Standardshift: ExtendedFAQ

Extended FAQ (FAQ 2.0)

Note: To see the FAQ 2.0 thread, please visit: http://www.standardshift.com/forum/viewtopic.php?t=3812

Downshifting

_{by jomotopia}

There are a few reasons to downshift:

1. You need to accelerate quickly, usually for passing.
2. You are going to slow down but not stop, and then re-accelerate, usually for a turn, or changing traffic speed.
3. You are going down a long decline, you can put it in a lower gear to have engine braking maintain speed without riding and burning up your brakes.

There are many different ways of doing just about anything in a manual, and this is especially true of downshifting. It's largely a matter of preference and driver style. The basic choices are:

• Rev-matched vs. non rev-matched
• Single clutch vs. double clutch
• What gear you are going to downshift to.

There are various situations that would call for a downshift, and every shift is different. Generally, quicker downshifts at medium to high revs should be rev-matched, while slower and lower downshifts, usually accompanied by braking, can be done without a rev-match if desired. Many people rev-match almost every downshift.

Many decisions will be based on your specific car and it's gearing and powerband. Below are some common situations and examples of how to handle them.

Cruising in 5th in the lower portion of your powerband and you need to pass quickly. You may have a little power down there but your real power is up higher and you need to go. You downshift to 4th (or maybe even 3rd depending on your car, speed, etc.). It is generally recommended that this be done with a rev-matched downshift in order to be quick and smooth, and avoid sudden engine braking and excess clutch wear. The process is outlined below:

Single clutch rev matched downshift

1. Off gas
2. Clutch in
3. Blip throttle (learning how much will be a process of practice)
4. Shift to lower gear
5. Clutch out
6. On gas

Double clutch rev matched downshift

1. Off gas
2. Clutch in
3. Shift to neutral
4. Clutch out
5. Blip throttle
6. Clutch in
7. Shift to lower gear
8. Clutch out
9. On gas

Now of course that's written as a list but it's been pointed out that you can't really think if it like a list of steps of what to do. Each one flows into the next and it's a very quick, smooth action. Especially numbers 3 and 4 from the single clutch downshift, generally you will blip the throttle and move the shifter at the same time.

Turning. You're coming up to a turn in 5th gear. Depending on your car and the speed of the turn, you will probably need 2nd or 3rd when you come out of the turn. You should try to finish both downshifting and braking before turning. There are numerous ways to achieve this. You can rev-match directly to the desired gear and then begin braking, intersperse sequential rev-matched downshifts with braking until you reach your desired gear, brake slightly early and rev-match into the desired gear after releasing the brakes and right before turning, or do a non rev matched downshift going to the turn as outlined below.

Non rev matched downshift (Recommended to be done at low revs, usually while braking)

1. Begin braking for the turn
2. When the revs reach a low level (idle to 1.5k or so), clutch in
3. Continue braking while you shift to the lower gear
4. Wait until you are just about to finish braking and then let the clutch out slowly and smoothly

Approaching a relatively steep downhill grade in 5th gear. At the top of the hill you can do a rev-matched downshift to a gear that will help you maintain a constant speed going downhill. Learning which gears for what grades will come with experience, but 4th is usually a good place to start.

Hand Brake Method

For starting on inclines

_{by JackBauer}

1) the hand brake method- Verrry simple. -You put the hand brake all the way up. -let go the foot brake -disengage clutch (push it in) -rev engine- like you usually would before taking off -let the clutch out till it gets to the catch point- at this point you will feel the car want to move -keep the clutch at the friction point when the car wants to move -let the hand brake all the way down -add a little or ease off gas- depending on how high the rpms are ( you know- just like you would when starting not from an incline) & let off the catch point. - your moving! and you didn't move backwards a single millimeter

Alternative to hand brake:

2) -right foot on brake- left foot on clutch - let out clutch to catch point -quickly move right foot from brake to accelerator & keep a constant rev -get off the clutch - let it slip real quick -add gas - voila

Speed Bumps / Humps

For a speed bump: 1. approach in 2nd 2. brake to very slow speed 3. clutch in 4. coast the front wheels over 5. now if still over 5mph slip the clutch a little in 2nd to creep the back wheels over 5b. if under 5mph drop it into 1st and do a "slow start" to pull the back wheels over

for a speed hump, you can probably creep over it with a little bit of gas in 2nd without ever clutching in.

Alternative: For speed bump (taken at much slower speeds than humps), slow down to almost a stop, shift into gear 1, and ease over it.

Also many people just approach the bump/hump, clutch in, and coast over it. Then grab 2nd or 1st depending on speed and go.

Why is my 1-2 shift so jerky?

_{by jomotopia}

The 1-2 shift is the most difficult to get smooth. This is because the change in gear ratio is the greatest of all the gears. The cause of the jerk will be different depending on your car and your shifting. When upshifting, the revs need to fall to the right level for the higher gear. On some cars, the revs fall very fast. On others, the revs fall slowly. The ideal is to catch the revs at the exact right spot.

You can tell whether the revs are falling too fast/far or too slowly/not far enough by the way that the car jerks when you engage the clutch. If the car jerks back, sending you forward in your seat, the revs were too low. If the car surges forward, pushing you back in your seat, the revs were too high.

