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Registered:
November 2002
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 GT4 Boost Arrangements Question
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Fri, 29 August 2003 01:27
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Hi all.
Can someone please help me out with my thinking as to how the various model GT4's produce their boost ?
I have made up a table below and put in my best guesses after reading a few dozen web pages. Please correct my mistakes, thanks !
ST165
Wastegate: 5psi
T-VSV: 4psi
Max. Boost: 9psi
Fuel Cut: 10psi
Std ECU mapped to: 12psi
ST185
Wastegate: 7psi
T-VSV: 4psi
Max. Boost: 11psi
Fuel Cut: 12psi
Std ECU mapped to: 14psi
ST185RC / ST205
Wastegate: 11psi
T-VSV: 4psi
Max. Boost: 15psi
Fuel Cut: 16psi
Std ECU mapped to: 17psi
I would really appreciate your help with this.
Thanks.
Cheers,
Mitch.
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Location:
Canberra
Registered:
April 2003
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Registered:
November 2002
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 02:11
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wiso,
Thanks for that link mate.
Your project car is a beast - well done !
Cheers,
Mitch.
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Location:
Canberra
Registered:
June 2003
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 02:19
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I have quite a few changes to make there Mitch. For starters you can't have the VSV less than the wastegate, that's impossible. Heres' what i have measured off my own and others
ST185
Wastegate: 6psi
T-VSV: 6psi
Max. Boost: 9psi
Fuel Cut: 12psi
Std ECU mapped to: 12psi
ST185RC
Wastegate: 6psi
T-VSV: 6psi
Max. Boost: 9psi
Fuel Cut: 16.7psi
Std ECU mapped to: 16.7psi
The 185 and 185 RC have exactly the same boost control, only the ECU mapping is different so you can get more boost with a bleed valve etc. The RC ECU is mapped to 1bar which is also where the fuel cut is set, however, the fuel cut in practise does seem to cut in later, usually over 17psi and sometimes as much as 19psi. Although not mapped to 19psi the RC ECU will run mixtures just fine at that boost and the turbo is still pushing out enough efficiency to make that boost level worthwhile. Any more and it's really diminishing returns plus you run the extra risk of meltdown 
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Registered:
November 2002
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 02:28
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Justen,
Thanks for clearing this up for me and setting me straight about the T-VSV. There are heaps of pages that all say different things about the ST165 and ST185 models and its good to get some real world figures.
I take it that given a boost controller and disabled fuel cut, the ECU runs in fully rich condition above the boost levels that the ECU is mapped to ?
One question - I thought the T-VSV set the maximum boost level, but I take it that the ECU does this instead?
Thanks again.
Mitch.
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Location:
Canberra
Registered:
June 2003
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 03:30
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No probs Mitch.
You kinda have it right. The VSV is just a solenoide valve that pulses open and acts as a bleed valve to control boost. There is much debate about hown it pulses and what engien conditions cause it to do what. What everyone agrees with though is you piss it off real quick as it is veruy inconsistent
The VSV valve is controlled by the ECU and limits boost to just the actuator setting (6psi) when cold and up to the max (9psi) once warm.
Yup, once you are past the boost cut you are in 100% duty territory but the actual A/F ratio is pretty good...around 12:1. For that extra coupla psi i don't think it's worth doing anything other than a zener diode mod on the GrpA ECU.
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Registered:
November 2002
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 03:39
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Thanks again mate.
That info is good to know.
I really should just ask my original question and get some advice from there.
I'm looking at building an ST165 to what is basically Group N spec to compete in tarmac rallies. The rules don't allow much but ECU's are free as long as they plug in to the original harness. I wanted to get some idea if its worth doing a G-Force style mod and get the original ECU reprogrammed ?
Cheers,
Mitch.
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Location:
Canberra
Registered:
June 2003
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 03:43
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My Advice Mitch depends on how serious you are. Autronic will do a plug in for you but it's big bucks. A cheaper option is a Power FC for a 205 but you'll need to rearrange a few of the wiring loom pins. Not a trivial job but very doable. I would do both of these in preference to a G-Force upgrade and the Power FC coulod be done for similar cost and a much much better result.
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Location:
Perth
Registered:
June 2002
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Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 03:44
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Mitch, your not looking at putting a big 3sgte in your black beast are you......... 
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Registered:
November 2002
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 Re: GT4 Boost Arrangements Question
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Fri, 29 August 2003 13:11
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No Gabe !
3S-GTE's into TA22's or 23's are starting to get as common as 1G-GTE's into RA23's, 40's and 60's !
I'm looking at a car that car be modified to Group N regs that can run in events like Targa Tasmania, which has a strong focus on standard spec cars with a racing/rallying heritage.
Cheers,
Mitch.
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Location:
Colac, Victoria
Registered:
May 2002
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Re: GT4 Boost Arrangements Question
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Sat, 30 August 2003 04:39
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heh - i only know of two ta22's - trevors and shanes ( cool 1)s
where are the rest!
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Registered:
November 2002
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Re: GT4 Boost Arrangements Question
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Sun, 31 August 2003 01:01
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I need to get this thread back into the original topic. Thanks Justen for your input before. I have heard a lot of differing opinions too when it comes to the opertaion of the TVSV valve. Does it just act like a switch so that when fully open it bleeds away up to an additional 3psi when that is produced, or does it have a variable opening mechanism ? Does anyone have the definitive knowledge of how it works ? Given that it can't be less than the the actuator's rating of 6psi why can't TVSV give you 6psi also and a max. boost of 12psi, which is right on fuel cut ?
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