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 5th Anniverary 2007  Mediacorp - Mission4 <创业无敌手IV>  Picnic 2007 RAVers' LATEST PICS------------- Simon aka heckers  Kwek aka kwek  Simon aka heckers | |
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 | | Reads: R4E 6th Anniversary 2008 Celebration
Wednesday, October 29 @ 23:32:31 SGT heckers
(21 reads) | 
Read about the event, click HERE. Registration of the event is now open, click HERE. This is an Official R4E Annual Event. Strictly for RAVers only.
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Messages: Stepping Forward and Passing of the Baton
Tuesday, July 29 @ 02:41:40 SGT heckers
(190 reads) | Anyone who had in one way or another had interactions with R4E will know that despite being a Car Club, it is really about the people more than the car or the club. The Committee would like to acknowledge RAVers who had unselfishly stepped forward to offer their precious personal time and many times effort to ensure that everyone here enjoy the overall R4E experience. As we do not have the budget to advertise in The Straits Times to recognize them, this is the best we can do. The following RAVers will be stepping down from their appointment held with immediate effect. Do let them know how you feel if you ever bum into them, give them a pat on the back for a job well done. Stepping down....Name | UserID | Identification No. | Previous Appointment | Duration | RAVer Since | Wong Mun Chong | mun_chong | 62 (Retired) | Committee RAVer | Dec 2005~Jul 2008 | Apr 2004 | James Tan | Sprint | 130 (Retired) | Committee RAVer | Jan 2007~Jul 2008 | Sep 2004 | Henry Yew | vodkabuddy | 40 (Retired) | Committee RAVer | Jan 2007~Jul 2008 | Apr 2004 | Darren Wong | Tian | 83 (Retired) | Merchandiser | Jan 2007~Jul 2008 | May 2004 | Jeremy Goh | VirginKilla | 166 | Merchandiser | Jan 2007~Jul 2008 | Dec 2004 | Christopher Kwan | ChioBu | 176 (Retired) | Events | Jan 2007~Jul 2008 | Mar 2005 |
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Events: Endau Rompin 5 (ER5)
Tuesday, April 01 @ 13:37:17 SGT heckers
(295 reads) | 
Registration of the event is now open, click HERE.
This is an Official R4E Annual Event.
Strictly for RAVers only.
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The Danger of Power Pulleys & Understanding the Harmonic Damper
Saturday, March 01 @ 04:16:17 SGT heckers
(267 reads) | slowwalker writes
"The Danger of Power Pulleys & Understanding the Harmonic Damper
By Steve Dinan of Dinan BMW
I have been threatening for a long time to write a series of technical articles to educate consumers and to dispel misconceptions that exist about automotive after-market technology. Motivated by problems with customer's cars resulting from the installation of power pulleys, I wish to explain the potential dangers of these products and address the damage they cause to engines.
The theory behind the power pulley is that a reduction in the speed of the accessory drive will minimize the parasitic losses that rob power from the engine. Parasitic power losses are a result of the energy that the engine uses to turn accessory components such as the alternator and water pump, instead of producing power for acceleration. In an attempt to minimize this energy loss, many companies claim to produce additional power by removing the harmonic damper and replacing it with a lightweight assembly. While a small power gain can be realized, there are a significant number of potential problems associated with this modification, some that are small and one which is particularly large and damaging!
The popular method for making power pulleys on E36 engines is by removing the harmonic damper and replacing it with a lightweight alloy assembly. This is a very dangerous product because this damper is essential to the longevity of an engine. The substitution of this part often results in severe engine damage.
It is also important to understand that while the engine in a BMW is designed by a team of qualified engineers, these power pulleys are created and installed by people who do not understand some very important principles of physics. I would first like to give a brief explanation of these principles which are critical to the proper operation of an engine.
1) Elastic Deformation
Though it is common belief that large steel parts such as crankshafts are rigid and inflexible, this is not true. When a force acts on a crank it bends, flexes and twists just as a rubber band would. While this movement is often very small, it can have a significant impact on how an engine functions.
2) Natural Frequency
All objects have a natural frequency that they resonate (vibrate) at when struck with a hammer. An everyday example of this is a tuning fork. The sound that a particular fork makes is directly related to the frequency that it is vibrating at. This is its "natural frequency," that is dictated by the size, shape and material of the instrument. Just like a tuning fork, a crankshaft has a natural frequency that it vibrates at when struck. An important aspect of this principle is that when an object is exposed to a heavily amplified order of its own natural frequency, it will begin to resonate with increasing vigor until it vibrates itself to pieces (fatigue failure).
