The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support STM Tuned
Please Support Morrison Fabrication

Clutch Too Aggressive? Here's a way to calm it down, requires a little fabrication

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Ok I think I see where you are getting confused. The flywheel does not multiply engine torque and is not multiplied by engine torque, rather the RPM at which the motor is spinning the rotating assembly is what multiplies the torque. It is the speed of the rotating assembly that multiplies the torque produced by the rotating assembly. The torque it produces has nothing to do with the torque the engine is producing. The only thing the engine can do to increase the torque the rotating assembly puts out is spin faster. The faster it spins the more inertia the more torque is produced completely independent of torque produced from the engine itself.

Okay cool, now we're on the same page completely.
[...]

The flywheel torque is enough to get a factory dsm a 1.7 60 foot with a 5500 rpm launch. So a car launching with about 100 instant lbft plus flywheel weight can overcome the 3200 lbs of potential energy and drivetrain loss because of this instantaneous torque spike.

I want to reply to your entire post but save space on the page, haha. We're all at least understanding each other well now, :).

The potential energy in the flywheel isn't going to change regardless of how it is applied, either by the edge, or near the edge or even at the center. However in a clutch system, the flywheel is going to transfer its potential into the clutch, where the clutch is spinning around the input shaft at the exact center of the inertia forces.

When I take a wheel and spin it, stopping it from the outside is of course harder than stopping it in the middle. To me, something running on the inside (gear type) is a reduction type.
You must be logged in to view this image or video.


But the clutch disc really isn't a reduction.. so help me here??
 
Well this is what I'm talking about. There is respect to time, if time is involved there's no way in my minds eye, that 100% of the actual force is immediately transferred from the front to the back. It has to have feedback otherwise there's nothing to overcome and no force is realistically applied in any great number to anything between the flywheel and the wheels that are spinning.

And since we both agree that the ground is applying force back to the drive train, how do you not agree with me that the force is actually built up, but rather immediate ?

Here's one you might go outside and try for yourself. Let's make a crude attempt to separate stored inertia energy from engine power. This exercise will give you a rough demonstration of inertia energy and the torque it can add to your transmission's input shaft during a launch...
...Take your car somewhere safe and do a 6000rpm launch, but this time at the precise moment you drop the clutch, also hit the ign kill switch and release the throttle. It's stored inertia energy alone that will power your car...does your car still move? I know your tach isn't going to work, but how long do you think it took for rpm to drop from 6000 to 4000rpm...did that loss of 2000rpm happen in a couple tenths of a second? The engine wasn't making any power, but how much torque do you think was applied to the transmission's input shaft for that happen that quickly?
 
When I take a wheel and spin it, stopping it from the outside is of course harder than stopping it in the middle. To me, something running on the inside (gear type) is a reduction type.
?
Stopping it from the outside would be easier actually. That's why bigger disk brakes stop better. Put a flywheel or some heavy rotational mass on a mandrel or something to spin on. Try stopping it by pressing your finger down about half an inch to an inch from the center. Now do it again but right on the outside. It takes MUCH less force to stop it in the same time and will thus stop faster if the same amount of force is applied.
 
The potential energy in the flywheel isn't going to change regardless of how it is applied, either by the edge, or near the edge or even at the center. However in a clutch system, the flywheel is going to transfer its potential into the clutch, where the clutch is spinning around the input shaft at the exact center of the inertia forces.

When I take a wheel and spin it, stopping it from the outside is of course harder than stopping it in the middle. To me, something running on the inside (gear type) is a reduction type.
You must be logged in to view this image or video.


But the clutch disc really isn't a reduction.. so help me here??

A flywheel is an energy storage device much like a battery, flywheel rpm is what provides the exponential component. Double it's speed, it stores 4 times the power. Stated another way, you will have to charge the flywheel with 4 times the energy to double it's speed. It's speed is what indicates how much it's energy content has changed.

