[Jaggu]

Originally Posted by rajivr1612

Hi I have a few queries.
1) I have seen maxi cab drivers while braking shift to neutral and when the speed is reduced downshifting. Is this method correct?
2) my liva GD does not have a tachometer. How do I know if the engine RPM is low or in the power band?

1) Very bad way to drop speeds, when you are in neutral you are losing engine braking and hence loose bit of control also. Right way is to stay in gear and gently apply brakes, followed with smooth gear shift to lower gears as speed decrease.

2) Engine note is the only way to go, if its sounding gruff you are at high rpm. Or you need to make couple of reference with another Liva with RPM meter to understand the RPM ranges in each gear. Most often the feel/tone of the engine is good enough to make out the rpm.

[IndigoXLGrandDi]

I have read that shifting gears at higher rpms burn the clutch faster.
How is that possible?
The Clutch wear should be identical when the gears are shifted at 2 K rpm or 3 K-3.5 K rpm.
Am I not getting it correct?

[amitwiz1]

Originally Posted by dutta_d1

This is absolutely correct. The clutch is nothing but a slip disc. So if the clutch is engaged, both discs are rotating at same speed and hence, no friction. If the clutch is fully depressed, again there is no friction as the discs are separate.

But if the clutch is half pressed, both discs are partially in contact and rotating at different speeds which causes friction and wear.

So in that case cruising with the clutch fully depressed should actually cause no harm to the mechanicals ?

[zenren]

Originally Posted by dutta_d1

The clutch is nothing but a slip disc. So if the clutch is engaged, both discs are rotating at same speed and hence, no friction. If the clutch is fully depressed, again there is no friction as the discs are separate.

But if the clutch is half pressed, both discs are partially in contact and rotating at different speeds which causes friction and wear.

Originally Posted by amitwiz1

So in that case cruising with the clutch fully depressed should actually cause no harm to the mechanicals ?

Technically yes and practically no. When clutch is fully depressed while cruising, there is no wear and tear on mechanicals as the two rotating discs are separate. Since the discs are separated, the rotating speeds would be different between the two discs. Speed of one disc would depend on the speed at which the vehicle is moving and the speed of the other disc depends on the engine and gear combination. When you release the clutch under this condition, the two discs get connected back and would try to bring the other disc to its speed of rotation, causing wear and tear.

If you can make sure both discs would be rotating at same speed before releasing the clutch after cruising for a while, there shouldn't be any load on the mechanicals, but this is not that easy unless you can judge the speed of the disc connected to the wheel from the speedometer and the speed of the other disc from the tachometer.

Originally Posted by di1in

That sounds fair, but then what about the dip right after ignition?

Originally Posted by dutta_d1

My explanation is that initially it takes some more amount of fuel to start the engine from a stop. Once it is running good, the fuel can be reduced. This happens in case of any type of engine.

Regarding the initially increased RPM while starting that slowly settles down, I think this is programmed in the ECU for the newer engines to handle the cold start condition. The function of choke (depressing the throttle slightly to the optimal point for starting) in the old carb engines is built into the ECU for the newer MPFI engines. Hence the reason we see a slightly increased RPM immediately after starting (choke engaged) which gradually settles down to normal idling RPM (choke slowly disengaged)

I know I'm replying to an old post but still, let me see if my understanding is correct. If not, I'm sure the experts here would give the correct one.

[mooza]

Originally Posted by amitwiz1

So in that case cruising with the clutch fully depressed should actually cause no harm to the mechanicals ?

When you re-engage the clutch (release the clutch pedal) after the cruising, the clutch can get damaged if the vehicle speed is on the higher side for the particular gear.

For example, if you are cruising in the 5th gear with the clutch fully depressed at 110 kmph on the highway, and your speed gradually drops down to 90 kmph, and you re-engage the clutch (release the clutch pedal) at 90 kmph, you will notice the sudden effect of engine braking. This can surely harm the clutch, if done repeatedly.

On the other hand, if if you are cruising in 5th gear with the clutch fully depressed at 70 kmph, and the speed drops down to 60 kmph, and you re-engage the clutch, you will experience much lesser engine braking, and so the harm to the clutch will be relatively less compared to the above scenario.

I shift gears at speeds where I experience the least engine braking effect while releasing the clutch. Though one may not achieve the best power / torque bands with this practice, one can achieve longer clutch life. Take care not to lug the engine, though

[mashmash]

Good thread. I make sure the driver does not cruise in neutral or clutch pressed, that gives me a headache. I am ok when vehicle is constantly in gear, but frequent changes to neutral then gear then neutral then gear while cruising makes my head go round.

MaSh

[amitwiz1]

Thanks for the responses.

Originally Posted by zenren

Regarding the initially increased RPM while starting that slowly settles down, I think this is programmed in the ECU for the newer engines to handle the cold start condition. The function of choke (depressing the throttle slightly to the optimal point for starting) in the old carb engines is built into the ECU for the newer MPFI engines. Hence the reason we see a slightly increased RPM immediately after starting (choke engaged) which gradually settles down to normal idling RPM (choke slowly disengaged)

That seems to be right. This works in the same way in newer generation motorbikes too, the ones which do not have a choke.

