RB20 with VG30 problem

[Naife]

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.

[Waldo]

it prob has sumthin to do with maybe fuel or boost cut.....i had the same prob but mine was boost cut at 1.2 bar so i just ran 1 bar

[jnr32r]

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

[Naife]

it's only running 10psi atm.

is got a fmic and turbosmart BOV so it's not equipment. the car ran perfectly fine with the t25 till he had the vg30bb put on.

[Naife]

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.

[32drift]

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.

[Naife]

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.

[32drift]

just a idea? check to make sure the bleed value is in correctly, the small pin like hole on the T piece is facing the right way?

[jnr32r]

even better bypass the bleed valve altogether... joint both ends of the hose.

[Naife]

yeah i rang him just earlier and said to disconnect the bleed valve and plug the pipe. will find out it there is any change tomorrow.

cheers

[Naife]

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.

[32drift]

my car would hit about 12psi then drop to about 9psi. This was discovered when i put my car on the dyno.

[Naife]

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?

[mjfawke]

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.

[Naife]

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]

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.

[Naife]

i know of about 6 other rb20's runnin the vg30bb turbo.

redtop and silvertop.

at 7pounds thoe i wouldn't think it would be as bad but its still fairly bad.

[mjfawke]

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?

[Naife]

don't know get's goin roun 4-4.5

but thats to be expected with a 3ltr turbo on a 2ltr.