Clutch Slipping?

Printable View

09-11-2010, 10:34 PM
bluespire

Clutch Slipping?

I posted this on my local forum, but I'll post this here too.

Quick question. My car and clutch work just fine below 4000 RPMs. However, if I get in 2nd gear and take off, at some point over 4k-5k I can feel what I think is the clutch slipping. Now, just to let you know, I am not hitting the throttle at 100%, more like maybe 50% when taking off. I go up to around 15 lbs boost as I accellerate, but the boost backs off by the time I hit the 4k-5k RPMs (because I am backing off the gas), so it is all natural engine at the high RPMs, and yet it still feels like the clutch is slipping (by slipping I mean I feel stuttering).

Is this a normal indication of slippage? Or could there be something else wrong? I figured the clutch would be more likely to slip at the lower RPMs where I'm putting a much higher degree of torque on it.
09-11-2010, 10:37 PM
DocWalt

Put the car in top gear at low RPMs and got WOT. You'll know if it slips if your revs jump up and the car doesn't go faster.

Stuttering generally isn't a sign of a slipping clutch, especially under those conditions. It sounds like a boost leak, or something.
09-12-2010, 12:35 AM
bluespire

Quote:

Originally Posted by DocWalt

Put the car in top gear at low RPMs and got WOT. You'll know if it slips if your revs jump up and the car doesn't go faster.

Stuttering generally isn't a sign of a slipping clutch, especially under those conditions. It sounds like a boost leak, or something.

I'll try what you said in the morning. But like I mentioned, I am not boosting at the higher RPM, so I doubt it's a boost leak. Maybe a fuel management problem? Maybe my caps are going bad in the ECU. I've never had it opened since I bought the car 2 years ago.
09-12-2010, 12:41 AM
DocWalt

Just do a pressure test while you're at it. :)

Do you have any A:F controllers?
09-12-2010, 04:22 AM
bluespire

Quote:

Originally Posted by DocWalt

Just do a pressure test while you're at it. :)

Do you have any A:F controllers?

Oh yes. I have a S-AFC. My tune is good, at least it was.

The car ran like a champ at NG09. I did not have this problem on the drag or autoX (didn't do road course). If you were there, you may remember the car. It looks like VR440's but the silver stripes are wider, and it still has a V6 lol.
09-12-2010, 04:39 AM
DocWalt

Do you have a wideband? If so, what does it do when the stuttering is happening? If it's bad enough, it may be noticeable in a regular log as well.
09-12-2010, 05:26 AM
bluespire

Quote:

Originally Posted by DocWalt

Do you have a wideband? If so, what does it do when the stuttering is happening? If it's bad enough, it may be noticeable in a regular log as well.

Wideband? It's been so long since I did any of that reading, that I honestly can't remember. Isn't wideband required for speed density? If so, I don't think I have that setup. My SAFC is set to show throttle, correction, RPM, and knock. None of which I remember looking out of the ordinary. On the other hand, I'm not entirely sure exactly what the correction values are supposed to be for this tune, but I think they have not changed.
09-12-2010, 12:52 PM
DocWalt

Wideband O2 sensor. What's your setup injector wise?
09-12-2010, 12:56 PM
stealthee

Clutch slippage usually only happens in higher gears. One thing to check is the pedal engagement. On a TT I beleive its .5-.8 inches. I would need to verify that though.
09-12-2010, 12:56 PM
DocWalt

IIRC, you're right Brian. My money is still on a boost leak though.
09-12-2010, 08:34 PM
MaxClass

This may seem off base but what are the condition of you plugs? You could also be running into blowout if the gaps are too wide. Just a thought.
09-12-2010, 10:43 PM
bluespire

So I tried what was suggested on my way to work. I started at about 40mph, dropped the gear into 6th, and opened the hammered the gas. SAFC showed 90+% throttle open, and although it was kinda slow, I did get from 40 to 60 steadily, and I did not feel any kind of stuttering. At the same time, I was showing around 5 PSI of boost, which I suspect is normal, since my boost usually kicks in better around 2k-3k RPMs. So correct me if I'm wrong, it looks like it is NOT a clutch slipping.
09-12-2010, 10:47 PM
stealthee

Yeah, if clutch was slipping it would have done it at that point.
09-12-2010, 10:50 PM
bluespire

Quote:

Originally Posted by DocWalt

Wideband O2 sensor. What's your setup injector wise?

I have 550 injectors.

Quote:

Originally Posted by stealthee

Clutch slippage usually only happens in higher gears. One thing to check is the pedal engagement. On a TT I beleive its .5-.8 inches. I would need to verify that though.