[dutta_d1]

Originally Posted by zenren

Technically yes and practically no. When clutch is fully depressed while cruising, there is no wear and tear on mechanicals as the two rotating discs are separate. Since the discs are separated, the rotating speeds would be different between the two discs. Speed of one disc would depend on the speed at which the vehicle is moving and the speed of the other disc depends on the engine and gear combination. When you release the clutch under this condition, the two discs get connected back and would try to bring the other disc to its speed of rotation, causing wear and tear.

If you can make sure both discs would be rotating at same speed before releasing the clutch after cruising for a while, there shouldn't be any load on the mechanicals, but this is not that easy unless you can judge the speed of the disc connected to the wheel from the speedometer and the speed of the other disc from the tachometer.

That is correct. However, a little wear is tear is unavoidable. I was comparing the minuscule wear and tear between engaging the clutch from fully depressed and half-clutch riding. In my opinion, the benefits of the former (less fuel consumption, smoother stopping to a halt) outweighs a little wear and tear.

Of course, there is no point of free-clutch riding unless there is a potential stop or slowdown ahead (like seeing a red light or intersection ahead) in which case the clutch would have to be used anyway.

[anaraman]

Rehaan

The link does not work
Regards

Originally Posted by Rehaan

Hey Tom,


Read up about double clutching and what it does and how it works in this thread on double clutching.

Give it a shott and see if you notice a difference and let me know!

cya
Rehaan

[VSRK]

When I was learning driving, trainer advised me to depress clutch every time I apply brake and it became as habit almost. I was applying clutch while driving around corners, speed humps, B2B jams etc. But I came to know that it will harden the clutch and increase wear and tear of clutch. Now, I'm slowly unlearning that habit and already got rid of it 50% . Now-a-days, I do not apply clutch while turning corners (just reduce speed and lower the gear) and on speed humps. If B2B jam is on the flyover with down ward slope, turn to neutral and only use brake alone to stop and move the vehicle. However not depressing clutch during some situations backfires on two aspects 1) engine switching off if speed is too less not matching to the gear 2) causing more jerk on speed humps if clutch is not used.
Still trying to master this skill balancing only brake and gear without using clutch . Depressing clutch gives smooth ride over uneven terrains (pits and humps) as you can fine-tune the speed to great extent using clutch.

[lapis_lazuli]

Originally Posted by VSRK

turn to neutral and only use brake alone to stop and move the vehicle.

Why to neutral? Foot off the accelerator and just stay on gear.....this way you save fuel also (DFCO: Deceleration Fuel Cut Off) and utilize engine braking. Progressively downshift, to stop faster and you end up saving the brake pads too!

[VSRK]

Originally Posted by lapis_lazuli

Why to neutral? Foot off the accelerator and just stay on gear.....this way you save fuel also (DFCO: Deceleration Fuel Cut Off) and utilize engine braking. Progressively downshift, to stop faster and you end up saving the brake pads too!

While stuck in B2B traffic jam in downward slope of flyovers, change to neutral and use only brake. Releasing of brake will cause car to move (due to downward slope) and only apply brake if you want to stop. Thereby you need not engage clutch and gear every few seconds in B2B jam. As the speed itself will be less than 10Km/hr, one can easily coast safely .

[a4anurag]

Originally Posted by VSRK

While stuck in B2B traffic jam in downward slope of flyovers, change to neutral and use only brake. Releasing of brake will cause car to move (due to downward slope) and only apply brake if you want to stop. Thereby you need not engage clutch and gear every few seconds in B2B jam. As the speed itself will be less than 10Km/hr, one can easily coast safely

You can coast but you will be experiencing temporary brake fade as the usage of brakes is more causing heat build-up hence low braking effectiveness.

I'd suggest to stick to first gear and use the clutch +brakes so that engine braking is also available at all times. Since the engine is in gear the ECU will not supply fuel and you save the brake pads too.

No engine will stall (ECU has a anti-stall) feature that will prevent the engine from stalling.

Anurag.

[VSRK]

Originally Posted by a4anurag

I'd suggest to stick to first gear and use the clutch +brakes so that engine braking is also available at all times. Since the engine is in gear the ECU will not supply fuel and you save the brake pads too.
Anurag.

. Key here is whether to save clutch pad or brake pad or gear box. I use Foot brake and hand brake in balance so that brake pad doesn't heat so much. Moreover, in B2B jam, you will be applying brake only for 3-5 secs that too only light press and not hard. I try to use clutch only during change of gears and trying to avoid for other scenarios which we discussed.

[RiGOD]

While taking somewhat bigger potholes, I have a habit a downshifting to 2nd, pressing down the clutch and maneuvering through it (using half clutch and slight revving whenever necessary). Is this the right way to do the same? I always have a feeling that the engine would knock if I don't press the clutch while maneuvering through very bad roads low speeds.