ClutchTamer Tuning Guide

When launching with a manual transmission, every car/clutch combination has it's own "sweet spot" in the clutch pedal's release travel. That's the spot in pedal travel where the clutch hits just right, and slips a perfect amount to efficiently launch the car. Below that sweet spot the clutch doesn't grab hard enough, allowing it to slip too much which may damage the clutch. Above that sweet spot the clutch grabs too quickly, causing it to either bog the engine, spin the tires, or breaks parts. But in between those two extremes, there lays a perfect "sweet spot" level of slippage that doesn't either damage the clutch or bog the engine. The ClutchTamer's purpose is to make it easy to instantly hit that sweet spot consistently, then give you control over how long it takes for the pedal to travel thru that sweet spot. You won't need tuning help from a clutch guy, you will become your own clutch guy!

In the graph below, the "Psi" numbers along the left side basically represent an amount of clamp pressure being withheld at the throwout bearing. The top/left corner represents the clutch pedal being fully depressed, which results in maximum pressure at the throwout bearing. As the clutch pedal is released, pressure at the throwout bearing drops as the clutch's clamp pressure increases. The bottom of the graph represents time in seconds, with "0" representing the instant that the clutch pedal was released.

...The "Hit" point of each line on the graph is the point where that line suddenly transitions from initial vertical drop to secondary horizontal travel.
...The ClutchTamer's inner "Initial Hit" dial controls how far down the graph a line vertically drops BEFORE it reaches it's "Hit" point.
...The ClutchTamer's outer "Secondary Delay" knob then controls each line's horizontal drop rate AFTER it reaches it's "Hit" point.


Initial Setup For Your ClutchTamer...

One of the quickest/safest ways to "ballpark" your ClutchTamer's initial hit adjustment at home is to use what we call the "rolling launch" method. It's also easy on equipment, and not likely to get you in trouble with law enforcement. This method can even be used while rolling down the freeway in 4th gear on the way to the races. Always be sure to find a safe, legal, and consistent location to conduct your test sessions.

Adjustment #1- Initial Clutch Hit...

This adjustment controls the amount of initial vertical drop on the graph BEFORE the "hit" point, or how far clutch t-bearing pressure initially drops before delay takes over.

The graph below is a composition of 9 separate tests. As you move down the graph, each colored line represents a separate test with one additional turn of "initial hit" adjustment than the line above it. All these tests share the same "Secondary Delay" setting, as all the secondary delay angles AFTER the hit points are basically the same.

Let's say for example that the "sweet spot" for a particular combination is the horizontal band between 200-100 Psi on the graph.
...The upper end of this particular "sweet spot" band is 200 Psi, which represents an amount of clutch clamp pressure that basically matches the output of the engine. Basically, the clutch would hit with just enough pressure to hold WOT engine rpm steady with very little loss of rpm over the first few tenths of a second after the "hit".
...The lower end of this particular "sweet spot" band is 100 Psi which represents an amount of clutch clamp pressure that either pulls engine rpm down to the bottom of it's power band in the first few tenths of a second after the "hit" (locks up too quickly), or causes excessive wheel spin.

Lines 1/2/3/4 all hit with too little clamp pressure, and take an excessively long time to reach the 200Psi "sweet spot" band threshold.

Line 5 line (dark green) is the first one that drops instantly into the upper "sweet spot" area with a "hit" point of 200 Psi. Lines 5/6/7/8 hit increasingly harder and all instantly hit within the sweet spot band. Lines 5/6/7/8 would also all be in the ballpark with one another ET wise.

If your goal is to protect the drivetrain... line 5 would be a softer hit but with a compromise on reaction time.
If your goal is putting down power and low ET's... line 8 will be quicker and 60' better than line 5.

Line 9 represents too hard of a "hit" that would either damage the drivetrain, or cause ET to drop off.

Step 1- Initially set the "Outer Delay Knob" clockwise to a point where the clutch pedal takes more than 20 seconds to return. This is important as it effectively dials out the delay function, which allows us to concentrate specifically on dialing in a properly firm amount of initial hit.

