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![]() | #31 |
BHPian ![]() | ![]() mr netarchie i think its better u use the owners manual. u may get too confused otherwise. engine braking, brake pads, friction, cutting gears its all just too much too soon. |
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![]() | #32 |
Team-BHP Support ![]() ![]() Join Date: Feb 2004 Location: Bombay
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| ![]() Ok, I'm going to try to clear things up here, and can pretty much guarantee that this IS the best method. (Ofcourse open to debate). ![]() NEVER keep the clutch pressed or shift into neutral when braking UNTIL you have reached 10km/h or less. (just before the engine is about to start shuddering/knocking) Netarchie, First - let me negate your "saving fuel" arguement... When you are in neutral or have the clutch pressed, the car has to keep fuel going to the engine in order to keep it running. This uses fuel, naturally. When you are in gear, and you take your foot off the accelerator, modern cars (which are fuel injected and pretty intelligent) sense the decelerating load on the engine and CUTS ALL FUEL SUPPLY TO THE ENGINE. This uses virtually NO fuel. The only thing keeping the engine spinning is the rolling of the tires transfering power back up the drivetrain, keeping the engine spinning. And at the same time you are getting engine braking! Talk about a sweet deal. Secondly - a small point to note about "shifting to neutral on the expressway". When you drive at a high speed for a long time, a phenomenon called velocitizing occurs. It basically means you dont have a realistic feel of exactly how fast you are going, which means slowing down will be harder than you think, which means ANOTHER REASON TO USE ENGINE BRAKING. If you want to just roll to a hault over 1000mts, feel free to do so, but STAY IN GEAR, the higher the gear (eg. 3rd, 4th, 5th gear) will make your rate of deceleration slower, whereas a lower gear (2nd or 1st) will slow the car down more rapidly. Regardless of the gear you are in, if you are not pressing the accelerator, chances are that NO fuel will be being used. Thirdly - Vivek, for tips on driving an automatic, check out this thread. Fourthly, and finally - Why engine braking is better! 1. It saves your brakepads from overheating and causing VERY dangerous brake fade. (Believe me, your brakes just WONT work when they get hot!) 2. It will save fuel, as mentioned above. 3. It will give you better control when turning. (try this out by taking a corner at Xkm/h and in 2nd/3rd gear, and then try doing it at the same speed in neutral and see the comparative lack of control you feel.) 4. YOU WILL STOP FASTER using engine braking. Vivek2kny, your point about the quantity of friction between the tyres and the road being the limiting factor (so what difference if it comes from the brakes or engine?) makes sense in theory, BUT it doesn't take in several other factors. For eg. getting the maximum out of your brake pads is not easy. If graphed, there is a non-linear curve of the amount of braking you are getting for a constantly increasing brakepad pressure on the rotor. Several factors influence this curve, including temperature, type of brakepad, type of rotor, speed of rotation etc. Hence, getting it consistently perfect is nearly humanly impossible, so if you have engine braking on your side, its much easier to get the maximum deceleration. Still not convinced? - Try this - Find an empty peice of straight, clean surfaced road. Make sure noone is behind you, get upto about 60-70km/h and shift into neutral. At a predetermined marker on the road brake as best as you can. Make a note of when the car comes to a complete halt. Now, do it again. Get upto the same speed, but stay in 2nd gear. Make sure theres no car behind you, and at the same marker brake as best as you can, KEEPING THE CAR IN 2nd gear, only to press the clutch just before your car comes to a hault. Take a note of where the car came to a stop. I am pretty sure that you will find that your stopping distance was significantly shorted when you left the car in gear, as well as much more confidence inspiring! Try it out and let me know. If i havent explained anything clearly enough, please let me know. cya R Last edited by Rehaan : 18th September 2011 at 14:56. |
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![]() | #33 |
BHPian ![]() Join Date: Mar 2006 Location: new delhi / pune
