Rb25det Boost Problem

[Quinny]

I posted a question about this issue in the General Discussion area, I apologise for the double post, but I now realise the question should be asked here.

I bought an R33 GTS-T Series 2 a couple of days ago. I noticed what seems to be a flat-spot in the rev range at about 3000rpm. Once it gets past 4000rpm, it revs quite well. The sound is kind of like a clutch slipping or a sloppy down-change from an auto gearbox.

I was suspecting a boost issue, but I had a look tonight when I took the car for a drive, I revved the car to 7000rpm in 2nd & 3rd, and the boost guage was sitting on about +370mm/Hg (so about 7 psi).

The car is basically stock except for a HKS pod filter, and an exhaust (I am not sure if it is right through or just cat-back), and as I mentioned above, the car seems to be running factory boost.

A couple of people have suggested to check the coils, and replace the plugs with 0.8mm units, this will be done soon. Can anyone think of any other reason that this might occur? I am pretty new to Skylines, so any help would be appreciated.

Edited May 11, 2006 by Quinny

[Quinny]

I took my R33 for a run last night, and I think I may have found the problem. It seems that the "flat-spot" comes on just as the turbo starts coming on boost. I am thinking that the "flat-spot" is actuallt the clutch slipping when the turbo hits boost.

Does this sound right?

[QRI05E]

From experiance, this sounds like the begining of coil pack issues which are very common in the S2 R33.. you might want to check a few things first and see how you go..

1. check spark plugs for any fouling and gap to 0.8mm (could help determine which coil may be misfireing)

2. check each coil VERY carefuly for any horizontal hair line cracks and burn marks.

3. make sure fuel filter is clean and run a injector cleaner with a fresh tank of premium.

If you find any horizontal hair line cracks and burn marks on the coils, read the 'misfire' thread and that could be the fix of your problem.

http://www.skylinesaustralia.com/forums/in...c=32356&hl=coil

I personally bought a tube of Selley's industrial Hi-Temp silicone from bunnings for $11 and that fixed my coils.. solved my problem 100%

Or if you got the cash.. pick up a set of Splitfire Di Coil Packs for around $600 - $900 new

Regards,

Sarkis

[Quinny]

I am starting to think you may be right. I am starting to see the symptoms of coil failure that I have been reading about.

One question, where are the coils located on an RB25DET, I can't seem to find them. How hard are they to replace?

[paulr33]

sounds like stock clutch dying. do you have any burning smells ?

does it free rev from 3 to 4 grand? like the engine gives a bit of a "berp" slip sounds when it happens?

[Quinny]

I was thinking it was a dying clutch, but I drove the car for over an hour, up a steep hill (Mt Ousley), and had no burning smell, so I am not so sure. The car does rev over 4000rpm, but still feels like it is struggling, but nowhere near as bad as at lower revs.

It seems to start "slipping" at about 2500rpm, then is pretty bad by 3000 to 4000rpm. I really don't want to spend money on replacing parts that I don't have to replace, so I really need some help on this one.

[QRI05E]

Easiest way to test your clutch would be to drive the car till its warm... stop the car on a slight incline... try to "normally" take off in 3rd gear... if your clutch is good your car will stall... if its slipping YOU WILL KNOW! hehe

As for your coil packs, theres no harm in checking them out just incase this is causing any misfiring as you described it to be a "flat spot" which is a slight jerky hesitation while accelerating...

The coils in the SII R33 are located under the black cover with 8 allan screws that sits on top of your motor... you will need to remove the throttle intake pipe to access it the coils... theres a thread on changing spark plugs that covers the whole procedure...

Let us know how you go..

Regards,

Sarkis

[Quinny]

Thanks QRI05E, that is the kind of info I am after. I might try the clutch out and see how it goes taking off in 3rd. The car doesn't seem to have any trouble with taking off normally (i.e. in first), but I will see how it goes in third.

So the coils are under the top cover on the engine? No wonder I couldn't find them.

I will take the car to the tuners on the weekend and put it on the dyno. Hopefully that may give some indication as well.

[Quinny]

Easiest way to test your clutch would be to drive the car till its warm... stop the car on a slight incline... try to "normally" take off in 3rd gear... if your clutch is good your car will stall... if its slipping YOU WILL KNOW! hehe

I just had a thought (doesn't happen all that often...kind of hurt a bit.. ). Usually, a slipping clutch will have the same problem in any gear, correct? My problem does not occur in first gear. It will rev cleanly through the whole rev range in first, but it has problems in all the other gears. 3rd is the worst, 2nd is still pretty bad.

Would the fact that the car does not have the problem in first let the clutch off the hook as a suspect? Would this still indicate the coil packs? Any other ideas?

