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Discussion Starter #1 (Edited)
A project to upgrade the hydraulic transmission components on the BM 2014-'18 Mazda 3 6MT:

Why?

1. I strongly dislike that Mazda has put plastic parts where I believe aluminum / steel should be used for strength, reliability and longevity. I want to replace it with a universal, easy to replace, more robust option.

2. By increasing the bore size I can decrease pedal travel and increase engagement / disengagement sensitivity, pedal feel and speed.

3. If / when I do find a better clutch option, the hydraulic system will need to be strong enough to handle the increased pressure required to push a stronger pressure plate

4. Rebuild-able / easily replaced alternative for CMC and CSC. The slave cylinder will end up being an aluminum slave cylinder from another vehicle. So far the RX7 looks like a possible candidate.

I purchased the cheapest CMC I could find on rockauto.com (Rock Auto P/N Wagner CM147016). I only needed it to take measurements so I wasn't worried about overall quality. I opened up the Wagner box to find a LuK / Mazda stamped part! See attached image below. So, what appears to be a cheap ($46) third party replacement part turns out to be an OEM manufactured part!

So for those who find themselves in the need of an OEM replacement CMC, go straight to Rock Auto or Wagner for a replacement if you want the OEM replacement at a fraction of the cost.



I am currently working on taking specs of the OEM CMC. The best / easiest option when it comes to mounting an available upgraded replacement seems to be an AP Racing bulkhead mount master cylinder (PN CP4400). Wilwood is much easier to source and cheaper, but it would require more extensive brackets for mounting while the AP unit will mount in a single round hole so a simple, flat sandwich bracket mounted to the existing OEM pedal bracket will be much easier / cheaper to fabricate. The AP unit has options up to 15/16" bore (over the factory 5/8" bore) that will provide more than enough added volume to push more fluid requiring less pedal travel.

The goal is to run a single stainless steel braided line with standard pressure fittings straight from the CMC to the slave, bypassing any hard lines and specialty connectors required in the OEM system. As for the slave, fitment wise the best prospect for a slave I have seen is an RX7 unit. These can be purchased cheap and have been proven to work with much stronger clutch systems.

If you are interested in seeing where this goes... stay tuned!
 

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Discussion Starter #2 (Edited)
Update (because I can tell you are all on the edge of your seats checking this thread hourly :| )

Parts:
Master cylinder: Wilwood GS compact master cylinder .75" bore.
Slave cylinder: 2008 NC Miata .75" bore.
Clutch line: Stainless braided 10mm banjo (Wilwood end) to 10 x 1mm inverted flare fitting (NC slave end).
Master cylinder adapter plates, a few screws, aluminum spacers, washers, and a custom hacked master cylinder ball end to fit the Wilwood push rod into the factory plastic socket piece that seats in the pedal arm.

Master cylinder plates are cut, drilled, tapped, and ready for install as soon as I get the clutch line. No permanent modification will have to be done to the car itself. The Miata slave will need a little drilling to enlarge / angle the mounting holes. There is also a little nub on the end of the slave push rod that will need to be ground off.

I will update with pictures of the prototype setup very soon.

Advantages:

OEM CMC is .625" bore, OEM CSC is about .81" bore. This equals 28mm of active travel on the oem master piston yields about 18mm travel on the CSC to push the clutch arm and disengage the clutch (7:4.5 ratio) Enlarging the master bore to .75" and reducing the slave bore to .75" means that the ratio is now 1:1. The new master will now only have to travel 18mm to fully disengage the clutch which means, that's right kids, shorter pedal travel! Side effects are stiffer pedal, better pedal feel (less squishy, more positive/ sensitive) and more developed thigh and calf muscles. May also be more reliable if you plan to upgrade the clutch with a heavier pressure plate (if any companies ever make one, or you decide to get a custom one made).

My plan is to get parts quoted from a machine shop and have them produced if anybody is interested in doing this upgrade. It all depends on how many sets are requested and how much I can reduce cost with higher quantities. If you are interested (serious buyers only), you can post your intentions on this thread or send me a private message.

