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Exedy dual disc clutch

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6,288
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Doing what I said I would never do, installed a 2D clutch. The original in my 07 Gt500 died around 24K miles. I replaced it with a Spec single. The pedal was always low, but acceptable, Spec didn't do me any favors in the customer support area concerning throwout bearing shims. 24K miles later, I noticed the synchros dragging, so I decided to take it apart and add a shim.
Dean at Kohr Motorsports, talked me into the Exedy 2 disc. Besides the low pedal, the other thing I didn't like was the massive flywheel in the Spec. I'm not a fan of heavy wheels.
So we installed the Exedy, a much lighter flywheel, throwout bearing and pilot bearing.
I just took it on a 70 mile trip.
I have to get used to the super light pedal, and the car accelerates much faster with the lighter flywheel. It's too soon to do any smokey burnouts, but so far, I would highly recomend this clutch.


20231102_093722.jpg
 
The clutch is almost too easy to push in. I'm an old school linkage guy and this is like pushing on a marshmallow
I've had race clutches that made my leg quiver, this is the exact opposite
Yeah I remember holding the left pedal down on a transplanted 428 dual quad monster in a 67. My hesitation with going to the lightened flywheel is driveability when creeping around town.
 

xr7

TMO Addict?
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812
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Yeah I remember holding the left pedal down on a transplanted 428 dual quad monster in a 67. My hesitation with going to the lightened flywheel is driveability when creeping around town.
My 1st car was a 63 Galaxy 406 4 speed. The short block was toast, swapped all the stuff onto a 352 short block. Very stiff Long clutch. Everybody that I ever tried to teach to drive it couldn't believe how hard the clutch was. Then I would offer them to come down to the shop and try a truck or coach.
 

xr7

TMO Addict?
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Minnesota
The clutch is almost too easy to push in. I'm an old school linkage guy and this is like pushing on a marshmallow
I've had race clutches that made my leg quiver, this is the exact opposite
Blacksheep-1,
Is the clutch very noisy when its pushed in? I'm looking at this job this winter.
The engine is still stock only going to put headers on it.
Thanks
 
6,288
8,019
Blacksheep-1,
Is the clutch very noisy when its pushed in? I'm looking at this job this winter.
The engine is still stock only going to put headers on it.
Thanks
It's actually noisier when the clutch is out and the trans is in neutral
 

Dave_W

Cones - not just for ice cream
963
1,251
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
Looks like this has a full-circle solid friction disc, whereas the Hyper-Single has a puck-style sprung disc. But this uses organic friction material versus the "cerimetallic" on the Hyper-Single. I don't think one design is necessarily better than the other from a generic perspective. Just guessing, but it could be the organic material is easier to slip on engagement, so it doesn't need the shock absorption of the sprung disc that the grabbier cerimetallic material uses. Will be intereted in hearing how it feels after it's broken in.
 
384
483
Exp. Type
HPDE
Exp. Level
5-10 Years
Wisconsin
The clutch is almost too easy to push in. I'm an old school linkage guy and this is like pushing on a marshmallow
I've had race clutches that made my leg quiver, this is the exact opposite
The manual Mach’s have Tremec 6-speed manual with 215 millimeter dual clutch and dual mass flywheel. Double thick marshmallows when I push that in with a bit of being vague on engagement. Not to hijack your thread bs1, but the old track car still has its original 2d in it & has 88K miles on it (not all of those are track miles) so maybe your new setup will last a bit longer.
 
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8,019
@xr7 lol, I've worked on a few 405HP 406 Galaxies

@dragoon The original 2D in the Gt500 was toast at 24K miles. The Spec clutch would've been fine if the proper throwout shim was installed. I would still be using it. Spec wasn't very helpful in that respect. The clutch is actually fine, even with quite a few high RPM first gear starts.
 