I believe the pedal engagement is fine. I once thought I had a problem, but I did some testing a while ago and the clutch does disengage not too far from the top. From disengagement, there is a long travel in the pedal. I assume that is normal.

Quote:

Originally Posted by DocWalt

IIRC, you're right Brian. My money is still on a boost leak though.

I have no idea if my boost is leaking. I am set to a max boost of 22 or 23 PSI. I can easily still get up to around 12 with normal driving, and if I punch it, I get into the high RPMs where that problem occurs. But again, this is happening with high RPMs with me not allowing boost over 0 PSI. If a boost leak can still cause this with no boost in the picture, then it could be the problem. How would I test for that?

Quote:

Originally Posted by MaxClass

This may seem off base but what are the condition of you plugs? You could also be running into blowout if the gaps are too wide. Just a thought.

To be honest, I am a bad owner in this respect. While I had VR440 go over the condition of my car when I bought in OCT 2008, I have done very little other maintenance and have no idea what the condition of the plugs are. I had thought this might be a problem, but wasn't sure.
09-12-2010, 11:24 PM
bluespire

Another quick question: what is the average life of a clutch? I've always wondered. I have ever only had one clutch go out on me, and that was my Mazda Protege with 181k miles on it.
09-13-2010, 12:00 AM
stealthee

It depends on the clutch and how you drive. I was told when I bought my car at 104k miles, that the clutch was replaced at 100k. At around 142k miles it started slipping and I had to replace it. Mind you that clutch had a ton of clutch dumps, burn outs, and drag races on it too and it was just an OEM style. I replaced it with an ACT clutch set up. I had to replace the disk after 20k miles because the center was pushed out, but the disk still had plenty of meat on it.
09-13-2010, 12:18 AM
bluespire
Quote:

Originally Posted by stealthee

It depends on the clutch and how you drive. I was told when I bought my car at 104k miles, that the clutch was replaced at 100k. At around 142k miles it started slipping and I had to replace it. Mind you that clutch had a ton of clutch dumps, burn outs, and drag races on it too and it was just an OEM style. I replaced it with an ACT clutch set up. I had to replace the disk after 20k miles because the center was pushed out, but the disk still had plenty of meat on it.

OK. So tell me what components I should check and test to help diagnose my problem, please. So far:
- Plugs
- Boost Leaks (not sure how to test)
09-13-2010, 12:42 AM
stealthee

Someone already posted about a homemade pressure tester using a 3" pipe cover and a tire stem. If you do a quick search I am sure you will find it.
09-13-2010, 04:55 PM
bluespire

Quote:

Originally Posted by stealthee

Someone already posted about a homemade pressure tester using a 3" pipe cover and a tire stem. If you do a quick search I am sure you will find it.

I could not find that post when searched. Can you point out which thread it was?
************************************************** ***********
Update!
Not sure how much this proves or disproves a boost leak.
I got a long stretch of back road today, and did a pull from 2nd into 3rd. I got my boost up to over 20 PSI, so it was near max, but not max @ 23 PSI. I will not do crazy speeds on civilian roads, so I couldn't get up to full boost, or even accelerate enough to maintain that boost for any longer than a couple of seconds. It did feel a little bit like the car was starting to stutter at the max boost. I'm not sure if that is my imagination, the road at that speed, of it was my car not able to boost higher than very low 20's.

So, can a boost leak still allow ataining very high boost levels? Or, should it have reared its ugly face first?

It is still possible the stuttering I'm sensing has to do with high RPMs and not the boost levels, hence a spark of fuel problem, correct?
09-13-2010, 05:16 PM
DocWalt

Boost leak or spark blowout. I'm pretty damn sure anyway :lol: I don't run boost levels nearly that high, but I've had blowout and boost leaks, and it sounds exactly like one of those.

I can't find the thread, but I'm also too lazy to really try, lol
09-13-2010, 05:43 PM
bluespire

Quote:

Originally Posted by DocWalt

Boost leak or spark blowout. I'm pretty damn sure anyway :lol: I don't run boost levels nearly that high, but I've had blowout and boost leaks, and it sounds exactly like one of those.

I can't find the thread, but I'm also too lazy to really try, lol

OK, so I looked up spark blowout. You really think that might be an issue? Most of what I read seems to cause spark blowout under boost conditions, but my problem appears to be under both boost and vacuum conditions at high RPMs. I suppose it is best to just get the damn things replaced either way, as I have no idea the condition they are in, and I always have had a bit of a strange idling problem (not that noticeable, I thought it was a glitch in the tune) that could be attributed to shitty plugs.
09-13-2010, 05:46 PM
DocWalt

Blowout will happen under high boost, but if the plugs are crummy, it can stutter a lot all the time.