When we rate a clutch kit for performance use, we use engine torque as our defining parameter. Torque is the "twisting" force exerted on the drivetrain that gets you up and out. It is the force (lbs.) multiplied by the distance (ft.) (normally expressed in lbs.-ft.). Imagine using a big wrench to tighten a nut to a certain torque value. One pound at one foot is 1 lb.-ft. Three hundred pounds at two feet is 600 lbs.-ft. The more force or the greater distance increases the torque value. Horsepower is the force that keeps you moving. One horsepower equals a horse pulling 180 pounds 181 feet in one minute. Today it is usually expressed as 550 pounds for one foot in one second. It will keep you moving until the engine redlines or the rev-limiter kicks in.
A Dodge Ram 3500 Cummins 5.9L Diesel can exert 610 lbs.-ft. of torque at the engine and only generate 325 hp while a BMW V10 M6 generates 383 lbs.-ft. and 500 hp. In both cases, we concentrate on the torque output of the engine because it is the twisting force that causes a clutch to slip. All of our ratings are done in accordance with the OE SAE practice of allowing for a 20% safety factor for occasional extraordinary demands on the clutch package. This may be an overloaded vehicle, a heavy trailer, steep hills, tire size change or a tuning modification. We would prefer to have the clutch kit step up and do its job in the time of need.
There are clutch suppliers that state their clutch kit capacity without the 20% margin to give the appearance of a heavier duty clutch while in fact it has the same clamp load and mating components as ours. In fact, they would take a cheap import clutch and call it heavy duty because they rate it without any safety margin.
We also rate our clutch kits based on engine torque capacity because the numbers are readily available either through measurement directly or from credible published sources. Torque ratings at the wheel need to take into account parasitic drivetrain loss which has been estimated to range between 15% and 25% of the engine torque rating. There are a lot of discussions on how to determine this loss and on whether it remains constant (i.e. always 50 lbs.-ft.) or declines as a percentage when a motor is upgraded. We have decided to stay with the engine torque number because it is more readily determined and directly affects the choice of the clutch kit.
Other factors that we consider are how things like Power Density affect the ability of the chosen friction materials to handle the BTU output of the slipping action generated during the engagement cycle. The failure of the material to handle the power within its optimum temperature range can cause excessive heat buildup, coefficient of friction decline, and rapidly increased wear rates. The engagement characteristics of friction material can change from moment to moment depending on factors such as stiction (mating surfaces moving together [static state] or slipping past one another [dynamic state]), internal bellhousing temperatures, friction material temperature, heat sink ability of the mating surfaces (heavy cast iron flywheel versus lightweight aluminum or steel flywheels), material transfer (proper and adequate bedding in procedures followed), and contamination.
If you have modified your engine and you have an idea of what the horsepower is, you can estimate the engine torque using the following example. A chip manufacturer states for example a 50 hp gain for a 2016 Subaru WRX STi which has a base hp of 305 hp at 6000 rpm. Use (5252 x hp)/rpm to get the engine torque. The number 5252 is a constant that happens to be the rpm where the horsepower and torque values are the same. The new HP amount is 305 + 50 = 355 hp. It would then be (5252 x 355)/6000 which equals 310 lbs.-ft. of engine torque.
If you have any questions or concerns regarding the proper clutch for your vehicle, please don't hesitate to contact us. We are glad to be of service.
Many newer vehicles are equipped with a dual-mass flywheel to control a portion of the engine’s torsional vibrations, which causes various types of gear rattle noises. A dual-mass flywheel exhibits unique damping characteristics that cannot be replicated with a single-mass design.
When converting from the heavy, original dual-mass flywheel to any lighter, single-mass, aftermarket flywheel, much of the original torsional damping is defeated (with a partial exception when also using a spring-centered or damped clutch disc). As can be expected, the result is an increase in gear noise. In general, the lighter the flywheel is, the louder the gear noise will be.
