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Old 9th October 2009, 17:06   #16
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A question I have wrt engine braking (coincidentally on a Civic):

1. Should you use the clutch for a longer duration to smooth the revs down (to maximize passenger comfort by ensuring deceleration is uniform but brisk)? OR
2. Do you use more of the accelerator to match revs so as to minimize use of the clutch (at the cost of fuel economy, and a less than optimum braking duration)?

I know many of you will say a mix of both but isn't that a really hard line to define as far as the optimum mix is concerned?

Here is how I reduce speed:
[emergency braking] Clutch fully depressed, brake fully depressed (ABS cuts in). I guess if the ABS cuts in, there is no real point of additional braking power from the engine - I also think that the brakes will also have to take on the engine flywheel, which will hinder retardation than aid it under heavy braking (under most circumstances you won't even have time to downshift...).
[medium braking] Clutch, downshift, release clutch slowly while gliding on the brakes. Repeat till desired speed is reached.
[light braking] Clutch, downshift, release clutch slowly while using the accelerator to match the revs to achieve uniform deceleration.
[coasting] Full clutch, downshift to appropriate gears without ever releasing clutch.

Should I alter any of the above?
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Old 9th October 2009, 17:08   #17
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Quote:
@shan2nu: In most cases you can let the synchromesh do it for you. My style of changing gears is to pause for a second in neutral before moving on. As a result I am able to handle some baulky gearboxes without noticing a thing.
Im not talking about double clutching (which was done on cars without synchros), this is single clutch rev matching to match the engine speed with the transmission speed. If you pause in neutral, this will make the engine drop down to idle rpm and then it'l have to revv up all the way. Instead, you revv the engine while shifting which saves time and makes for a safer/smoother downshift.

Rev matching
Rev matching is a technique used to prevent unnecessary weight transfer during down-changes in a manual transmission car. For a demonstration of why this concept is useful, select third gear and accelerate to about 3000rpm, then quickly select second and release the clutch fairly rapidly. You'll notice a large forward weight transfer as the engine speed is forced to increase. This can also cause the driving wheels to lock in extreme situations.

Rev matching will make you a much smoother driver when changing down through the gears, a skill which is essential for the track and can lead to faster lap times. This technique is performed by depressing the clutch, selecting the required lower gear, increasing the throttle, and then releasing the clutch smoothly. You'll need more revs if changing from forth to second that from fourth to third. With practice, this can result in very rapid and very smooth changes, and is almost essential if driving on the track. Rev matching can also be performed while braking, this is known as heel and toe. When you first start to learn this technique, you might find it hard to predict the amount of revs you'll need for each gear, but remember any increase in revs is better than none.


Source : Smooth driving techniques guide

Quote:
This will require heel and toe and that needs practice.
Heel n toe only comes into the picture when you need to downshift while braking. But if you're stuck behind a slow truck and need sudden acc, you can downshift revvmatch without having to worry about "heel n toe".


Quote:
Most of the modern day cars have a rev limiter and hence one cannot cross the redline!
What you're talking about is electronic overrevving. But the over revving in this case is not caused due to throttle but due to the momentum of the vehicle. Yes there will be no fuel supply after the cut off point but if you shift into 2nd at say 130kmph, the engine will be forced to revv way beyond the electronic limit which could damage the engine.



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Last edited by Shan2nu : 9th October 2009 at 17:20.
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Old 9th October 2009, 17:18   #18
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I use a combination of gentle braking as I change down through all the gears in quick succession. This way you get the best of engine braking and lighter wear on brakes. Also when you go through all the gears you don't stress the clutch as much. On my Landcruiser even at 48k the original pads weren't worn. The Toyots service guys were shocked to see that. They claimed a normal car needs pads at 25k. And that's one heavy beast.
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Old 9th October 2009, 17:31   #19
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Single Clutch downshift -


Double Clutch downshift -


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Last edited by Shan2nu : 9th October 2009 at 17:35.
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Old 9th October 2009, 17:50   #20
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Quote:
Originally Posted by DKG
I use a combination of gentle braking as I change down through all the gears in quick succession. This way you get the best of engine braking and lighter wear on brakes. Also when you go through all the gears you don't stress the clutch as much. On my Landcruiser even at 48k the original pads weren't worn. The Toyots service guys were shocked to see that. They claimed a normal car needs pads at 25k. And that's one heavy beast.
Perhaps it impresses the Toyota mechanics, but its not good for the transmission or the engine.
Brake pads are far far cheaper and dead easy to replace. Opening gearbox or engine isn't!

IMO, there should be a 50-50 balance between engine braking and braking.
I've watched a lot of people on the tracks using mostly engine braking and little brakes only to find out that a few rebuilt the transmission after the track day.

That said there are advantages of engine braking vis a vis normal brakes
1) No fade
2) Minimal and Controllable traction loss

Cheers
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Old 9th October 2009, 17:54   #21
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Originally Posted by nitrous View Post
but its not good for the transmission or the engine.
That is absolutely not true Nitrous. The use of down shifting and engine braking has no negative consequences. Obviously you need to learn to do it fluidly and not go down too many gears and stress the mechanicals. My Civic had over 150k when I sold it and it never needed a clutch replacement or gearbox overhaul.

