[SS-Traveller]

Originally Posted by Kumar R

2. While coming down from heavily jammed flyovers where traffic moves bumper-to-bumper I sometimes switch off the engine and just keep lighting the foot on/off the brake to let the car inch forwards. Is there any adverse effect on the car due to this?

NEVER switch off the engine when ANY car is in motion. You'll lose braking AND steering control (for power steering and servo-assisted brakes-equipped cars) (wouldn't matter in a M-800/Omni).

Originally Posted by a4anurag

...modulate the sod...

???

Originally Posted by a4anurag

All new generation cars have the anti-stall feature which will keep the car going in gear without any throttle input.

When dropping below 1200 rpm (or slowing below 20 km/h), it's nicer to shift to neutral, esp. in diesels, to prevent the anti-stall system fighting the brakes.

Originally Posted by a4anurag

...the servo motor is not getting power from the engine.

No motor there.

Originally Posted by Soumyajit9

...it me out when I see the RPM needle shoot up when I upshift to slow down the car.

While I am saving the brake discs from wear and tear, am I not putting a load on the engine, and will it not affect my FE when the RPM needle shoots up ?

Answering to a question which many would ask - what RPM range it shoots.

I am in 5th Gear at 80kmph at 2.2k RPM.
The speed breaker is about 500 mts ahead (I know where the speed breakers are on my route).
I let the RPM come down to 1.8k and then upshift to 4th Gear.
The RPM zooms to about 3k range for 2-3 seconds and then comes down to 1.5, adjusting with the 4th gear rev.

So this 2-3 seconds of 3k range - Isn't it a load on the engine and the FE ?

Sorry if I sound silly. Please advise.

No harm to engine, even if revved to the redline for a few seconds. The shock is being taken up by the clutch - so clutch wear is likely. Letting out the clutch hard may damage the clutch otherwise than simple wear. In any case, why downshift at 1800 rpm? You are in the "rev band" of the engine, and it'll pull out well from that rpm. Allow the rpm to drop below 1500 as Anurag said...

Originally Posted by a4anurag

80kmph @ 5th gear was at 2000 so downshift to 4th gear yob the RPM to 2500 which is fine. When I downshift near 1500 - 1600 RPM, the resultant RPM is near 2100 which is in the peak turbo range anyway.

I advise you to downshift when the RPM drops near 1500, so the resultant RPM will be near 2100 - 2200 which is fine. 3500 - 4000 RPM is harmful but anything near 3000 is fine.

[a4anurag]

Originally Posted by SS-Traveller

???

Apologies, didn't proof read. It was 'speed' and not 'sod'.

Originally Posted by SS-Traveller

When dropping below 1200 rpm (or slowing below 20 km/h), it's nicer to shift to neutral, esp. in diesels, to prevent the anti-stall system fighting the brakes.

I guess the lowest RPM should be between 1200 - 1300 to prevent lugging.

Anurag.

[SS-Traveller]

Originally Posted by a4anurag

I guess the lowest RPM should be between 1200 - 1300 to prevent lugging.

Lugging is different from the anti-stall system fighting the brakes. Discussions on lugging here.

[joybhowmik]

SST
Must say this thread has been an eye-opener for many of my friends, who first read it when I shared the article on my FB page some time ago.
Not sure how much of a role the article will play in being the evangelist for TBHP in terms of new applications for membership here!

But even it has managed to persuade one person outside TBHP, to be a little more gentle with his car, it can be therefore said, that that's one more person who will possibly drive a little more safely as well. Which augurs well for the city and the world.
Thanks much for keeping this thread alive with useful tips and suggestions!

[thoma]

Originally Posted by Soumyajit9

However, it me out when I see the RPM needle shoot up when I upshift to slow down the car.

...

I let the RPM come down to 1.8k and then upshift to 4th Gear.

This is called downshift, you up-shift to a higher gear not lower.