If the revs are too high (falling slowly), you can do one or a combination of the following:

• wait longer for the revs to fall before engaging the clutch
• slip the clutch a little bit more to pull the engine revs down and smooth it out.

If the revs are too low (falling too fast), you can do one or more of the following:

• Shift faster. Try to get the car into 2nd gear quickly before the revs drop too much.
• Add a bit of gas when bringing up the clutch.
• Don't take your foot fully off the gas when shifting from 1 to 2.

Why is it so jerky when I let off the gas in lower gears?

_{by jomotopia}

This is perfectly normal. Because of the short gear ratios and direct connection between the wheels and engine, any modulation of gas is felt through the car. It is very important in a manual to be smooth and gentle on the throttle. If you are cruising in 2nd and dump the gas, you will feel a lot of jerkiness. Ease off the gas to smooth it out. When slowing down in a low gear, not taking your foot completely off the gas can help keep it smooth as well. The whole key is throttle manipulation and modulation. If you are coming from years of driving an automatic, this will be difficult and you will basically have to "reprogram" your right foot to be smooth and gentle.

Is it better to over rev or under rev a rev-match downshift?

_{by Prodigal Son, jomotopia, eaglecatcher, thepsyche35, grievre, Sypher}

• Prodigal Son wrote:

I'm trying to work something out in my head, so I though I would put it out there for the combined brain power of the standardshifters to comment on.

It seems to me, based on both logic and experience, that it is better to over-rev a rev match than to under-rev one.

Experience says that when I have over-revved one, a slight slow-down on the engagement is enough to smooth it out, whereas if I under-rev it, there is always a tug that gets transferred to the car.

Logic suggests to me the the engine, without gas, is trying to slow down, so the clutch can more easily slow it done by 500 RPM than speed it up by 500 RPM. In addition to that, the resistance that the engine provides in engine braking (usually attributed to compression, though I have seen that disputed) is acting to prevent the engine from speeding up, and is either neutral or assertive in helping it slow down.

The reason for my thinking along this line is that if it is correct, and given that exact rev matching is really hard to do, it would make sense to aim to slightly over-rev ones rev matches so that one almost always errs on the side of too high. I suspect that it what I do now -- just as a matter of naturally adapting my behavior based on what works. But with all this talk about technique, I'm now interested to work out if this is a valid principle that is worth passing on.

• jomotopia wrote:

i also think you are correct about aiming a little high for the rev match. not only because of the reasons you stated, but also to give the driver a little time to catch the right revs as they're coming back down.

• eaglecatcher wrote:

I think your 're right too. It's easier to slow the engine down, which you really won't feel, than to abruptly slow the wheels down, slowing the entire car, and its contents.

• thepsyche35 wrote:

I think it was IMboring who once posted that it would wear less on the clutch/drivetrain as a whole if you over-rev it because with an over-rev, the parts will be going with friction to slow the engine down, whereas under-rev will cause you to go against friction to make up the RPM difference, which one would think causes more wear.

• grievre wrote:

It's better to aim high, as when your foot is off the gas the engine is slowing down, and it's better for the clutch to be pushing the engine in the direction it already wants to go.

• Sypher wrote:

Over revving is better than under revving. It is easier for the clutch to slow the engine down because the engine originally wants to slow down when no gas is fed to it.

How do I move the shifter from one gear to another?

_{by jomotopia}

Examples for a 6 speed, left hand drive car:

Upshifts:

• 1-2: Pull straight down with a little pressure towards you
• 2-3: Push straight up, no horizontal pressure, the stick will center itself, straight up into 3rd
• 3-4: Pull straight down, no horizontal pressure
• 4-5: Up, right, up (or diagonally up and right, it varies by transmission)
• 5-6: Straight down with a little pressure away

Downshifts:

• 6-5: Straight up with a little pressure away
• 5-4: Down, no horizontal pressure so it centers itself, straight down
• 4-3: Straight up, no horizontal pressure
• 3-2: Down, towards you, down (or diagonally down and left)
• 2-1: If you must, straight up with a little pressure towards you

Double Clutching

_{by Johnf514}

Double clutching is a technique used most commonly on big rigs and manual transmissions without syncros. When you double clutch, you allow the transmission speed to sync up to the engine speed, which is what syncromesh gears do in most stick passenger vehicles.

Here's the process:

Situation - in 4th at 45 MPH at 2200 RPMs, downshifting to 2nd

1. Clutch in and hold
2. Shift into neutral
3. Clutch out
4. Rev to roughly 4400 RPMs
5. Clutch in
6. Shift into 2nd
7. Clutch out

Double clutching can also be used for upshifting, and therefore may not require the rev-match in step 4 if completed in a timely manner.

Slipping the clutch is bad, right?

_{by jomotopia}

Nope! The clutch is designed to slip. That is its purpose, and slipping the clutch is required for starting from a stop in 1st and reverse. The clutch smooths things out and reduces shocks through the rest of the drivetrain.

Any time the clutch is not fully engaged or disengaged when the car is running, it is slipping against the flywheel. As the clutch comes up and reaches the friction point it begins touching the flywheel, and they are spinning at different speeds. They must sync up and during this time the clutch is slipping. When it is slipping it is wearing. The clutch is designed for this purpose and it is designed to wear. But excessive and unnecessary slipping will reduce clutch life. Longer slips of the clutch and higher rpms produce more clutch wear.

