Using engine braking with an auto box

[Common Rail]

Inspired by the other thread on coasting in N, I've a related but different question.

I frequently use engine braking when decelerating for junctions, etc. i.e. 'tip'ping down through the gears.

In the same way, having coming from decades of manual boxes, I supplement downhill braking with 'tip'ping down. It saves the brakes (and gives the displayed mpg a surprising lift).

Is this likely to cause excessive wear to the auto box components, outweighing any of the benefits to brake lifetime?

ta.

 

[television]

This depends on the car and the box.

With the 722.3 4 and 5 and you are going down hill, if you pop the car into N and then back to D, the engine will speed up to the road speed.

If you are doing the same with the 722.6 box, the engine will not speed up by going from N to D.

If you want engine braking on the 722.6 box you must select it in the quadrant.

Brakes are far cheaper to replace than transmission parts

 

[popuptoaster]

Tis true, i only ever use engine braking when im "pressing on" and need the extra braking from the back of the car as well, otherwise i just stick with the brakes, being poor and having to do my own servicing and after 20 odd years of it its obvious to me i'd rather replace brake pads than clutches or get the autobox fixed.

 

[jamesmc]

I use engine braking when I wish because I feel that using engine braking with an Auto Box imposes no more or less strain/wear on a box than that imposed on it when making use of the opposite effect - engine acceleration.

Whilst on the move I would never pop the box into N and hope for the best As the car comes to a gradual halt 'Oops! that didn't work', might prove to be a very expensive afterthought!

Am I not correct in thinking that 'coasting' is deemed as 'not being in full control of the vehicle' from a (UK) legal perspective?

 

[television]

Yes it is against the law to coast in N

For the gear box, modern cars do not have a rear pump in the box, this is why they cannot be tow started, and when towing, a max of 30 miles at 30 MPH is all thats allowed

 

[psmart]

Yes it is against the law to coast in N

Several issues here, 1 being a manual box, if your going down hill and change down, your in danger of breaking the law as your coasting, especially if you dont engage the gear straight away, for whatever reason. The Prius, if your foot is off the accelerator, you engage re-generative braking, but if you slightly depress the accelerator, the car goes into Neutral (the Prius is an auto box) and the engine turns off, so again, theoretically, your breaking the law. Its a case of a political law (circa Suez crisis) has been overtaken by technology.

 

[delboy777]

Inspired by the other thread on coasting in N, I've a related but different question.

I frequently use engine braking when decelerating for junctions, etc. i.e. 'tip'ping down through the gears.

In the same way, having coming from decades of manual boxes, I supplement downhill braking with 'tip'ping down. It saves the brakes (and gives the displayed mpg a surprising lift).

Is this likely to cause excessive wear to the auto box components, outweighing any of the benefits to brake lifetime?

ta.

Am i right in thinking what you mean is manually changing down the box using the tiptronic shift, thereby inducing engine braking by using the lower gears ?

 

[television]

Am i right in thinking what you mean is manually changing down the box using the tiptronic shift, thereby inducing engine braking by using the lower gears ?

Yes thats the only way it can be done with tiptronic or via the gate on cars without

 

[Common Rail]

Am i right in thinking what you mean is manually changing down the box using the tiptronic shift, thereby inducing engine braking by using the lower gears ?

Spot on, delboy. Again, coming from a manual background, I want to feel as though I'm in control.

All we should be talking about is changing gear, NOT coasting along in neutral. (I shouldn't even have mentioned the dreaded N 'word' in the OP:Oops:!)

This is all about making use of the brakes, gears and engine braking in a safe and legal manner in an automatic car. To be clear: N doesn't come into it.

 

[delboy777]

I certainly do it if i think that i am not going to slow in time a couple of flicks and it slows down then immediately back into drive again. Dont know if this does any harm, although i wouldnt have thought so. Unless anyone else does ??

 

[djb]

the car goes into Neutral (the Prius is an auto box) and the engine turns off, so again, theoretically, your breaking the law. Its a case of a political law (circa Suez crisis) has been overtaken by technology.

it might be in neutral, but is the electric motor still connected? if so,not deemed as coasting.

 

[djb]

Inspired by the other thread on coasting in N, I've a related but different question.

I frequently use engine braking when decelerating for junctions, etc. i.e. 'tip'ping down through the gears.