Step 2- Perform a series of "rolling launches". We usually drive a less travelled backroad in 3rd gear at around 2500, push the clutch pedal against the stop raise rpm to around 4500, then go WOT and watch the tach while quickly releasing the clutch pedal.
...If rpm quickly gets pulled down to match road speed in less than a second, give the clutch a little time to cool, then turn the inner "initial hit" dial 1 or two turns counter-clockwise and repeat Step 2 until it doesn't.
...If rpm holds steady or quickly flares above 4500, give the clutch a little time to cool, then turn the inner initial hit dial 1 or two turns clockwise until rpm gets pulled down around 1000 rpm in about 1 second. If you have an organic or Kevlar disc, or have a lightweight mini clutch, wait 5 min or so before repeating to protect the clutch from overheat.

Step 3- If things feel good, you are ready to make a rolling start 1st gear pass thru 2nd gear. If the clutch seems to slip way too long on the 1-2 shift, that's an indication the car wants more "initial hit". Add 1/2 turn of "initial hit" (inner dial clockwise), then repeat the pass thru 2nd gear. Keep repeating (adding another 1/2 turn each time) until the shifts are firm but not violent.

Step 4- You are ready for a short 20' test launch from a 4500rpm standing start in 1st gear at the track. At this point we are still looking for the clutch to pull the engine down only somewhere around 1000rpm in about 1 second or 20'. These test launches are only 20'
...If the clutch pulls the engine down less than 500 rpm in 20', abort the run. Give the clutch a little time to cool, then turn the inner dial 1 click clockwise and repeat step 4.
...If the clutch pulls the engine down more than 1000 rpm in 20', abort the run. Give the clutch a little time to cool, then turn the inner dial 1 click counter-clockwise and repeat step 4.
...If the clutch pulls the engine down somewhere around 1000rpm in 20', continue the pass thru 2nd gear. If the shift seems too soft, add another 1/2 turn of "initial hit" (inner dial clockwise).

Step 5- measure/record your setting. The most common method is to measure the gap between the inner "Initial Hit" dial and the inner part of the dash bracket's slide bushing. A small dial caliper works great. The gap you are measuring can be seen in the center of the picture to the right.

Adjustment #2- Secondary Clutch Lockup Delay...

This adjustment controls the secondary horizontal drop/angle on graph AFTER the "hit" point. This angle determines how long clutch pressure stays within the sweet spot band.

The "Initial Hit" adjustment controls how quickly the clutch enters the "sweet spot" band, the "Lock-up Delay Knob" controls how long the clutch stays within that band before the clutch locks up.

Step 1-...rotate the outer "Lock-up Delay Knob" counter-clockwise until you can feel the added resistance to rotation when it reaches the end of it's adjustment range. This point is what we call the "0 Turns" adjustment.

Step 2-...It is suggested that you begin delay tuning with an initial "Lock-up Delay Knob" setting of "3" turns, simply rotate the outer "Lock-up Delay Knob" clockwise "3" turns from it's initial "0" turns starting point.

Step 3- ...Stage at around 4500 rpm, then make a run thru 1st gear while observing your tach. Have an outside observer watch for tire spin.
...If the engine loses more than 1000rpm in 1st gear, rotate the outer "Lock-up Delay Knob" 1 click clockwise, then return to step 3.
...If your engine loses less than 500rpm in 1st gear, give the clutch some time to cool, then rotate the outer "Lock-up Delay Knob" 1 click counter-clockwise, then return to step 3.
...If your tires spin more than a little, try adding a clockwise turn of "Initial Hit". Sometimes a chassis needs to hit the tires just a little harder, which gives weight a little more time to transfer. If more "Initial Hit" makes the tire spin worse, you might have to lower stage rpm (or take a little gear out) to keep from overpowering the tires. Basically when a properly geared car is launched, we want engine RPM to dip somewhere between 500-1000 rpm below the 4500 "staged" RPM at it's lowest point.

Step 4- Record your outer "Lock-up Delay Knob" setting.

NOTE- The above procedure will get you to about 95% of your potential. To get that last 5%, you will likely need some data. Timeslips from the track are very useful, but adding a data recorder can save a lot of trial/error testing.