Once I get the last of the parts I will be doing the install and subsequent testing.

-CR
 

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Discussion Starter #3
Because reading is boring:

Pictures!

Oh, and also, the Wagner boxed slave cylinder being sold on Rock Auto is also actually a LuK / Mazda stamped OEM part, just like the Wagner master cylinder as stated in the first post.
 

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I mean.... most people probably aren’t interested in this “upgrade” because the OEM CMC is perfectly fine for your average daily beater.

Mine has 80k miles on abusive driving and feels fine... but I have been flushing it with Valvoline DOT 3/4 synthetic fluid since about 30k miles and have flushed it 2x since mostly due to a brake job more then just replacing old fluid.

I found that the pedal and clutch engagement feels better with fresh Lube in there, especially the synthetic. Not sure what OEM spec is, but who cares.

Do try to take before / after pics of the clutch pedal and how much shorter the travel is. I’d probably upgrade once the tranny is dropped for a clutch replacement or throw out bearing. Mine has been making an increasing noise for the last 10k or so. Even if the clutch is fine, I’ll probably end up dropping the trans just due to the freakin bearing wearing out.
 

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Because reading is boring:

Pictures!

Oh, and also, the Wagner boxed slave cylinder being sold on Rock Auto is also actually a LuK / Mazda stamped OEM part, just like the Wagner master cylinder as stated in the first post.
In the factory piece, do you see anything that resembles a clutch delay valve?
 

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Discussion Starter #7
In the factory piece, do you see anything that resembles a clutch delay valve?
I know exactly why you are asking which is yet another reason I cannot wait to see what difference this upgrade makes. I did not bother to really check but I did notice that there is a rather small orifice inside the factory slave cylinder output. The hole in the grey insert you see (image below) inside the outlet of the slave cylinder is approximately 2.5mm in diameter at the first opening, and the smaller one all the way in appears to be about half that or smaller. There is also a gap between the back side of that first grey piece with the larger opening and the surface which contains the smaller opening. If the smaller hole is acting like a sort of flow restriction I wouldn't be surprised. There might be some flow diversion going around the smaller opening between the gap upon pedal initiation, and maybe a forced diversion through the little tiny hole when the pedal is released to make for 'smoother' shifting... which basically means more slipping on the clutch. If I find a hook pick in my toolbox I will try to dissect it and see what is really going on in there. If I can't find a pick, a hammer might do just as well.
 

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Curvy you are the man, that certainly does look like a clutch delay valve! The challengers CDV is setup in a very similar way. The ribs in the 3 and 9 position is that a metal clip that can be pulled out?
 

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Discussion Starter #9
Curvy you are the man, that certainly does look like a clutch delay valve! The challengers CDV is setup in a very similar way. The ribs in the 3 and 9 position is that a metal clip that can be pulled out?
Yes, that is the clip that retains the factory hose connector. It is easily removed. Just a simple spring clip that is a little thicker than a paperclip which can be pulled off with a set of needle nose pliers. It won't help me get into the actual inlet of the slave though. Being plastic, the slave and master cylinders are pretty much permanently assembled either by friction welding or chemical adhesion, hence no ability to rebuild. The master cylinder seals are deep inside the bore of the cylinder, not around the plunger that pulls out.

The new system might be installed this weekend pending time to do so. Results to come soon.

-CR
 

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Discussion Starter #10
System installed. Quick impression and results:

Pedal pressure: VERY stiff compared to stock. Keep in mind, the master bore matches the slave bore, thus making it 1:1 for pressure to disengage the clutch. So you are basically pushing the clutch fork with your foot. Driving in traffic is no longer going to be easy.

Pedal travel: VERY short. Even with the OEM clutch, it feels almost like an on/off race clutch, but more forgiving when it comes to friction. You just have to remember (especially when you first drive it), not to lift off the clutch as you normally would. It is driveable but takes some real getting used to.

Clutch engagement / disengagement: VERY quick. Pedal travel is just about half what it used to be, again, 1:1 from master to slave.


