Wednesday 30 November 2011

Gear shift in "time" the engine & difference in car oils


The gear ratios are a means used by vehicle manufacturers to provide the same torque than the torque that is supplied by the engine. If have you heard the phrase "the engine is the heart of the vehicle" it is time to know that, by this point of view, "the gearboxare the muscles of the vehicle"
Neutral x clutch driven
All torque and rotation in a gearbox is supplied by the engine, so the "speed entry" in a mechanical transmission is the spin that we read when we look at the tachometer.
Come on a little better analyze the behavior of the engine and gearbox, through two simple experiments:
1. With the engine on and the vehicle in neutral exchange, take a quick 'nudge' in the fast with your foot and watch the engine roar and the highest of the tachometer pointer to swing to a higher markup and then back to idle, something around 1000 rpm. As the vehicle is stopped with the exchange being in neutral, just watch the motor spin faster without any effect on vehicle speed, which remains stationary.
2. Step on the clutch and engage first gear. Keep stepping on the clutch and repeat the 'nudge' in the accelerator, as above, and note again the behavior of the motor and tachometer. Again we note that the engine roars and stronger than the tachometer indicates a rise in the engine and then back to idle speed.
Relatives in both experiments to the same thing, to accelerate the vehicle remains stationary, the engine spins increases and nothing else happens, so the exchange-motor behavior is exactly the same.
Before starting to agree with the above statement we have to stop and think a bit, let's draw a parallel between the two experiments using the clutch and exchange scheme to help us:
Power flow showing how the movement is transmitted by the disc is transmitted to gearbox
  • Exchange in neutral:
    • The engine is running and clutch engaged
    • The rotation of the engine passes into the clutch disc and on to the pilot shaft of the gearbox
    • The pilot shaft is always engaged with the counter shaft, so when the pilot shaft rotates, the counter-shaft also rotates.
    • All counter-shaft gears are meshed with their partners on the main axis, so if the pilot shaft rotates, the counter-shaft and also rotates with it, all the gears that are in the main shaft.

  • Exchange coupled with the clutch thrown:
  • The engine is turning and the clutch is disengaged.
  • The motor rotation is not transmitted to the clutch disc and therefore the pilot shaft remains stationary, without turning.
  • As the pilot shaft does not rotate when the vehicle is stopped, no other components of the gearbox turns.
  • Of course you noticed it is much easier to get the engine rotation when we set foot on the clutch pedal while the exchange coupled or not, and the explanation is quite simple: with fewer components to rotate, therefore, more income, the motor increases the rotation soon. This is due to resistance offered by the disc clutch, axles, gears, bearings, bushings and even the oil exchange to spin, consuming power of the engine when the clutch is engaged.
    Therefore, "when starting the engine, hold the clutch pedal pressed.This will cause the game is faster and more efficient. "

    Motor rotation speed of the vehicle x

    We have seen as keeping the clutch thrown allows a departure "softer" the engine. We now understand a very simple way, how the different gear ratios in an exchange may no longer be a nuisance in the act of changing gear and give us pleasure to drive.
    We now understand a very simple way, at some point in our learning the art of direct spend by the situation, when engaging a gear, the vehicle leaves the 'hopping' with the engine almost 'erasing'. At the other extreme reductions in sudden motion, causing the passengers almost hit his head on the windscreen with the engine speed increases too, with little to damage it. Fortunately, over time we learn to avoid these situations in an almost automatic, without realizing what actually are we doing to prevent them.
    Let's look a little diagram of a mechanical exchange:
N ote that the spindle motor shaft to enter the pilot in gearbox undergoes a first reduction to be transmitted to the counter-shaft. This joint pilot / counter shaft is called the "pair of input." The counter-shaft transmits the rotation axis received from the pilot, with less speed as the engine, the gears of the main shaft. Each of these gears have different speeds. The largest, such as first gear or in reverse, rotate more slowly but transmit higher torque. The smaller gears, as the 4 th and 5 th spin more quickly, albeit with less force. That for us, day by day, is intuitive. We know we need a little more speed and strength to come out with the vehicle than when they're on a motorway and we want to 'take off'.