It seems to be a general consensus on this forum that people worry about their clutch more than they need to.

Detailed explanation of clutch release (and why you don't need it)

_{by Prodigal Son}

The reason that your mother can still do it after 15 years, and can't explain how she does it, is muscle memory, which is a way of saying that the knowledge of how to do physical tasks (walking, shifting, releasing the clutch) gets transferred from the conscious mind to the cerebellum, which is the bit at the back of your brain that is responsible for all the things you do without thinking about them. The cerebellum never forgets. But it is not part of your conscious brain, so it can't express what it knows in words.

Now, why are you continuing to have problems? In a nutshell, your conscious mind is not letting go. You are thinking about it to much. The only way I know to help you with that is to really give you something to think about. So pull up a chair and get comfy and let's review every stage of the release of the clutch pedal, starting from when it is pressed all the way to the floor and moving all the way through until it is full engaged and your foot is fully off the pedal.

Stage 1: Full disengagement to the friction point As you begin to bring up your foot, you release a spring that pushes the clutch plate toward the flywheel. The point as which they first touch is called the friction point. The friction point is always at the same place in your car, no matter what gear you are in or how fast the engine in revving. (It may change slightly over time as the clutch wears, but too slowly to notice.) Not a lot happens at the friction point. You may hear a slight drop in the engine note. You may see a slight dip in the tach. You may feel a slight vibration in the clutch pedal. However. the car will not move.

Why does the car not move? Because there is not yet enough friction between the clutch and the flywheel to transfer enough torque to the wheels to overcome the inertia of the car.

You can complete step one as fast as you like as long as you do not overshoot the friction point. Once you learn where the friction point is, this step will be virtually instantaneous.

Step 2: Friction point to catch point As you continue to release the pedal, the pressure between the clutch and the flywheel increases until the friction is great enough to transfer enough torque to the wheels to overcome the inertia of the car. The car then starts to move.

So, where is the catch point? It depends. The catch point is the point at which enough torque is being transferred to move the car. Where that is depends on a lot of things. If you are on a hill, more torque will be needed to move the car than on flat ground. If you have four people in the car, more torque will be needed than if you were alone. On the other hand, the amount of torque available at the flywheel depends on how high you rev the engine. So, the location of the catch point is different every time depending on the weight of the car and the speed of the engine.

This means that you can't learn where the catch point is. You have to feel for it. Because the amount of gas you give changes the catch point, you can also move the catch point forward and back with the gas pedal.

You can't go too fast through this step because, although the car is not moving, you are feeling for the catch point. Over time you will get better at feeling it and you will be able to find it faster.

Step 3: Catch point to sync point When the car starts moving, the clutch is still not fully engaged and is still slipping against the flywheel. You have to keep letting the clutch out until the you reach the sync point, where clutch and flywheel are traveling at the same speed. As you do so, the amount of torque being transferred from the flywheel to the clutch increases, which means that the car accelerates. Just as with the catch point, you can change were the sync point is with the gas pedal. If you give more gas, the sync point will move outwards and the clutch will slip longer. If you let off the gas (or if you move the clutch too quickly, the clutch may sync up abruptly) causing a bump.

The sync point is also to a certain extent a function of time. If you hold the clutch above the catch point, the clutch and the flywheel may be able to sync up over time without you advancing the clutch. Not recommended, but the point is that the syncing of the clutch and the flywheel depends on time, pressure, resistance, and force. Things sync up when these things even out.

This also means that you can control the amount of acceleration you are getting by manipulating the clutch between the catch point and the sync point. This is often done to control speed while reversing.

This step must be done at a moderate speed if you want the clutch and flywheel to sync up smoothly without jerking. This can actually be done very quickly once you get the feel for it, but it has to be done more slowly while you are learning. Like finding the catch point, this is done by feel, and by a balance between the gas pedal and the clutch pedal.

Step 4: Sync point to full engagement Once you pass the sync point you can move to full engagement with your foot completely off the clutch. You can do this as fast as you like, since the clutch is already in sync with the flywheel. However, since you have to feel your way to the sync point, and the sync point moves depending on a bunch of variables, you can't simply learn one position where you can jump off the clutch. Once the clutch is in sync, you can jump off the pedal. Learn to feel for the sync point and then release the pedal.

So, what is the point of telling you all this? It is to show you just how complex it is so that you will accept that you can't think your way through the engagement of the clutch. You have to feel it. It's like walking over rough ground. No two steps are exactly the same, and if you think about what you are doing you are likely to fall flat on your face. But leave the job to the cerebellum, and you can walk over uneven ground without even thinking about what your feet are doing. Feel it, don't think it.

So, forget all that stuff, and all the other stuff people have been telling you and just do this: Release the clutch until you feel the car start to move, then use the clutch and the gas to accelerate smoothly until you feel everything hook up. Then get off the clutch.

That's it. Pretty soon your cerebellum will take over for you and it will all just be natural and will seem like a single quick motion.

