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Thread: Basic Info for the New Owner...

  1. #1

    Basic Info for the New Owner...

    I thought that I would be a little constructive and put together a basic information thread. A detail of descriptions for components and their operation.

    Volumetric efficiency in internal combustion engine design refers to the efficiency with which the engine can move the charge into and out of the cylinders. More correctly, volumetric efficiency is a ratio (or percentage) of what volume of fuel and air actually enters the cylinder during induction to the actual capacity of the cylinder under static conditions. Therefore, those engines that can create higher induction manifold pressures - above ambient - will have efficiencies greater than 100%. Volumetric efficiencies can be improved in a number of ways, but most notably the size of the valve openings compared to the volume of the cylinder and streamlining the ports. Engines with higher volumetric efficiency will generally be able to run at higher RPM, and thus power, settings as they will lose less power to moving air in and out of the engine.
    There are several standard ways to improve volumetric efficiency. A common approach for manufacturers is to use a larger number of valves, see multi-valve, which cover a greater area of the cylinder head. Carefully streamlining the ports increases flow capability. This is done with the aid of an air flow bench for testing. Today, automobile engines typically have four valves per cylinder for this reason. Many high performance cars in the 1970s used carefully arranged air intakes and "tuned" exhaust systems to "push" air into and out of the cylinders through the intrinsic resonance of the system. Two-stroke engines take this concept even further with expansion chambers that returns the escaping air-fuel mixture back to the cylinder. A more modern technique, variable valve timing, attempts to address changes in volumetric efficiency with changes in RPM of the engine -- at higher RPM the engine needs the valves open for a greater percentage of the cycle time to move the charge in and out of the engine.

  2. #2

    Re: Basic Info for the New Owner...

    Knocking (also called pinking or pinging)—technically detonation—in internal combustion engines occurs when fuel/air mixture in the cylinder has been ignited by the spark plug and the smooth burning is interrupted by the unburned mixture in the combustion chamber exploding before the flame front can reach it. Combusting stops suddenly, because of the explosion, before the optimum moment of the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber and pressures increase catastrophically, creating a characteristic metallic "pinging" sound.

    The fuel/air mixture is normally ignited slightly before the point of maximum compression to allow a small time for the flame-front of the burning fuel to expand throughout the mixture so that maximum pressure occurs at the optimum point. The flame-front moves at roughly 33.5 m/second (110 feet/second) during normal combustion. It is only when the remaining unburned mixture is heated and pressurized by the advancing flame front for a certain length of time that the detonation occurs. It is caused by an instantaneous ignition of the remaining fuel/air mixture in the form of an explosion. The cylinder pressure rises dramatically beyond design limits. If allowed to persist detonation will damage or destroy engine parts.
    Detonation can be prevented by:
    • The use of a fuel with higher octane rating
    • The addition of octane-increasing "lead," isooctane, or other fuel additives.
    • Reduction of cylinder pressure by increasing the engine revolutions (lower gear), decreasing the manifold pressure (throttle opening) or reducing the load on the engine, or any combination.
    • Reduction of charge (in-cylinder) temperatures (such as through cooling, water injection or compression ratio reduction).
    • Retardation of spark plug ignition.
    • Improved combustion chamber design that concentrates mixture near the spark plug and generates high turbulence to promote fast even burning.
    • Use of a spark plug of colder heat range in cases where the spark plug insulator has become a source of pre-ignition leading to detonation.
    Correct ignition timing is essential for optimum engine performance and fuel efficiency. Modern automotive and small-boat engines have sensors that can detect knock and retard (delay) the ignition (spark plug firing) to prevent it, allowing engines to safely use petrol of below-design octane rating, with the consequence of reduced maximum power output and efficiency.
    A knock sensor consists of a small piezoelectric microphone, on the engine block, connected to the engine's ECU. Spectral analysis is used to detect the trademark frequency produced by detonation at various RPM. When detonation is detected the ignition timing is retarded, reducing the knocking and protecting the engine.

  3. #3

    Re: Basic Info for the New Owner...

    Pre-ignition is a different phenomenon from detonation, explained above, and occurs when the air/fuel mixture in the cylinder (or even just entering the cylinder) ignites before the spark plug fires. Pre-ignition is caused by an ignition source other than the spark. Heat or hot spots can buildup in engine intake or cylinder components due to improper design, for example, spark plugs with heat range too hot for the conditions, or due to carbon deposits in the combustion chamber, or also due to overheating of the air/fuel mixture during compression.
    Pre-ignition and "dieseling" or "run on" are the same phenomenon, except in the latter case the engine continues to run after the ignition is shut off with a hot spot as an ignition source. Pre-ignition might cause rough running due to the advanced and erratic effective igniton timing and may cause noise if it leads to detonation. It may also cause "rumble" which is fast and premature but not detonating combustion.
    This heat buildup can only be prevented by eliminating the overheating (through redesign or cleaning) or the compression effects (by reducing the load on the engine or temperature of intake air). As such, if pre-ignition is allowed to continue for any length of time, power output and fuel economy is reduced and engine damage may result.
    Pre-ignition may lead to detonation and detonation may lead to pre-ignition or either may exist separately.

