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Location:
West Hobart
Registered:
December 2004
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 Overboosting ST185
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Thu, 13 January 2005 02:19
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My ST185 hits fuel cut if you accelerate too hard in 3rd. (It's easy to do in highway driving)
It has a manual boost controller installed but is turned down as far as it can go.
It also has a BOV and a 3" exhaust system. I've read elsewhere that the 3" exhaust won't provide enough back pressure for the wastegate, is this true?
Anyone have any ideas?
I think it cuts out around 15psi, can't be too sure though, it happens too quickly for me to take notice.
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Location:
Adelaide
Registered:
May 2003
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Re: Overboosting ST185
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Thu, 13 January 2005 02:30
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err....not to sure bout the over boosting problem. but i cant understand why a wastegate would want any back pressure at all!!! that would only slow the turbine down causing lag.
why do so many people have wastegates venting straight to atmosphere??? no back pressure or restrictions there!
id disregard that info that you got given.
the only pressure the wastegate does want is to the ACTUATOR, from the compressor outlet tube. this is what will open the wastegate and regulate the boost. perhaps you have a leak in that hose causing the gate to stay close on cause over boosting. im not to familiar with st185. but id be looking at those things first.
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Location:
newcastle
Registered:
April 2004
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Re: Overboosting ST185
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Thu, 13 January 2005 02:30
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get a FCD on it
they only run 5 to 7 psi std
what sort of controller?
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Location:
West Hobart
Registered:
December 2004
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Thu, 13 January 2005 02:47
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This is a summary of the back pressure thing that was posted on www.gt4oc.net
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Couple of things, it's not that the wastegate is too small to flow the required gas to stop boost creep - it flowed enough before changing exhausts - it's that you've made is so much easier to flow through the turbo than through the wastegate, by reducing back pressure, similar to how a FCD works by changing a resistor value to bleed off more voltage in one path than another
Because of that, there's a few things you can do - increase back pressure as people have already suggested, but you can also increase the flow of the wastegate by porting so that more air can exit via that route again - depending upon your amount of boost creep though, that may or may not be enough on it's own - going external wastegate is the same principle
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Location:
Canberra
Registered:
June 2003
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Re: Overboosting ST185
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Thu, 13 January 2005 02:53
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A GrpA or non GrpA 185?
The GrpA has the fuel cut around 17psi and the non GrpA has it around 12psi....varies slightly between cars.
Either way you are getting the cut in 3rd (and above no doubt?) as the egine is under greater load which generates more exhaust gas and therefore more boost.
It could be your controller just won't allow less boost or you may have a leak in the actuator lines.
Either way if you want to run more than 12psi you'll need a boost cut remover of some sort.
The CT26 is good for 19psi before it starts running out of Eff but you air/air set up isn't so i'd be inclined to keep it around 12 psi unless you plan some other upgrades.
It's definitely not a wastegate flow issue as the twin gates on the 185 CT26 can handle a lot more flow than you are generating before they become a problem. Your exhaust flow has no effect on this wastegate, unlike say the Supra wastegates where extra flow will mean the gates find their boost control limits and you get boost spikes.
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Thu, 13 January 2005 03:02
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Thanks Justen
It's a non group A
So if there are no leaks and no problems with the actuator what can I do about it?
I might be able to add a FCD but would want to push it past 14psi.
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Location:
South Australia
Registered:
July 2002
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Re: Overboosting ST185
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Thu, 13 January 2005 03:19
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well you can either turn your boost down (below 12psi) or you can add a FCD and you should be able to run higher boost.
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Location:
Canberra
Registered:
June 2003
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Re: Overboosting ST185
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Thu, 13 January 2005 03:26
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The only option if the lines etc are OK is to get a better controller...what are you running?
If you engine/fuel setup is in very good condition then you could get away with running as much as 16psi but i'd be doing the 1st few runs on a dyno and listening very very carefull for det. Otherwise just leave it at 12psi until you can do a proper upgrade.
