Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 8th September 2007, 21:53   #16
Distinguished - BHPian
 
Thad E Ginathom's Avatar
 
Join Date: Jun 2007
Location: Chennai
Posts: 7,847
Thanked: 7,244 Times
Default

Approaching any potential hazard, a change down is often good.


Having said that, I find myself wondering how I ever get out of First gear on the Chennai roads!
Thad E Ginathom is online now   Reply With Quote
Old 8th September 2007, 22:37   #17
Senior - BHPian
 
DieselFan's Avatar
 
Join Date: Mar 2007
Location: Bangalore
Posts: 1,570
Thanked: 233 Times
Default

It is a common mistake done by many people to shift to 5th gear as soon as possible. It takes more effort for the engine to pull the car in 5th gear at speeds less than 35 kmph than the 4th gear and hence consumes more fuel. This is the reason why we need to upshift after we attain a certain RPM. usually 2500 for petrol and 2000 for Diesel.

Last edited by DieselFan : 8th September 2007 at 22:39.
DieselFan is offline   Reply With Quote
Old 9th September 2007, 17:18   #18
BHPian
 
skandyhere's Avatar
 
Join Date: Jan 2005
Location: Charlotte/Blore
Posts: 347
Thanked: 88 Times
Default

Quote:
Originally Posted by DieselFan View Post
It is a common mistake done by many people to shift to 5th gear as soon as possible. It takes more effort for the engine to pull the car in 5th gear at speeds less than 35 kmph than the 4th gear and hence consumes more fuel.
i'm not sure if the ECU business changes the situation, but i had thought that only the RPM of the engine determines fuel consumption. the more revolutions (power strokes) of the engine per minute, the more fuel is consumed.

of course, if the car is driven at 2000 rpm in 1st gear, it consumes more fuel than in 2000 rpm in 5th gear - but only because the car moves slower, taking much longer to cover the same distance.

i doubt that the engine would drink more fuel lugging the car at low speeds just because it lacks the torque at that rpm. but i need to know more about this - maybe i'm wrong about how it works.

Last edited by skandyhere : 9th September 2007 at 17:22.
skandyhere is offline   Reply With Quote
Old 10th September 2007, 11:40   #19
Senior - BHPian
 
BUSA's Avatar
 
Join Date: Aug 2005
Location: Bombay
Posts: 5,130
Thanked: 10 Times
Default

Quote:
Originally Posted by DieselFan View Post
It is a common mistake done by many people to shift to 5th gear as soon as possible. It takes more effort for the engine to pull the car in 5th gear at speeds less than 35 kmph than the 4th gear and hence consumes more fuel. This is the reason why we need to upshift after we attain a certain RPM. usually 2500 for petrol and 2000 for Diesel.
Very well put dieselfanac - The thing is that i have noticed quite a few people who shift immediately to 5th gear and floor the car thinking they are saving fuel but when ever you stomp on the accelerator completely you are using more fuel then driving with half acclerator in lower gear. Under revving can cause harm to the engine and negatively affect your FE as well.
BUSA is offline   Reply With Quote
Old 10th September 2007, 16:44   #20
BHPian
 
Join Date: Aug 2007
Location: Mumbai
Posts: 73
Thanked: 0 Times
Default

Hi All,
I want to know is it OK if i change to 1st gear when the speed drops below 10 ?
Someone says that 1st should only be used when u start a vehicle which is stalled !!
Please advice.
I am a learner driver of Alto LXI !!!
saurabh159 is offline   Reply With Quote
Old 10th September 2007, 18:48   #21
Senior - BHPian
 
panky12345's Avatar
 
Join Date: Mar 2006
Location: New Delhi
Posts: 2,652
Thanked: 126 Times
Default

can somebody post a chart for Indica Diesel V2....I mean for the BEST FE, after what speed once should change gears? It would be a help for people like me who dont have tachos in our cars.
panky12345 is offline   Reply With Quote
Old 10th September 2007, 21:20   #22
Distinguished - BHPian
 
Thad E Ginathom's Avatar
 
Join Date: Jun 2007
Location: Chennai
Posts: 7,847
Thanked: 7,244 Times
Default

saurabh, all of the stuff we just said applies. It is not about speed, it is about circumstances.
Quote:
...1st should only be used when u start a vehicle which is stalled !!...
That is a strange way of putting it, and I think you have your terms confused.

If the engine is unable to propel the car because you are moving too slowly for the current gear, or if you release the clutch with the car in gear, but forget to release the brake, the engine will simply give up and stop. This is stalling. Just as you tend to take longer and slower strides (putting more power into each one) when you leave the flat and walk up a steep hill, so your engine needs you to change down.