  4. #4

    Re: Basic Info for the New Owner...

    Octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.
    The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

  5. #5

    Re: Basic Info for the New Owner...

    Blowoff valve (also known as a bypass valve, compressor relief valve, or sometimes hooter valve) is a vacuum operated valve that is located in the intake tract on an internal combustion engine after a turbocharger, but before the throttle body butterfly valve and intake manifold. Its use is to vent extra pressure being developed by the turbocharger when the throttle is closed, such as during a shift. During a shift in a car with a manual transmission, the throttle plate is closed. The pressure produced by the turbocharger has nowhere to escape to. This excess pressure could potentially cause damage to the turbocharger's impeller and may also slow or even stop it, thus causing turbo lag when the throttle is pressed again.A blow-off-valve is connected by a vacuum hose to the intake manifold after the throttle plate. When the throttle is closed, a strong vacuum develops in the intake manifold after the throttle plate and "sucks" the blowoff valve open. The excess pressure from the turbocharger is vented into the atmosphere or recirculated into the intake upstream of the compressor inlet; when vented into the atmosphere this can cause erratic engine behavior on motors that use an air flow meter for the electronic fuel injection. Engines using a MAP (manifold absolute pressure) are not affected. Externally-vented blowoff valves have a very distinguished "psshh" sound that is desired by many who own turbocharged sports cars. Some blowoff valves are marketed with trumpet shaped exits that amplify the "psshh" sound. Blowoff valves are generally not required on automatic transmission vehicles. Automatic transmission vehicles shift without closing the throttle, but are still fitted with blow off valves by many manufacturers so the turbo is able to provide boost sooner if the throttle is only released for a short amount of time.

  6. #6

    Re: Basic Info for the New Owner...

    Wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharger. Diversion of exhaust gases causes the turbine to lose speed, which in turn reduces the rotating speed of the compressor. The primary function of the wastegate is to stabilize boost pressure in turbocharger systems. The wastegate is controlled by a wastegate actuator.
    An internal wastegate is an integral part of the turbine housing. The wastegate actuator is commonly attached to the compressor housing with a metal bracket.
    An external wastegate is a separate self-contained mechanism designed for turbochargers that don't have internal wastegates. An external wastegate requires a specially constructed turbo manifold with a dedicated runner going to the wastegate. The external wastegate may be part of the exhaust housing itself. External wastegates are commonly used for regulating boost levels more precisely than internal wastegates in high power applications, where high boost levels can be achieved.

  7. #7

    Re: Basic Info for the New Owner...

    Intercooler is a device used on turbocharged and supercharged internal combustion engines to improve the volumetric efficiency and increase the amount of charge in the engine, thereby increasing power. The inter in the name refers to its location compared to the compressors; the coolers were typically installed between multiple stages of supercharging in aircraft engines. Modern automobile designs are technically aftercoolers because they appear most often at the very end of the chain, but this name is no longer used.
    Turbochargers and superchargers compress incoming air, causing it to become heated (see the universal gas equation). Since hot air is less dense than cooler air at the same pressure, the total charge delivered to the cylinders is higher than non-compressed air, but still less than it could be. By cooling the charge after compression, even more charge can be delivered, increasing power. Additionally, intercoolers help to increase the total amount of boost possible without causing engine knocking.An intercooler is essentially a radiator tuned for high volume flow rates and the increasing density of the charge as it cools. Most designs use ambient air for cooling, flowing through the radiator core, and often co-located with other radiators for oil or cooling fluid. This approach is also known as Air To Air (ATA).

  8. #8

    Re: Basic Info for the New Owner...