Clutch Tuning With A Data Logger...

G-meter output is affected by pitch rotation, which basically means a 6k/1.75g launch with a big wheelie could actually be slower than a 5.5k/1.45g launch with a smaller wheelie. You will be able to compare runs with more accuracy if you first zero the runs to the first movement of the g-meter, then overlay the runs to compare the differences in both Erpm and DSrpm traces.

Most important for clutch tuning is the angle/shape of the Erpm trace as it is falling, as this is the ONLY part of the trace that is basically controlled by the clutch when the engine is at WOT. This is where you will be able to see area added "under the curve" to the rpm trace after the launch and after shifts, which are generally indicators of increases to power production which were made possible by adding/controlling clutch slip.

To verify overall gains from clutch tuning, compare the time it took from first movement of the G-meter to a selected DSrpm just before the finish line. These are points in the run where wheel spin is least likely, which in turn means they are points more likely to be accurate indicators of vehicle speed (this assumes of course that you are concentrating on clutch tuning, with no changes to gearing/tire size/air pressure). Basically you are looking for the quickest time overall from first movement of the G-meter, to a selected DSrpm just before the stripe.

You can also compare clutch performance during individual shifts on different runs by selecting a DSrpm just before that shift, as well as a DSrpm just before the next shift, then comparing the times between those two points.


Please Read These Important Notes-

2-STEP / LINE-LOCK SWITCHES MUST NOT RELEASE FROM TOP OF CLUTCH PEDAL TRAVEL!!! With the ClutchTamer operating properly, your clutch pedal will not return to the top of it's travel until several seconds after the clutch pedal is released. Depending on your settings, it may not return to the top of it's travel until after your run is complete! If you use an oem style upper clutch pedal switch to release the 2-step and/or line-lock, the result at minimum will be a several second delay of when the pedal contacts the clutch switch. Late release of the 2-step will likely only cause a performance issue, but late release of the line-lock will cause a HUGE SAFETY ISSUE! Please make sure that your line-lock is not releasing AFTER the clutch hits!

ALWAYS RELEASE THE CLUTCH PEDAL FROM THE STOP WHEN CLUTCH TUNING or LAUNCHING !!! Before you install or test your ClutchTamer, it's very important that you install a clutch pedal stop and verify it's proper adjustment. By proper adjustment, we mean a setting that allows enough clutch dis-engagement to achieve clean hi-rpm shifts, also enough dis-engagement to be able to put the transmission into gear without grinding when the clutch is warm. Using a pedal stop helps ensure a consistent release point, which in turn helps ensure that you get repeatable results. If for some reason you have to change your pedal stop height after you begin the setup process (maybe you find the clutch isn't releasing cleanly which causes a shifting problem), you will need to go back to Step 1 and do the setup process all over again.

DO NOT "PRE-LOAD" YOUR CLUTCH BEFORE LAUNCH!!! It is important to release the clutch from a properly adjusted pedal stop. Many import racers "pre-load" their clutches in an attempt to minimize parts breakage, DO NOT do this when using the ClutchTamer. Pre-loading is basically releasing the clutch pedal to a point where the clutch starts to drag before the green turns on, an attempt to take all the "slack" out of the drivetrain. Pre-loading while using the ClutchTamer will result in less pedal travel on the launch and more pedal travel during shifts, which will result in excessive clutch slip after shifts made using the clutch pedal.

LAUNCH RPM CAN AFFECT YOUR CLUTCH TUNEUP!!! Even without any sort of "centrifugal assist", a typical 10.5" diaphragm style pressure plate can gain around 350lbs of clamp pressure going from 4000rpm to 7000rpm. You can choose any launch rpm you want, but it's a good idea to keep launch rpm consistent if you want consistent results.

CONSIDERATIONS FOR CLUTCH TUNING WHEN USING A SINTERED IRON DISC- it is important to allow plenty of time between test hits for iron disc temperatures to normalize. Basically no "back to back to back" test hits without some cooling time in between. The reason is the fact that the iron friction material actually bites quite a bit harder as temperatures go up. If you have an iron clutch where the "Initial Hit" setting was tuned to a much higher than normal disc temp, that clutch will likely slip way too much during a typical launch. If the engine is running, 5 min of cooling time between hits is usually enough. A non-running engine will need 10-15 min between hits due to less air circulation.


