Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review

gylmar814

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Good afternoon CivicX. Decided to do another write up on my latest modifications I thought I should share incase you haven't came across this very neat mod... I've done some research in the past and came up an article regarding the clutch delay valve (CDV) inside the slave cylinder and the positive outcome and results from deleting the valve. I've stumbled across several articles regarding the CDV delete anywhere from Bimmers to Honda's. Interestingly enough, I noticed @PRL Motorsports created a write up and did the CDV delete to their 10th gen Si as well... Now I personally haven't had any issues regarding clutch slippage during normal operation but when I'm WOT and shift in the upper RPM's its very noticeable the clutch slips briefly as I'm switching gears and causes a delay when shifting. I thought it was because of Rev Hang mixed with a weak OEM clutch (Although I still find the OEM Clutch to still be on the weaker end) and I just left it at that. I eventually found out the reason to the brief slippage is because there is a valve inside the slave cylinder the slows down the flow of the clutch fluid, therefore causing the clutch to slow down during engagement after shifting gears. Removing the valve allows the fluid to flow quicker, allowing the clutch to engage at a higher pressure. In other words, the clutch has a stronger bite and RPMs drop immediately when shifting gears like how a transmission is supposed to. Pretty much the point of having the CDV is for novice drivers who don't have experience driving manual gearboxes and really dumbs down the operation of the transmission.

To quote PRL:

"What does removing the CDV do? The engineers at Honda has been putting a CDV system on many of the recent platforms to reduce drivetrain shock. The CDV allows the clutch system to simulate "slip" in an attempt to save the transmission/drivetrain. However, for racers and enthusiasts looking for more of a raw driving experience in his or her car this can be annoying. Removing the CDV greatly improves clutch engagement which in turn improves 60fts and shift times. The other cool thing is this mod costs $0 aside from a new bottle of clutch fluid needed to bleed the clutch system. :thumbsup:"

"The CDV is located in the slave cylinder which is attached on the front of the transmission. The slave sylinder can be removed by taking out the two 12mm bolts holding it on. Next you will need a 14mm and 10mm wrench to remove the clutch line from the slave cylinder. Now the slave cylinder assembly should be able to be completely removed."

---------------------------------

After deleting the CDV, it made a world of a difference! It honestly feels like I have a whole new clutch inside the car, almost making it feel like I have a Stage 1 clutch...That noticeable of a difference. :yes: The Clutch bites instantly with no slips during normal driving and aggressive high RPM operation MUCH better and RPM's drop between gears and shifting motion became much more fluid and natural. Best part is, it cost me $0. Only thing I bought was a bottle of brake fluid to top of the reservoir during the clutch bleeding process.

I figured it only made sense that since I was taking apart the slave cylinder and having to bleed the clutch afterwards, I should buy PRL's Stainless Steel Braided Clutch line in the process and kill 2 birds with 1 stone. ;) With the combination of the CDV Delete and the PRL SS line I have nothing but good to say about this mod. You can tell the difference even with the foot. The clutch feels more stronger and firm when pressing & depressing the pedal, how it should have felt out of the factory. :doh:

Here is the link to PRL's thread for more information: https://www.civicx.com/threads/10th-gen-civic-1-5t-clutch-delay-valve-removal.13105/

Link to PRL's Stainless Steel Clutch line, only cost about $42 after shipping. : http://prlmotorsports.com/2016civic15tstainlesssteelbraidedclutchline.aspx#.WpdJT-jwaUk

Here are some pictures with captions for reference purposes, enjoy!

First and Foremost, I highly recommend a set of scribe/picking tools like this one. There is a "C" locking ring that locks a metal cap that is a bitch and a half to take off. Luckily for me, it only took about 10-15 minutes to wiggle it out. Once you take it off, you can use a set of needle nose pliers preferably with grip teeth and pull off the metal cap. Once you take it off you will see the white CDV valve in the inside (See pics below). You can use the same tools you used to take off the "C" locking ring to take off the valve and then throw the valve away!

Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180228_181609

Here is where the Slave Cylinder is. Its attached in front of the transmission. All it takes is a 12mm socket with a ratchet to remove the slave cylinder off the tranny and a 10mm wrench to remove the clutch line off the slave cylinder.
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180228_181726

How it looks after removal of the SC. I put a ziploc bag so it can catch the clutch fluid coming off the line.
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100434

Picture of the Slave Cylinder out of the Vehicle. On the left side of the SC is where the metal cap and locking ring is located. I completly forgot to take a picture of how it looks but its self explanatory once you take off the SC and see it for yourself! This is also when you use the picking tools and pick out the locking ring.
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100501


Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100543

This is how it looks once you take off the C locking ring and the metal cap on the other end of the slave cylinder. This is the Clutch Delay Valve inside the SC
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100518

This is the C locking ring and the Metal cap that needs to be removed. This is to be installed back exactly how it was, once you remove the clutch delay valve inside.
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100536

This is the Clutch Delay Valve the needs to be removed and thrown away.
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100704

This is how the inside of the SC looks once you take off the Clutch Delay Valve
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180225_100725

PRL Stainless Steel Clutch line Installed
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180228_164705

Zoomed in shot of the Clutch Line
Honda Civic 10th gen Clutch Delay Valve Delete/ PRL SS Clutch Line Install & Review 20180228_164717
 
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coopermidnight

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How dangerous would it be for the car's internals if an average driver were to take out the CDV? Rev hang pisses me off, but I worry I'd do more harm than good by taking this component out.
 

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How dangerous would it be for the car's internals if an average driver were to take out the CDV? Rev hang pisses me off, but I worry I'd do more harm than good by taking this component out.
internals are fine, no relation. but you could potentially put allot more stress/sock the transmission
 

coopermidnight

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internals are fine, no relation. but you could potentially put allot more stress/sock the transmission
I meant the internals of the car itself, not the engine. But thanks! Sounds like I should probably wait til this thing's paid off before trying anything like this.
 


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gylmar814

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How difficult was the process?
Not hard, just remove the slave cylinder from the front of the transmission, its held by two holts and the clutch line. Remove the metal cap off the SC, take out of the valve, assemble and put everything back in reverse order. Bleed the clutch, if you don't know how it's easy. Look it up on Youtube.
 
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gylmar814

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How dangerous would it be for the car's internals if an average driver were to take out the CDV? Rev hang pisses me off, but I worry I'd do more harm than good by taking this component out.
You won't do more harm . The valve is an added safety feature honda puts to dumb down the manual gearbox driving experience. Essentially, it cuts out the rev hang between shifting gears once removed, that my experience
 

Brian17Si

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You won't do more harm . The valve is an added safety feature honda puts to dumb down the manual gearbox driving experience. Essentially, it cuts out the rev hang between shifting gears once removed, that my experience
Ha! I was always wondering about the rev hang during quick shifts...
 
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gylmar814

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Ha! I was always wondering about the rev hang during quick shifts...
Yep thats why.. Notice when you shift quick the rpms surge up briefly and then go down. Thats the CDV letting the clutch slip then grabbing afterwards.
 

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So basically this thing is meant to assist engagement, but just by being there it "assists" disengagement, too. Looks like removing the CDV is a great choice as long as you're very good at rev matching.
 


Brian17Si

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Yep thats why.. Notice when you shift quick the rpms surge up briefly and then go down. Thats the CDV letting the clutch slip then grabbing afterwards.
Yes! Exactly, I tried my hardest to not have this happen and thought it was me.
 

callmehandsum

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So basically this thing is meant to assist engagement, but just by being there it "assists" disengagement, too. Looks like removing the CDV is a great choice as long as you're very good at rev matching.
I don't think you have to be good at rev matching. As it is, when we release the clutch, at least I do, I always let it slip a bit as soon as I feel it begin to bite, then release from there gradually. In real-time of course, I shift in less than a second. I guess that's why it's tricky getting perfect shifts, because the CDV is adding extra slippage.
 

10GenPearlSi

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I don't think you have to be good at rev matching. As it is, when we release the clutch, at least I do, I always let it slip a bit as soon as I feel it begin to bite, then release from there gradually. In real-time of course, I shift in less than a second. I guess that's why it's tricky getting perfect shifts, because the CDV is adding extra slippage.
Yes, the bite becomes time delayed. Like you, I let the clutch out to just as it is starting to grip and the CDV causes it to grab before I am ready for it to.
 

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Yes, the bite becomes time delayed. Like you, I let the clutch out to just as it is starting to grip and the CDV causes it to grab before I am ready for it to.
I have been driving a manual since the day I learned to drive, 30 years ago. I wondered why I was having an issue getting smooth shifts from time to time.
 

Brian17Si

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yeah I’ve only noticed this delay in the higher gears. Or at least for me it just seems like the RPMs jump. lower gears feel great to me.
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