Engagement Points and Clutch Feel

_{by CaliforniaZX}

There are many different clutches made by many different car manufacturers. Each car manufacturer has clutches that feel very exclusive to that brand. Clutch feel can be classified by Resistance (heavy vs. light), Travel (long vs. Short), and Engagement points (high vs. low). These three characteristics make different clutches distinguishable. People who have driven many manual transmission cars in their life time can testify to theses differences of clutch feel throughout their many cars, and even comment on how it has affected their driving ability.

When first entering a new vehicle (by new, I mean new to you) you must find out the characteristics of the clutch first before you begin driving. The first test you perform is simply depress the clutch all the way to the floor and come back up. Do this several times to get the feel of how much resistance you are dealing with, and also the length of the clutch travel.

The second test you perform tells you where the engagement point, or where the clutch catches, is. This test will be referred to as the no-gas launch. This test is also a good drill for new manual drivers to get used to their car's engagement point. To execute this test you would:

1. Depress the clutch and turn on the engine.
2. With the clutch still depressed, shift into 1st or reverse.
3. Bring you clutch up slowly until your car starts moving.
4. memorize this location, because that is where your engagement point is.

I find that It is easy to memorize this engagement point by comparing its relative position to you brake pedal and also the floor. In my Z, the engagement is about 1 inch under the level of my brakes. On the other hand, my friend's Si's engagement point is about 2 inches off the ground. Once you get used to all the three aspects of your clutch, you will be more comfortable with your everyday driving.

No Rev-Match Downshifting

_{by CaliforniaZX}

There are a few reasons for a no-rev match downshift:

1. You have already braked so much that your RPMs have dropped almost to idle and you are on the brink of lugging so you need to downshift.
2. You have not quite mastered the rev-matched downshift quite yet, but still want to get in the habit of downshifting before a turn.

The no rev-match downshift is pretty self explanatory but here are some pointers:

1. Make sure your revs are low enough to attempt to downshift without rev-matching. By low I mean from 1-1.5k.
2. When downshifting, hold the clutch in for about one second for the RPMs to drop a little more.
3. Do not dump the clutch, rather bring it out slowly, like you would a normal launch.
4. ALWAYS finish your shifts BEFORE you turn.

Here are some example scenarios:

A. You are traveling 30 miles in 3rd gear and approaching a 90 degree turn.

1. Start braking and wait for your rpms to drop.
2. Once your Rpms are around 1.5K clutch in and shift down to second.
3. Hold clutch in until RPMS drop to about 1k and let out.
4. Take the turn.

B. You are traveling 45 mph in 4th and you suddenly have to slow down to 30 because of a slow car.

1. Start breaking until your RPMs drop again to 1.5K
2. Again, once your Rpms are around 1.5K clutch in and shift down to Third.
3. Hold clutch in until RPMS drop to about 1k and let out.

Remember that Rev-match when your in doubt, but remember you do not always have to rev-match in certain situations.

What is Coasting?

_{by Sypher}

Basically, think of coasting like a roller coaster. The roller coaster moves by applying a force or building up momentum at the beginning and then from that point forward, it's basically brought along with it's own momentum. No other force is applied to it. This is same with a car. When you coast, you basically are adding no gas. you are moving along with only the momentum of the car.

_{Added note from CaliforniaZX}

Coasting should always be done in gear. Do not coast to a red light in neutral. In contrary to beliefs, it does not save you gas but rather eats up more gas then coasting in gear. This is because when you are coasting in gear the wheels are running the engines and the fuel injectors are shut off. On the other hand, when you are coasting in neutral, your engine is using gas to keep the engine idling. Coasting in neutral is also dangerous because you do not have any control of your car because your drivetrain is disconnected. So for safety and economy sake, please coast in a high gear like 4th, 5th, or 6th when appropriate.

Push Starting Your Car

_{by Johnf514}

It should be noted that push-starting a stick should only be done in an emergency or when you cannot jump-start.

1. Hold down the clutch and shift into 2nd
2. Start pushing up to a brisk walk
3. Release the clutch quickly; as you do, turn the key to "on"
4. The car should come to life, at which put you should floor the clutch and rev a bit to keep the engine going
5. Don't turn the engine off until you've been driving for a bit.

Good luck, and hopefully you won't have to use this.

Types of Shifting

_{by Victim}

Powershifting - Shifting with the gas floored, you need to be very fast, and skilled to do this. If you are, there is really no damage done to the drivetrain, if you only do it a few times, doing it all of the time, with a weak drivetrain can be hazardous. True drag racers that have fast cars also powershift, if they don't, they are giving up so much time trying to shift their cars, that they may even lose a few seconds off of their ET

Clutchless Shifting - Shifting without a clutch - Yes it is possible, and if you know how to do it, you are putting virtually no wear on the drivetrain

Double Clutching - When you take your car out of gear, let the clutch out in neutral, and press the clutch back in and go to the next gear. It is said to help lessen the wear of your cars syncros.

Heel-Toe - used when you downshift for a sharp turn, you press on the brake with your heel, and are hitting the gas pedal with the side of your shoe, revving it up to do your downshift... It is really good to accelerate through the turn.

What RPM in X gear at Y speed?

