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Old 19th October 2009, 10:30   #31
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@nandan2005: None on the clutch since it is locked!
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Old 19th October 2009, 11:55   #32
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Sgtik,


Can you come again, please explain whats LOCKED ? MEAN ?
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Old 19th October 2009, 16:15   #33
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Quote:
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 .
Well if you are in the habit of downshifting to engine brake, without revv matching, there is a chance you will increase clutch wear during the shift since you will need to slip the clutch in order to get a smooth transition from a higher gear to a lower gear.

Using engine braking in the same gear will not cause the clutch to wear out faster.

Shan2nu
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Old 19th October 2009, 16:34   #34
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Quote:
Originally Posted by nandans2005 View Post
Sgtik,


Can you come again, please explain whats LOCKED ? MEAN ?
Locked is the same as fully engaged. The synchromesh takes care of the engine rev matching, so unless you do something crazy do not bother.

May I repeat the golden rule - the gear for coming down is the same as for going up. Also, the vehicle should be driven in a d-eclutched state for the minimum amount of time. In the UK if you free-wheel around a corner during your driving test say goodbye to the pass!
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Old 19th October 2009, 17:20   #35
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In any gearbox the input drive (input to the gearbox from the engine) connects to the maindrive (gearbox output to the prop shaft) through gears enabling variable input to output rotation ratios(your gear ratios). All that the synchronisers do is to match the rotation speeds of the these two drives for a particular gear ratio.

I think what Shan2nu is referring to is to match the engine revs to the input drive, and he has a point. When downshifting if you don't blip the engine up, the clutch when released has to do the hard work of matching the engine and input drive speeds, much like a giant synchroniser. By giving some throttle you aid the process of the engine speeding up to match the new higher input drive rotation during downshifting allowing for a smoother transition.

That said in a critical situation where you really need that extra engine braking then you can let the engine at lower revs on a downshift provide that strong bite killing speed as the clutch engages and slows the car down. In such a case you may not have the luxury of blipping the engine and having enough time for the revs to climb back down causing engine braking.

Under normal driving when I approach a bend I do blip to match and slow down. But in a tight situation I would let the clutch do the hard work of scrubbing off speed using the inertia of an engine at lower revs

Last edited by DKG : 19th October 2009 at 17:34.
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Old 19th October 2009, 19:55   #36
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anyone has any additional specific inputs for engine braking in an automatic civic?

while i don't use the paddles much in the city, i recently took a highway trip and found the paddles very useful for engine braking, even in D mode.
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Old 19th October 2009, 20:40   #37
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Quote:
Originally Posted by Axe77 View Post
anyone has any additional specific inputs for engine braking in an automatic civic?
Modern auto gearboxes are "idiot proof". You can't change down into a gear when the speed is beyond its range. Try going into 2nd when doing 150, it simply won't respond.

Therefore you can use the paddles without fear of doing any damage. Once you get used to it the real pleasure of paddle shift becomes apparent.

Enjoy
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Old 19th October 2009, 22:14   #38
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for those who enjoy their cars working the gearbox you may be interested to know that the current M6 has this function of blipping the throttle when you downshift. Its autobox actually blips the throttle automatically when you downshift.

I was once behind an M6 on my VFR and was pleasantly surprised when I heard that glorious v10 blip as the driver downshifted. i knew the car had an auto gearbox so was curious how it did that. When I asked, the owner said it does so automatically.

Last edited by DKG : 19th October 2009 at 22:15.
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Old 20th October 2009, 10:50   #39
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Hey Guys,

After all said and done, would you guys explain in detail how the ENGINE BRAKING WORKS PLEASE, i mean technically.

As i understand, the engine braking phenomenon is different in petrol and diesel engines.

Would anybody come with technical working of how the effect of engine braking is got?
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Old 20th October 2009, 12:10   #40
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Quote:
Hey Guys,

After all said and done, would you guys explain in detail how the ENGINE BRAKING WORKS PLEASE, i mean technically.

As i understand, the engine braking phenomenon is different in petrol and diesel engines.

Would anybody come with technical working of how the effect of engine braking is got?
The phenomenon is the same for petrol and diesel engines. When you come off the acc, there is very less air entering the cylinder. This lack of sufficiant air creates a certain amount of vacuum which the engine has to fight against. Mechanical friction also adds to engine braking.

Its like taking a syringe (without the needle), compressing it completely, then covering the intake hole with your finger and trying to pull the plunger. If its completely sealed, you will not be able to pull the plunger out.