How much do clutch and flywheel weigh blacksheep-1 ? My spec stage 2+ w aluminum flywheel and that billet pressure plate option was just over 38lbs.. i.e. LIGHT AS F. and its been unstoppable, drag race road race. it is starting to get tired though with some high rpm stickyness could be dirty fluid tho. Hope the excedy does well for you.. did you consider RPS carbon twin? Thats my next one.. i've seen two installed and ran and they are game changers - 26lbs total cultch and flywheel on S197.
 
6,288
8,019
How much do clutch and flywheel weigh blacksheep-1 ? My spec stage 2+ w aluminum flywheel and that billet pressure plate option was just over 38lbs.. i.e. LIGHT AS F. and its been unstoppable, drag race road race. it is starting to get tired though with some high rpm stickyness could be dirty fluid tho. Hope the excedy does well for you.. did you consider RPS carbon twin? Thats my next one.. i've seen two installed and ran and they are game changers - 26lbs total cultch and flywheel on S197.
I didn't weigh them, I'm guessing the Spec was around 50 pounds total, the Exedy was prolly 40. I'm a big fan of light flywheels.
The thing is, I had about 4 hours to get this done so it was going together no matter what it weighed.
 

Dave_W

Cones - not just for ice cream
963
1,251
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20+ Years
Connecticut
Forgive me for the following tangent into physics.

With things like clutches that you are trying to change rotational speed on, weight is important but Moment of Inertia is the proper way to measure it. The same amount of weight takes more energy to spin up and slow down the further away from the center it is. That's why high-end race cars use tiny multi-disc clutches when a larger-diameter single-disc clutch could hold the same torque. Moment of Inertia is the physics term for the combination of the amount of mass and the distance from rotational center of that mass.

(back-of-napkin level math here)
A 10" diameter clutch has around a 31.4" circumference; if it's spinning at 3000 rpm then the edge is moving at around 90mph. At 6000 rpm, the edge is moving about 180 mph. Imagine you've got a pound of steel (or aluminum) that you're trying to accelerate in a straight line from 90 mph to 180 mph in just a couple seconds - that's the same energy/work it takes to spin a pound of weight at the edge of a 10" clutch from 3k to 6k rpm over the same time. Now, a 4" diameter clutch edge is only moving about 35 mph at 3k rpm and 70 at 6k rpm. It takes much less work to accelerate that pound of weight on the edge of a 4" clutch from 35 mph to 70 mph in the same time as the 10" clutch.

Here's why MoI is more important than just "on the scale" weight for clutches (or even wheels & tires - anything that rotates and changes rpm). If you add another pound of weight to the edge of the 10" clutch, that's another pound you need to accelerate from 90 mph to 180 mph. But, if you add that pound only 2" from the center instead of 5", you only need to accelerate it from 35 mph to 70 mph for that same 3k to 6k rpm change. Even though the clutch weight is the same in both cases.
 
6,288
8,019
Forgive me for the following tangent into physics.

With things like clutches that you are trying to change rotational speed on, weight is important but Moment of Inertia is the proper way to measure it. The same amount of weight takes more energy to spin up and slow down the further away from the center it is. That's why high-end race cars use tiny multi-disc clutches when a larger-diameter single-disc clutch could hold the same torque. Moment of Inertia is the physics term for the combination of the amount of mass and the distance from rotational center of that mass.

(back-of-napkin level math here)
A 10" diameter clutch has around a 31.4" circumference; if it's spinning at 3000 rpm then the edge is moving at around 90mph. At 6000 rpm, the edge is moving about 180 mph. Imagine you've got a pound of steel (or aluminum) that you're trying to accelerate in a straight line from 90 mph to 180 mph in just a couple seconds - that's the same energy/work it takes to spin a pound of weight at the edge of a 10" clutch from 3k to 6k rpm over the same time. Now, a 4" diameter clutch edge is only moving about 35 mph at 3k rpm and 70 at 6k rpm. It takes much less work to accelerate that pound of weight on the edge of a 4" clutch from 35 mph to 70 mph in the same time as the 10" clutch.