[paulr33]

it sounds more like a clutch slip now. in first gear there isnt as much load on the engine. much more load in 3rd, then a bit more load in 2nd

its much more likely to slip in 2nd/3rd on load, when coming on boost from 2500sih to 3500 as there is where the bulk of the torque is made

[Quinny]

it sounds more like a clutch slip now. in first gear there isnt as much load on the engine. much more load in 3rd, then a bit more load in 2nd

its much more likely to slip in 2nd/3rd on load, when coming on boost from 2500sih to 3500 as there is where the bulk of the torque is made

Hmmmmm... I suppose you are right. It still doesn't explain why I had the car sitting at 3000rpm, right where it slips worst for an hour cruising up a steep hill, and no burning smell from the clutch. Clutches usually stink really bad when you slip them bad like that. Also, why is it that I get less slippage at higher revs, when full-boost is on?

Thanks for your help PaulR33. One step closer to finding out the problem.

[paulr33]

clutch slip is related to pressure / stress on the flywheel and clutch

the bulk of this occurs when coming on hard from 2500 to around 3500

as boost comes on hard. going up an inclinde steadily may not generate enough load to make it slip. its hard to say, theres no definate exact set of events to make it happen, only rough. if you continue to try and make it slip it will get worse and worse and eventually just fail so thats not recommended.

mine didnt smell too much, only a tiny bit when it started slipping the first time. every other time it slipped there was no smell.

i was able to rev mine to redline on full load once i stopped slipping at 4000 so just cos you can rev it out doesn't mean its not slip.

slip basically looks like the rev needle freely jumping a couple hundred RPM when it happens

[Quinny]

clutch slip is related to pressure / stress on the flywheel and clutch

the bulk of this occurs when coming on hard from 2500 to around 3500

as boost comes on hard. going up an inclinde steadily may not generate enough load to make it slip. its hard to say, theres no definate exact set of events to make it happen, only rough. if you continue to try and make it slip it will get worse and worse and eventually just fail so thats not recommended.

mine didnt smell too much, only a tiny bit when it started slipping the first time. every other time it slipped there was no smell.

i was able to rev mine to redline on full load once i stopped slipping at 4000 so just cos you can rev it out doesn't mean its not slip.

slip basically looks like the rev needle freely jumping a couple hundred RPM when it happens

Yeah, that sounds like my problem. The clutch was slipping quite a bit going up the hill, but not all the time. Although, I did notice it getting worse as I drove longer. I won't drive it all that far again until I fix it. It is really starting to sound like the clutch. Maybe the smell (or lack of) is just related to the compound used for the clutch plate.

I guess a new sports clutch is in order. I will get the gearbox pulled and clutch checked first, but it sounds like a prime suspect.

Thanks Paul. Cheers.

[Quinny]

I was driving the car today, trying to keep an eye on the boost level when the clutch starts slipping, it seems that under acceleration, as the boost just starts coming on (at around the 0 on the factory boost guage), and around 2000-2500rpm is when the slipping starts occuring. It also seems to have gotten worse at higher revs and also in first gear.

So, it sounds like I am up for a new clutch. What is the best kind of clutch for a mildly modded R33? I can get a brass-button clutch with a sprung centre for $530, would that be the way to go? Does anyone have any recommendations for a new clutch? I wouldn't mind the clutch being a bit heavier, as long as it will take a bit of punishment from around 200rwkw.

[paulr33]

where are you located

[Quinny]

South-West Sydney, Campbelltown area.

[Modena]

With my car I have a slight spluttering problem at times... so we inspected one of the coil packs and it was clean... the spark plug looked worn out though so we gonna change them this week.

Gonna go for NGK...

[The Mafia]

BKR6EYA

THey are $18 for a set, gapped to 0.8mm, work 150%.

[justin911]

yeah i had the same thing... just had my clutch replaced with one of those cheap '240kw' organic exedy ones from that guy c&b.. was only like $320.. i havnt tested it out properly yet, ive only done like 200km but seems pretty good so far. Im sure the more expensive ones would be better and maybe live abit longer, but for $320 u cant go wrong

you should get it replaced soon so u dont have to pay towing fee's

oh yeah themafia whats the diff between those plugs and the bcpr6es ones ??

I was driving the car today, trying to keep an eye on the boost level when the clutch starts slipping, it seems that under acceleration, as the boost just starts coming on (at around the 0 on the factory boost guage), and around 2000-2500rpm is when the slipping starts occuring. It also seems to have gotten worse at higher revs and also in first gear.

[Quinny]

With my car I have a slight spluttering problem at times... so we inspected one of the coil packs and it was clean... the spark plug looked worn out though so we gonna change them this week.

Gonna go for NGK...

My car isn't really spluttering, it is feels and sounds just like the clutch is slipping, it is only happening when boost starts coming on, when the engine starts developing is torque. I am pretty sure that it is the clutch, but I will be getting new plugs etc when I get the car serviced pretty soon.