Silvia Club of NSW
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GT2860RS boost drop-off issue
https://forum.silviansw.com/viewtopic.php?f=1&t=33576
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Author:  radism [ Tue Jul 28, 2009 6:34 pm ]
Post subject:  GT2860RS boost drop-off issue

Hey all, my problem is as follows:

Car setup:

1997 180SX
SR20DET
78,000 km's

GT2860RS
Greddy FMIC kit
Greddy Profec B Spec II
Tomei Poncams
Z32 AFM
Nismo 740cc Injectors
3-inch turbo-back exhaust
Catco Cat
Walbro in-tank flowing fine
Nistune Daughterboard ecu
Apexi pod filter
Stock S13 BOV


Car has been tuned by Yavuz at Unigroup Engineering to 201rwkw. See below dyno sheet.

Image

The problem is that the boost is dropping off from 19psi to 14psi resulting in the somewhat disappointing power figure given the setup.

Yavuz mentioned to me when I first picked up the car that it's an actuator problem and that I should look at getting an adjustable actuator. GCG Turbo's have confirmed that the actuator that comes with the GT2860RS is already adjustable with a base pressure of 14.7psi and capable of around 22psi.

Yavuz now says that the boost drop off problem is attributable to the turbo itself and not being able to keep up with the engine as it breathes throughout the whole rev range.

I know that the stock S13 BOV will most likely be leaking in this setup but Yavuz doesn't think that it will make a huge difference when it's replaced with a stronger one.

He also went through the entire system when he was tuning the car and is happy with minimal boost leakage throughout it.

Can anyone confirm that getting a different adjustable actuator will rectify this boost drop-off issue or not, or any other possible solutions? I'd like to see at least 210rwkw with this system given the higher-flowing injectors and Poncams.

Thanks in advance guys.

Author:  too_much_boost [ Tue Jul 28, 2009 7:18 pm ]
Post subject: 

I'd be getting rid of the stock bov for starters.

Next thing- what intake piping are you running? If you are running the stock rubber stuff, that would cause a problem.

Otherwise i'd be looking at the actuator.

That turbo with your setup SHOULD hold about 16-17 at the top and make around 220rwkw

Author:  <<Ronin>> [ Wed Jul 29, 2009 5:43 am ]
Post subject: 

I'd say actuator, Looks like your reaching peak boost about 800 - 1000 rpm too late.

Author:  CUE-02C [ Wed Jul 29, 2009 9:04 am ]
Post subject: 

hey mate,

i have nearly identical setup.

i have the exact same problem, im running .86 rear.

think he suggested the actuator aswell, think i pulled round 220rwkw mine was dropping back to 16psi from memory.

i never solved the problem just dealt with it as im upgrading to 2871r but it would be nice to know if you fix the problem what it was.

cheers
Mitch

Author:  radism [ Wed Jul 29, 2009 10:47 am ]
Post subject: 

I am actually still running the stock rubber intake piping. I'll be replacing that as well too as it reduces from the Z32 3" to 2.5".

Also, apparently there's lots of oil in my cooler piping and core on the intake side.

So when you guys say it's an actuator problem, should i look at getting a stronger actuator? Seeing as its already an adjustable actuator, GCG have said it's capable of around 22psi. But if it's not doing the job properly, perhaps I should get a heavier duty one? Any suggestions?

Author:  too_much_boost [ Wed Jul 29, 2009 11:04 am ]
Post subject: 

Piss off the stock rubber piping then. I had a similar issue in the sil80 (boost dropping to 13psi - The intake piping seemed to be getting sucked closed), but once i changed the piping to steel, it held boost much better

Author:  radism [ Wed Jul 29, 2009 11:50 am ]
Post subject: 

Thanks Anthony, I'll fix that up for sure. So do you think the actuator might not be the problem then?

Author:  too_much_boost [ Wed Jul 29, 2009 4:06 pm ]
Post subject: 

Perhaps the actuator is contributing to the problem. What boost does the turbo run when the boost controller is turned off?

Author:  radism [ Wed Jul 29, 2009 4:36 pm ]
Post subject: 

14.7psi which is apparently the GT2860RS's stock actuator base pressure.

Author:  <<Ronin>> [ Wed Jul 29, 2009 8:47 pm ]
Post subject: 

radism wrote:
I am actually still running the stock rubber intake piping. I'll be replacing that as well too as it reduces from the Z32 3" to 2.5".

Also, apparently there's lots of oil in my cooler piping and core on the intake side.

So when you guys say it's an actuator problem, should i look at getting a stronger actuator? Seeing as its already an adjustable actuator, GCG have said it's capable of around 22psi. But if it's not doing the job properly, perhaps I should get a heavier duty one? Any suggestions?


Could it be that the actuator isn't adjusted correctly, or is faulty ?
The wife's car has the same turbo, and was laggy to come onto boost, then couldn't maintain boost. It turned out to be the bracket which holds the actuator was broken and had been looseened off to mask the problem.

Author:  radism [ Thu Jul 30, 2009 12:07 am ]
Post subject: 

<<Ronin>> wrote:
Could it be that the actuator isn't adjusted correctly, or is faulty ?
The wife's car has the same turbo, and was laggy to come onto boost, then couldn't maintain boost. It turned out to be the bracket which holds the actuator was broken and had been looseened off to mask the problem.


How can I identify this problem if it exists? Do I have to just play around with the actuator and bracket and see if there's play in it?

Yavuz said he played around with the actuator alot when tuning but I don't know what exactly he did and to what extent.

Author:  <<Ronin>> [ Thu Jul 30, 2009 5:30 am ]
Post subject: 

Maybe go and see Luis from Drift Garage, he identified and fixed our problem.

Author:  radism [ Thu Jul 30, 2009 2:34 pm ]
Post subject: 

I'll get him to look at it and get my guards rolled at the same time :lol:

Author:  Aym23q [ Mon Aug 03, 2009 5:16 pm ]
Post subject: 

how did u go man, did u figure it out?

Author:  radism [ Tue Aug 04, 2009 4:02 pm ]
Post subject: 

No not just yet. I'm going to try and address all the potential issues raised above before I take it to Yavuz to try and re-tune it. I think the bov and intake piping might be big factors. Got the bov, just looking for piping now.

I'll see why he's got it tuned to come on to boost so late as well. I'll post an update as soon as I take it back to Yavuz.

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