Clutch Function

The function of the clutch is something more than stopping the flow of power from the engine to the transmission. It allows you to make soft couplings avoiding jerky when driving. The most critical situation is to use the clutch when we left the vehicle at rest. Let's see why. The vehicle is stopped, so the exchange is not transmitting torque or rotation to the drive shaft. Engage first gear, we release the parking brake and we slowly accelerating the engine while you release the clutch pedal, so that the vehicle departs.
The flywheel rotates at approximately 1000 rpm at idle. When we release the clutch pedal, we are making the hard 'lean' on the wheel and go home, without rotation, to achieve the same speed as the wheel.Means that the disk has to be achieved, from scratch, about 1500 rpm for the vehicle to start its movement and this is all done by the friction between the face of the disc and the flywheel face.
The disc always comes late in relation to the wheel and while not match their speed, there will be slipping and 'burning' clutch, wearing it, often followed by the distinctive smell of 'burning clutch. "
L ess obvious but equally damaging, every time you change speed, especially in the shift, to compensate for these variations, the clutch 'patina' and wears away. This can be seen easily through the heat generated by it.

Synch

Same way as the clutch, the synchronized rings are also submitted to each gear change. This is due to the fact that in order to engage a gear with any moving vehicle, the rotation of the gear they want to engage must be stabilized in the same rotation of the gear when the vehicle was before starting the process, so we employ the term "sync", or "spin the same speed." synchronized rings act as brakes and the wear is proportional to the difference in speed between starting and running gear that is intended to engage, represented in the figure below the main shaft .
And sforce exaggerated on these rings, such as coupling the exchange after leaving the vehicle in "toothless" or err in the selection of a march as when accelerated to engage 5th and by mistake, hook the 3rd, can make these rings merge. Usually the cost of this type of error goes beyond the simple exchange of synchronizers, often involving breaches of shafts and gears.

Dual disengagement: the professional engagement

F alarms using the double disengagement us back to the old exchange is not synchronized. Imagine that such exchange would not admit mistakes, not knowing if the driver engages a gear on the 'time', there was the characteristic noise of scraping, as when the defendant engaged hastily, and may even damage the exchange, being necessary to take it apart to fix it . Less serious errors were sufficient for the driver needed to stop the vehicle and start all over again.
The inda Exchange today there are designated by the generic name of "Constant-meshed" using this principle, are usually employed in heavy exchange that travel primarily on highways. These are very robust exchange with very high reliability but require technical professionals to operate them.
Despite all this, nothing prevents us to use this same technique on a daily basis to enhance performance driving light vehicles and sincronizados.Vamos explain, then, how to apply the dual disengagement.
  • Reduction gears, vehicle in motion:
  • Take your foot off the accelerator
  • Step on the clutch pedal and put the shifter in neutral
  • Take your foot off the clutch pedal
  • Accelerate the engine to the proper rotation to new gear
  • Step on the clutch pedal again and engage the new gear

V masters understand well what we did. You may have noticed that by reducing a march to the moving vehicle, two things occur:
  • The vehicle slows.
  • The engine speed increases.

I magine this: you're driving on a highway at 120 km / h in 5th gear. In this hypothetical situation, the tachometer to 3500 rpm mark your vehicle. Its intention is to reduce to 4th gear and of course, would be great if there were no leaps or any discomfort in this operation. How to proceed?
W e must bear in mind that when we reduce the running, the vehicle tends by its inertia, continues at the same speed it was, therefore, the vehicle will 'want' to continue to 120 km / h. As the 4th gear is more 'reduced' to the 5th gear to keep the same speed, the engine needs to provide more rotations. This explains why the engine 'roar' when we strongly decreases abruptly.
I n accordance with the maximum comfort in this situation, all we have to do is memorize the necessary rotation to the engine, to maintain 120 km / h in 4th gear. Let's say that by doing this test we found that the engine has to provide 4000 rounds, so refining the technique of dual disengagement explained above, for such a vehicle under the conditions described, we have:
  • Reduction gear, vehicle moving at 120 km / h in 5th (3500 turns):
  • Take your foot off the accelerator
  • Stepping on the clutch pedal and put the shifter in neutral
  • Take your foot off the clutch pedal
  • Accelerate the motor to the rotation of 4000 spins (rpm)
  • Stepping on the clutch pedal again and engage the 4th gear
  • Release the clutch pedal

V masters explain: When we took the foot off the accelerator, the car stops accelerating and continues traveling at the speed it was, in the case of 120 km / h, by inertia. We can not take much at this stage because the tendency is to lower the engine rotation, 'holding' the vehicle.
W hen embragem stepped into first, release the motor vehicle and we have two effects:
  • the vehicle is free and remains longer at the pace was due to inertia because it has to 'win' the engine, e. ..
  • facilitates the release of the motion to put the shifter into neutral.