During testing, ClutchMax identified two types of gear noise that commonly occur when using a lightened flywheel: 1) idle mode rattle (also called neutral rollover noise), which occurs when idling in neutral with the clutch engaged, and 2) burst rattle (or start-up rattle), which is heard when accelerating heavily at very low rpm. Although annoying to some drivers, the additional gear noise should pose no harm to the transmission.
ClutchMax manufactures 3 types of flywheels. Factory style, Lightweight Chromoly steel and Ultra lightweight Aluminum versions. Chromoly steel version is manufactured with integral ring gear that allows a greater weight reduction and eliminates the chance of gear breakage. ClutchMax heat treats the entire forging for strength and durability. Chromoly steel and Aluminum flywheels provide safety, improved throttle response, better feedback to the driver and increased acceleration. Nodular Cast and Chromoly steel are able to be resurfaced, if needed, which can save from having to purchase additional parts, as is common with any two-piece units.
Increased gear rattle noise may occur when changing to an aftermarket performance clutch and/or flywheel, including ClutchMax’s products. The most common gear rattle noise occurs when a vehicle is idling in neutral after a long drive or on a hot day. It sounds like a light knocking or growling sound. Gear rattle is an audible noise transmitted from the impacts between the transmission gear teeth. A vehicle engine’s torsional vibrations (momentary angular acceleration) pass through a transmission causing the separation and resulting impact of the gear teeth. Gear rattle is not to be confused with clutch chatter or out-of-balance vibrations; both of which are conditions mostly felt and generally, not heard. In general, gear rattle is not harmful to the transmission, but can be an annoyance to the driver. It can become a serious concern if misdiagnosed as a transmission or engine problem. Traditionally, automakers have dampened torsional vibrations by using a clutch disc with a spring-centered design and a heavy flywheel. More recently, however, many have started using a dual-mass flywheel to silence the gear rattle in the transmission. Typically, when a dual-mass flywheel is used, the clutch disc features a solid, or rigid-hub, instead of a spring-centered. When changing from a dual-mass flywheel to a solid flywheel, a spring-centered clutch will help dampen the torsional vibrations and reduce, but not eliminate, gear rattle noise. Other contributors to increased gear noise include: dual-mass flywheel to a single-mass flywheel conversion, a solid or rigid-hub center instead of a spring center, stronger dampening springs in the clutch disc, increased engine performance modifications or a lighter flywheel or clutch assembly. Gear rattle is a commonly accepted trade-off for performance. Gear rattle noise is not a manufacturer’s defect and ClutchMax will not accept warranty claims because of increases in gear rattle noise.
The hydraulic clutch master cylinder used on the 2002-2006 Acura RSX, 2002-2015 Honda Civic Si and 2004-2008 Acura TSX have a feedback plate which is known to fail when installing any performance clutch that has a higher clamp load over the factory clutch. ClutchMax is fully aware of the issue and recommends replacement of the factory Honda/Acura hydraulic clutch master cylinders with a clutch master cylinder from a 2001-2005 Honda Civic (Honda Part Number 46920-S5A-G06). This hydraulic clutch master cylinder is a direct replacement designed without the feedback plate and can be installed with minimal modifications.
If you have any questions please feel free to contact our technical service department.
The alignment hole in the flywheel must be lined up with the crankshaft dowel. It is possible for the flywheel to be mounted in a misaligned position. If the alignment hole is not positioned properly, the car will not start or run properly because of incorrect timing of the crankshaft, speed triggers machined into the flywheel.
The installation procedure for this type of clutch is very different than for the older Mitsubishi Eclipse or various other Mitsubishi/DSM vehicles. This vehicle utilizes an efficient pull-type clutch that offers more clamp force without adding excessive pedal effort for it to function. However, irreparable damage can occur to the pressure plate’s release bearing clip if improper techniques are used in disassembly and installation of the release bearing. The factory repair instructions must be strictly followed to prevent damage. The release bearing clip is not sold separately, so replacement parts are not available. If damage occurs to the release bearing clip during installation or disassembly, it will not be covered under ClutchMax warranty. ClutchMax will replace this clip only if the customer’s original stock pressure plate is provided as a core with a functioning release bearing clip.
