# Won't hold full Boost?



## Jethro1013 (Jan 26, 2007)

So I have only recently got my VRT setup running and still doing some troubleshooting. 

First off the setup was a budget build that someone else started so im slowly purchasing better parts 
United Motorsports #42 chip
9:1 Head Spacer
XS power wastegate 38mm 10lb spring
HKS SSQV Bov recirculated
DRC 268 Cams
Intercooled 2.5 inch piping
Very small T3 .48 A/R turbo 


As of my boosting issue is I have the boost controller set around 9lbs, It hits 9lbs around 4,000 RPM then slowly drops to 5-6lbs as the RPMs increase. 

My thoughts are that the 
-wastegate is unable to hold back the exhaust pressure so the turbo isnt continuing to spool.
-Turbo is just to small and runs out of air
-I may not have fully figure out the Greddy Profec Spec B boost controller yet
-Leak somewhere in the piping/intercooler

Any input would be appreciated


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## PjS860ct (Dec 22, 2002)

*-Turbo is just to small and runs out of air
-I may not have fully figure out the Greddy Profec Spec B boost controller yet
-Leak somewhere in the piping/intercooler*
*^* _double check everything *^*
_
.48AR is tiny!

its like a ko3 on a 1.8t lol

it should spool up in any gear as soon as you hit the gas...


pics of the setup?


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## cstanley19 (Sep 23, 2006)

definitely a small turbo. I doubt it's a boost leak because if your making boost and hitting a certain psi, it's not leaking. I guess it could potentially be a loose coupler clamp that only blows excess boost might be able to sneak out and lose boost but highly doubtful. 

Do you notice a drop in performance or are you judging strictly because of the gauge? Maybe there is a vacuum leak to the gauge if there is no drop in the "feel" or pull. 

If there is no spool in first it kind of perplexes me. A .48 would spool almost instantly like PjS said, it's just like a k03 = instant spool. 

What are you pulling for vacuum?..


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## Jethro1013 (Jan 26, 2007)

Correction on spooling in 1st it does spool so ignore that part my bad. 

And vacuume at idle is around 7, but performance deffinatly drops with the boost level it doesn't have the same urgency as when it's at 9lbs lower in the Rpms


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## PjS860ct (Dec 22, 2002)

Jethro1013 said:


> .
> 
> And vacuume at idle is around 7,


something is off/wrong with a 7 vacuum at idle


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## Jethro1013 (Jan 26, 2007)

What should it be then?


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## PjS860ct (Dec 22, 2002)

there is a vacuum leak somewhere... where i dont know... double check the fmic setup, all the couplers and clamps, intake manifold etc

try to pleasure test the intake system or bring it to a shop and do a smoke test

also is it timed correctly? 

goodluck:beer:


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## Jethro1013 (Jan 26, 2007)

It's deffinatly timed correctly, ive been leaning towards a leak somewhere I just need to find it.


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## TBT-Syncro (Apr 28, 2001)

cstanley19 said:


> definitely a small turbo. I doubt it's a boost leak because if your making boost and hitting a certain psi, it's not leaking.


incorrect.


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## TBT-Syncro (Apr 28, 2001)

whats your timing and air/fuel at idle?

vac will be way down if its' running pig rich.


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## Jethro1013 (Jan 26, 2007)

At idle air fuel actually sits around 14.7 then gets richer around 12 in boost.


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## cabzilla (Jan 3, 2000)

he's out of turbo guys, come on now.


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## TBT-Syncro (Apr 28, 2001)

cabzilla said:


> he's out of turbo guys, come on now.


spooling at 4k doesnt make sense. something is wrong.


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## Jethro1013 (Jan 26, 2007)

It starts spooling 2800-3000rpm but I only see full boost around 4000 I have the boost controller set to bring in boost alittle slower than the turbo would regularly boost just trying to prevent hard hitting boost in the low end to prevent trans problems down the line. 

Im just trying to find out why the boost falls off as rpms increase

If its the boost tubes/intercooler system leaking I can only imagine it is leaking from a bad weld on the tubes, or the BOV mounting area isnt sealing. I have good heavy (I think) 4ply couplers and Tbolt clamps.


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## TBT-Syncro (Apr 28, 2001)

just run it off the wastegate and see what happens. right now there are too many variables.


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## CorradoFuhrer (Mar 21, 2002)

Jethro1013 said:


> So I have only recently got my VRT setup running and still doing some troubleshooting.
> 
> First off the setup was a budget build that someone else started so im slowly purchasing better parts
> United Motorsports #42 chip
> ...


my moneys on the boost controller run with out and see if you make the 10 lbs or not.


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## Jethro1013 (Jan 26, 2007)

Tried that before and again today still doesnt hold full boost with the boost contoller off


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## cabzilla (Jan 3, 2000)

out.of.turbo.



hotside too small.


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## Jethro1013 (Jan 26, 2007)

Are those the characteristics of a turbo too small? 

For some reason in my mind I imagine a turbo too small only hitting a certain level and not being able to boost more, not having it lose pressure.


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## andykoh (Aug 12, 2011)

guys,

It's been awhile I have chance for long distance drive after my car got remapped.

Need some idea to know what is going with my car. Here's the thing, Was on the way back to KL from Penang, whacking 160 to 200km/h average. When I was on 160km/H, 3800rpm, when I pressed the throttle to accelerate abit, the Boost meter was spiking from 0.6 to 1.0 up down up down for 3 times, making the car feel like pulling and pushing, but rpm remained at 3800rpm. But when I floored the throttle, then only the car accelerating like it should and boost went up 1.1 to 1.4 like normal.

Fyi, I'm on Stg2, I have just changed to Forge DV recently, was using the hard spring given by Forge, but I have also checked using VCDs, no fault code, and have changed the DV springs to the soft 1, just now tried, the problem still persist.

What could be the issues here? Exhaust leaking? Misfiring? Hope can hear some ideas from you guys.

Peak Boost for that day.
[attachment=0]IMG-20120109-01006.jpg[/attachment]


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## cabzilla (Jan 3, 2000)

Jethro1013 said:


> Are those the characteristics of a turbo too small?
> 
> For some reason in my mind I imagine a turbo too small only hitting a certain level and not being able to boost more, not having it lose pressure.


yes. look at a 1.8t. once you max out the k03 it starts losing pressure as you near redline.


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## Big_Tom (Aug 19, 2007)

cabzilla said:


> out.of.turbo.
> 
> 
> 
> hotside too small.


this :thumbup:


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## MaxVW (Nov 4, 2004)

I have this issue where my boost falls down about 2-3 psi as i rev it out. but i was under the assumption this is because my external WG is basically Tee'd onto the exhaust mani. Although i didn't notice when i was getting my car dyno'd you can hear some sort of leak

this is a VR5 2.3L with a t04be cold side and t3 .48 ar hot side. 

http://www.youtube.com/watch?v=s30Z1i9AnM8

I have yet to solve the issue as it doesn't matter since the car continually makes more power till I hit red line











Does your car feel like its running out of power or does it pull harder the higher you rev?


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## Jethro1013 (Jan 26, 2007)

The car pulls to redline but not like it's holding full boost it loses some urgency as the Rpms get higher. 

So the consense is turbo to small which I knew it was small to begin with and it's only temporary till I save the money to fully finish the setup how I want. This helps so I'm not chasing a boost leak that doesn't exsist and it's just the turbo.


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## cstanley19 (Sep 23, 2006)

I think cabzilla has said it enough.. your out of turbo.


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