Here's why MoI is more important than just "on the scale" weight for clutches (or even wheels & tires - anything that rotates and changes rpm). If you add another pound of weight to the edge of the 10" clutch, that's another pound you need to accelerate from 90 mph to 180 mph. But, if you add that pound only 2" from the center instead of 5", you only need to accelerate it from 35 mph to 70 mph for that same 3k to 6k rpm change. Even though the clutch weight is the same in both cases.
True, we went through this with kart clutches, but purely from the flywheel weight ( not counting any disc, or pressure plate influence) a .. say 12 in wheel, that is lighter will be easier to accelerate than a 12 inch wheel that is heavier. The thickness ( and other parameters that cannot be changed) staying the same, such as aluminum vs steel. The old L88 Chevy flywheels were kind of legendary in that their outside 2 or 3 inches were very thin, only the inner portion of the wheel ( where it had to bolt to the crank, and accommodate the clutch) was thick. Dave W is spot on in his assessment, I've cut many a kart flywheel down in my lathe.
An example of thos is when we went to axle clutches, they had massive amounts of disc area and were about 6 inches across, the engine clutches were only about 3 inches, but when you did the math, the axle clutch would win every time.
Accelerating that little clutch to around 18K RPM was much harder than accelerating that 6 inch axle clutch, at maybe 1/3 of that.
 
Last edited:

ArizonaBOSS

Because racecar.
Moderator
8,728
2,732
Arizona, USA
Rob:

Not sure if the '07 500 has a clutch-assist spring behind the pedal. The 11+ Coyote cars had one. When we added a twin-disc clutch (we used McLeod RXTs back then), we would pull the assist spring so the pedal required more effort and felt more normal.
If you have an assist spring on the 500, might be worth removing to see how you like it.
 
6,288
8,019
Rob:

Not sure if the '07 500 has a clutch-assist spring behind the pedal. The 11+ Coyote cars had one. When we added a twin-disc clutch (we used McLeod RXTs back then), we would pull the assist spring so the pedal required more effort and felt more normal.
If you have an assist spring on the 500, might be worth removing to see how you like it.

If it has one, I'll probably leave it in, you're talking to the guy witht he bionic back. We used to remove those in the old days because they wore the linkage out twice as fast, on movement, pushing the pedal wore one side, the return spring wore the other side.
 
4
1
Exp. Type
HPDE
Exp. Level
10-20 Years
Indianapolis
If it has one, I'll probably leave it in, you're talking to the guy witht he bionic back. We used to remove those in the old days because they wore the linkage out twice as fast, on movement, pushing the pedal wore one side, the return spring wore the other side.
Doing what I said I would never do, installed a 2D clutch. The original in my 07 Gt500 died around 24K miles. I replaced it with a Spec single. The pedal was always low, but acceptable, Spec didn't do me any favors in the customer support area concerning throwout bearing shims. 24K miles later, I noticed the synchros dragging, so I decided to take it apart and add a shim.
Dean at Kohr Motorsports, talked me into the Exedy 2 disc. Besides the low pedal, the other thing I didn't like was the massive flywheel in the Spec. I'm not a fan of heavy wheels.
So we installed the Exedy, a much lighter flywheel, throwout bearing and pilot bearing.
I just took it on a 70 mile trip.
I have to get used to the super light pedal, and the car accelerates much faster with the lighter flywheel. It's too soon to do any smokey burnouts, but so far, I would highly recomend this clutch.


View attachment 91025
I ran this Exedy all season. 13 track days. Completely cured the high rpm lockout. It is indeed a bit more difficult to modulate on the street. I used to pride myself on making passengers feel like they were in an automatic. Not quite possible with this clutch. However, the pros far outweigh the cons for my purposes.
 

PatientZero

@restless_performance
824
860
Exp. Type
Autocross
Exp. Level
10-20 Years
Kansas City, Missouri
In the Nissan world(GTR's and Silvias) Exedy is highly respected. I had an Exedy in my S14 and it was great other than not being able to hold the power when I went to a bigger turbo. I wouldn't run a Spec if you gave it to me.

I had a twin disk OS Giken in my Skyline and I was a big fan. Much better than a crazy stiff single in my opinion.
 

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