_{by jomotopia}

This gets asked a lot, and the answer is that it depends entirely on your specific car. It depends on the gear ratios, final drive ratio, and wheel/tire size. From the following site you can enter your car's gear ratios etc to get a general idea of speed vs RPM: http://www.car-videos.net/tools/speedrpm.asp

How Do I Improve My Gas Mileage?

_{by Prodigal Son}

The thought that strikes me is this: The efficiency of the engine is not the same thing as the efficiency of the car. In fact, the whole point of hybrid technology is to exploit that fact.

The efficiency of the engine, qua engine, is a measure of how much fuel it takes to produce a given amount of torque. At a certain RPM an engine produces the highest amount of torque for the fuel it consumes. What that RPM figure is will presumably vary depending on where the torque curve is in the engine, and probably other stuff as well.

When running at higher than its most-efficient speed, an engine consumes more fuel and produces less torque per liter of fuel used. But this does not mean that when the engine is running at a lower speed it also burns more fuel. At a lower speed, an engine burns less fuel, but it produces less torque per liter of fuel used, making it less efficient as an engine. At a lower speed it will still burn less fuel per hour of operation, it just won't be as efficient in terms of producing torque for the fuel consumed.

Hybrids (in my somewhat vague understanding) take advantage of this fact by trying to run the engine at its most efficient speed and using the excess torque produced to charge the battery. Since a regular car can't do that, trying to run the engine at it's most efficient RPM will sometimes involve creating torque you don't need and essentially throwing it away. The engine is at its most efficient; the car is not.

I have no idea whether the loss of torque per liter at a lower speed is ever enough to offset the lower lit re per hour of a slower engine (thus making it more efficient to run in a lower gear). Frankly, I'm scared of the math. And, of course, it will be different in every car. But I don't buy the general idea that you will get lower fuel consumption overall by running in a lower gear so as to keep then engine nearer to its peak efficiency --- not unless you have some mechanism, like a battery, for storing the excess torque produced for later consumption.

How much torque a car needs at a given moment is a function of what it is doing:

Coasting: The car requires no torque. You can coast down to stall speed in fifth, since the car requires no torque from the engine. (This is why some people suggest that it is better to coast in gear -- letting the wheels drive the engine, consuming no fuel -- than to coast in neutral -- forcing the engine to idle, which consumes fuel and produces unusable torque.

Cruising: The car requires relatively little torque. A hybrid can cruise the highway just as well as a more powerful car (except at really high speeds where torque is required to overcome high wind resistance). The hybrid engine is producing just enough torque. A regular engine is producing more than is needed, and essentially wasting it. Getting the engine speed down as low as possible helps, but IC engines have a limit to how slow they will turn, so you are almost certainly going to waste torque while cruising.

Accelerating: The car requires lots of torque, and the faster you accelerate, the more torque you need. Most engines produce enough torque to provide a particular amount of acceleration and essentially waste the torque that they produce the rest of the time. (People call a car ‘fast’ based mostly on its maximum acceleration rate; not its top speed.) Hybrids use the electric motor to supply additional torque for acceleration (though still not enough to please some folks).

You can decrease gas consumption by producing torque more efficiently and by not producing more torque than you need. If you produce torque efficiently but then don’t use it, your car will not be more efficient.

The chief ways you can reduce how much torque you need are by accelerating slowly and using high gears while cruising.

The chief way you can reduce the amount of torque you produce but don’t use is by buying a car with no more engine than you actually need for daily driving, or by buying a hybrid that stores the excess torque that your engine produces most of the time so that you can use it later.

Or at least, so it seems to me. Real mechanics may feel free to scoff.

What should I do when coming to a stop?

_{by jomotopia}

If you are definitely going to be stopping, there is really no reason to downshift. It's a common misconception amongst new manual drivers that you have to downshift through all the gears when you are coming to a stop. That is not the case.

There is one basic thing to remember: If you come to a stop without either shifting to neutral, or disengaging the clutch, you will stall.

The easiest, most common, and most recommended (from what I have seen on these forums) method of coming to a stop is:

-Begin braking in whatever gear you are currently in. -Leave the car in gear and continue braking until the RPM falls to around 1000. -Continue braking while you clutch in, shift to neutral, and clutch out -Stop.

How do Anti-Lock Brakes (ABS) work?

_{by GarySheehan and DW10+BE4/5L}

GarySheehan says: Here is an example of a tire's mu slip curve. The Y axis is the tires tractive capability and the X axis is the amount of slip between the tire and the road surface.

The curve relating to straight line braking is the Longitudinal Mu Slip Curve.

The far left of the curve is zero slip. So at zero slip, the tire has no traction. A tire needs to be in slip to generate traction.

The peak of the curve is the tire's maximum grip level, which occurs at a given amount of slip. A very good racecar driver is capable of modulating the brakes to keep the tire operating at or very near the peak of this curve. This is called threshold braking.

Once you exceed the peak of the mu slip curve, traction becomes unstable and the wheel rapidly slows down relative to roadspeed and locks up. This happens very quickly. It is not possible to modulate the brakes to have the tire stay in a given location past the peak of the curve. The tendency will always be towards lockup.

As you can see, as the tire approaches lock-up (towards the right of the graph) the tire's traction decreases. So a locked wheel/tire is much less efficient than a tire operating at the peak of its mu slip curve.