Lets take an example flywheel spinning at 1000rpm. It contains enough energy to supply 10 ft/lbs of torque for 100 seconds before it's speed drops to zero rpm. Basically, it contains 10 ft/lbs x 100 seconds (1000 ft/lb seconds) @ 1000rpm. That 1000 lt/lb seconds can be extracted as 1 ft/bl for 1000 seconds, or 1000ft/lbs for 1 second, but it still only contains 1000 ft/lb seconds total energy. Let's see how much energy that same flywheel stores when the speed is increased...
1000 ft/lb seconds @ 1000rpm
4000 ft/lb seconds @ 2000rpm
9000 ft/lb seconds @ 3000rpm
16000 ft/lb seconds @ 4000rpm
25000 ft/lb seconds @ 5000rpm
36000 ft/lb seconds @ 6000rpm
49000 ft/lb seconds @ 7000rpm
64000 ft/lb seconds @ 8000rpm
 
Last edited:
36000 ft/lb seconds @ 6000rpm
49000 ft/lb seconds @ 7000rpm
64000 ft/lb seconds @ 8000rpm
Notice the unit of energy is in ft/lb seconds. This is what we were trying put point out early on in the thread. It is the energy released over a period of time and the clutch is usually released pretty quickly which is why the torque put out from it is so high. Think of it like a battery or supercap like clutchtamer said. You could have 5000mAh and discharge it very quickly while releasing a lot of current(a lot of torque), or release it slowly over a longer period off time which will mean less current(less torque) is put out. Makes sense now?
 
Inertia isn't a force, and it doesn't break anything. Inertia is a storage medium. A large body at rest has lots if inertia even though it has 0 potential or kinetic energy. Inertia acts through a change in motion to create a force. In this case it is a change in angular velocity creating torque.

Must be frustrating to hear me keep referring to "inertia energy" :)
 
Must be frustrating to hear me keep referring to "inertia energy" :)
Well is it though? Newton says it keeps a body at rest at rest yada yada unless acted upon by a force. On the other hand there is papers published called the force of inertia. Idk maybe using bastard's words an object is the storage medium that uses inertia to store energy. Whether inertia is a force or not is still fought over quite frequently, but we all understand the mechanics of what it does so maybe that can be a discussion for another time. I think it would be cool to have a debate section with a poll on the forum just to settle and discuss stuff like this in a mature way. Maybe something Chris can implement in the future. :)
 
Last edited:
So now your back pedaling on your initial post, and your god of driving? I'd like to see you repeatidly launch a twin disc car with no launching aids, and do well... We look at this becasue with an agressive clutch you might have .5" of engagement zone out of 5-6" of pedal travel, it is tough to slip it enough to get the car out of the hole.

Why don't you bring your car down to my house, and I'll show you how a real man does it ? I've driven plenty of DD vehicles in my hay days, the thing I hated most was the idle noise, sorry.

But in all seriousness, it isn't uncommon for my truck to have dual discs, and yet no one complains about having a hard time launching their truck.

What I'm happy about seeing here is a more accurate description of the things that are really happening. When I first read through it was implied that flywheels were multiplying torque output. Which that's finally been cleared up.

What I don't get is how the energy stored in the tire that causes it to buckle and run over itself, still isn't understood. If the tire needs to spin clockwise to propel the vehicle forward, and it flexes and buckles, the opposite reaction is for it to want to rotate counter clockwise, which would be backwards. Everyone else seemed to figure that out once I showed the picture.


Since we have math on our side, is is actually possible to figure out a rough estimate of potential energy stored, knowing your gear ratios, weight, and acceleration ?
 
Just got am email from a guy that ran MIR last weekend with his '89 Mustang. He runs NMRA Factory Stock, been trying to get his radials to work with a manual trans for about a year. There's very few manual guys left, most switched to auto. He's been playing with springs/shocks/chassis, tried a few different clutches, not much improvement. A week before this race, he called and had me send him a ClutchTamer, it arrived on thurs before the race.

Here's a typical run without the ClutchTamer, 1.72 60', either bogs or spins the radials. 2 passes later he broke 1st gear...
You must be logged in to view this image or video.