But in an engine, there is still some air entering through the idler port. So its not a complete vacuum which allows the engine to keep moving without locking the wheels.

The amount of deceleration through engine braking will depend on many factors like engine speed, vehicle speed, gear ratio, cylinder compression, vehicle weight, road surface, wind resistance, rotational mass etc etc...

Shan2nu

Last edited by Shan2nu : 20th October 2009 at 12:14.
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Old 20th October 2009, 12:30   #41
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I Use Engine Braking Always - 100% in my driving. Its not only Safe but also recommended by rally drivers to keep your car in control in curves, bends, slopes, etc.,. People have a wrong notion that engine braking will reduce the life of the engine, but the fact is it does not. Below the redline rpm range, engine braking makes you use minimal brakes, and also only 2 pedals - clutch and accelerator. in my past 20 years driving experience, i have braked heavily from 120-130kmph speeds to an emergency halt, using engine braking heavily - and had always stopped short of hitting obstacles, thrown before the vehicle. i have never skidded the vehicle with tyres screeching, even at 120kmph speeds.

my suggestion, all drivers should practice engine braking daily, in everyday road conditions. if you master this, you will use the brakes, brake pedal only when you come to a complete stop. other situations never will need you to use the brake pedal, other than an occasional jab, touch of the brake pedal.

modern engines have rev limiters, and engine life usually outlives the car's age. so all teambhp members, try to advocate the positive facts, in your safe driving.
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Old 20th October 2009, 12:47   #42
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Quote:
People have a wrong notion that engine braking will reduce the life of the engine, but the fact is it does not.
I wouldn't say it doesn't but it's not a serious prob.

When you downshift to a lower gear, the engine has to revv higher causing more wear as compared to keeping it in a higher gear (low rpm) and just using the brakes.

Just bcoz its below the redline doesn't mean there is no wear and tear. The higher you go through the revvs, higher the wear rate (even if it's below the redline).

But then again, the rate of wear is so less that you maynot face any issues for a long long time (unless there is a manufacturing defect).

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Old 20th October 2009, 22:42   #43
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This is a little off topic and my apologies in advance for this but don't know where else to fit this - the only link to this thread is this post's co relation to engine braking as well. [mods pls feel free to move this to a more appropriate thread]

i'm relatively new to automatics having driven manual hatches all my life until my civic A/T. So far, particularly on the highway, I found the paddle shifts immensely useful for (a) engine braking; (b) downshifting to stay in the power band; and (c) occassionally upshifting a little earlier than the D mode would ordinarily upshift.

I believe most A/T cars in that broad price range (altis; civic; jetta/ laura/ accord; city; superb; outlander) have some sort of complete manual override functionality - either through paddles or through the tiptronic feature.

I find it quite incredible then that the H - CRV at almost 30 L on road does not feature tiptronic or paddles. Having used paddle shifts, i find it unthinkable how CRV owners are not able to implement something as basic as engine braking in their cars - or is there some other manner in which this is implemented in an A/T CRV that I'm not aware of?

I also simply cannot fathom why Honda would provide paddles in the City / Civic and Accord but not the CRV.

Separately, how does the "1"; "2" gear settings in the CRV work? Are they in some manner superior to the D / S mode combo provided in the Civic? Does the Accord also have the "1"; "2" gear settings like the CRV or does it have D and S?

Apologies for what is probably a very basic question for many on this forum.
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Old 21st October 2009, 09:45   #44
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Quote:
Originally Posted by Axe77 View Post
how does the "1"; "2" gear settings in the CRV work?
These functions are just for that to hold the transmission in a lower gear. Especially when driving down a ghat road in an automatic you don't want the transmission to keep shifting into higher gears and speed up. So you move into D3 or D2 or in some rare cases D1 to hold the gearbox in that gear and allow engine braking to keep the car slowed down rather than finish your brakes.

As for your query regarding the CRV not being offered with paddle shift, it is a SUV and not meant to be driven like a sport sedan. On the other hand a City or Civic are really enjoyable to drive on the limit and with the paddle shift they take on a very sporty character. Hope that makes sense

Last edited by DKG : 21st October 2009 at 09:50.
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Old 21st October 2009, 10:06   #45
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@DKG: Another thing you hinted at but did not make explicit is the while in D the AT free-wheels when the road speed is higher than engine speed. In a lower range i.e., 1, 2 engine braking comes into play. This is very essential when you are driving downhill.
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