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Thu, 13 January 2005 06:41
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The current boost controller I'm running is a "Boost Tee Gated Boost Controller" (FG-GBCV-BT) from http://www.turbosmart.com.au
Thanks to everyone for the help. I'll take a look for leaks tonight.
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Location:
Colac, Victoria
Registered:
May 2002
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Re: Overboosting ST185
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Thu, 13 January 2005 09:01
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Ill have an HKS FCD calibrated for a Gt4 available soon - if your interested - ts been made redundant by my new ECU
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Thu, 13 January 2005 22:15
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Yeah, I'm interested in that. PM me when it becomes available.
Justen, I just joined the dots and realised you are the guy that was in the recent Speed magazine that put a V8 into a GT4 
Respect 
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Location:
Low Head (Tasmania)
Registered:
September 2004
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Re: Overboosting ST185
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Fri, 14 January 2005 01:09
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yeh i got that speed too, was a good article.
didnt you say that ur boost controller is turned down as far as it goes? try another boost controller or put it back to standard.
i had a 185 RC and it used to spike something shocking, it would hit 15 to 16 psi hard in first and second, but no more then that. then anything above that it would spike to 15 then drop to about 12 psi. wastegate is too small for high boost levels.
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Fri, 14 January 2005 01:30
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Can you get aftermarket wastegates for the CT26? Would they be any good?
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Location:
Low Head (Tasmania)
Registered:
September 2004
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Re: Overboosting ST185
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Fri, 14 January 2005 02:03
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no becuause they are internal wastegates, u can get them reconditioned, or get a bigger valve put in, but if ur gonna go to this much trouble just get a aftermarket turbo.
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Fri, 14 January 2005 03:04
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Any recommendations for an aftermarket turbo to suit the GT4?
How much do they go for approx?
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Location:
Colac, Victoria
Registered:
May 2002
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Re: Overboosting ST185
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Fri, 14 January 2005 08:02
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that depends on what you want
a little more boost to play with but not other changers - just highflow with a t04e wheel
More than that - as far as ive seen - Gt25/28/30's in various combinatons seem to eb used in bigger HP chasers ..
Figures in $ - 1000 - 5 grand +
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Registered:
August 2004
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Re: Overboosting ST185
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Thu, 20 January 2005 11:42
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I have the same problem with my st185 3sgte byt it is running stock
boost around 7 psi and in 3rd when i put my foot down it boost till 10 psi then fuel cuts. So any information whould be handy guys.
Sorry i'm not trying to steal your thread its just on topic.
Cheers guys
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Registered:
May 2002
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Re: Overboosting ST185
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Thu, 20 January 2005 11:54
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Check your hoses that connect your intercooler to the turbo and throttle body if they are ok then make sure that your T piece is installed the right way around. Make sure that the VSV line is blocked also.
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Registered:
August 2004
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Re: Overboosting ST185
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Thu, 20 January 2005 13:24
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I forgot to mention that i have not installed an aftermarket boost controller the stock item remains. Can anyone can assist in what steps to take to rectify the problem
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Toymods Social Secretary
Location:
Sydney
Registered:
July 2002
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Re: Overboosting ST185
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Thu, 20 January 2005 21:22
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the problem here might lie in the fact that you still have the factory "low boost 1st & 2nd gear" thingo connected along with your bleed valve.
I would recommend tracking back the boost line from the wastegate actuator to the intake manifold, and seeing if there is anything along that line like a vacuum switching valve, t-piece to another place etc etc. If there is, change the line so that it goes DIRECTLY from the intake manifold to your wastegate actuator, and T-piece the bleed valve into that.
Really you should be using an Electronic boost controller if you are experiencing creeping and spikes... and that's where i can help 
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: Overboosting ST185
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Thu, 20 January 2005 22:18
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| THE WITZL wrote on Fri, 21 January 2005 08:22 |
the problem here might lie in the fact that you still have the factory "low boost 1st & 2nd gear" thingo connected along with your bleed valve.
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The "low boost 1st & 2nd gear" thingo is called the "Turbo VSV" and it will appear on the vacuum diagram sticker stuck under the hood.
You can stop the line from doing anything altogether by chopping the line and blocking it up at both ends.