In the same way, having coming from decades of manual boxes, I supplement downhill braking with 'tip'ping down. It saves the brakes (and gives the displayed mpg a surprising lift).

Is this likely to cause excessive wear to the auto box components, outweighing any of the benefits to brake lifetime?

ta.

by your mention of tipping down I presume you have one of the modern 5 spd boxes. These down change during braking. brake harder ,you get more down changes. particularly noticeable with the 7 spd box.

so my view, for what it is not worth it , would be .... it must cause wear, but probably a more stable car as the slowing force is more evenly distributed. Personaly I wouldnt tip down, butthen I dont press on much these days, other than on duals & m way.

 

[television]

On another note when descending a long hill with tiptronic it can lock up into what may seem a tow low gear, several nudges to the right with the stick will release that gear and it will go into the next

 

[Common Rail]

by your mention of tipping down I presume you have one of the modern 5 spd boxes. These down change during braking. brake harder ,you get more down changes. particularly noticeable with the 7 spd box.

so my view, for what it is not worth it , would be .... it must cause wear, but probably a more stable car as the slowing force is more evenly distributed. Personaly I wouldnt tip down, butthen I dont press on much these days, other than on duals & m way.

Its a W203 C220 with a five-speed box.

As an example, there's a mile-long downhill stretch on the way to work. I'll brake to let those behind know I'm doing so, and change down to 3rd. This limits the speed to 45 - 50mph with no accelerator and little brake.

[It'll be interesting at 6am tomorrow if we get much more than a dusting of snow tonight.]

Malcolm: It's not locked up on me yet, but that's useful to know.

 

[GeorgeA]

Its a W203 C220 with a five-speed box.

As an example, there's a mile-long downhill stretch on the way to work. I'll brake to let those behind know I'm doing so, and change down to 3rd. This limits the speed to 45 - 50mph with no accelerator and little brake.

[It'll be interesting at 6am tomorrow if we get much more than a dusting of snow tonight.]
.

Simply using the tip function should not do any harm to the box - surely this is what it is designed to do?

I have the same car and frequently use the tip function, both up and down, and have experienced no issues. In fact, as your example states using the tip down function on hills and in icy conditions makes safe and sensible driving sense to me.

 

[psmart]

it might be in neutral, but is the electric motor still connected? if so,not deemed as coasting.

No, its in the drive train but out of circuit. If the control circuit fails then its no different to coasting in Neutral. My comment about a manual changing down gear on a downhill, if you fail to get the car back into gear (linkage failure etc) then you are no different to coasting and present the same problem the law was supposed to overcome, so in-gear braking should also be illegal.

From my understanding, the law was brought in because during the Suez crisis people used to freewheel, overheat the brakes etc and bump into each other. Brakes etc are better these days and so long as the engine is running, then power steering and assisted brakes are operational. Hence a law outdated by technology and given the drive to get better mpg/pollution lowered, freewheeling should be encouraged, at least via the car mechanics/electronics.

 

[psmart]

by your mention of tipping down I presume you have one of the modern 5 spd boxes. These down change during braking. brake harder ,you get more down changes. particularly noticeable with the 7 spd box.

Just comeback from a trip in the sequentronic (C220), this topic in mind and it too down-shifts automatically during braking, regardless of braking intensity, so Merc seem to design their vehicles with transmission braking as an overall component of braking.

 

[television]

Just comeback from a trip in the sequentronic (C220), this topic in mind and it too down-shifts automatically during braking, regardless of braking intensity, so Merc seem to design their vehicles with transmission braking as an overall component of braking.

Its something that you do not think about till you go and play, so even on an emergency stop the box is going to drop down then

 

[GeorgeA]

Just comeback from a trip in the sequentronic (C220), this topic in mind and it too down-shifts automatically during braking, regardless of braking intensity, so Merc seem to design their vehicles with transmission braking as an overall component of braking.

Yes box will down shift upon slowing down but tip function puts more control in the hands of the driver. Original question was, will using tip function cause any harm to box. I do not think so, what do other think or indeed do?

 

[psmart]

Original question was, will using tip function cause any harm to box. I do not think so, what do other think or indeed do?

Most threads diversify when its a topic that needs debate. The original question was answered in so much as Mercedes program their boxes to downshift during braking, therefore all you are doing is pre-empting the electronics, just like shifting up gear wih tiptronic before the electronics decides to (ie. my 7G is always in to low a gear, I always have to use the paddles to force it into 6 or 7).