As SST rightly pointed out, downshifting to a very high RPM is going stress your clutch. FE is not an issue as most cars now have a cut-off. It is specifically mentioned in my Micra Owners's Manual not to over-rev while shifting to a lower gear to avoid engine damage.

[Soumyajit9]

Originally Posted by a4anurag

Good to see the practice put in place to save the brakes. IIRC you drive a Beat D. Right?!The engines which we drive have been put to much higher stresses and load conditions before they are actually produced for the mass market. Though FE will drop slightly but wear and tear will not be a problem but it depends on the frequency you do this and also the gear:speed relation that witnesses the RPM blip.
I did try the downshift in my Swift ZDi after reading your query.
80kmph @ 5th gear was at 2000 so downshift to 4th gear yob the RPM to 2500 which is fine. When I downshift near 1500 - 1600 RPM, the resultant RPM is near 2100 which is in the peak turbo range anyway.
I advise you to downshift when the RPM drops near 1500, so the resultant RPM will be near 2100 - 2200 which is fine. 3500 - 4000 RPM is harmful but anything near 3000 is fine. Not alarming at all but it all depends how frequently you do it. Load wise no problem but FE will drop slightly.
Apologies for not understanding your real question.
Slowing down from 50 kmph to 5 kmph in 4th gear will kill the engine. Every gear has a designated speed in which it will be comfortable to drive on.
I am giving the gear and speed for my car - Swift ZDi:
0 - 20 kmph = 1st to 2nd
20 - 35 kmph = 2nd to 3rd
35 - 50 kmph = 3rd to 4th
50 - 60 kmph = 4th to 5th
All of the above are we've the RPM is at 2000 where I upshift. Coming to downshifting, I do when the RPM drops to 1600.
Follow the above and you shouldn't be in a problem.
Hope it helps.

Thanks for the tip Anurag !! I drive a Beat Petrol.
Will see if I can reduce the RPM to the 1500 range.
The idling of my car is ~900. It pulls ahead without Acc input at 900.
So at 1500 it can still pull in 5th gear. Infact today I slotted into 5th gear at 1000 and it went smooth.
The issue is while slowing down. I will see if I can get to 1500 before I hit the brake or get near the hump. May be my braking distance calculation has to be improved.

Originally Posted by SS-Traveller

No harm to engine, even if revved to the redline for a few seconds. The shock is being taken up by the clutch - so clutch wear is likely. Letting out the clutch hard may damage the clutch otherwise than simple wear. In any case, why downshift at 1800 rpm? You are in the "rev band" of the engine, and it'll pull out well from that rpm. Allow the rpm to drop below 1500 as Anurag said...

Thanks SST for the inputs. The clutch wire, plate, etc (the entire mechanism) is in good condition for my car.
In Feb this year, I had a problem of a ring sound coming whenever I accelerated.
The Chevy A.S.S people diagnosed a lot and tried a lot to adjust the clutch but it didn't go. They said that the clutch plates may have gone, so wanted to replace it. So when they opened up, they saw the clutch plate was perfectly fine for my 24k driven Beat. So they replaced the entire mechanism under warranty. So now I have a new clutch mechanism and the ring sound has also gone. So now I can say that the clutch is new and should behave well with the engine praking practice. Have to see in the long run if it gets affected.

Originally Posted by a4anurag

I guess the lowest RPM should be between 1200 - 1300 to prevent lugging.Anurag.

My Beat Petrol moves ahead without Acc input in 1st gear at 900.

Originally Posted by thoma

This is called downshift, you up-shift to a higher gear not lower.
As SST rightly pointed out, downshifting to a very high RPM is going stress your clutch. FE is not an issue as most cars now have a cut-off. It is specifically mentioned in my Micra Owners's Manual not to over-rev while shifting to a lower gear to avoid engine damage.

Err, my bad. Got confused with the terms upshift and downshift.
Makes me little relived to get to know that FE wont be impacted much due to the fuel auto cut off mechanism.

[a4anurag]

Originally Posted by Soumyajit9

Thanks for the tip Anurag !! I drive a Beat Petrol.