    Differential is a device, usually consisting of gears, for allowing each of the driving wheels to rotate at different speeds, while supplying equal torque to each of them.
    A relatively new technology is the electronically-controlled Active differential. A computer uses inputs from multiple sensors, including yaw rate, steering angle, and lateral acceleration and adjusts the distribution of torque to compensate for undesirable handling behaviors like understeer. Active differentials used to play a large role in the World Rally Championship, but in the 2006 season the FIA has limited the use of active differentials only to those drivers who have not competed in the World Rally Championship in the last five years.
    The first use of this technology on a production automobile was in the 1995 Nissan Skyline GT-R Vspec. The lockup of the rear differential and center coupling were controlled as part of the ATTESA-ETS Pro system. Fully integrated active differentials are used on the 2005 MR Ferrari F430 and on rear wheels in the Acura RL.
    The second constraint of the differential is passive – it is actuated by the friction kinematics chain through the ground. The difference in torque on the tires (caused by turns or bumpy ground) drives the second DOF, (overcoming the torque of inner friction) to equalise the driving torque on the tires. The sensitivity of the differential depends on the inner friction through the second DOF. All of the differentials (so called “active” and “passive”) use clutches and brakes for restricting the second DOF, so all suffer from the same disadvantage – decreased sensitivity to a dynamically changing environment. The sensitivity of the computer controlled differential is also limited by the time delay caused by sensors and the response time of the actuators.
    Limited slip differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In an automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity.
    The main advantage of a limited slip differential is found by considering the case of a standard (or "open") differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate at twice its intended velocity – the torque transmitted will be zero and the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use however, such as driving off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels.


  9. #9

    Re: Basic Info for the New Owner...

    Wheel offset, measured in millimeters, can be negative or positive, and is the distance from the mounting surface to the rim's true centerline. A positive offset means the wheel is front of the mounting surface, closer to the center of the fender; a negative offset means the wheel is away from the mounting surface and projecting from the fender.
    Camber angle is the angle made by the wheel of an automobile; specifically, it is the angle between the vertical axis of the wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering and suspension. If the top of the wheel is further out than the bottom (that is, away from the axle), it is called positive camber, if the bottom of the wheel is further out than the top, it is called negative camber.
    Camber angle alters the handling qualities of a particular suspension design; in particular, negative camber improves grip when cornering. This is because it presents the tire, which is taking the greatest proportion of the cornering forces, at a more optimal angle to the road, increasing its contact area and transmitting the forces through the vertical plane of the tire, rather than through a shear force across it. On the other hand, for maximum straight-line acceleration, obviously the greatest traction will be attained when the camber angle is zero and the tread is flat on the road. Proper management of camber angle is a major factor in suspension design, and must incorporate not only idealized geometric models, but also real-life behavior of the components; flex, distortion, elasticity, etc. What was once an art has now become much more scientific with the use of computers, which can juggle all the variables mathematically instead of relying on the designer's intuitive feel and experience, and as a result the handling of even low-priced automobiles has improved dramatically in recent years.
    In older cars with double wishbone suspensions, camber angle was usually adjustable, but in newer models with McPherson strut suspensions it is normally fixed. While this may reduce maintenance requirements, if the car is lowered by use of shortened springs, this changes the caster angle (as described in McPherson strut) and can lead to increased tire wear and even impaired handling. For this reason, individuals who are serious about modifying their car for better handling will not only lower the body, but also modify the mounting point of the top of the struts to the body to allow some lateral movement for caster adjustment. Aftermarket plates with slots for strut mounts instead of just holes are available for most of the commonly modified models of cars.
    Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the conact patch would begin to lift off of the ground, therby reducing the contact patch. By applying negative camber, this effect is reduced, therby maximizing the contact patch.



    TOE is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e. both wheels point to the left or right, in parallel (roughly). Positive toe, or toe in is the front of the wheel pointing in towards the centreline of the vehicle. It can be measured in linear units, at the front of the tyre, or as an angular deflection.
    In a rear wheel drive car, increased front toe in (i.e. the fronts of the front wheels are closer together than the backs of the front wheels) provides greater straight-line stability at the cost of some sluggishness of turning response, as well as a little more tire wear as they are now driving a bit sideways. On front wheel drive cars, the situation is more complex.
    Toe is always adjustable in production automobiles, even though caster angle and camber angle are often not adjustable. Maintenance of front end alignment, which used to involve all three adjustments, currently involves only setting the toe; in most cases, even for a car in which caster or camber are adjustable, only the toe will need adjustment.
    One related concept is that the proper toe for straight line travel of a vehicle will not be correct while turning, since the inside wheel must travel around a smaller radius than the outside wheel; to compensate for this, the steering linkage typically conforms more or less to Ackermann steering geometry, modified to suit the characteristics of the individual vehicle.
    It should be noted that individuals who decide to adjust their car's static ride height, either by raising or lowering, should immediately have the car properly aligned. The goal is to bring total front and rear toe settings to 0°, as toe is the major contributor to abnormally increased rate of tire wear. The common misconception is that Camber angle causes an increased rate of tire wear, when in fact camber's contribution to tire wear is usually only visible over the entire life of the tire.