When using a lightened flywheel, the check engine light (CEL) has been known to come on for no reason on some vehicles. Because the high inertia of the factory flywheel is not there to smooth out the idle, it can be slightly rougher than stock with a lightweight, aftermarket flywheel. The CEL is the ECU interpreting the change in idle as a misfire in the electrical system. There is no misfire in the electrical system, but this is the only way the ECU has to interpret the change in idle with its programming. The only way to avoid getting the CEL is to use a heavier flywheel, such as the stock flywheel. This has been observed occasionally with flywheels within 20% weight reduction from stock flywheel but more commonly with significantly lighter flywheels such as aluminum flywheels.
Smooth and flat flywheel surface is critical for proper clutch operation and longevity. It is extremely important to maintain the proper step in the flywheel, when applicable. A good automotive machine shop will also be able to rebalance the flywheel to ensure that the engine stays smooth and can reach higher RPM without damage to the engine. For special applications, the flywheel may be altered for better performance. For example, racers using a slow-wearing, sintered, metallic clutch disc may change the flywheel step to put the pressure plate closer to peak clamp load because they are not worried about shortening the longevity of the clutch. This job should be left to an expert performance clutch rebuilder, who can properly analyze the characteristics of the flywheel, pressure plate and disc used.
On some applications, when a ClutchMax pressure plate is installed, the engage/release point may become closer to the floor. As long as the hydraulics are working properly, this change may be due to flex caused from the added forces placed on the pressure plate and linkage from the increased pressure. A disc that has excessive marcel could also take extra travel to release. In most cases, a small adjustment of the clutch master cylinder pushrod reducing pedal free play will cure the problem. This adjustment is made by screwing the pushrod farther into the clutch master cylinder to allow it to actuate the cylinder sooner. You may also desire to increase pedal travel by adjusting the pedal stop (when equipped). You should never preload the clutch master cylinder. Most repair manuals include instructions and adjustment specifications, which is a great starting point. Clutch pedal travel can also be limited by aftermarket clutch pedals, floor mats or carpet.
Some owners have reported an increase in transmission gear rattle after installing a Solid Flywheel Conversion Clutch Kit in their vehicle when it’s in neutral and idling. This is known as Gear Roll Over. It is a rapid tapping, clicking, or rattling sound. Some owners say it sounds like marbles in a jar. It occurs in every transmission to varying degrees, no matter what type of gears are used. The rattle and vibration is caused by gears moving back and forth relative to each other. When teeth bounce off of each other, they make a rattling noise. This gear rattle occurs when the vehicle is at idle, in neutral, with foot off the clutch pedal.
The gear roll over noise heard will not affect transmission or drivetrain wear per the OE manufacturers, all of which sell a stock version of these kits. If you would like to reduce the level of noise, the following fixes have been offered up under several of the Diesel oriented blogs. ClutchMax offers these fixes as merely as references to what is being discussed amongst vehicle owners. We do not sell these items.
· For a Cummins 5.9L - Add a Fluidampr Harmonic Balancer – provides 80% better vibration dampening with Silicone fluid. The 6.7L Cummins comes equipped from the factory this way.
· Add additional two quarts of ATF and remove sensor (may void manufacturer’s warranty).
· Add 24 ounces of Lucas Transmission Fix
· Replace ATF with 7.5 Quarts of high performance Gorilla Juice Manual Transmission Fluid
These suggestions all assume that prior to the conversion the transmission was inspected by a qualified technician for excessive end-play or movement of the input shaft caused by worn bearings or the housing. Also make sure that the transmission is filled to the correct level. Less fluid will cause more noise