3) Fatigue Failure
Fatigue failure is when a material, metal in this case, breaks from repeated twisting or bending. A paper clip makes a great example. Take a paper clip and flex it back and forth 90° or so. After about 10 oscillations the paper clip will break of fatigue failure.
The explanation of the destructive nature of power pulleys begins with the two basic balance and vibration modes in an internal combustion engine. It is of great importance that these modes are understood as being separate and distinct.
1) The vibration of the engine and its rigid components caused by the imbalance of the rotating and reciprocating parts. This is why we have counterweights on the crankshaft to offset the mass of the piston and rod as well as the reason for balancing the components in the engine.
2) The vibration of the engine components due to their individual elastic deformations. These deformations are a result of the periodic combustion impulses that create torsional forces on the crankshaft and camshaft. These torques excite the shafts into sequential orders of vibration, and lateral oscillation. Engine vibration of this sort is counteracted by the harmonic damper and is the primary subject of this paper.
Torsional Vibration (Natural Frequency)
Every time a cylinder fires, the force twists the crankshaft. When the cylinder stops firing the force ceases to act and the crankshaft starts to return to the untwisted position. However, the crankshaft will overshoot and begin to twist in the opposite direction, and then back again. Though this back-and-forth twisting motion decays over a number of repetitions due to internal friction, the frequency of vibration remains unique to the particular crankshaft.
This motion is complicated in the case of a crankshaft because the amplitude of the vibration varies along the shaft. The crankshaft will experience torsional vibrations of the greatest amplitude at the point furthest from the flywheel or load.
Harmonic (sine wave) Torque Curves
Each time a cylinder fires, force is translated through the piston and the connecting rod to the crankshaft pin. This force is then applied tangentially to, and causes the rotation of the crankshaft.
The sequence of forces that the crankshaft is subjected to is commonly organized into variable tangential torque curves that in turn can be resolved into either a constant mean torque curve or an infinite number of sine wave torque curves. These curves, known as harmonics, follow orders that depend on the number of complete vibrations (cylinder pulses) per revolution. Accordingly, the tangential crankshaft torque is comprised of many harmonics of varying amplitudes and frequencies. This is where the name "harmonic damper" originates.
Critical RPM's
When the crankshaft is revolving at an RPM such that the torque frequency, or one of the harmonic sine wave frequencies coincides with the natural frequency of the shaft, resonance occurs. Thus, the crankshaft RPM at which this resonance occurs is known a critical speed. A modern automobile engine will commonly pass through multiple critical speeds over the range of its possible RPM's. These speeds are categorized into either major or minor critical RPM's.
Major and Minor Critical RPM’s
Major and minor critical RPM's are different due to the fact that some harmonics assist one another in producing large vibrations, whereas other harmonics cancel each other out. Hence, the important critical RPM’s have harmonics that build on one another to amplify the torsional motion of the crankshaft. These critical RPM’s are know as the "major criticals". Conversely, the "minor criticals" exist at RPM's that tend to cancel and damp the oscillations of the crankshaft.
If the RPM remains at or near one of the major criticals for any length of time, fatigue failure of the crankshaft is probable. Major critical RPM’s are dangerous, and either must be avoided or properly damped. Additionally, smaller but still serious problems can result from an undamped crankshaft. The oscillation of the crankshaft at a major critical speed will commonly sheer the front crank pulley and the flywheel from the crankshaft. I have witnessed front pulley hub keys being sheered, flywheels coming loose, and clutch covers coming apart. These failures have often required crankshaft and/or gearbox replacement.
Harmonic Dampers
Crankshaft failure can be prevented by mounting some form of vibration damper at the front end of the crankshaft that is capable of absorbing and dissipating the majority of the vibratory energy. Once absorbed by the damper the energy is released in the form of heat, making adequate cooling a necessity. This heat dissipation was visibly essential in Tom Milner's PTG racing M3 which channeled air from the brake ducts to the harmonic damper, in order to keep the damper at optimal operating temperatures. While there are various types of torsional vibration dampers, BMW engines are primarily designed with "tuned rubber" dampers.
It is also important to note that while the large springs of a dual mass flywheel absorb some of the torsional impulses conveyed to the crankshaft, they are not harmonic dampers, and are only responsible for a small reduction in vibration.
In addition to the crankshaft issue, other problems can result from slowing down the accessories below their designed speeds, particularly at idle. Slowing the alternator down can result in reduced charging of the battery, dimming of the lights, and computer malfunctions. Slowing of the water pump and fan can result in warm running, while slowing of the power steering can cause stiff steering at idle and groaning noises. It is possible to implement design corrections and avoid these scenarios, but this would require additional components and/or software.