Fixed the transmission and added the ClutchTamer for this race, next 2 runs were 1.45 60's...
You must be logged in to view this image or video.

Needless to say, he can't wait until the next race so he can dial things in a bit more.
 
Last edited:
I put the following article together to help illustrate the benefits of clutch slip, same guy/car in the videos above...

Here's some feedback from a NMRA Factory Stock racer. Powered by a 302ci crate engine, the stick cars are required to run a diaphragm clutch. This guy was having a terrible time, as he was a slick racer switching to radials (radials are a class requirement). With a 4300 launch, the radials bogged the engine to 2300rpm and 1.71 60's. Stepped up to a 4800rpm launch in an attempt to eliminate the bog, this is what happened to his faceplated TKO...

You must be logged in to view this image or video.


He repaired the transmission, and I sent him an in-dash version of the ClutchTamer to try. He installed the ClutchTamer, made a few test hits in the driveway to get familiar with it, then went to the track. Results were dead hooked radials and back to back 1.45 60's. This graph is from a 1.42 run...

You must be logged in to view this image or video.


Several months later, still 1.4 60's at class weight and no transmission failures from 5200rpm launches.

Here's the same graph w/ a couple lines added to help illustrate the benefits of delaying clutch lockup. His graph is fairly easy one to understand, as there is very little wheelspin to confuse things...

You must be logged in to view this image or video.


The added orange line is a rough representation of the engine's ability to gain rpm in 1st gear.
The 1st added vertical black line represents the beginning of clutch engagement.
The 2nd added vertical black line represents the point of clutch lockup.
The distance between the two vertical black lines represents the time it took for clutch lockup to occur.

Clutch slip duration was roughly .7 seconds, engine rpm at lockup was about 5100.
…If clutch lockup had occurred at .4 seconds, engine rpm would have been pulled down to appx 4200 on the orange line.
…If clutch lockup had occurred at .25 seconds, engine rpm would have been pulled down to appx 3500 on the orange line.

The basic point is- the earlier clutch lockup occurs, the lower the rpm point on the orange line that the engine will have to accelerate from.

This is a bit of a simplified explanation, as reduced engine output at the lower rpm would also reduce the engine's ability to gain rpm. That added power loss is not reflected here.

Here's another point I'd like to expand on- controlled clutch slip after the shifts is quicker than minimal clutch slip. Don't waste time trying to eliminate clutch slip after the shift, thinking that it's only a waste of power that could otherwise could be applied to the track. Truth is that the engine is burning more fuel spinning at the higher rpm, producing additional energy beyond that which is being absorbed as heat in the clutch assembly.

Anyone wonder why that orange line on the graph aligns with 2700rpm at launch instead of zero rpm? It's because the line representing rate of acceleration is actually even steeper before the clutch locks up. This happens because no power was used to accelerate the rotating assembly prior to lockup, so more power was available to accelerate the car. Here's the same graph, with a red line added to represent acceleration rate before clutch lockup...

You must be logged in to view this image or video.


See how much steeper the car's acceleration rate was before clutch lockup?

This launch could have reached it's shift point even quicker if the clutch had slipped longer, as the car would have rode the trajectory of that steep red line to a higher point before switching to angle of the orange line. Same applies to the shifts as well, a car can simply accelerate quicker before the clutch locks up. The longer the clutch experiences controlled slip after a shift, the longer you can ride a steeper acceleration rate.

The lightest clutch assy may not necessarily be the quickest when it comes to exploiting clutch slip, as the clutch needs to have enough thermal capacity to absorb the slip without overheating/warping. Having plenty of clutch capacity for the task is the 1st requirement, then it's a matter of controlling the application of clutch pressure to match engine power.
 
Last edited:
Something else to add for the radial guys...

The big thing with a radial is that you basically have a line that you don't want to cross when it comes to shocking the tire. Anything you can do to smooth out power delivery is going to make it easier to operate closer to that line. Any torque peaks that you have in your power delivery need to be shaved down, which basically allows you to elevate the average amount of power you can deliver to the tire...make sense?

