In last week’s article, we differentiated between manual and automatic transmissions.
Sadly, we had no clear winner on which is best (because everyone has their opinion and taste), but, irrespective of your preference, how well do you know how to work whatever gearbox your car is equipped with?
Drivers of manual cars might claim to be the “real” drivers, but do they know of double-declutching, heel-and-toe shifting, engine braking, left-foot braking, power-shifting or “crash” shifting? Power peaks? Torque peaks? Shift points?
And before worshippers at the automatic shrine start pointing and laughing, do they know of kick-down? Engine braking? Shift locks? Economy runs? It gets worse for both sets of drivers if their cars are fitted with turbochargers, factory or after-market. Well, fear not. It is all broken down here for you.
In an automatic, it is as simple as selecting D and opening the throttle. A smooth take-off calls for gentle prodding of the right pedal. A violent or rushed take-off (coupled with a bit of wheel-spin) requires a cockroach-killing pedal-to-the-metal stomp on the hot pad.
As explained earlier, with a manual, it is a bit more involved. Depress the left pedal fully. Select First. Declutch slowly while gently throttling up. For a smooth take-off, a gentler and more skilful declutching is mandatory.
To burn rubber and screech off in a spectacular manner (accompanied by palls of smoke for powerful cars), depress the clutch fully, send the accelerator pedal all the way down and, with the engine screaming, lift your foot off the clutch pedal completely.
Teenage girls might be impressed by your style, but your mechanic will not — as you run the risk of burning the clutch mechanism.
Maintain your throttle foot in the position that best reflects your desired speed. To speed up, apply more pressure. To ease off, simply ease off the accelerator.
That is how it is done in an auto. In a manual, you will be required to shift up yourself when the revs rise and shift down when the revs dip. That is the obvious part.
What about when really ambling along, when a surge of acceleration is required, such as when overtaking or when escaping from an angry spouse? This is where we have kick-down in automatic cars and double declutching in manual.
Kickdown in automatics can be done in two ways: one is by simply flooring the accelerator. This applies if the gearbox was in a slightly higher ratio, such as when cruising.
Below the accelerator pedal is a kickdown switch that is clicked when the pedal is mashed to the bulkhead. The switch causes the gearbox to downshift, one of the few instances in which you can tell an automatic what to do.
If you were accelerating (meaning the box was in a lower gear), the other way to kick down is by “shift-lock”. Most automatic transmission gates have 2 and 1, or 2 and L just after D, meaning second and first (or low) gears.
When the lever is pushed into these positions, the gearbox is locked into those gears and will not shift up until the gear lever is slotted back into D.
So if you were accelerating in third and kickdown is not got by stomping the accelerator, pushing the gear lever into 2 or 1 will force the box to shift down, giving a more violent acceleration.
Gearing down in a manual is as simple as clutching, downshifting and declutching. Not always. A smoother downshift calls for a driving technique called the double declutch, better known as rev matching.
This is how it is done: when the need to downshift arises (when in need of more power), come off the throttle and depress the clutch pedal. Shift into neutral and declutch. Rev the engine. Clutch in again, select the lower gear and declutch for the second time, hence the name double-declutching.
This technique is common among drivers of heavy commercial vehicles, and was used before synchroniser technology came about. It can also work for upshifts, by the way.
The double declutch matches the engine revs in a particular gear to instantaneous vehicle speed. This prevents the vehicle from surging when the clutch is engaged in a lower gear.
Hill descent control
By ‘hill descent control’, I am not talking about Land Rover’s electronic toy in their Discovery, but referring to checking your speed when going downhill without necessarily applying the brakes.
Instead of conventional braking, engine braking is more pertinent — for two reasons: you do not want to slow right down anyway, and it will be gentler on the vehicle braking system, especially for Heavy Commercial Vehicles.
So, what is engine braking? Under power, an engine delivers force; when off power, the same engine now offers resistance; due to the compression stroke in its cycle (this will be explained elsewhere).
This compression resistance can be used to slow a vehicle, especially when gravity helps in increasing your speed. Lower gears offer greater compression resistance compared to higher gears, so engine braking works best with downshifts.
It is for this exact reason that automatic transmissions are manufactured with shift-lock options.
The downshift in an auto for engine braking is as simple as engaging the shift lock into whatever gear will slow you best.
Downshifting in a manual calls for the double declutch or yet another technique referred to as the heel-and-toe technique. Heel-and-toe is called that because those are the parts of your foot that you will use when applying this technique.
It is common in the world of racing as it saves time and economises movement of the driver’s appendages for maximum efficiency — and a possible world title.
This is how it is done:
When slowing down under braking, brake pressure is applied with the toe of your right foot. With your left foot, clutch in and shift down. At the same time, the heel of your right foot should tickle the throttle to raise the revs slightly.
Declutch immediately. It is a more professional form of rev matching, and works better than the double declutch in race situations, but it only applies if you were braking in the first place.
It is a hard technique to master (believe me, I have tried it with varying levels of success), but it mostly depends on vehicle design in general and pedal positioning in particular.
Engine braking not only controls your descent speed; it is also an aid to conventional braking. Braking force, which acts as resistance, is supplemented by the compression resistance of an engine on a closed throttle, thereby creating more stopping power than usual. In a manual, this is where the heel-and-toe would be perfect.
Sharpen your swords again, people, for here comes another myth-buster. Driving in neutral is not the best way to save fuel, irrespective of what your bus driver friends might insist.
If you want to use no fuel whatsoever when trickling downhill, simply come off the throttle completely while still in gear.
Automatic: Slide the lever into N or P, apply the parking brake and turn off the car. Neutral is neutral, we all know what that is, but Park locks the transmission into both forward and reverse.
You could safely park your automatic with the parking brake off, provided you put in P first. It won’t roll away. Anyway, vehicle design nowadays does not allow you to remove the key from the ignition if the car is in gear; you have to engage P or N first, even when it is off.
You will not be able to start it either unless either of the two positions is engaged. Manuals are funny. When coming to a dead stop, you either have to depress the clutch pedal all the way down or shift into neutral; otherwise your vehicle will stall.
This, by the way, is another way of turning off your manual car without using the key, but it is hard on the crankshaft bearings and should not be encouraged. Once stopped, apply the parking brake and turn off the car.
Now, there arises a small situation. We said an automatic can be safely parked without the parking brake engaged. What about a manual. What if you are on a slope, your parking brake does not work and you still have to leave your car? What now?
There is a way out, and it depends fully on the same compression resistance that slowed you down.
When your car is off, before releasing the brake pedal, shift the vehicle into gear, with or without clutching-declutching; it barely makes a difference anyway. Make sure the clutch pedal is in the fully out position.
Release the brake pedal and watch what happens.
This is what happens: the vehicle will move slightly before gently rocking to a stop.
This is because the engine spins until the first compression stroke is reached, after which it cannot continue turning since there is no power stroke the vehicle is off, remember? To understand what I have just said, see a later article (Engine Four-Stroke Cycle).
So there you have it: How to efficiently drive your manual or automatic car. How badly have you been driving yours?