The CT26 wastegate has two lines going into it, one from the compressor and one from the manifold via the Turbo VSV.
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Location:
Low Head (Tasmania)
Registered:
September 2004
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Re: Overboosting ST185
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Sat, 22 January 2005 00:01
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if anyone goes on gt4oc here they will know there is big questions about the vsv. look at how it works, turbo goes to actuator then from there goes next to the block towards the firewall. if it bleeds air from the wastegate then the wastegate will get less air to open the wastegate and actually INCREASE boost not decrease it. The low boost in 1st and second is a big myth i reckon, and so do a lot of ppl on gt4oc.
I put a boost guage in my "4" when i had it and it actually made more boost in first and second.
as for turbo's depends on what you want? do you want big power, or do you just want something more efficient. my opinion stick with garret oldest and biggest of the turbo manufactures, as a lot of other companies buy garret turbos, stick their name on it and sell it for twice as much.
for a "4" ide go with garret GT30 good for up to 550 hpm ball bearing, but it is external gate, which means u gotta buy a wastegate and modifly your exhaust manifold and dump pipe., but external gates have a lot more control over boost.
If you want a internal gate then a GT28 would be the better option good for 350 hp still ball bearing. both wouldnt have much turbo lag. look around, even ebay.
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: Overboosting ST185
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Sat, 22 January 2005 07:21
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if anyone goes on gt4oc here they will know there is big questions about the vsv. look at how it works, turbo goes to actuator then from there goes next to the block towards the firewall. if it bleeds air from the wastegate then the wastegate will get less air to open the wastegate and actually INCREASE boost not decrease it. The low boost in 1st and second is a big myth i reckon, and so do a lot of ppl on gt4oc.
I put a boost guage in my "4" when i had it and it actually made more boost in first and second.
as for turbo's depends on what you want? do you want big power, or do you just want something more efficient. my opinion stick with garret oldest and biggest of the turbo manufactures, as a lot of other companies buy garret turbos, stick their name on it and sell it for twice as much.
for a "4" ide go with garret GT30 good for up to 550 hpm ball bearing, but it is external gate, which means u gotta buy a wastegate and modifly your exhaust manifold and dump pipe., but external gates have a lot more control over boost.
If you want a internal gate then a GT28 would be the better option good for 350 hp still ball bearing. both wouldnt have much turbo lag. look around, even ebay.
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Does it bleed air from the wastegate though?
You've got me thinking... I'd best be off to the workshop to push some air through the wastegate on my spare turbo!
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Location:
Low Head (Tasmania)
Registered:
September 2004
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Re: Overboosting ST185
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Sun, 23 January 2005 01:33
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well thats the only way it can affect boost. i reckon its supposed to raise boost in first and second. maybe to try and overcome the lack of load in those gears, ie so it holds a constant boost level.
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Toymods Vice President
Location:
Sydney
Registered:
May 2002
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Location:
South Australia
Registered:
July 2002
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Re: Overboosting ST185
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Sun, 23 January 2005 07:02
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The low boost in 1st and second is a big myth i reckon, and so do a lot of ppl on gt4oc.
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It's definitely not a myth...and if the VSV or ECU is faulty or the lines are faulty then you won't see anything over about 7psi of boost on the 1st gen 3SGTE.
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Location:
Low Head (Tasmania)
Registered:
September 2004
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Location:
Sydney
Registered:
September 2004
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Re: Overboosting ST185
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Wed, 11 May 2005 16:55
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i didnt mean the vsv was a myth, just how people think its a "low boost" in first and second. i think it bleeds are away from the wastegate to allow equal boost in first and second, because there might not be enough load on the engine to get to full boost.
also 7 psi would be standard boost in a 1st gen.
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I know this is an old thread, but im currently researching this topic myself and have to set the record straight. It is true that the job of the T-VSV is to bleed air away from the actuator, but your looking at it the wrong way round (I did exactly the same thing until i nutted it out too )
The stock ST185 actuator is rated to 6 psi before it starts to open the wastegate. What the T-VSV does is it stays shut in first and second gear so that full pressure from the turbo is acting on the actuator limiting boost in those gears to the actuators rating.