This project is not finished, but it is a good start. I am highly considering reducing the master bore which will add a little bit of pedal travel (still much less than OEM), but require less pressure. The reason for this is I am a bit worried about something on the pedal assembly failing from stress due to the increased load. When I say the pedal is VERY stiff, I am not kidding. I practically lift myself off the seat to press the pedal. Not to mention, if / when I do upgrade the clutch, a heavier pressure plate is just going to make it very difficult to drive and increase stress on the pedal components even more. I am probably going to pick up a spare used pedal assembly just in case this one fails.

OEM pedal top position


Wilwood master top position


Pedal fully depressed


Pedal assembly


Wilwood CMC mounted in the engine bay
Sorry, I forgot to rotate the image. Clearance is close to the top nut on the CMC, but it fits. I have to figure out a way to seal the gap in the firewall, although i do like being able to hear more of the subtle noises from the engine bay. Those lines blocking the view are a bit of a pain to work around as they are rigid, but it fits.


2008 NC Miata Slave cylinder
Drilled out the top mounting hole to 3/8" and the bottom hole to 1/2" (could be 7/16" but I didn't have the drill bit. 1/2" is a bit too oversized and made the wall around the hole too thin for my liking). Minor clearance issue between the radiator hose and the bleed nipple. For now, I have the radiator hose pulled closer to the radiator by about 1/2" to prevent contact. May require some tweaking of the metal bracket bolted to the transmission housing that holds the hose.


All for now. I will update a little further down the line after more driving.
 

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Interesting setup. Definitely not for me. I’d want maybe 15% stiffer peddle for more feel since the OEM is a bit soft but driving it is easy so you win some and lose some. Can’t have it all.
 

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Discussion Starter #12 (Edited)
Interesting setup. Definitely not for me. I’d want maybe 15% stiffer peddle for more feel since the OEM is a bit soft but driving it is easy so you win some and lose some. Can’t have it all.
The whole point of this setup is that you can pick and choose a different master cylinder bore to make the clutch feel the way you want it to. Wilwood offers .7", 5/8", and 1/2" bores in this particular cylinder so you can ease up the pedal pressure and elongate the pedal travel incrementally. I am thinking for my preference, a .7 would balance things out a bit. You might prefer a 5/8" bore. Even if you matched the OEM master cylinder with a 5/8" bore Wilwood, you would still experience decreased pedal stroke and better feedback since the slave cylinder bore is reduced with the Miata slave. So yes, you can still have it all. :wink2:

And this is where my testing will continue. I started on the more aggressive end of the spectrum by matching the master to slave ratio 1:1. I will try a smaller bore master to see if it gets me to a happy medium.
 

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Hmmmm. Do keep us updated then. If you can find a slight increase over stock without having to use your whole body weight to push the pedal in, I’ll be interested in upgrading. Lol.
 

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My Other Car is a Holden
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Seems like it would be easier to just buy a spare master cylinder. What's gained by making the clutch more difficult to disengage if these engines can't make a ton of power to warrant an upgraded clutch?
 

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Discussion Starter #15
Seems like it would be easier to just buy a spare master cylinder. What's gained by making the clutch more difficult to disengage if these engines can't make a ton of power to warrant an upgraded clutch?
Easier would be to buy a car and do nothing to it, take it to a shop to have all the maintenance done by someone else, and be completely satisfied with everything as-is. Heck, why buy a manual transmission? Automatic is MUCH easier. Everybody needs a hobby :) Mine happens to be making adjustments to my car to make it work and feel the way I like it.

The goal isn't to make the clutch super stiff, the goal is to improve the feel of clutch engagement and shorten pedal travel. As I said previously I started at the extreme end of the spectrum and am working my way back to find a happy medium. I absolutely HATE the squishy factory clutch and the CDV. That being said, if I could shorten the pedal travel to where it is now and only have it be 20% stiffer than stock, I would. Alas, the laws of physics and fluid dynamics don't allow it, so I am hoping that I can step down to the next smallest bore cylinder and decrease the stiffness but still keep the pedal relatively short.

