Silvia Club of NSW

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 Post subject: S14 not holding boost!
PostPosted: Mon Feb 14, 2011 1:50 pm 
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T03

Joined: Mon Apr 23, 2007 8:36 pm
Posts: 137
Location: Sydney
Car: 1998 200sx S14a
Hey All,

Recently got my car back from the tuner and what do you know i have issues...
i have been enlightened on the situation and have organised for it to be taken to Josh for a diagnosis, but thought i'll share some pain with the rest of you guys :)

Basically the car is not holding boost at high RPM's on the dyno sheet it boosts fine to 15psi (stock turbo) but it then suddenly drops to 7psi so the curve looks like a hill/mountain and it does so 3 times so theres like 3 hills on the dyno sheet (at work now so im unable to attach it) only making 173kw max, with the parts i have it should be on the line of 200kw as besides the usual support mods i have z32afm, stage 1 camshafts and 555cc injectors.

i was told it could be a few possibilities which some he did test and i'll do my best to remember it so correct me if i mis-explain things.

first - was a bov leak (mines hks ssqv plumb back)but he double checked it and it was fine he also said the symptons werent of a bov leak to begin with but he did test it anyways - not the problem
second - he checked the actuator (apfc) think he saw that i had a "T-piece" connected and removed that with a straight hose, (bad explanation i know)- not that either
thirdly - he said i think the cam timing? as i did get camshafts installed, when i told him josh did it he removed that thought immediatly :lol:
lucky last - wastegate is blocked from fully opening, turbo area issues, dump pipe diaphragm.

so now that the cars booked in, i hope its nothing major and will be as simple as settings on the boost controller were set incorrectly or something

has anyone else experienced a similar situation?

lets hope i dont get any other problems..


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PostPosted: Tue Feb 15, 2011 1:44 pm 
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Quad T88
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Joined: Mon Jan 24, 2005 6:18 pm
Posts: 3569
Location: Sydney
Car: S15
If the wastegate couldn't fully open then you would have overboosting issues

If it's the first dyno since the cams were done i'd check the cam timing anyway, i have had a problem with it before and it's very hard to pick. Just take the rocker cover off and crank it till the dots line up, if they never do then you've got a problem.

Probably actuator though

_________________
Boost, the substitute for corner speed.


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PostPosted: Tue Feb 15, 2011 7:02 pm 
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T03

Joined: Mon Apr 23, 2007 8:36 pm
Posts: 137
Location: Sydney
Car: 1998 200sx S14a
on the wastegate part the tuner did explain that the boost spikes over 15psi which is probably the reason why he wants me to only drive it 'cruise' style until the problem is fixed, seems that anything over 5000revs the check light flashes.

my mistake for not adding that part it.

yes it is the first dyno since the cams were installed, i'll have a look at that definitely

the tuners best is on the wastegate or actuator.

on the mechanics point of view he prefers to diagnose from the minor possibilities that could be causing this issue i.e. avcr settings/installation and then after the worse case possibility i.e. removing turbo

i hope for the best.

Thanks for the reply magnet! 8)


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PostPosted: Tue Feb 22, 2011 9:52 pm 
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T03

Joined: Mon Apr 23, 2007 8:36 pm
Posts: 137
Location: Sydney
Car: 1998 200sx S14a
update!

Good News
Got a call back from Josh and you are right Magnet it was indeed the actuator, indeed the turbo is 150k km old :-? a few hairline cracks on it as well, guess we found the culprit.

Bad News,
Financially and with the limited time i have, i decided not to purchase a new turbo (wasnt expecting it to be so soon) so i decided to change the actuator for now.
waste of money yes and no, yes because the turbo might really shit itself in the next who knows 6 months? and no because the car is up and running and able to be tuned 100% this time.

At least thats solved for now.. 8)


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