Once you hit third gear is when it starts bleeding air. The amount of air it allows to bleed away from the actuator is controlled by the ECU which gets the MAP pressure from the Turbocharger Pressure Sensor. This is how the ECU regulates the standard boost setting of about 8-9 psi in the higher gears.
Further to this the reason why you need to block the lines going to the T-VSV when installing an aftermarket boost controller is that the ECU is oblivious to it, so when your in 3rd gear or above the ECU will continue to use the T-VSV to bleed pressure away from the actuator at the same time that your aftermarket boost controller is bleeding pressure which is what you dont want. Obviously the only way to successfully control boost pressure is to have a single point where boost pressure is bled away from the actuator, because from either point of view the second 'bleed valve' is essentially a leak, which renders your aftermarket unit useless.
Hope this clarifies the matter.
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Location:
SA
Registered:
February 2005
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Re: Overboosting ST185
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Wed, 11 May 2005 23:49
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Just questioning your overboosting problem. I had a familia that had the same problem and it turned out to be the exhaust. The exhaust size was too big and freeflowing, which meant the wastegate could not handle the amount of air trying to be drawn through it, forcing the air through the impeller. This caused severe overboosting and fuel cut until the exhaust was limited. Thought this may help.
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Location:
Dubbo
Registered:
April 2005
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Re: Overboosting ST185
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Thu, 12 May 2005 06:46
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Hey guys,
I think the exhaust may be too free flowing. I have an 185 also and i can hit fuel cut in 3rd gear (not easly mind u but it will do it) and the only think done to my car is a full 3 inch system, no boost controller. the TVSV is disabled however. I find that when i am under it and watching the boost gauge (aftermarket one of course) it will quickly get up to 9psi then as i get to 4000 onwards it will climb above 9psi. Highest i have seen it was at around 13-14psi, with no fuel cut for some reason (my dad was driving it, maniac he is!) so the 3" zaust could be doing it to ya
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Location:
Sydney
Registered:
September 2004
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Re: Overboosting ST185
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Thu, 12 May 2005 06:55
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The original issue was raised about 5 months ago. I would say AaronST185 has the problem sorted by now. I ressurected this thread last night doing research on the T-VSV because i wanted to dispell the myths and confusion surrounding it because a lot of the assumptions and theories posted were incorrect.
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Thu, 12 May 2005 07:26
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Nah, he hasn't yet
By the sounds of SilverGhosts research it seems like my actuator might be stuffed. I can easily reach 12psi boost in any gear. Either that or the wastegate itself is stuffed.
I have heard the free flowing exhaust theory a lot too and some people have said they fixed the problem by adding in a restrictive plate into their exhaust.
I'm still not sure what to believe.
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Location:
Sydney
Registered:
September 2004
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Re: Overboosting ST185
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Thu, 12 May 2005 07:32
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IMO for the turbine to be an easier route for exhaust gas than the wastegate you must have dialled in some crazy level of boost, which inturn overwhelms the wastegate through sheer volume. infact I might even go as far as to say that i feel the turbo (in standard form, i.e. not highflowed etc) does not have enough puff to create enough exhaust volume to overwhelm the wastegate in the first place.
Highflowed turbos or turbos with modified compressor housings might do the trick...but when you think about it the wastegate and turbine both vent into the same downpipe/exhaust so one would think the lowering of exhaust restriction would apply to both wastegate and turbine...
....I might be way off, but it makes sense to me atm....
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Location:
SA
Registered:
February 2005
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Re: Overboosting ST185
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Thu, 12 May 2005 13:17
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I guess only a small amount of air can go through a tiny wastegate, then it has no choice but to spin the impeller faster. My problem was fixed by limiting the exhaust, then when I could afford it, I got my wastegate opened up with a bigger valve. Worked a treat!
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Location:
West Hobart
Registered:
December 2004
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Re: Overboosting ST185
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Thu, 12 May 2005 23:01
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How much did that set you back?
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