Frequently Asked ClutchTamer Tuning Questions...

Is there a ballpark "initial hit" setting that I can use to get started?
No, there are just too many variables. Even two cars with identical engines and clutch setups, but with different pedal stop adjustments, will require different initial hit settings.

My clutch pedal doesn't have enough time to return all the way up before it's time to shift. Is this a problem?
That's normal, and more noticeable when the clutch has a lot more capacity than the engine. Basically it's because the target window between a "properly firm initial hit" and "clutch lockup" is very narrow, and we are using the ClutchTamer's delay function to widen that window. It's not a bad thing and actually speeds up your wot shifting, as it effectively shortens pedal travel. Because the pedal has not yet returned all the way back to the top, now your foot won't have to waste time pushing the pedal thru that deadband area when you reach your shift point.

Can I make the Clutchtamer active only on launch, with no slip after the shifts?
Generally if someone is experiencing too much slip after the shifts when using the ClutchTamer, it's because their "Initial Hit" setting is not yet aggressive enough (needs more clockwise adjustment to inner "Initial Hit" dial).

That said, if one wants to experiment with "active only on launch, with no slip after the shifts" while using the ClutchTamer, they can simply set the pedal stop deeper- basically use the pedal stop for launch only, then just stab the pedal for shifts instead of bouncing it off the stop. A more precise alternative is to keep the pedal stop setting that's optimal for shifting and install a drop out spacer between the delay knob and dash bracket for launch. Gives you the same result but allows bouncing the pedal off the stop during shifts.

Here's a comparison of two nearly identical back-to-back ClutchTamer passes. Both feature zero wheelspin during launch (no wheelspin variable), and "clutchless" faceplate shifts (no human pedal actuation variable). Both of these runs share the exact same ClutchTamer "Initial Hit" setting.
...The blue pass has a lower than optimal ClutchTamer "Delay" setting, and bogs to 4622 rpm at .728 sec into the run.
...The yellow pass has an additional 1/2 turn of clockwise of "Delay" added.
The basic result of adding more clockwise "Delay" was a decaying amount of additional slip time to be added after each successive shift. That added slip time after launch raised bog rpm to 5202, which increased the engine's hp output thru the low point of the bog. That added power helped the car reach the top of 1st gear 0.089 sec quicker. That added slip time also slightly reduced wheelspeed spikes after each shift, which improved net power overall to the point where the yellow pass reached the same driveshaft rpm 0.502 seconds quicker at the top of high gear. Notice that the car gains rpm at exactly the same rates in each gear on both passes. All the improvements come on the parts of the graph where the engine is losing rpm, which are basically the only parts of the graph that are controlled by the clutch...

Here's a graph with just the engine/driveshaft ratio displayed, so you can better see the differences in clutch slip time...

As you can see, it didn't take much of an increase in slip time to make a huge difference in ET.

Can I use a ClutchTamer with a SoftLoc style clutch?
Yes, you can. The main benefit will be that you will no longer have to compromise your launch to keep your clutch from slipping in high gear.
...If you are shifting using the clutch pedal and your PP has plenty of spring, we recommend that you remove all your counterweights and maximize your base pressure. If your PP doesn't have enough base pressure available to lock up the clutch in high gear on it's own, we prefer to install stiffer springs to achieve high gear clutch lockup, but in a pinch you can add just enough counterweight to get the job done.
...If you are shifting clutchless, you will be able to raise your 2-step setting to gain a little performance in 1st gear, we also recommend higher delay settings as a way of adding a decaying amount of slip after each clutchless shift. By adding a little slip after the shifts you will gain a little power production as the engine will not get pulled down as far, but you will also be reducing the size of the wheelspeed spike which represents an efficiency gain.


Congrats to Coyote Stock Winner and ClutchTamer user Charlie Booze Jr & his crew, shown here picking up a $3600 check at the NMRA/NMCA SuperBowl event!

If you have any questions, feel free to e-mail me