clutch bites slow?
 

Not sure if it is just me or all 370Z users get this issue.

When I shift up, the clutch bite is quite sluggish. It takes good 0.5sec (may be a little exaggerated) after I let go my clutch pedal, especially worse going from 2nd to 3rd (redline) where the rpm drop is larger than going from 4th to 5th etc

It feels like the clutch is almost slipping, although it does not slip once it fully bites.

I am suspecting that this is due to the super heavy flywheel on these cars, but my old 350z did not have this problem even with stock flywheels.

I remember seeing some posts about slave clutch cylinder being pos in the 370z, is this one of the symptoms?

Here's a simple test: press the clutch pedal all the way down then suddenly pull your foot back quickly, as if you were doing a clutch kick. Does the pedal almost chase the sole of your shoe or does it lag behind and slowly reunite with your sole?

The Z has a restriction orifice in the clutch fluid circuit. There is at least one that i know of but there might be a second, in the master cyl but i've never inspected our masters to be sure. google clutch delay valves and you will find heaps of disgruntled owners of other sports or non sports oriented cars. Pretty much the same problem.

Simple braided replacement lines wont fix or eliminate it. To get rid of it you need to remove the restrictor which is in the left fender well and get a custom 4mm braided line made up. Most braided lines for our cars are only -3AN. You'll understand the need for -4 inner diameter hose when you take out the restrictor piece and have a look at the hard line that goes INTO the restrictor. It will make you wonder whyyyyyyyyy Nissan, whyyy? Get the line made long enough to reach the slave cylinder port directly and terminate it with a union fitting rather than a banjo because the inlet to the banjo will probably be 3mm or 2.5mm.

Downside is a slightly heavier feel in the pedal but oh man, it makes a massive difference with quick shifts. Slow shifts will take a tad more concentration

wow awesome information, that's exactly it.

I did some search and found a few posts regarding this including yours too..

I wonder if drilling out the inside of the 'restrictor' will yield the same result? It looks like a simple brass block from photo.. the lines itself probably are the same diameter as the old 350Z's..?

you can drill it out or replace it with a suitable brass union joiner. i have the thread specs at home. But seriously, replace it with a 4mm ID line all the way to the slave. there's another section of hardline between the flexy hose and the slave cyl so there's more (potential) restriction there.

On a side note, the stock setup isnt as bad as a lot of performancs oriented cars - eg R56 JCW, RS megane, M3... The R56 is the worst of the 4. The shifter begs you to shift fast but the clutch delay valve makes you look/sound like a noob driving it.

U need to bleed ur clutch with a new motul brake fluid, i had that be4 and get all the gunk out, also about 2k miles later it will start doing it again, but after the second bleed its good for a long time. Theres a DIY on this site on how to do it, best results when done with a buddy. GL OP.

yeah - only use Motul RBF 600 or better, for the clutch system. I was already running Motul fluid prior to unchoking the hydraulic lines

Thanks for the input guys

juld0zer, I think you are right, might as well just replace the whole lot while it is all opened up. was just thinking of drilling it out because I am lazy to measure the hose and have it made up etc.. haha it would be great if you can find the thread specs :D

DOOMMONKEY777, yeah although it has been flushed a few times, I think it would not hurt to do another flush.. replacing the lines will force me to flush it anyway so I think it is a double whammy haha

and race fluid always of course ;)

Also wrap your clutch line with insulation by the exhaust pipe. ;)

http://youtu.be/grZZR4r5Zi4

here is a vid from the track, you can easily hear how slow the bite is at every up shift.

I dont have my Z anymore but what you can do is get a length of whipper snipper line and use that to simulate how you'll route it because a coathanger wont simulate the tendency of braided hose to not like bends.

Mine didnt look neat but i cut a hole in the wheel arch liner to make it neat enough.

Yes, definitely Motul RBF6xx fluid only and definitely get it wrapped in insulation like Earl's firesleeve although any fibreglass lined foil sleeve would be fine.

i have the same problem for my stock clutch im not happy how it doesnt grab right away.....if i get a clutch kit flywheel master cylinder and slave cylinder like SOUTHBEND stage 3 clutch will it grab rite away like no DELAY perfect shifting WITHOUT any custom stuff or what?????