Will see if I can reduce the RPM to the 1500 range.

The idling of my car is ~900. It pulls ahead without Acc input at 900.

So at 1500 it can still pull in 5th gear. Infact today I slotted into 5th gear at 1000 and it went smooth.

The issue is while slowing down. I will see if I can get to 1500 before I hit the brake or get near the hump. May be my braking distance calculation has to be improved.

Was thinking your Beat was diesel hence the RPM I mentioned keeping the diesel engine in mind.

While slowing down to reach a hump you'll have to let go the accelerator a bit earlier to reach 1500 before braking. Will come with practice.

Anurag.

[ramzsys]

At highways when i am driving sedately, i have acquired this habit of keeping constant rpm range around 1800-2000 and changing gears according to the desired speeds.

This owing to the engine's limited torque range and the desire to get better fuel efficiency.

Is there any long term drawbacks to this practice?

[SS-Traveller]

Originally Posted by ramzsys

...
Is there any long term drawbacks to this practice?

None that comes to mind. All engines are quite happy to run in the way you describe.

[CoolCarNi]

While approaching a signal or a traffic snarl, instead of downshifting gears I just bring it to neutral position, take my leg off the accelerator, slow down and then brake to come to a standstill. Am I doing right?

[a4anurag]

Originally Posted by CoolCarNi

While approaching a signal or a traffic snarl, instead of downshifting gears I just bring it to neutral position, take my leg off the accelerator, slow down and then brake to come to a standstill. Am I doing right?

Simple answer: No!

What you are doing is putting both your car and yourself in risk. What you are doing I'd called 'Coasting'

When you have the car in-gear but of the accelerator pedal the ECU cuts-off fuel supply and keeps the engine running by inertia so there are advantages:

1) You have power ready always, in case of emergency you can just step on the pedal, the car would move.

2) Less use of brakes due to engine braking do liber life if the braking system.
3) You save fuel as ECU doesn't send any to the engine.

So conclusion is, DO NOT shift to Neutral and glide. It is ultra dangerous as you have to grip / hold on the car (refer to point 1) in case of an emergency.

Anurag.

[CoolCarNi]

Thanks Anurag,
But I do this may be for 100 or 200 m and may be a few seconds... My concern was regarding what is the difference between downshifting and neutralising, if I may say so? Also, didn't get your second point.

2) Less use of brakes due to engine braking do liber life if the braking system.

[a4anurag]

Originally Posted by CoolCarNi

My concern was regarding what is the difference between downshifting and neutralising,

A few seconds can change many a things on our roads. Why be sorry at a later stage!

You'll be wearing you clutch too as you'll have to use it to shift from gear to Neutral and back to gear again.

Downshifting: This will give you engine braking to slow down the car without harming the engine or transmission (if done sensibly).

Neutral: This is coasting where the car is just a object with lots of energy. You have no power here (though the engine is running at idle RPM).

Originally Posted by CoolCarNi

if I may say so? Also, didn't get your second point.

2) Less use of brakes due to engine braking do liber life if the braking system.

Apologies for the typo. I'll put it correctly here:

2) Less use of brakes due to engine braking so better life if the braking system.

Anurag.

[comfortablynumb]

Originally Posted by CoolCarNi

Am I doing right?

Originally Posted by a4anurag

Simple answer: No! .

Related threads:

https://www.team-bhp.com/forum/techn...ing-right.html (Shifting to Neutral or Pressing the Clutch when Braking - Is this right?)

http://www.team-bhp.com/forum/techni...save-fuel.html

Cheers,
Vikram

[KkVaidya]

Originally Posted by a4anurag

When you have the car in-gear but of the accelerator pedal the ECU cuts-off fuel supply and keeps the engine running by inertia so there are advantages:

3) You save fuel as ECU doesn't send any to the engine.

Anurag.

You said the ECU cuts off fuel !! But then how would the engine idle without the fuel cut off at injectors?