Counterweight style clutches produce an RPM drop trace that looks more like a backwards "J" with a hook at the bottom. Their sharp, near vertical drop indicates a quick loss of rpm (intense discharge of inertia energy), which transitions into a gradual "hook" near the bottom when the clutch begins slip more. That hook area at the bottom of the "J" is where most of an adjustable's slip actually occurs. The intense vertical drop is something you have limited control over, as a centrifugal design dictates that rpm must come down before clamp pressure can be reduced. This is a big reason why SoftLoc's and such are only marginally effective when trying to run radials, as they still have a relatively intense discharge of inertia energy just after the shift, until rpm comes down enough for the bulk of their slip to occur.

A diaphragm PP combined with a ClutchTamer makes it possible to build a slipper clutch that has a more diagonal/linear rpm drop trace than the typical centrifugal. This softer engagement in the instant just after the shift helps keep those radial tires stuck.

If you have a clutchless transmission, the basic ClutchTamer will not give you any slip after your shifts, so your only current solution would be to use a traditional adjustable PP that has a centrifugal component. That gets you at least some form after shift slip, even though the "J" shaped rpm drop is less than optimal. The future will bring a system much like a fuel car, which will use some form of pneumatics or hydraulics to get the control needed to change that.

The ClutchTamer is just a brutally simple way to control a clutch. I'm sure myself and others will soon come up with more sophisticated/expensive means to get basically the same job done, you will have to wait if that's what you are looking for.
 
So, have you actually tested this with real world data on your car yet? Or just looking at whatever the other dude is doing with a hardware store part welded to his pedal assembly.

I have seen hydraulic and air cylinder setups before on clutch pedal assemblies either by valving duration, or by electronic control to air cylinder. It is not exactly ground breaking. I have no issues slipping out a twin disk and pulling 1.4's in my car with relatively gentle launches.
 
My personal car is a nitrous street car that runs 5.73 w/ 1.30 60's. Here's what happened when i dis-connected it's ClutchTamer a couple years ago in an attempt to conduct a before/after test...

You must be logged in to view this image or video.


Here's the url to my car's webpage... http://tntrc.com , scroll down to see it's ClutchTamer install.
 
Last edited:
Actually, I have been on your website before, back in my Rotary days I followed the Grannysspeedshop page closely in the 1990's-2000's.

Though the driveshaft failed in your car, it could have been already stressed and just needed the shockload to pop. I fully agree that a consistent clutch slip-out with a full face disk (solid hub or sprung hub) or multi-disk clutch is a good thing and it would likely reduce the drivetrain shock on the launch and help with launch consistency. I utilize a hydraulic staging brake and twin disk to preload the car on the launch. The problem with air-assist or other solenoid options is all the setup and tuning time, and I agree that the simple hydraulic assist with a simple manual adjustment is the most cost effective and easiest style to hook up. From the factory, the 2G DSM had a hydraulic residual valve before the slave cylinder to create the same effect.

I am not completely discounting the slip-out pedal setup, but on our setups with AWD, it typically works better with a multi-disk clutch or a full face Feramic or Ceramic or sintered Iron disk. Utilizing a single disk puck clutch with this style of device can easily have a driveline failure.
 
It twisted the slip yoke splines as well on that launch, that's never a problem with the ClutchTamer in place. Exact same spec shaft and yoke are in the car right now.

I agree, if you are going to fully exploit clutch slip you need to have plenty of clutch capacity. But that does not mean that you can't enjoy at least some of the benefits with a lesser clutch. It does not take much slip to effectively reduce peak shock to the drivetrain.
 
Thought i'd add an update as to where things have gone since l posted my simple fabrication project here over a year ago...

Last June I had a Honda performance shop come to me that wanted to swap out a Magnus unit for one of my ClutchTamers on their 1500hp triple disc shop car. Their shop car was plenty fast with the Magnus, but the r/t's sucked. They installed the ClutchTamer and r/t's greatly improved, so far they have purchased 4 more for other projects. The shop car is now a record holder with 7.804 @ 190.27 1.384 60'.