    Caster (or castor) angle is the angular displacement from the vertical axis of the suspension of a steered wheel in a car or other vehicle, measured in the longitudinal direction. It is the angle between the pivot line (an imaginary line that runs through the center of the upper ball joint to the center of the lower ball joint) and vertical. Car racers sometimes adjust caster angle to optimize car performance in particular driving situations.
    The pivot points of the steering are angled such that a line drawn through them intersects the road surface slightly ahead of the contact point of the wheel. The purpose of this is to provide a degree of self-centering for the steering - the wheel casters around so as to trail behind the axis of steering. This makes a car easier to drive and improves its straight line stability (reducing its tendency to wander). Excessive caster angle will make the steering heavier and less responsive, although, in racing, large caster angles are used to improve camber gain in cornering. Caster angles over 10 degrees with radial tires are common. Power steering is usually necessary to overcome the jacking effect from the high caster angle.
    The steering axis (the dotted line in the diagram above) does not have to pass through the center of the wheel, so the caster can be set independently of the mechanical trail, which is the distance between where the steering axis hits the ground, in side view, and the point directly below the axle. The interaction between caster angle and trail is complex, but roughly speaking they both aid steering, caster tends to add damping, while trail adds 'feel', and returnability. In the extreme case of the shopping trolley (shopping cart in the US) wheel, the system is undamped but stable, as the wheel oscillates around the 'correct' path. The shopping trolley/cart setup has a great deal of trail, but no caster. Complicating this still further is that the lateral forces at the tire do not act at the center of the contact patch, but at a distance behind the nominal contact patch. This distance is called the pneumatic trail and varies with speed, load, steer angle, surface, tire type, tire pressure and time. A good starting point for this is 30 mm behind the nominal contact patch.
    Like a shopping cart wheel (left) the trail created by the castering of the steering axis pulls the wheels in line.



    With toe-in (left) a deflection of the suspension does not cause the wheels to initiate a turn as with toe-out (right).



    (TOP RIGHT) Positive camber: The bottoms of the wheels are closer together than the tops. (TOP LEFT) Negative camber: The tops of the wheels are closer together than the bottoms. (CENTER) When a suspension does not gain camber during deflection, this causes a severe positive camber condition when the car leans during cornering. This can cause funky handling. (BOTTOM) Fight the funk: A suspension that gains camber during deflection will compensate for body roll. Tuning dynamic camber angles is one of the black arts of suspension tuning.



    Heel-and-toe is a driving technique used in performance driving. It involves operating the accelerator and brake pedals simultaneously with the right foot, while facilitating normal activation of the clutch with the left foot. It is used when braking and downshifting simultaneously (like when going around a turn), and allows the driver to "blip" the throttle to raise the engine speed and smoothly engage the lower gear.
    Heel and toe braking has the following steps:
    1) Brake with the ball (left edge) of your right foot while the car is in gear
    2) Disengage (press) the clutch once the car has slowed down significantly (if double clutching, shift to the neutral position and engage the clutch)
    3) Blip the throttle to match the engine rpm to the rpm needed for the selected gear using either the heel or the right edge of your right foot
    4) Shift the gear lever to correct gear (disengage the clutch first if double clutching)
    5) Engage the clutch, release the brake and roll your foot onto the accelerator
    Heel-and-toe is used before entry into a turn while a vehicle is under braking, preparing the transmission to be in the optimal gear to accelerate out of the turn. One benefit of downshifting before entering a turn is a jolt to the drivetrain, or any other unwanted dynamics, will not upset the vehicle as badly when going in a straight line; the same jolt while turning may upset the vehicle enough to cause loss of control if it occurs after the turn is begun. Another benefit is "heel-and-toeing" allows you to downshift at the last moment before entering the turn, after you have started braking and the car has slowed, so the engine speed when the lower gear is engaged will not be too high.

  10. #10

    Re: Basic Info for the New Owner...

    hey whats up its me the guyt from the armylol alot of good info i have one question i have a hks ssqv bov in my evo and i was wondering if that would affect my car does does the evo com with map or the air fuel meter thanks :mitsu:

  11. #11
    Tofu Specialist LakaiorDie's Avatar
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    Re: Basic Info for the New Owner...

    Quote Originally Posted by SmEjKd10gsr
    Hey everybody just purchased my very first evo x actually its my fist mitsu ever. Had some complications when I bought it though. The owner before me put a tsudo exuast on it which I don't even know if that's a decent exuast system then he removed the cat replacing it with a straight pipe. Needless to say forgot replace the o2 sensor causing my new evo to go into limp mode and a bright service engine light in my face after a 3 month battle with the dealership they finally reiemburted my account after I had to purchase the factory cat and o2. Well anyways thanx for the time guys oh and if you can through any sugestions my way on what I should do first that would be great.
    here one suggestion dont post in the wrong thread newb.
    ill give you a little bit of slack since your new. lol

  12. #12

    Re: Basic Info for the New Owner...

    Pre-ignition is a different phenomenon from detonation, explained above, and occurs when the air/fuel mixture in the cylinder (or even just entering the cylinder) ignites before the spark plug fires. Pre-ignition is caused by an ignition source other than the spark.

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