ABS operates in the range of slightly before the peak to slightly past the peak of the mu slip curve. When the ABS computer senses excessive slip (by comparing a given wheel speed to the wheel speed of the other tires), the ABS system releases brakeline pressure to the wheel with excessive slip to get it rolling near road speed again. The tire is now operating to the left of the peak. It then reapplies brake pressure until it senses excessive slip again and repeats the cycle. Many times per second. So ABS keeps the tire operating around the peak of the mu slip curve, but does not maintain at the very peak of the slip curve.

The more sophisticated the ABS system, the closer it is able to operate at the peak of the mu slip curve.

DW10+BE4/5L says: The slip-mu curve, as in friction coefficient as a function of slip, depends heavily on the surface. On loose gravel and snow the greatest friction, or longitudinal force, is reached when the wheel is locked. This is because the tire deforms, i.e. digs into, the surface. IIRC, on ice the best grip is at low slip rates. Concrete and asphalt are somewhere in between.

To achieve the best braking force the ABS system should know the slip-mu curve of the surface which it of course doesn't. The ABS compromises over maneuverability and braking force.

The software of an ABS system is a closely guarded secret of its manufacturer (Bosch, Teves, Denso to name but a few). Even car manufacturers don't know what goes on in those black boxes which they just plug in. Writing such software is a tricky business because you also have to consider what happens when the friction level at the left side differs from that at right (the car might spin rapidly).

My guess is that depending on the ABS system and on how (un)lucky you happen to be, it's possible to stall the engine. In my experience (don't know whose ABS and which generation) the ABS first uses a slower cycle. It probably somehow measures the friction during the slow cycles. So if you disengage the clutch during this time the engine just might stall presuming both driven wheels are locked at the same time.

Braking with a 4WD car is more complicated because the three differentials may distribute the braking moments in many more ways than is possible with one differential.

The best way to emergency brake is IMHO to floor the brake pedal first and then worry about the clutch. If you first depress the clutch you will lose precious time that you could use to start braking. If the engine stalls you will lose power steering if it's hydraulic. I'm not sure if you will also lose brake boost during ABS braking. It depends on the system I think. In most cases there is an electrically driven hydraulic pump that restores the brake pressure during each ABS cycle, so I guess it doesn't lose the vacuum used to boost the brake pressure even if the engine is stalled and isn't generating any suction.

The best way to avoid an accident depends on the situation of course. It might be best to hit the clutch to give the best side force for steering. or it may be best to brake as hard as you can.

Quote: By hitting the clutch at the same time as the brakes, you will lose your engine braking (though only a slight amount anyway) plus your drive wheels are no longer active and you can lose traction.

The braking torque of the engine is negligible compared to the torque of the brakes. The brakes always win even in 1st gear. And you are trying to slow down so I wouldn't worry about traction. The best thing about depressing the clutch is that the car handles better because the engine isn't braking and thus consuming precious side force of the tires or producing yawing moments. People, including me, tend to instinctively let go of the accelerator when their car starts to slip sideways. Usually this just makes the slipping worse.

I think that the ABS is at its best when a n00b like me notices too late that he should have taken that turn to the right, steers to the right, hits the brakes because he's going too fast, locks the wheels and slides to the snow bank in the corner but luckily doesn't hit any of the traffic control devices and avoids any damage at all. Been there, done that. In a van without ABS.

Heel-Toe Downshifting

_{by jomotopia}

The purpose of heel-toe downshifting is to get into the proper gear for a turn while braking continuously.

A situation where you would use it is if you're coming up to a turn that you normally take in 2nd gear, and you are in a higher gear. So for example, if you are approaching the turn in 4th gear, you can heel-toe downshift either directly to 2nd, or sequentially to 3rd and then to 2nd. The goal is to brake smoothly and constantly while you downshift, and finish both downshifting and braking while still moving in a straight line before entering the turn.

Then you are in the proper gear for the turn, you can release the brakes and turn in, and accelerate out of the turn.

Heel-toe is not a required technique, and some consider it advanced or really only for racing. In my opinion, if you get proficient with it, it is very useful on the street.

The way you execute a heel-toe downshift is as follows:

1. Begin braking
2. Clutch in
3. Downshift and blip the throttle, while still braking(*)
4. Release the clutch.

(*)This is the tricky part. You are already using your right foot to brake. In order to blip the throttle, you need to use part of your right foot to apply steady brake pressure, while using another part of your right foot to blip the throttle. The parts of the foot that you will use will depend on your car's pedals, your feet, and your preference.

It doesn't have to necessarily be your heel and your toe, although the classic way of doing it is braking with the toe, and blipping the gas with the heel.

Many people prefer a side/side method, using the left side of the right foot, or the ball of the foot, on the brake, and blipping the gas with the right edge.

I have also heard of people using their heel on the brake and toe on the gas.

You want to raise the rpm to what it will be in the next gear, however you are continually slowing down because you are braking, so the rpm you aim for keeps dropping. It will require a much smaller blip than a rev-matched downshift done at speed.

The most important thing in a heel-toe maneuver is the braking. When learning make sure there is nothing around for you to hit if your foot were to slip off the brake pedal.

Some cars are harder to heel-toe than others, depending on the relative height of the gas and brake pedals, and also how close together they are. The shoes you are wearing can also play a large part.

