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Stock Turbo Overboosting with No Bleeder...

strutto

By strutto,
in Engines & Forced Induction

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BHDave Grand Master

BHDave

Posted
Posted

If it's not dropping back it sounds a bit like wastegate creep as you have improved the efficiency of the system. I had this problem once i installed a full exhaust on a series 4 13bt but they are notorious for creep.

The car should make a small amont of boost late in the rev range with the gate wired open but not that much!

For a long shot: does the car definately have a stock turbo on it? It hasn't been swaped for an rb20 one maybe?

strutto Grand Master

strutto

Posted
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Posted
  cameron said:
Sounds like oil in the actuator, I've seen it happen to a R33 recently. Boost will keep rising under accelleration intil you back off. This was using avc-r and it wasent that solinoid because we swaped it into another and it worked fine.

It's got nothing to do with the actuator...

  cameron said:
If its wired open it shouldnt make any boost at all. :uh-huh:

Well it does... Thanks anyway...

  BHDave said:
If it's not dropping back it sounds a bit like wastegate creep as you have improved the efficiency of the system. I had this problem once i installed a full exhaust on a series 4 13bt but they are notorious for creep.

The car should make a small amont of boost late in the rev range with the gate wired open but not that much!

For a long shot: does the car definately have a stock turbo on it? It hasn't been swaped for an rb20 one maybe?

Yeah hopefully dropping the exhaust after the front pipe might reveal something... It seems like an efficiency problem to me but why am I the only one experiencing it?

Car has a 3" dump and front in one... (not split wastegate)... 3" Trust cat back... Fairly old cat back though... 3 mufflers in it too... All straight through but... Hmmm wonder if I'm up for a new exhaust...

I expected a little boost up high with the gate wired open, but it's making heaps...

Car was stock as can be when I bought it... First owner in Australia... So I doubt the turbo is different... Looks like a 33 unit to me... No signs of any work being carried out around there in the past either...

:mad:

Weq Contributor

Weq

Posted
Posted
  strutto said:
It's got nothing to do with the actuator...

 

   

 Well it does...  Thanks anyway...

 

 

Yeah hopefully dropping the exhaust after the front pipe might reveal something...  It seems like an efficiency problem to me but why am I the only one experiencing it?

 

Car has a 3" dump and front in one...  (not split wastegate)...  3" Trust cat back...  Fairly old cat back though... 3 mufflers in it too...  All straight through but...  Hmmm wonder if I'm up for a new exhaust...

 

I expected a little boost up high with the gate wired open, but it's making heaps...

 

Car was stock as can be when I bought it...  First owner in Australia...  So I doubt the turbo is different...  Looks like a 33 unit to me...  No signs of any work being carried out around there in the past either...

 

:)

if u wired the gate open and its still making boost. something must be up with ur wastegate flapper or there is a blockage on the diversion port. its the only explanantion as to why the ehxuast gasses arnt bypassing the turbine.

Pandaemonaeon Enthusiast

Pandaemonaeon

Posted
Posted

I noticed the same problem when I got my exhaust fixed. It's a full 3.5" setup and the front pipe had a big dent in it. When I took this dent out and removed the cat on stock boost it was maxing at about 0.8 bar. On saturday it was real cold and was maxing at about 0.9 bar, so the car had bugger all power from 5000rpm upwards as it was hitting the boost cut.

RBVS Community Regular

RBVS

Posted
Posted

ok we can all stop talking about the controling system , he has said more than once that he had the waste gate wired fully open. This is not that un common after fit ment of a larger exhaust system. the turbo becomes more efficient (free flowing) increasing boost in the top end. ways to combat this is to..

modify the dump in a way to incrase the flow of the waste gate gas, at the moment it simply cant divert enough pressure from going though the turbo wheel to get your desired boost level.

If that has been done or is done to the best you can the next step is a bit more hard core but i have done it and got resaults and so have others that i told. (may fined on a search)

this is to drop the exhaust of the back of the turbo to acess the gate.

you will see that the the gate over laps the waste hole buy about 3 to 4mm.

with a die grinder or round file would be safer increase the diameter of the hole buy 1 to 2 mm but make shore the gate will still easly cover the hole. also pay attention to the angle the hole is in relation to exhaust flow.(90 degrees) taking a bit of the inside edge out will make it flow better also. 1mm in diameter will make a big differance.