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| ![]() rehaan ,this is what i understand from your post suppose the force needed for minimum possible braking distance is Y when you brake ... you don't know how much to press the brake to get retarding force equivalent to Y ... you the brake too hard ... you risk locking let braking force be X and engne braking force be Z X + Z in practical situations will be closer to Y ... thus less braking distance but then what happens if X + Z is greater than Y ... skidding ??? and what about cars with ABS/EBD ... the effect of engine braking should technically(and even practically) be minimal , right ?? coz the car will apply force Y(or very close to it) Last edited by Fiero : 11th May 2006 at 22:01. |
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![]() | #34 |
BHPian ![]() | ![]() Thanks, Rehan and others, i am convinced now 100% and find no significant advantage of this neutral method. good that i posted this query or else i would have never known. Maybe this habit creeped into me because i used to drive a diesel car till late I had also read about this method somewhere in the internet, somehow cannot find the exact link now. i also thought this was one way of avoiding the clutch plate wear and tear more than increasing the FE.In my indica it would not allow me to ride in a high gear with a low speed and low gears used to make lot of engine noise, so this was one way of shutting its mouth. Just to quote an example with my Indica, say iam driving at 70 odd Km/Hr and i am in 5th gear, i see a red light ahead, so i have to slow down now, if i remove my foot of the gas and apply brakes gently, sooner or later its going to knock. so to come to a lower speed i need to downshift to 2nd gear. which means pressing the clutch 3 times to match the correct revs in each gear 4,3,2. If i use the neutral method i have to press the clutch only twice. once during fift to neutral and again during neutral to 2nd or 1st depending on the speed. This was the logic.And this neutral thing is only possible whn the road ahead is free, withouse or less traffic, cant be done in a bumper to bumber traffic. But now when i am using a petrol car, it exact opposite, i dont have downshift so often.So when i went for a drive to actually study my driving habbit i found that i dont neutral it so often as i usd to do it earlier.here for e.g. what i observed as to what exactly i did was when i was approacing a speedbreaker and i was abt at 50km/hr speed and in 5th gear,i slowed down gently till i aproached the breaker, i shifted to neutral when my front tyre just climbed the speed breaker, my speed would have been 10 km/hr that time, whn my rear wheel also passed the breaker i put it 2nd nd continued. And abt driving downhill in neutral. when i mentioned downhill in my earlier post, it was small slopes or inclines like maybe a flyover in mumbai and not the hilly (ghats) downhills. I know much abt engine braking and haVe used it quite efficiently in real downhills drives. The whole logic of the neutral method was to avoid wear and tear of the clutch plate and the brake liner. FE was only the by-product of the method or a bonus as you may call it. Since this does not hold true, best is to change my driving style. by the way Fiero made an intersting comment and my car has ABS... :-) |
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![]() | #35 |
BHPian ![]() | ![]() Never do that, alsways use engine braking , and drive like a professional ![]() |
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![]() | #36 | |
BHPian Join Date: Apr 2006 Location: Bangalore
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| ![]() Quote:
Never go on neutral in the downhill and also when the engine is running and you want to slow down. Its always a best practise to shift the gears according to the speed of the of the engine in that way you are best utilising the fuel and you also have the better control over the enigine and the vehicle. Thank god you are not shutting off the engine and applying brakes to save fuel ![]() *Happy driving* | |
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![]() | #37 | |
Senior - BHPian ![]() Join Date: Feb 2005 Location: cincinnati, jabalpur,chennai
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I agree, as i said, for the planned braking. but still I can't convince myself to do a gear shift when i see an urgent need of braking, I guess my eyes will be clenched closed and full force on the brake may be i will learn, or may be the airbags will take control. ![]() | |
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![]() | #38 | ||
Team-BHP Support ![]() ![]() Join Date: Feb 2004 Location: Bombay