The take away your foot from the clutch pedal, the engine and begins to transmit the rotations into the exchange quite easily because, with the shifter in neutral, all the torque is only used to rotate the gears. The vehicle continues to move by inertia.
N the above condition, when the motor to accelerate the rotation of 4000 turns required to 4th gear to keep the vehicle in inertial speed, we are matching the rotation of the output shaft of the exchange with the major axis of rotation provided by the counter shaft.
In the we step on the clutch again, turn off the engine to do the exchange coupling gear safely, preserving the shifter and clutch damage to operational errors that could commit to engage the 4th gear.
N ote that this whole process takes only a few fractions of seconds to complete. This explains why the inertial speed of the vehicle remained virtually constant during the operation.

Marches upward

The elevating the gears, for example, from 3rd to 4th gear is also convenient, although not necessary for light vehicles, the use of this technique. This is due to the fact that the engine to climb the gears, need less spin than it had earlier in the march. Light vehicles in the fit is almost automatic, but the following variation on the technique is advantageous:
  • Marches upward:
  • Take your foot off the accelerator
  • Stepping on the clutch pedal and put the shifter in neutral
  • Take your foot off the clutch pedal
  • Accelerate the engine being careful not to exceed the safety limits in mind spins (rpm)
  • Stepping on the clutch pedal again and shift to
  • Engage the crank up
  • Release the clutch pedal

A s the rotation has to fall you will not feel any discomfort in this type of operation. Of course in commercial vehicles using this technique is mandatory because the 'weight' of the vehicle causes the engine speed drops very quickly below the required rotation to gear engaged itself in step 1 (take your foot off the accelerator), forcing increasing speed for the coupling even in marches upward.

Advantages in using this technique

The race, if we switch gears to change the 'time', using the dual disengagement means that the rotations of the beginning and end of engagement will not have significant difference in rotation, so as far as the clutch synchronizer rings will suffer a shortfall minimum, greatly increasing the useful life of these components.
Can seem somewhat daunting to drive in this way, but with a little practice can have the advantages of its use in everyday life. The following chart will help in understanding the same:
this graph represent the vehicle speed on the horizontal axis and vertical axis, the rotation of the engine.The horizontal line represents the 3000 turns the torque of the engine, that information can be obtained from the vehicle owner's manual.
The line represents a spins at 4500 engine rpm above which can not accelerate otherwise damage it. Each line represents a diagonal movement of the vehicle, as identified. Let's do a little exercise for understanding the dual disengagement using the same example we gave earlier:
  • Find the speed of 120 kph on the horizontal axis
  • Puche a perpendicular line across the length of the height of the graph
  • In the place where crossing the line of 120 km per hour under the line representing the 5th gear, look at the scale of the left (rpm) which required rotation for the motor to achieve this speed in 5th gear, or 3500 turns.
  • Rising a little in the line of 120 km / hour to cross the line for the 4th gear, found in the range of rpm, where the rotation required to achieve that the engine speed in 4th gear and 4000 rounds found.

Be easy to understand that, by reducing from 5th to 4th, at 120 km / hour, we have to raise the engine speed with the shifter in neutral, from 3500 to 4000 turns. The same reasoning should be employed for the other gears and speeds.