Last edited by DKG : 9th October 2009 at 17:55.
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Old 9th October 2009, 18:37   #22
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Originally Posted by anoopap View Post
Can u pls explain that.

Clutch is not engaged. Engine is running free. How does it become damaging ?
Apart from anything mechanical, it's theoretically unsafe to coast for any extended period, as you're not in complete control of the car.
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Old 9th October 2009, 19:05   #23
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Thanks all for the replies especially shan2nu about the rev-matching info and other videos etc

Engine braking is an enjoyable part of the driving experience and Im glad I can continue with modern cars like the Civic.

There was a question about whether this can be done on diesels too and IINM the answer is no?

Okay, now how do i go about measuring whether i am doing some good engine braking? anyone care to mention what is the average life of a civics brakes before requiring replacement, thus we can judge whether we do it properly if the brakes (pads/discs) dont need to be skimmed/replaced for longer?
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Old 9th October 2009, 19:39   #24
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Engine braking can be used, but only if you know how to use it. If you rapidly shift down, like from 5th to 3rd, you will face jerks and this is overall not good for you and your car. The jerks can be dangerous and this can even lead to loss of grip on slippery roads.

First practice engine braking and once you have confidence you have mastered it, start using it. The most basic way to know if you have got a good grip over engine braking or not is lack of jerks when you use engine braking. If when using engine braking you get more than reasonable jerk, you have not mastered it. If the jerks are very small, you know how to do it.

I dont use engine braking much in city, but on highways where one can anticipate better for over larger distance, engine braking is done.
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Old 9th October 2009, 19:46   #25
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I didnt see any answer about doing this on diesels. I too have the same question: Suppose you are running below the RPM where turbo kicks in and you downshift for braking. The revs go up and if turbo kicks in isnt that a problem?
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Old 9th October 2009, 20:47   #26
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Quote:
There was a question about whether this can be done on diesels too and IINM the answer is no?
Quote:
I didnt see any answer about doing this on diesels. I too have the same question: Suppose you are running below the RPM where turbo kicks in and you downshift for braking. The revs go up and if turbo kicks in isnt that a problem?
For the turbo to work efficiently, you need exhaust velocity which can only happen when the throttle valve is letting enough air in (ideally during WOT). When you engine brake, the only air that enters the engine is through the idler port which is a tiny hole in the intake manifold.

So even if the rpm goes into the boost zone, you should still have enough engine braking.

I've done this on the Indigo Turbo Diesel and it works like any other car.

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Old 9th October 2009, 21:11   #27
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Originally Posted by sgiitk View Post
What is no desirable (unfortunately very common) is to run de-clutched/in neutral. You must be in proper gear at all times.
+1 to that. This practice is more common on ghat roads, unfortunately where people exhibit the penny wise and pound foolish attitude !
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Old 9th October 2009, 22:46   #28
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Engine braking has nothing to do with petrol or diesel. In a 530d which I drove it was simply fantastic to slow down the car by down shifting. Infact in paddle shifts this really is the most enjoyable aspect. Ofcourse in the automatics you have a guard against shifting into too low a gear at the wrong speed. In a manual you can follow a simple technique. As you progressively shift down the revs climb up to a max before the engine starts cutting speed. Just make sure that peak is always a 1000-1500 rpm below redline. When you find yourself inching into this range stop shifting down further and you will be ok.

Basically every manufacturer will list a specific speed range for every gear. While downshifting as long as you enter that gear within its specified speed range you do no harm at all to your gears. Within a gear's permissible speed range actually the gear experiences more stress when the engine is driving the wheels as opposed to the wheels driving an "idle" engine

Those who wish to practice may keep track of permissible speed ranges initially and in no time it will become second nature. Once you get good at it you can sit behind the wheel of any car and in no time you can guage what speeds are appropriate for which gear.

But when you do get it right and the whole acceleration deceleration routine as you work the engine with the gearbox becomes fluid the experience is magical in a car

The Honda Civic is a fabulous car and you will love every bit of its pedigree when you experience its fine balance when pushed hard.

Last but not the least as a driver when you work the tarmac with a combination of gear change and braking you end up retaining traction at all times and this is critical for safety. When negotiating bends the fluidity with which gear changes allow you to slow down while not compromising traction becomes startlingly apparent as its a total diasaster to drive around bends using brakes.

Its just for this reason that modern manuals offer close ratio gearboxes so you can shave off speed more efficiently without compromising momentum

Last edited by DKG : 9th October 2009 at 22:56.
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Old 17th October 2009, 19:05   #29
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Just took delivery of a silver Civic this afternoon and the manual briefly talks about the goodness of engine braking so all is well

(started a thread in the test-drive/initial ownership section)
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Old 17th October 2009, 19:58   #30
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Guys,

Are we all forgetting something here in the whole discussion ?

While accepted the fact that engine braking is good, even the manufacturer suggests it, but whats the effect of engine braking on the clutch, since the clutch does take the load during the engine braking ? Will doing this regularly tend to reduce the clutch life ?

Opinions please .

Last edited by nandans2005 : 17th October 2009 at 20:03.
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