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Just Got A Gt30 On

GunMetalR33

By GunMetalR33,
in Engines & Forced Induction

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GunMetalR33 Mentor

GunMetalR33

Posted
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My theory is this:

The new turbo has a better bearing cartridge and I know for a fact that it spins way more when you turn the car off, so you would assume that it will spin faster & longer when the clutch is pressed in.

So, with a higher turbo rpm with clutch in combined with the fact that the GT30 comp housing is flowing much more air I am getting compressor surge...

Its either this, or the guys who made my intake piping blocked the BOV return pipe near the mouth of the turbo

What do you guys think?

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

its not a lot to do with RPM, and little RB25 turbo would spin faster to make 12 psi than a GT30... if my brain is thinking logically

check your BOV, like make sure its working, not just hooked up.

Worst case, just purchase GTR ones.

They work perfectly

GunMetalR33 Mentor

GunMetalR33

Posted
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Yea, it will vent small amount of pressure like 5psi for example. Its when you get higher presure that it start to flutter.

The GT30 certainly does flow the 12psi much easier... But at the end of the day 12psi measured at the intake plenum is 12psi no matter what turbo you use.

do you get flutter only at 12psi and a normal stock bov sound at say 5psi?

I have another question.

is 12 psi 12 psi?

I mean, 12 psi produced by the stock turbo = the same amount of air as 12 psi from the GT30?

My brain won't bend to work it out today....

TTT Grand Master

TTT

Posted
Posted

well if it can vent at 5 psi but not at the higher 12, then 2 things can be the issue.

1.) the bov can't flow enough.

2.) the return line is too small and can't flow enough to the inlet.

either of those will cause enough of a blockage to cause a fluttering.

Lordsnipe - you're right..

just thought about it now.. when I got an RB25 turbo on my RB20, on the same boost (11psi) it was making a decent amount more power than with stock turbo.

I just can't think of the theory behind it.

if it's 12 psi in the motor, then how does that effect flow wether it's from gt30 or T25...

brain broken..

simpletool Mentor

simpletool

Posted
Posted

Sounds like you need a bigger BOV or one that vents better or both.

Does this only happen at high rpm (high flow rates). ie. does it surge if you shift at 4000rpm? Cause that would be a similar flow rate to your stock turbo at 5000rpm (estimate)

As for the does a bigger turbo flow more than a stock turbo with 12psi in the plenum ??

Well it's 12psi in the plenum but the engine makes more power which means it has more flow. (ie. eats more volume of air per second) This is because the turbo is more efficient and uses less exhaust restriciton to make the intake pressure so it lets more air out of the engine for more air to go in.

Got it?

They would flow the similar in the midrange though where the stock turbo is still sort of efficient.

carl h Proficient

carl h

Posted
Posted

bah 12psi is too low on a gt30r not even on the compressor map........

boost it to 14 then tell us how it goes.

also the stock bov is good for stock turbos but big tubos need some flow for the BPV.

another option would be to run dual bov's to vent boost but at that point the fab work and cost would make it cheaper to buy a highflow bov/bpv

GunMetalR33 Mentor

GunMetalR33

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Arr,

That makes sence. I have always wondered how that worked, thanks for clearing it up!

As for my BOV, it seems to have loosened up a little. Now it will vent fine for low boost & low rpm but as soon as you get a little more boost (~10psi) & rpm she goes PSSSHHH flutter flutter flutter :)

As for the does a bigger turbo flow more than a stock turbo with 12psi in the plenum ??

Well it's 12psi in the plenum but the engine makes more power which means it has more flow. (ie. eats more volume of air per second)  This is because the turbo is more efficient and uses less exhaust restriciton to make the intake pressure so it lets more air out of the engine for more air to go in. 

Got it?

GunMetalR33 Mentor

GunMetalR33

Posted
  • Author
Posted (edited)

Does anybody have some pics of a Plumb back installed on a RB25DET???

An aftermarket one I mean...

just try an aftermarket plumback one... if it doesn't flutter at high revs, then you're done.

if it does, then the bov return line would be the restriction.

Edited by GunMetalR33
bigcarl Experienced

bigcarl

Posted
Posted

i had to change my stocky over after gt30 installation , it was leaking at high boost. put a blitz supersound on and it works fine , i have no compressor surge problems. gunmetal ive got pics now to of oil lines and of the turbo actually on my car, if you want i can send you photos, just pm me your email and i will send photos.

GunMetalR33 Mentor

GunMetalR33

Posted
  • Author
Posted (edited)

Its OK now mate, I have it fitted and sorted. Now I just have the injectors left to do and a tune. At what PSI did your BOV leak? I thought the stock BOV would be fine. Did you get any compressor surge with the old BOV?

Is your Blitz BOV a plumb back and if so do you have any pics of it mounted?

i had to change my stocky over after gt30 installation , it was leaking at high boost. put a blitz supersound on and it works fine , i have no compressor surge problems. gunmetal ive got pics now to of oil lines and of the turbo actually on my car, if you want i can send you photos, just pm me your email and i will send photos.

Edited by GunMetalR33

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