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RB20 with VG30 problem

Naife

By Naife,
in Engines & Forced Induction

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Naife Enthusiast

Naife

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Hey all. my mates just had a VG30bb turbo installed on his RB20 and underboost it jerks around, the car really want's to go but it feels like a real strong head wind. yah can hear the BOV go off at 5000. the mechanic said it had somethin to do with the fuel cut. any ideas and solutions?

Cheers

Nathan.

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Naife Enthusiast

Naife

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i dont think it would be fuel... sounds like it could be leaking air from somewhere, checked all the piping is connected up properly ?

not sure i won't see him till saturday. will check. the mechanics are highly recomended for turbo work so it doesn't seem likely. if it had a leak would it slightly splutter idleing? it runs smooth as. u put ur foot down. it'll spool up fine under small accleration.

Naife Enthusiast

Naife

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that did cross my mind. i remember hearing that some bleed valves can spike or go haywire.

he has the turbosmart bleed that you just wind.

was workin find before thoe thats whats puzzling.

cheers.

Naife Enthusiast

Naife

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my car has the same set up and and the same problem??? Have been told it is my cheap and nasty bleed value. Was told by two mechanics to invested in a electronic boost controller.     hope this helps.

when your's did this did your boost gauge jump around?

i was lookin at his and it would stay on 10 only dropping down 1-2 psi now and then but would drop to 5 when the BOV goes off @ ~5k but staight back to 10 after.

  • 2 weeks later...
Naife Enthusiast

Naife

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ok he finally got around to removin his bleed valve. it ran @7pound but no change.

it was dynoed after they did the upgrade but it wasn't a full tune. he's gettin a after market comp soon but it is weird that other ppl are havin no problems with their exact setup just this 1.

the engine is in an aus r31 would it have anythin to do with using the RB30 AFM? or should that be fine?

Naife Enthusiast

Naife

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If the "bov is opening at 5K" (the sound, anyway) without lifting off the accelerator, and you are getting fluctuating boost pressure, then it is compressor surge.  Simply a case of the turbo being too big for the motor.

yeah that seems right but why is this motor that is having that problem? no other rb20det running vg30 turbos are having this problem. it has a gtr cooler and the pipes are quite cool now, they were gettin real hot b4.

seems and if there not enuf fuel. still the std rb30 pump. doing his brakes tomorrow will do a pressure test underload and check fuel filter.

thanks for your comments.

mjfawke Collaborator

mjfawke

Posted
Posted

How many other RB20's are running with BB turbos? The plain bearing turbo would be the common one, and the compressor and turbine are different.

I mean, you using a turbo meant for an engine with 50% more airflow. Julian Edgars "21'st Century Performance" book has some doco on fitting the same turbo to a CA18, which basically sh*t itself with surge.

mjfawke Collaborator

mjfawke

Posted
Posted

A friend of mine runs a VG30DET with the BB turbo - only makes 14psi boost, and drops off the 9psi in the top end. Huge FMIC, EMS computer with boost controller - full boost at only 2k rpm, MASSIVE torque in the midrange.

Your friends turbo is stock isn't it? Hasn't had a super-60 wheel fitted or something like that?

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