On a side note, having driven a few miles on this setup, the clutch feels more like a button, than a pedal. Kind of nice in that sense, as heavy as it is.
 

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My Other Car is a Holden
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I've never thought of an on/off switch pedal that's ultra stiff and has limited travel as "improved feel".

Coming from the land of LSXs and Tremecs, people played around with master cylinder tweaks to improve clutch feel for years. Turns out the best way to make your clutch feel better is a better clutch.
I have the 13 year old factory master cylinder in my GTO connected to an OEM replacement slave cylinder and it feels great thanks to a twin-disc clutch upgrade with a much better pressure plate, braided steel clutch lines connecting things, and Motul 600 in the lines.

Maybe you'd find your results in a pressure plate upgrade or as you said, buy an automatic.
 

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Discussion Starter #17 (Edited)
Update:

Swapped the .75" bore Wilwood master cylinder to a .70" bore Wilwood with integrated reservoir.


Result: Perfect pedal pressure. Although I was getting used to the feel of the .75" (1:1 ratio) with its heavier pressure. I had finally gotten the timing between my shifts and accelerator dialed in to match the super short / heavy clutch, so I will admit, I cannot accurately say how much heavier the .70" is in comparison to the factory pedal pressure. If I went back to the factory master and slave at this point the pedal would probably feel like stepping on a feather pillow.



I believe this is a great balance of shorter pedal travel and increased feel / sensitivity in the pedal. With the oem pedal return spring removed, the clutch pedal sits almost level with the brake pedal at top , resting position to give you an idea of the decrease in pedal travel from stock. The pressure will be heavier than stock, but in my experience is no heavier than if you upgraded a clutch to maybe a stage 2 or 3 ACT (most of my experience being with Hondas). I am amazed how much difference was made with only a .05" reduction in bore size on the master cylinder.

Something to note:
Currently, the flanged hex bolt I am using at the bottom of my adapter plates is preventing the pedal from going in as far as it would without that interference (i.e. stock bottom position). The next adjustment will be to change that bolt to a button head socket cap screw which will allow me to shift the pedal travel probably about 5mm lower. So the top position with this new master cylinder and the new bolt will be slightly below the brake pedal with the same total travel distance.

Reason for switching to an integrated reservoir:
Reliability. The more connection joints there are, the higher the likelihood that one of those joints might leak air into the system if something isn't properly torqued / aligned / fails. With the previous Wilwood cylinder, it required me to cut the factory line from the reservoir, insert a barbed adapter from 1/4" to 3/8", and purchase the Wilwood AN barbed fitting and hose to flow into the cylinder. Although it worked just fine, it created lots of potential failure points. I also prefer keeping brake and clutch fluid separate. Whether or not it makes a difference performance wise, I just like to keep systems isolated. The only downside to this setup is filling the reservoir requires a tubed funnel as it sits under the overhanging cowl, and there are a couple other hard lines running in front of it that make it tricky to twist the cap on/off. Not a huge deal seeing as I shouldn't have to access the reservoir too frequently.

So all that being said, I think I am going to stick with this setup as it is now. No more experimentation. If anybody wants additional information and plans to do this modification themselves, feel free to post here or PM me. If enough people are interested, I will consider producing / selling kits, but thus far, I do not see that happening as most people are perfectly content and used to the factory hydraulic system.


Maybe you'd find your results in a pressure plate upgrade or as you said, buy an automatic.
That is ultimately the plan (minus the automatic part). Now that it looks like we may be able to use the Mazda 6 offerings from Clutch Masters, that is looking like the best option once my factory clutch dies after a track day or two. In my original post, I did mention that one of the reasons for this modification is to have a more robust hydraulic system to support a more aggressive clutch setup. I do not like the idea of relying on plastic parts in a pressurized system like a clutch. So with this setup now tuned to where I like it, I can move forward with upgrading the clutch minus the worry of failing plastics. The only worry I have now when I do upgrade is the clutch fork. I have seen many cases of forks failing over time under heavier clutch loads. But that will be a project for another day!
 
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