Many NMRA Coyote Stock and Factory Stock racers now using the unit, including the current Coyote Stock record holder. His former record before the ClutchTamer addition was 9.831 @ 131.25 1.389 60'. His new record is...

You must be logged in to view this image or video.


Keep in mind that Coyote Stock uses sealed crate engines and spec tunes, so everyone has basically the same power. They must run diaphragm pressure plates, adjustable long style not allowed. They are limited to certain 5 and 6spd od transmissions (they generally remove the od ratios and use 1-4) and have a limited list of spec ratios that that they are allowed to choose from. These guys are also required by the rules to use the clutch to shift, no clutchless shifts allowed. Same car, same driver. The big difference between the before and after times above, is that the ClutchTamer made it easier to exploit clutch slip to achieve a higher average rpm...both on launch, as well as after the shifts.

Here's a simplified generic example to help illustrate why you want to keep average rpm after launch as high as practically possible, same thing applies when you extend clutch slip a bit to minimize rpm drop after the shifts-

Lets say a car gains rpm at an average rate of 6k per second in 1st gear. Let's also have the clutch lock up .5 sec into the run with the tires remaining dead hooked. If it is launched at 6k, tires are stuck, and the clutch locks up at .5 sec, rpm is going to get pulled down to 3k by .5 sec into the run. From .5 to 1.0 seconds it climbs from 3k back up to 6k, regaining the lost rpm. What all this boils down to is that during the initial 1 second after launch, the engine's average rpm was 4500 rpm, which means the engine made 75 revolutions over that 1st second of the run.

Now suppose that same car launches at 6k, but the clutch slips just enough that the engine does not lose any rpm over that same 1 sec period. Now the engine's average rpm was 6000, which means it made 100 revolutions during that initial 1 second period.

Both left from the same rpm, but the launch that didn't lose any rpm actually packed 33% more revolutions of WOT power production into the same 1 second time period.

Not only does my ClutchTamer project reduce shock to your drivetrain and tires, it can also make you faster by allowing your engine to produce more power over the duration of your run.

Grant
 
Wow, what a gem! Never seen this thread before in all my 7 years on this website. Very interesting read
 
Anyone else think that this device just turns the rotating inertia of the engine and flywheel into clutch disc heat? I agree it will make the launches softer and help to not blow off the tires, but theoretically you are transferring energy less efficiently and therefore losing energy that could be propelling the car forward.
 
Yeah I ran one on my car. Worked pretty good in my opinionion. Way better than the magnus device. I had 2 problems with it.
1.temp changes threw it off.
2. The slip between shifts didn't work out to well for me. It took too long to retract and would keep the nlts engaged to long.


I wonder if you could somehow turn this off after the launch. I could see how it would really mess up the 2-3 & 3-4 shifts.
 
Added wear to the clutch is less than you would think. My personal street/strip car isn't DSM or even turbo, but currently has a 2800lb diaphragm with a 10.4" solid hub full face 5135 iron disc. It NEEDS that much clamp to hold 800ft/lbs for those times when the little 355 gets both kits turned on. But as you can imagine, that much clamp on an iron disc is going to hit pretty hard. Now imagine me trying to launch naturally aspirated or maybe just one kit with that much clamp on an iron disc...not pretty without the ability to dial out some clutch. When i was at 700whp I used a 900 series segmented iron disc and that lasted 2-3 years with about .5 to .7 seconds of WOT slip. But here's the thing- the car gets faster the longer i let the clutch slip. For me personally, dialing in 1 second of slip is a good compromise that puts me in the comfortable position of a clutch disc lasting a full season without needing maintenance. I'm mostly a no-prep guy, so smooth power delivery and being able to add power as i work my way thru the gears is big to me. Can’t do that with a typical adjustable set for a good launch, as bringing on more power down the track just blows thru the clutch.

