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Rb25det Boost Problem

Quinny

By Quinny,
in Engines & Forced Induction

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Quinny Rising Star

Quinny

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I had yet another thought with my car. The car seems to be flat-spotting at around 2500-3500 rpm. The more I think about it, the more it seems to be a flat spot rather than a clutch problem. Usually with clutch slip, the car will rev quickly but not go anywhere. Mine sort of revs, then hits 2500-3000, just as boost is coming on, and sort of dies in power, when I bury the foot, it is almost like a really sloppy auto downchange, the revs creep over 4000rpm, then it revs ok from there.

Would it be worthwhile resetting the ECU? I have read that a few people have fixed flat spots like that.

The car is getting serviced next week with new plugs, and the clutch will also be checked, but I am starting to wonder if it actually is the clutch.

I have also noticed that the car seems to run a bit rich - you can smell it (not too strong, but you can still smell it) - would this contribute to my problem?

Any other ideas - or is the clutch still #1 suspect?

justin911 Grand Master

justin911

Posted
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drive the car.... change to forth gear and make the car come on boost quickly.... if your revs are going up but the car isnt realy moving then its the clutch... from what you've said it sounds like the clutch... ( i just replaced mine a week ago.. i had the same problems)

if it was the spark plugs etc.. the car wouldnt be revving still

Quinny Rising Star

Quinny

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Yeah, 4th gear does the same thing, but it is most noticable in 3rd. In my previous experiences with clutch slip, the engine usually revs, but you don't go anywhere (or not very quickly), in this case the car sort of hits a dead patch where it just does not really want to rev, but once it gets over 4000 it is ok..... weird.

I might try resetting the ECU - no harm in that. If it is the clutch, then that will be replaced soon too...

MKDR33 Mentor

MKDR33

Posted
Posted (edited)

I used to get a similar problem, when i boosted my car to 12psi or more, got a flat spot between 4500rpm and 5500rpm.. Updated coil pack issue ---> http://www.skylinesaustralia.com/forums/in...howtopic=119403

Edited by MKDR33
Quinny Rising Star

Quinny

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I just took the car for a drive, it is definitely the clutch. I did a few tests - took off in 3rd gear, clutch slipped until boost came on and the car took off. I also tried mid-gear acceleration and the revs slipped right to 7000 before dropping back to 4000 or so to pickup again.

I am convinced now it is definitely the clutch, and it needs to be replaced soon.

Quinny Rising Star

Quinny

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easy way to tell if it's the clutch -

1. Stop

2. Put it in 4th Gear

3. Try and take off.

4. If the car stalls, then not the clutch

5. If the car rev's up and carries on, clutch is shagged.

I tried taking off easy in 3rd, and the clutch slipped until it hit boost then the car took off, so I think the clutch is stuffed. Also the fact that in any gear, if I bury the foot, the revs slip to 7000rpm before dropping back to about 4k to accelerate again.

Quinny Rising Star

Quinny

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with about $1k spare, you'll be able to get a nice 3100 poundJim Berry Special. It will never slip again :sweat:

(until you put about 350rwkw through it)

I can get a brass button clutch with a sprung centre for $430, so I think that might be the go. I have no intentions of 350rwkw at the moment.

I drove the car today...... clutch is screwed. Big Time., I think last night when I took the car for a drive to test the clutch out, I think I gave it a bit too much of a hiding, because the clutch slips at any revs now, even like 1000rpm.

Quinny Rising Star

Quinny

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go for it.

Don't be worried, a clutch is a consumable like tyres or a fuel filter. They wear out.

Just get her changed and you'll be back in business. Get a nice "on off" style clutch. They are fun.

Yeah, I am not too worried if it is only the clutch, I am glad it wasn't something worse. I will be getting the brass button clutch, but the sprung centre will help the on/off action a little, so it isn't quite as violent so it is better in traffic. The place I am getting it from says that it is the toughest single plate clutch they make for the GTS-T, and will take over 350rwhp with no troubles. Not bad for a $500 clutch.

Quinny Rising Star

Quinny

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Definately the clutch, i'd suggest you stop "testing it" before your flywheel is beyond machining.

Yeah, I have learned that lesson. The car won't go anywhere without slipping really badly. The only trip it will make now is down to the mechanic to get a new clutch. If the flywheel gets screwed, that is a pretty good excuse to get a nice lightened one. :)

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