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I understand what you are trying to say in your example, however, my point is that "Y" is not a constant, it changes according to the current speed you are at, temperature and lots of other factors. Hence, having "Z" as a constant added to "X" gives you more flexibility to control "X". Regarding ABS / EBD, keep in mind that they are not applying brake-force, but reducing/governing brake-force (atleast in the case of ABS, and probably EBD to the best of my knowledge? barring the new S class etc< is that even still called EBD?). Your question still is valid though, and i cannot give you a entirely knowledgable answer without going into details that i am not well versed in. Given the fact that brakes are basically friction, you should do some research on friction and look at graphs to get an idea of what i am talking about. etc. And hopefully somewhere in the midst of that physics talk and confusion you will feel that having engine braking will be better ![]() Sorry i cannot verbalize my thoughts on this accurately. But as i said in my earlier post. TRY IT...and see the difference. Quote:
BUT, its still better if you are IN GEAR in this kind of situation than if you were in neutral / clutch depressed. cya R Last edited by Rehaan : 13th May 2006 at 04:41. | ||
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![]() | #39 | |
BHPian ![]() Join Date: Jan 2006 Location: New Delhi
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i know old habits die hard, but you need to know the better technique to stop the car! donot rely heavily on airbags, etc. moreover, once you know how to stop well in time, might be there won't be any need for deployment of airbags! Happy Learning, Drive Safe!! | |
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![]() | #40 | |
BHPian ![]() | ![]() Quote:
PS : Automatic trannies may be the other cause. | |
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![]() | #41 | |
Senior - BHPian ![]() Join Date: Feb 2005 Location: cincinnati, jabalpur,chennai
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ebd abs airbags and what not is not to keep the car in control, but to save ur life when u actually crash. and do i see 'this will not happen to me' syndrome? lethargy is personal choice, but opting for these safety measures is a great favor one can do to his family. remember, it's not always ur mistake that can lead u into a crash. for the crashes in uae, apart from the model year, try geting statistics on the drivers' profil, and car purchasing capacity, to make it a fair comparison. don't just blame the cars. my earlier comment shud have been read with the smiley. ![]() | |
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![]() | #42 | |
Senior - BHPian ![]() | ![]() Quote:
EBD and ABS serve no purpose in an event of a collision. Then again, no matter how many safety features your car has, if you arn't alert, you will eventually hit something. Shan2nu | |
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![]() | #43 | |
Senior - BHPian ![]() | ![]() I never shift into neutral while coming to a halt, or for that matter press the clutch. If I'm doing 60kmph and I have to brake, I wouldn't press the clutch nor change the gear, till I brake to a proper speed and till I get the slightest hint that the car demands it (minor vibrations can be felt). If you still don't press the clutch after this, the car will jerk. On the turn I'd brake till the turn and when I reach the turn, I'd engage clutch and change gear and turn. If you press the clutch or enter neutral gear when you are on high speeds, its dangerous, since you're letting the car just flow without any control on it. You have no control on it. Its just moving freely. The only control you have is with the brakes. Quote:
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![]() | #44 | |
Senior - BHPian ![]() Join Date: Feb 2005 Location: cincinnati, jabalpur,chennai
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ABS starts releasing and rebraking only when it senses that wheels are locking, right? and i have never pushed my car to that limit. so it's useless for me (and @2fast4u) until i actually slam the brakes someday. | |
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![]() | #45 |
Senior - BHPian ![]() Join Date: Feb 2005 Location: cincinnati, jabalpur,chennai
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| ![]() tried this on my galant today. instead of braking in 'D' at the signal, changed to lowest gear first. not much diference, car behaved slightly heavier, but kept rolling. I had taken my foot off the gas pedal. then when i tried braking when close to the signal, whoa, that was much quicker than i expected. braking was much stronger. what i think is when i took the foot off the gas pedal, nothing much happened. but when I put my foot on brake, the fuel supply was cut off. Is it true? is there a connection between brake pedal and the car's computer that signals engine to cut off it's supply when braking? |
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