Let the sound of your engine, tell you when to change down, not the speedometer. Actually, the tachometer is a more appropriate tool, but get to rely on your car sense, not on needles: not all cards have all the gadgets, and if you need instruments to tell you when to change gear then you're not looking at the road enough!
Thad E Ginathom is online now   Reply With Quote
Old 10th September 2007, 21:46   #23
BHPian
 
wheelsNsqueals's Avatar
 
Join Date: Jun 2007
Location: Mumbai and Calcutta
Posts: 96
Thanked: 0 Times
Default

Well put Thad. You would find most of the taxiwallahs changing to a higher gear as soon as possible. As if their aim in life is get the car off and switch to the top, and almost all of them drive on half-clutch, without realising that the engine would be severely underpowered. With practice one gets the hang of it and shifts by instinct with the engine noise as the guide. Conversely it is also important that one doesn't keep the lower gears engaged at higher speeds. I have seen a lot of new drivers do that.
Maruti manual provides a driving chart for gear shifts, at least my '92 M800 manual has it. You could have a look and follow that till it comes automatically to you.
wheelsNsqueals is offline   Reply With Quote
Old 13th September 2007, 07:57   #24
BHPian
 
rosh_aveo1.4's Avatar
 
Join Date: Apr 2007
Location: Cochin, Kerala
Posts: 531
Thanked: 286 Times
Default

[COLOR=black]Guys. Thanks for the advice. All this time in my Accent 1.5 GLS, I used to up shift to 5th gear soon as the speed reaches 40. And yes, I do experience the jerk or shudder at times, which means I was lugging the engine, not good!! Just learnt that now.[/COLOR]
[COLOR=black] But, back home I have my 6 month old Aveo 1.4, and the sales guy kept raving about VGIS and the ability to cruise at 25 km [FONT=Verdana]IN 5TH [/FONT]without jerking or anything. It actually did work but to climb back to speed at that gear from 25 kmph or so was difficult!! It felt like a good idea at first, like, it could be useful in slightly heavy traffic but after reading all this, I think it's a bad idea. [/COLOR]
[COLOR=black] Anyone knows the best speed to shift gears in the Aveo 1.4. My Accent manual says it for the Accent but the Aveo doesn't.[/COLOR]
[COLOR=black] So everyone has agreed that staying at top gear at less than optimal speed is [FONT=Verdana]NOT [/FONT]essentially the best way to increase the FE right?[/COLOR]
rosh_aveo1.4 is offline   Reply With Quote
Old 13th September 2007, 21:27   #25
Distinguished - BHPian
 
Thad E Ginathom's Avatar
 
Join Date: Jun 2007
Location: Chennai
Posts: 7,847
Thanked: 7,244 Times
Default

Quote:
Anyone knows the best speed to shift gears in the Aveo 1.4.
The point we are trying to make is that you do not change gear according to the speedometer (except, maybe, possibly, when running in a brand-new engine). You just don't.

Forget about speeds to change gear at. They do not exist. Truly. Although I've noted whether various cars I've driven will run comfortably in higher gears in various city speed limits, I have never in my driving life changed gear by speed.

You can check the tachometer needle for when to change down, if you must --- but still no need. If the engine is labouring, or not pulling then change down (you guys seem to call it lugging; do you say 'labouring' here? Do we mean the same thing? Indian/British English!)



Listen to the engine and feel the car response.
Thad E Ginathom is online now   Reply With Quote
Old 14th September 2007, 06:54   #26
BHPian
 
rosh_aveo1.4's Avatar
 
Join Date: Apr 2007
Location: Cochin, Kerala
Posts: 531
Thanked: 286 Times
Default

OK. Got the point. Thanks a lot Thad!!
rosh_aveo1.4 is offline   Reply With Quote
Old 14th September 2007, 16:40   #27
BHPian
 
skandyhere's Avatar
 
Join Date: Jan 2005
Location: Charlotte/Blore
Posts: 347
Thanked: 88 Times
Default

you may actually go by a single point agenda when you're thinking about when the change gear. just stay at the highest gear that will allow you to move the car comfortably without depressing the gas pedal too much.

'too much' should not be too much of a problem to determine, i hope - subjectivity notwithstanding. upshift if u hear your engine crying for its life and downshift if the car isn't responding well to the accelerator.
skandyhere is offline   Reply With Quote
Old 14th September 2007, 18:29   #28
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by skandyhere View Post
of course, if the car is driven at 2000 rpm in 1st gear, it consumes more fuel than in 2000 rpm in 5th gear - but only because the car moves slower, taking much longer to cover the same distance.
Not quite, skandy.
The fuel consumption depends on the load, not rpm alone.
anupmathur is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Stop at nothing. Not even gears. The 1st A-Star AT ownership on Team-BHP supremeBaleno Test-Drives & Initial Ownership Reports 126 26th April 2014 16:43
RPM shoots up when changing gears lambdaplus Technical Stuff 110 3rd February 2013 03:23
Changing gears on bullet 500 Cast iron deepikins Motorbikes 6 1st February 2010 11:02
Esteem 2002 - RPM Fluctuation (Blip) After Changing Gears genesis Technical Stuff 7 28th July 2009 10:25
Changing gears without using the clutch Lalvaz Technical Stuff 32 30th July 2008 12:19


All times are GMT +5.5. The time now is 15:26.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks