already use acceleration sense to some degree without using it.
A Good description is in Roadcraft, as follows:"Aceeleration sense is the ability to vary vehicle speed in response to changing road and traffic conditions by accurate use of the accelerator. It is used in every driving situation: moving off, overtaking, complying with speed limits, following other vehicles and negotiating hazards. good acceleration sense requires careful observation, full anticipation, sound judgement of speed and distance, driving experience and an awareness of a particular vehicle's capabilities. A lack of acceleration sense causes many common mistakes: for example, accelerating hard away from a junction and then having to brake sharply to slow to the speed of the vehicles in fornt; or accelerating to move up behind a slower moving vehicle and then having to brake before overtaking. If you have good acceleration sense you are able to avoid unecessary braking".
I've had a quick check and acceleration sense is mentioned in Roadcraft, PYADT plus other books. It is taught on the IAM RosPa, HPC and other advanced courses. Police Class 1 drivers are taught to use it, as do other Advanced drivers (Security Personnel and other Professional drivers). It is mentioned on the Cadence commentary video amongst others.
Regards
Sally
P.S. let me know how you get on with it. I'll leave you alone now, so enjoy your driving whatever your style.
Edited by Lady Godiva on Monday 18th September 18:42
Lady Godiva said:
I'm about to put the Tuna on for tea for the Lump of Lard who got my hand, but not my mind!!!
Does he have to put up with this abuse all the time? Does he know? Does he mind? Am I on the wrong forum for this type of discussion??
Posted by a lump of lard waiting for a delicious dinner!
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