You will most likely over rev most of the time for a while, but an over rev is easier on the car than an under rev.

The Basics to Driving Stick - A Beginners Guide

_{by Hatchman}

1) On launches

• give it enough gas but not too much
• do not release the clutch too fast
• if you've started the launch and feel you've given too little gas or brought up the clutch too high, clutch in partially and increase the gas a tad
• lingering at the FP is necessary on launches

2) On 1-2 shifts

• no need to rest your foot on/just above the clutch anticipating the shift; get into the habit of resting the left foot on the dead pedal
• do not shift too early; take advantage of 1st gear's quick take-off capabilities
• get your hand off the shifter between shifts
• don't release the clutch too fast; linger at the FP briefly

3) Slowing

• choose 2nd gear and use the gas pedal to negotiate speed bumps and driveways/driveway entrances
• if no-gas downshifting from 3 to 2, be sure you've slowed enough in 3rd, but not slowed too much, before clutching in, shifting, and clutching out; always clutch out slowly on these shifts
• if rev-matching (for shifting on the fly) don't wait too long to release the clutch after the blip
• try to anticipate 2nd gear corners and complete the shift before the corner, while in a straight line

4) Stopping

• no need to shift to neutral when at a stop sign; while coming to the stop, with the clutch down and brake applied, go directly from previous gear into 1st

5) General

• try to avoid shifting while negotiating significant bends in the road; concentrate on steering/control; if you need 2nd or 3rd for bends, get into the gear before the bend

What to do in an Emergency Stop

_{by SteveUK, Prodigal Son}

SteveUK wrote: Emergency Stop with ABS. Press the brake as hard as you can and keep your foot on it. Both hands on the wheel. Foot on clutch at last possible moment to prevent a stall.

With this way you get the full ability from your brakes, plus some passive engine braking. You will be able to steer around obstacles.

Emergency Stop without ABS. Press the brake as hard as you can. When you feel the wheels locking up, release then instantly back down on the brake. Repeat until the wheels no longer lock. Both hands on the wheel. Foot on the clutch at the last possible moment to prevent a stall.

You will have less control during steering because you cannot "pump" the brakes as quickly as the ABS system can.

Thing you must not doNEVER change down (downshift) in an emergency stop. You are not in full control of your car when you need to be in the most control you can be.

I have 12 years of manual driving experience, plus my racing licence, my advance driving licence and my pursuit driving licence. I have to have a formal 2 week requalification every 12 months and a at least 4 refresher days in that 12 months.

There is a link in another topic (http://www.2pass.co.uk/video.htm) about the UK driving advice. In that there is an emergency stop. Yes, it is for the test, however, this is one move that you will always do the same whether it is in your driving test or not. Driving on a race track is completely different to driving on a public road.

I am in far more danger in my job than when I am on a race track. I have to take in to account other motorists, pedestrians and other things also. I drive at my limit, but NEVER past it. I don't want to kill someone or more importantly me! The average driver (so 99% of those here) should do the following.

ABS - Stomp and Steer No ABS - Pump and Steer

Prodigal Son wrote: Unnecessary elaboration will get you killed. Modern brakes are very good. In an emergency, keep it simple: brake and steer.

How to Handle Hills

_{by jcprov21}

Well you will meet a hill at once in your life, and I can tell you. You are terrified of them when you first start out right? Well that's normal. My tip for this is simply, find a deserted hill where you don't have to worry about rolling back and hitting someone, and learn to, without e-brakes or other techniques, quickly getting the car going, the quicker the better, this is provided that you can start on a flat surface very well. The trick is to be ready, stop in 1st gear hold the clutch down, after the stop, super quickly get that clutch out to the FP while adding gas. It's just like a normal start, just done at 10 times the speed. Really, It's like chirping the tires on a flat surface, just do it super quickly and you will be good to go. Remember, the first time may not be so pretty, but with enough times, the hills of San Francisco will be a joke. Some people will cry and tell you it's impossible, but it's not, I did it, without any e-brake or other assorted technique. Just learn to do a super quick start. Hill fear will be a thing of the past.

Does revving my engine up hurt it?

_{by jomotopia}

No. It doesn't. Your engine is designed to operate in any range below redline. As long as your car is well maintained (keeping up with oil changes, not running low on oil or coolant, etc) revving your engine up will not hurt it. It will burn more gas, and will put a minimal amount of added wear on the engine, but this wear will be negligible in the grand scheme of things.

Even if you rev past the redline, you will hit the rev limiter. The rev limiter is designed to prevent engine damage from revving too high. So even hitting the rev limiter will not hurt your engine, just don't go bouncing off of it repeatedly.

The only thing that is really worth worrying about as far as actually damaging the engine is a forced mechanical over-rev by shifting into too low of a gear for your current speed. In this case the rev limiter can not help you.

How do I know if my clutch is worn out/nearing replacement?

_{by jomotopia, scionkid}

jomotopia wrote: You may notice the engagement point moving higher in the clutch pedal travel as the clutch wears out. But until the clutch is actually slipping when fully engaged, you don't need to replace it.