See the thing is the system all works well in the stock set up but once you change one thing it has an effect on another so you have to even the ratio back.

Doctor Mentor

Doctor

Posted
Posted

Instead of wiring the wastegate open, you should be able to slide the wastegate control arm of the flap, so that the wastegate flap can be left......flapping.

This way you will definately know that the wastegate is 100% open when on boost instead of trusting your wiring job.

You should not be making any boost if this is done correctly.

Have you checked to see if the wastegate arm has not be bent? May have been suggested before?

I dont think you really need to go the the extent of what RBVS is suggesting as its not a common problem you are experiencing.

My money is on the wastegate arm being bent.

The shitty thing is its probably something really simple. Thats cars for you...

strutto Grand Master

strutto

Posted
  • Author
Posted

OK, from the top...

  R31 POWER said:
Probally a long shot but that DIY boost controller you had before did you have to put a restrictor in the actuator line?

The restriction was adjustable (ball valve) and has definately been removed... Good idea thought... :cheers:

  RBVS said:
ok we can all stop talking about the controling system , he has said more than once that he had the waste gate wired fully open. This is not that un common after fit ment of a larger exhaust system. the turbo becomes more efficient (free flowing) increasing boost in the top end. ways to combat this is to..

  modify the dump in a way to incrase the flow of the waste gate gas, at the moment it simply cant divert enough pressure from going though the turbo wheel to get your desired boost level.

  If that has been done or is done to the best you can the next step is a bit more hard core but i have done it and got resaults and so have others that i told. (may fined on a search)

  this is to drop the exhaust of the back of the turbo to acess the gate.

  you will see that the the gate over laps the waste hole buy about 3 to 4mm.

  with a die grinder or round file would be safer increase the diameter of the hole buy 1 to 2 mm but make shore the gate will still easly cover the hole. also pay attention to the angle the hole is in relation to exhaust flow.(90 degrees) taking a bit of the inside edge out will make it flow better also. 1mm in diameter will make a big differance.

  See the thing is the system all works well in the stock set up but once you change one thing it has an effect on another so you have to even the ratio back.

Firstly, you are correct... This has nothing to do with the controling system... The front half of the exhaust is about as good as it's going to get ATM... I still haven't had a chance to drop the cat back and take it for a spin to see how that goes... I understand what your saying about the wastegate outlet and I've heard of this being done before... But as Doctor says below, it's not a common problem... I'm honestly not confident enough myself to go filing / grinding away at the exhaust housing of my turbo... If it comes to that, I'll send it to GCG and they can "go to town" on it...

  Doctor said:
Instead of wiring the wastegate open, you should be able to slide the wastegate control arm of the flap, so that the wastegate flap can be left......flapping.

  This way you will definately know that the wastegate is 100% open when on boost instead of trusting your wiring job.

  You should not be making any boost if this is done correctly.

 

  Have you checked to see if the wastegate arm has not be bent? May have been suggested before?

 

  I dont think you really need to go the the extent of what RBVS is suggesting as its not a common problem you are experiencing.

 

  My money is on the wastegate arm being bent.

 

  The shitty thing is its probably something really simple. Thats cars for you...

Doctor, when I wired the gate open, I did remove the actuator arm from the gate flap... The flap was, as you say, flapping... I then wired the flap open so there was no chance of it flapping closed when I was testing it... I hope you understand what I'm saying... There was no tension / preload on the wastegate flap at all... It was 100% open for 100% of the time I tested it...

With this setup, it still made excessive boost...

So I don't think it's the control arm as this was disconnected...

As you say though, it's probably something really simple... I just can't for the life of me work it out... :D

Thanks all...

RBVS Community Regular

RBVS

Posted
Posted

i interpreted it as the waste gate being disconected and instead of flapping around its just sucured in the fully open position buy some wire. If thats right and in doing that its running 12psi plus how could it be a bent aculator rod, all the controling of boost is eliminated form the situation and it just leaves us with the way the gass exits.(flow)

as iv said i have had hands on with this situation. Ive had my waste gate flapping and made 14psi at 7000rpm. So i did what i sudjested above and boost droped to 10psi.

also done with a mates car. ill try and fined the other thread were someone ealse also has done it.

like i said it is a bit hard core but i can only offer my advise. most times just fixed with a proven dump pipe like a hks twin which offers better flow for the waste gate than a stock dump conected to a 3'' system.

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