Bump

Can someone take a picture of where this clutch damper valve is on a Z? Google only pulls up BMW threads.

bump

Sorry, I was hoping someone else would be able to chime in on this issue. But I have a Southbend Stage 3 clutch and 'Quiet Disk' flywheel. Upgraded Zspeed CSC as well. I've noticed that *I think* it was an improvement, but I wasn't paying attention to this specific issue when I changed those parts out - my stock parts were slipping under power, so that was the focus. As far as the shift lag, I also reprogrammed my throttle tables at the same time, so that's why I was waiting for someone else to respond. The biggest differences aside from the new parts holding the power, was the weight of the clutch pedal and the grab point. But even with these parts, I'm still feeling a bit of delay on the release at high RPM's. So it might help, but if your parts are holding the power, I would think that the clutch delay valve would make more of a difference.

im just disappointed at the issue since im used to shifting like a street bike haha I like NO DELAY....whats up with the delay valve I haven't heard of that

Second post in this thread.

I bought a replacement restrictor a few years ago but never bothered to located the stock one to replace lol. Will have to look into this again :tup:

Has anyone else done this anymore reviews how safe is it any issues?

Can you confirm the size of the union fitting? I think I read somewhere that it is a M10x1.25 bubble flair union, but when I went to look it up, I couldn't find it. What size do you have?

Alright guys, I took care of this on my car. I ended up drilling it out because I couldn't find the union fitting. Here are my pics:

This is where it is located. You have to remove the rear half of the fender liner in the front left (front, driver's side) wheel well. Once you remove that, you will see this. The restrictor block is in the right side of the shot, in the bottom rear of the wheel well:

https://im1.shutterfly.com/media/47a...D720/ry%3D480/

This is what the actual restrictor block looks like:

https://im1.shutterfly.com/media/47a...D720/ry%3D480/

Close up of the restrictor block:

https://im1.shutterfly.com/media/47a...D720/ry%3D480/

Once you remove the clutch lines and the mounting bolt in the center, you can pull it off the car. Here is a shot of the restriction:

https://im1.shutterfly.com/media/47a...D720/ry%3D480/

I drilled it out with a 5/32" (4mm) drill bit. There isn't much to have to drill through. Basically, as soon as the bit started cutting, it fell through. Here is a shot of it drilled out:

https://im1.shutterfly.com/media/47a...D720/ry%3D480/

Then everything gets bolted back together the same way as it came out of the car. Pretty simple.

After refilling and bleeding the clutch, I went out for a quick test drive, and I gotta say, it made a difference! It's hard to tell how much quicker it shifts since it's 40 degrees out, so I don't have any grip from my tires. On high rpm shifts, it either wheelspins, or traction control comes in and softens the shift. But the clutch feel improved, and I do think that helped remove the clutch delay. I'm excited to test this when it's warmer out.

Pm me or post on here when u test plzz try today lol im really curious if it will be like street bike shifting no delay perfection reason why cause im trying to be in top 5 and fastest 6 speed all motor here in 1200 elevatiom AZ i wanna get on that list and maybe one day drive to sacramento 0 elevation and be second on that list cause guy that got 12.2 idk how he did it maybe it was like 30mph winds helping him lol

I found one at my local AutoZone based on the post below. But as you can tell, it doesn't open it up that much (from 2mm to 3mm).

And thanks for the photos - I'll definitely be sending a rep your way :tiphat:

Yes, if you're drag racing, definitely do this. Every tenth of a second counts!

Today it was much warmer and I had a chance to give it a try. Big difference. It's not sport bike quick, but it definitely makes a difference. If you really want to make it super quick, you might want to look into making a whole new steel braided line that connects directly from the master to the slave. You could probably cut off a foot of extra length by doing that, and you could make it out of a larger line. But short of doing that, drilling this out is probably the best you're going to get. If you trace the line from the master to the slave, there isn't any other restriction in it, so eliminating the restriction in this block, the next point of restriction would be the size of the line itself. Unless there is a restrictor in one of fittings, which is possible.