There are a couple of tests you can do to determine if your clutch is worn to the point of needing replacement:

1> Get moving and put the car in 3rd gear or higher and low rpms, where you normally do not have enough power to accelerate quickly. Floor the gas. If the revs shoot up but the car doesn't go, you need a new clutch. If the engine bogs and the revs raise relative to the car's acceleration, your clutch is fine.

2> From a stop, put the car in 3rd gear or higher and drop the clutch. If the car doesn't stall, you need a new a clutch.

scionkid wrote: Go to a freeway on ramp doing about 10 mph. Have the car in 3rd and floor it until it reaches maximum speed in that gear. If the clutch slips, you'll hear the engine noise go up unproportionally to vehicle speed. If that happens, start saving up some money for a new clutch.

I don't agree with the 5th gear clutch drop because the engine may not be making enough torque for a bad clutch to slip. But you won't know the clutch is, indeed bad, until you go up a steep hill with no power to go up and no room to hang a U turn.

Full throttle and short shifting for fuel economy

_{by scionkid, Standardshifter, Prodigal Son, Johnf514}

scionkid wrote: Generally, the less power you use to accelerate, the more fuel you'll save. There are 2 ways to limit the engine's power output. The universal way is to tread lightly on the throttle and this limits the amount of air an engine can aspirate. The 2nd way is to use a high gear and WOT. Since the high gear limits engine speed, this limits the number of air intake.

The theory is that WOT is somewhat more efficient because the engine doesn't have to burn extra fuel to suck in air through a small throttle opening. However, it burns more fuel per engine revolution, which means more heat is transferred to the cooling system, and you need to keep an eye out for the temperature gauge.

I can see my mileage go from 31 to 33 using the short shifting and WOT technique. And I don't go WOT during shifts. I ease off the throttle, double clutch the shift, let the clutch completely out, then go deep on the throttle. Even when I go WOT, there's not much power going through the transmission because the engine speed is quite low.

Standardshifter wrote: Ideally, WOT and short shifting will give best mileage. Most cars switch to set fuel tables that usually are a bit richer than the feedback loop model at part-throttle, so real-world mileage might not reflect the savings.

Prodigal Son wrote: Yes, it's an interesting theory, but as you say, not necessarily applicable in practice. There are all sorts of factors that make it a less than practical or economical practice in the real world. Like for instance, traffic. And then there is the consideration of what happens if you try to go WOT in first. Burn-outs are not necessarily efficient. And how do you shift in a smooth and equipment-preserving way at WOT? If you blend the throttle in and out to achieve a smooth shift, there goes your WOT. If you bang the shifter through the gates to get a quick shift, there go the synchros. The stuff you are wearing out (and potentially breaking) will probably cost more than the gas you are saving.

The thing is, when it comes to optimization, you have to look at the system as a whole. You do not optimize a system by optimizing the individual components of the system. You have to look at it as a whole and configure each component in a way that contributes to the optimal performance of the system as a whole under real world conditions. This frequently means that the individual component is not optimized for its own most efficient operation.

Not only does economical driving require a systems approach to optimization, economy is also part of a broader systems calculation that factors in safety, comfort, convenience, and time along with economy in the design of both cars and roads.

Johnf514 wrote: Some folks promote WOT short-shifting, which essentially consists of using full throttle and shifting very quickly at low(er) RPMs. In theory, this is a great idea, as it minimizes or negates any pumping losses or inefficiencies that come from accelerating. However, it is absolutely impractical and nearly impossible in everyday driving, and most things don't as work well in reality as they do in theory. Instead, I recommend accelerating slowly and shifting early. Usually between 2000-2500 RPMs will yield good MPG.

How do higher RPMs affect engine output and wear?

_{by mdocod}

RPMs do not translate *directly* to wear. overall work load does. Work load includes the work required just to turn over the engine. (an engine idling, is a work load, but it is a very small work load)...

Best thing I can do to explain this... is to give an example: Lets say you are pulling a long steady hill. At 45MPH the engine may be capable of chugging along in 5th gear (throttle wide open) at lets say 2000RPM. The car is able to maintain a steady pace but you are loading every stroke of the engine with as much air and fuel as it is designed to take, this produces powerful combustion strokes that transfer a lot of force to the crank per revolution. The engine is turning slowly so the number of strokes is less. In contrast, you could down-shift to 4th and pull the same hill at the same speed around 2400RPM.... but now you can ease back on the throttle because the engine does not need to load every stroke of the engine to the max to do the same amount of work. More strokes means each stroke can do less work but add up to the same total work as was being accomplished beforehand. The strokes in this state are gentler, they are not pressing as hard on the crank.

So... if all things were created equally- it could be said that in either case, the engine wear would be almost exactly the same. But the reality is that some engines have different "sweet spots" than others. Some engines have very specific "power bands" that should be used when pulling a hill or accelerating because they will deliver the best power for the least fuel used and do so with minimal engine wear. Large over-the-road trucks with massive diesel engines that can produce insane torque(over 1000lb/ft), will benefit from the selection of a lower gear to pull a hill (1600rpm with less throttle compared to 1400rpm wide open throttle) spinning that engine slightly faster, but reducing the force on the crank and associated bearings is much better for that type of engine. (keep in mind redline on many of those engines is 1800-2200rpm depending on the engine)