Our motto at Dinan is "Performance without sacrifice" We feel our customers expect ultra high performance along with the legendary comfort and reliability of a standard BMW.
While it is common that a Dinan BMW is the fastest BMW you can buy, performance is not our only goal. Dinan isn't just trying to make the fastest car. Instead a host of considerations go into the development of our products. Dinan puts much more effort into these other areas than does our competition.
These considerations are Performance, Reliability (Warranty), Driveability, Emissions, Value, Fit and Finish. We feel that the power pulley is a bad way to get extra power from and engine and the potential for serious engine damage is too great.
This is a simplified explanation meant to be comprehensible by those who are not automotive engineers. In trying to simplify an extremely complex topic some precision was sacrificed although we believe this explanation to be as accurate as possible. We encourage our customers to educate themselves and understand the automotive after-market because we believe that our products are the best researched, engineered, and fabricated products available."
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Events: R4E 5th D&D Celebration 2007
Sunday, October 07 @ 01:46:03 SGT heckers
(408 reads) | R4E 5th Dinner & Dance 2007
HAPPY 5TH BIRTHDAY R4E!!!
We would like to thank all RAVers who took their time off to make this celebration a success.
Also to all the sponsors whom have made a lot of us go home with a smile.
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Events: R4E goes to Desaru: Musings of a RAV4
Sunday, June 10 @ 04:03:48 SGT heckers
(903 reads) | 
Please stay tune for event report...
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Tech Info: Ceramic Brakes
Monday, May 28 @ 03:01:19 SGT heckers
(574 reads) |  kwek writes
"Why Ceramic Brakes?
We want our vehicle's brake system to offer smooth, quiet braking capabilities under a wide range of temperature and road conditions. We don't want brake-generated noise and dust annoying us during our daily driving.
Articles & pixs extracted from Tire Rack.
Posted by "heckers" on behalf of "kwek".
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Messages: New Appointments
Monday, January 15 @ 17:13:53 SGT heckers
(665 reads) | Firstly, on behalf of R4E, I would like to thank 2 Committee RAVers who steps down today (15th January 2006). Namely Joseph aka PaiKia & Edmund aka mafia. Most of you should know who they are, and we would like to thank them for their contribution. Without their passion, hard work, planning & execution, R4E will not be where it is today. With immediate effect, they will now be converted to be Advisory RAVers.
Secondly, with the decreasing number of Committee RAVers to lead R4E, I would like to announce the newly appointed Committee RAVers namely Henry aka vodkabuddy & James aka Sprint. With their commitments, contributions, time, effort, plannings, we are assured that R4E will soar to greater heights.
Thirdly, I would like to introduce our newly appointed Senior RAVers cum ModerRAVers & Executive RAVer. Namely Samuel aka samail to take on "New Introduction" thread, Chris aka ChioBu to take on "Events" thread & Hannas aka steelheart as our official Designer. With them around, our R4E forum will always remain clean, neat & tidy. Most importantly, our forum culture will be maintained.
Once again, I would like to congratulate all of the above & may the Spirit of R4E reigns forever.
Well done, guys...
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Messages: R4E has successfully Migrated
Sunday, January 07 @ 22:07:57 SGT heckers
(802 reads) | With the forum hosted locally now, you will experience much faster access.
Also, now R4E will be more fun with NEW FEATURES
- All new smileys, ANIMATED. Go try it!
         
- AVATAR now supports 120 x 120pixel / 36kb
So get yours change and show it off!
More will be added, so stay tune.
If you have any ideas or suggestions how we can improve even further, do drop us a note : admin@rav4expedition.com
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Tech Info: Tire Pressure :Correct, Overinflate, Underinflate
Monday, May 22 @ 15:23:02 SGT anthony
(1311 reads) | kwek writes
"Advantages of Correct Tire Inflation
Maintaining correct tire inflation pressure helps optimize tire performance and fuel economy. Correct tire inflation pressure allows drivers to experience tire comfort, durability and performance designed to match the needs of their vehicles. Tire deflection (the tread and sidewall flexing where the tread comes into contact with the road) will remain as originally designed and excessive sidewall flexing and tread squirm will be avoided. Heat buildup will be managed and rolling resistance will be appropriate. Proper tire inflation pressure also stabilizes the tire's structure, blending the tire's responsiveness, traction and handling. " Note:
Articles & pixs extracted from Tire Rack.
Posted by "anthony" on behalf of "kwek".
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