Rpm goes up when the clutch pedal is pushed in?

[93_jdm_fd]

I just installed a os giken twin plate and love it but when I push the clutch in(engine/tranny cold) the rpm raises up and slowly come back down. When the engine/tranny warms and I push the clutch in it's fine and idles perfect at 950rpm.

I've adjusted my pedal free play and the clutch does not slip and engages/releases properly so is this normal?

[Skym]

Sometimes ECU raises rpm higher than normal when in neutral. Sometimes caused by faulty / sticky IACV and needs to be cleaned or replaced, if cold only (same with AACV that might need cleaning). Does turning engine off, then on stop it??? In some cases it's just an intake airleak near throttlebody (loose intake hose clamps) or intake airleak somewhere.

[93_jdm_fd]

I'll check out AAC valve but i've cleaned it before. It's just odd that it just started happening since saturday after the clutch install.

[caliber676]

Maybe the added stress of the twin plate clutch and when releasing it takes load off the crank and allows a bit of wind up. I could be pulling that out of my ass though

[NismoS-tune]

I had a similar problem years ago but it was crank walk. My twin Carbonetic killed the thrust bearing. Could be an issue with your master cylinder though. In my case, you could see the torque damper pulley move with the clutch.

Then again, it kill my new engine at the time.

[93_jdm_fd]

I ordered a 12mm bearing sleeve and new oem release bearing because that's what I was told by os giken. I removed the little rubber release fork cover and found the release being right up against the fingers on the pressure plate. I checked the bag that the 12mm bearing sleeve came in and the part numbers says it's a 16mm sleeve, pretty cool. Parts guys are right on.

So now they tell me that the 12mm sleeve is a nissan japan part only and could take weeks to get. The clutch pedal feels great, the clutch doesn't slip but now I'm worried about the sleeve being the wrong size. I can live with the rpm raising a bit when the engine is cold I guess but not with a wrong size sleeve. The rpm really only goes up maybe 100rpm and come back down and when warm it doesn't change all all when the pedal is pushed in.

So is anyone else running a 16mm sleeve with any issues?

[nimblestix]

Mine does this, I was wondering if its from the lightened flywheel in my case.

[93_jdm_fd]

I think that's all it is, I have no other issues and only goes up while the engine/tranny are cold.

[Skym]

What you have described sounds normal to me, just ECU playing with ignition timing, etc (might need to be adjusted to suit the mod).

Most ECU's have idle stabilisation tables that advance, retard the ignition timing + or - 4 degrees or so and it switches between different cells on those tables (different amount of ignition timing). Stock ECU has alot of tables that prevent engine stalling, depending on what car is doing (stationary, moving, at certain speed or rpm, in or out of gear at idle or off idle, etc).

If datalog (igniton timing, etc) what ECU is doing in realtime via tuning software, it should be obvious at what is causing it.

[93_jdm_fd]

Just an update for those who search on here or google pops this post up. So for anyone using the os giken twin plate and you need to know what bearing sleeve to use, go with what os giken says and use a 12mm sleeve(for my clutch) with a oem release bearing.

I used the 16mm(this being only 4mm taller), sitting at a light with the pedal pushed in, you have to hold it hard because it wants to push back and is really hard on the clutch pedal bracket.

I think it's because that extra 4mm pushing on the pressure plate fingers pushing them a little to far in. I've tried adjusting the pedal free play with no change. I finally got the proper 12mm sleeve, installed it yesterday and it's 100 times better. The clutch is stiffer than stock(of coarse) but at light with the pedal to the floor it doesn't feel like my clutch pedal is going to break off.

A lot of guys use a 16, 14mm sleeve but the 12mm is the proper one and that's what os giken says to use. It's a little harder to get I guess because it's a Nissan japan special order item but I got a little excited and installed the 16mm they sent me first, tried it and didn't like it. Got the 12mm installed that one and now I can sleep at night knowing the clutch is working properly, I've had the massive tranny out 4 times now and hope it will last a while.

[Skym]

That's interesting, thank you for sharing that info.

[93_jdm_fd]

Oh and the rpm does not move at all now when the clutch is pushed in while the engine/tranny are cold.

[NismoS-tune]

I don't know why I thought he said rpm goes down lol I was on a tangent with my responses... Glad to hear you didn't wreck your thrust bearing with the longer sleeve!