Chart sawtooth in practice

The evolution of the vehicle speed relative to engine speed, in the same way, is linear, ie if we are 20 km / hour in a certain rpm, doubling the speed will double the speed.
So this is quite easy to build graph "sawtooth" for any vehicle that has a tachometer, for this part and help out a friend for a ride in his car, armed with pencil and paper:
  • In each gear, accelerate to achieve a particular spin that does not force the vehicle, in our example, about 3500 spins
  • Note the speed for each gear

T ermine the ride, turn on the computer and plot the chart in the following steps:
  • From the cell "H5", start with zero and increment each cell along the same lines, from 10 to 10 km, the maximum speed that your car reaches or you think you can achieve.
  • From the cell "G6", vertically, enter "1st gear", "2nd gear," and so on until the last march, in our example, the transmission has five gears.
  • In cell "H6", enter the formula "= Int (5 * $ H $ D6)
  • Copy this formula to the range [H6: X10] X10 because in the example we considered the maximum speed (160 km / hour)
  • Insert a line chart type and enter the data range between [G5: X10]
  • You should get something like shown in the figure above, if you prefer, download the spreadsheet example. The link is at the end of this article.

Precautions

The cost of repair of an exchange is quite high and its proper use will cause you never have to do any maintenance other than periodic oil change, for a very reasonable time.
O ne must take every precaution that is: always use the clutch on gear changes. Remember the experiments we did in the beginning of this article? If you do not disengage the clutch during a gear change and commit some sort of error, it will be the Synchronizer attempts to make the motor rotate in accordance with the speed of the gear that you want to engage, and we agree, there is no synchronizer that resists this.
The above statement may sound funny, but it occurs with very high frequency when we substitute the word "if not disengage the clutch" by "is not disengage the clutch perfectly with problems in their operation."Therefore it is important to have the clutch working, and well, since its cost is only a fraction of the cost of maintaining an exchange.
Finally, just try the technique described here is at ease in driving his vehicle. This technique should be used at your own risk and we do not advise beginners to use it.

What is Oil and Why is it in My Engine?

First of all, oil is the substance that lubricates the internal moving components of your vehicles engine. There are many different types of oils on the market suitable for car engines but there are some basics that you should know when purchasing an oil.
Viscosity
This is simply how readily the oil flows. A higher viscosity oil will withstand more heat than a lower viscosity oil. However, at colder temperatures it can actually become so thick that your starter cannot turn over the engine - and worse yet it won't flow to all the moving parts it should. A viscosity that is too low won't maintain a lubricating film on engine parts - allowing them to make metal-to-metal contact. Either extreme is very bad!
SINGLE GRADE VS MULTI-GRADE
Single-grade engine oils (such as SAE 30) used to be the standard for engines operating at high temperatures (such as air-cooled engines). Since the advent of the American Petroleum Institute (API) rating system, the multi-grade oils that proliferate shelves now-days are suitable for nearly all applications. I did have an older gentleman tell me today that his '30 Ford won't build oil pressure with multi-grade oil - but then again, I'd be surprised if his '30ish Ford builds oil pressure at all....
Coincidentally, SAE stands for Society of Automotive Engineers.
SELECTING YOUR GRADE
So which oil you should choose will mostly depend on what you're driving. If your car is not an antique or air-cooled, the safest bet is to use a multi-grade oil. The first number on a multi-grade oil indicates the "cold" viscosity of the lubricant - the second number the "hot" viscosity. For example, a SAE 10W-40 motor oil would have a viscosity rating of 10 at 0-degrees Fahrenheit (the W indicates "Winter") and a 40 rating at its maximum recommended temperature (not engine operating temperature - ambient air temperature).
The following chart is a good place to start. Determine the temperatures you'll be driving in and select an oil accordingly.

The Breakdown

Multi-Grade Oil Viscosity Chart

ADDITIONAL INFORMATION

Also consider your driving habits and the condition of your car. If you drive hard - keeping the engine near redline for extended periods of time - or you do a lot of high RPM "freeway" driving - then you may want to select a higher viscosity oil for your car. Also, if your engine is high mileage, a high viscosity oil will keep it a little quieter and may not slip through the rings to be burned (blue smoke).
If your car is newer, you will most likely want a lower viscosity oil. This is true of most newer high-performance cars also - they too have tighter bearing tolerances and recommend a low viscosity oil (it doesn't rob as much power from the engine).
Over-all, If you expect very cold weather ahead, definitely choose an oil with a lower "cold" viscosity. If you live in a warmer region, a higher winter rating (the W rating) will help keep your cam and valves from clattering when you first start your car.


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