The slip after the shifts adds area under the rpm trace, which means you make more power in a tighter time frame. It's generally a good thing, not bad. If you experience too much slip after the shifts, it likely means you could add power to the launch or raise the 2 step, which would in turn require a harder launch hit that would be a better balanced hit for after the shifts. Another solution is a friction material that gains cf with heat, which would also make it grab harder after the shifts.

This guy is also uses a slipper to get 1400hp thru his T56...
You must be logged in to view this image or video.


Here's a slip from a customer's NMRA Coyote Stock car record run. These guys exploit the shit out of clutch slip to get an edge on the competition, disc's don't last very long at their insane slip levels. Note the crazy 60' as compared to the mph. It's NA, but they run a factory sealed crate engine, spec tune in the ecu, spec fuel, spec transmissions/ratios, and 10 or 10.5" single disc diaphragm clutch. Previous best was 9.831 @ 131.25 1.389 60' before adding a slip controller, he used to just shim the pp to a compromise between loose enough fora good launch and tight enough to hold down track...

You must be logged in to view this image or video.


Adding the slip controller gives him more slip for a better launch, while still having enough clamp to hold down track.
 
The below graphs show "Psi" data recorded from a hydraulic throwout bearing, while using one of our ClutchTamer cylinders to control the release of the clutch pedal.
...The 1st graph below shows a range of incrementally increasing amounts of "initial hit" (controlled by the ClutchTamer's inner "initial hit" dial), basically giving you the ability to instantly release the clutch pedal to a precise point in the pedal's travel. This is important because it gives you the ability to temporarily withhold or "dial out" excess clutch clamp pressure, which would otherwise pull the engine down and cause a bog.
...The 2nd graph below shows a secondary range of pedal release rates (controlled by the ClutchTamer's outer "delay" knob). This gives you the ability to precisely and independantly control the clutch pedal's travel rate beyond the "initial hit" point, which is important because it gives you the ability to separately control how long the clutch slips...

You must be logged in to view this image or video.


You must be logged in to view this image or video.

In a drag race setting, controlled clutch slipping makes it possible to raise an engine's average rpm, increasing the amount of power it can produce in a compressed time period. Sure you lose some of that power increase due to heat absorbed into the slipping clutch assy, but there's plenty of that power increase left over to make the car quicker/faster. The NMRA Coyote stock guys are great examples of this, as they currently use a factory sealed crate engine that puts out 412hp @ 6500 / 390ftlbs @ 4250 using a class spec tune. At 3175lbs, the current class record is 10.075 @ 131.86. Calculators say 10.075 @ 3175lbs requires around 620whp.

Grant
 
Interesting. Poor mans proportioning valve, only done by mechanical means. Correct me if I'm wrong, doesn't the screen door cylinder work on air, thus adding slop, or lack of resistance in the first initial travel is due to compression of the air? Trying to grasp why the release is SO much better than what Magnus sells.
 
Last edited:
I would expect similar results could be accomplished with the addition of a line lock setup both parallel and inline to the Magnus system with the line locks wired to say a brake switch(s) or wired to an ECU.
 
There are improvements to the actual ClutchTamer over the "Hillbilly Slipper" version that this thread is about. The current ClutchTamer is much shorter than the VH440 hydraulic screen door closer used in the Hillbilly version, uses a much lighter internal spring rate, we have also added detents to both the initial hit and delay adjustments.

Basic differences between Magnus and ClutchTamer...

1- Magnus unit requires "pre-loading" to make the best of delayed reaction times.
...No pre-loading with the ClutchTamer and no delay of reaction times.

2- Magnus requires a solenoid bypass to eliminate excessive clutch slip after WOT shifts, resulting in clutch engagement that's too aggressive.
...Clutchtamer can actually create a productive amount of clutch slip after WOT shifts, making the car quicker while simultaneously reducing impact on drivetrain components.

3- Magnus solenoid bypass allows quick return of clutch pedal, meaning each push of the clutch pedal begins at the top and includes deadband travel.
...ClutchTamer controlled pedal does not have enough time to return to the top before WOT shifts, which effectively shortens pedal travel for quicker WOT shifts.

Grant
 
Last edited:
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top