But definitely do this if you're running against a clock.

Thank you sir! :tiphat:

Forgot to add, the whole thing took maybe an hour. Add a few minutes for bleeding the clutch lines. Oh, and last thing to remember is to have brake fluid on hand to be able to refill and bleed the system when it's all back together.

Just thought I'd add my 2cents to this discussion since I've done a lot of research and development on this topic lately with the HD master cylinder project. I just wanted to clear up a few things that I've noted reading thru this thread to maybe help out others.

First off near the top the recommendation of using -4AN lines because the -3AN lines aren't adequate is not correct. The AN system was developed by the US Army/Navy and has absolutely nothing to do with the metric system so saying -3AN is 3mm is inaccurate. The Dash Number is multiplied by 1/16ths of an inch to get the inside size of the flow tubing so -3AN is .1875" (3/16) or 4.8mm in metric INSIDE the tube for flow. -4 is huge at 0.25" Inside or 6.35mm

The factory hard lines that run from the master cylinder to the brass block and from the brass block to the transmission flex line point are all 3mm or 1/8" Inside diameter. The -3AN braided SS lines are 3/16" or 4.8mm inside and flows 50% more fluid than stock so no need to go huge with -4 lines.

Next since the factory hard lines on either side of the brass block in discussion here are only 3mm internally the largest size you need to drill this block to is 1/8" (3mm) and it will act like it's not even there. Going bigger like shown above is likely to destroy your brass block as you can see in the photo that almost all of the Inverted Flare sealing surface has been obliterated by drilling it to 5/32" and you're now relying on the treads to hold back fluid pressure instead of the invert flare union. RadioFlyer you may have gotten away with this, it may be slowly weeping fluid past the threads at both sides of the block already or may begin weeping down the road... only time will tell.

My recommendation is to drill this to 3mm MAX as it won't remove as much of the inverted flare sealing area.

Final note which I've not seen discussed or noted is that while everyone is fussing with this brass union block no-one has stopped to question the orifice size at the outlet of the factory master cylinder. The factory master cylinders outlet is only 2mm and exactly the same size as the brass block. So without eliminating the restriction at the MC you could add a sewer pipe connecting the MC to the slave but it won't get you any faster clutch release with this 2nd restrictor still in play.

Hope that adds to the discussion, helps save a few people destroying the brass block and clears up the miss-information early on in this thread.

Best Regards
Ryan@RJM

Great info, Ryan :tiphat:

I've given up on this mod since I've ordered your heavy duty clutch master cylinder kit that will take care of it :tup:

Excellent input, Ryan@RJM! Thanks!

Yes, that was the unknown - that drilling out the brass block was in fact, the actual bottleneck in the line. I did notice a difference by just drilling out the block, but it was a minimal difference. I have not experienced a leak at the brass block, so I'm all clear there. Car has been off the road for a few weeks because of an unrelated problem so I'll be able to get back into the car with a fresh feel for the clutch. I also upgraded the clutch/master/slave to HD units, so maybe that helped my car show a difference? :confused: I'll also look into drilling out the MC outlet!

What master cylinder did you use?

Good question. Not sure, it was ordered from Zspeed by the shop that did the install.

I was just checking to make sure that it wasn't some other hd master I hadn't heard of that also fit the Z. I know Joe doesn't have any options for the Z, so that answers that :tiphat:

I've got one of the first batch of RJM Performance's new hd masters reserved. I expect to have the product in my hands and installed in the next couple weeks :tup:

Unless its a prototype deal then as far as I'm aware they only offer replacement oem mc's and rebuild piston kits for the 370z and G37's. A quick photo of your mc from the engine bay side would show what it is though. I don't beleive there is any more room around the G37 master cylinder than on 370z and depending if you have an early model G37 the factory mc can be more difficult to remove then a 370z one.