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Location:
Perth
Registered:
October 2003
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1JZ boost pressure with mods
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Thu, 26 May 2005 09:37
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There is a couple of threads around ATM mentioning 1JZ boost cut etc. So I was wondering with different mods how the boost level changes, with stock turbos and wastegate springs of course.
My car has always had the boost controlled to around 14psi using Haltech control, but I noticed it would creep up to 16psi in gears after 3rd and lots of revs. The other day I disconnected the boost control resulting in the boost coming on quickly to 12psi then slowly creeps up linearly with rpm to about 16psi at 7000rpm. This was on a 22 degree day, id imagine it would be worse at night.
My engine is fully modded externally i.e. Big FMIC, POD filter, Twin Dumps and 3.5" zorst. What is everyone else getting?
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Registered:
June 2002
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Re: 1JZ boost pressure with mods
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Thu, 26 May 2005 09:44
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3" zorst
BFMIC
POD
No boost taps etc...
12psi rock solid.
I'd say the "boost creep" you are experiencing is from the Twin Dumps, the excess exhaust gases find it easier to go through the Turbines (thus more boost) than to go out the tiny wastegate holes where it is meant too.
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I supported Toymods
Location:
Sutho/Hills NSW
Registered:
September 2002
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Re: 1JZ boost pressure with mods
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Thu, 26 May 2005 09:54
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3" exhaust
FMIC
twin dumps
hiperboost controller
stock computer
constant 16psi
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 1JZ boost pressure with mods
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Thu, 26 May 2005 23:05
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It may help also to say what size intercooler pipes?
Before I had
3" exhaust (standard Y-pipe)
pod
JZX90 FMIC with stock piping
13psi rock solid
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Location:
Perth
Registered:
October 2003
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Re: 1JZ boost pressure with mods
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Thu, 26 May 2005 23:45
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Piping is 2.5" in 3" out.
Eviljack: I was talking without boost control.
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I supported Toymods
Location:
Sutho/Hills NSW
Registered:
September 2002
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Re: 1JZ boost pressure with mods
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Fri, 27 May 2005 00:49
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sorry skip my bad
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Location:
Central Coast
Registered:
June 2002
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Re: 1JZ boost pressure with mods
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Sat, 28 May 2005 02:52
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FMIC 3"pipes most of the way
dumps
3"zorst
pod
was getting anywhere from 0.8 bar to 0.97 bar
not really consistant either way, did get fuel cut alot
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Sat, 28 May 2005 09:55
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H.A.I apexi pod filter
stock fmic
stock dumps
3" downpipe
2.5" gutted cat
gtr middle muffler
genie rear canon
no boost control
steel wheels
11.6psi (.8bar)
same setup again but with twin dumps
full 3" system with 3" cat and resinator
13.1psi (.9bar) upon initial test drive.
will update when ive driven the car again.
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 1JZ boost pressure with mods
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Sat, 28 May 2005 23:02
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| Mofo III wrote on Sat, 28 May 2005 19:55 |
H.A.I apexi pod filter
stock fmic
stock dumps
3" downpipe
2.5" gutted cat
gtr middle muffler
genie rear canon
no boost control
steel wheels
11.6psi (.8bar)
same setup again but with twin dumps
full 3" system with 3" cat and resinator
13.1psi (.9bar) upon initial test drive.
will update when ive driven the car again.
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That is interesting. My mates jzz30 with nearly the same mods as the top ones except better flowing exhaust will only run 8psi without a boost controller. I suppose it does depend on how the turbos are steel wheeled and if they are highflowed. I just thought it was stranged for it to run so low with a free flowing exhaust.
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Registered:
June 2002
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Re: 1JZ boost pressure with mods
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Sat, 28 May 2005 23:16
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8psi is strangely low though, thats lower than stock isn't it??
Has it had the acuators changed maybe??
I was looking on my boost gauge/turbo timer thing (blitz) and it had recorded a peak of 1.42bar at somestage, I presume it must have only been momentary during a on-off-on throttle situation and the WG's not keeping up, as it has never hit boost cut before (that I have noticed)
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Location:
sunny coast, qld
Registered:
October 2002
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Re: 1JZ boost pressure with mods
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Sun, 29 May 2005 01:56
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| E30-323ti wrote on Sun, 29 May 2005 09:16 |
8psi is strangely low though, thats lower than stock isn't it??
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Yeah, AFAIK.
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Has it had the acuators changed maybe??
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Not that I know of. Haven't had a good look though. Nothing to compare against either.
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Location:
Brisbane
Registered:
May 2002
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Re: 1JZ boost pressure with mods
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Sun, 29 May 2005 06:14
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mine was running 8psi with one of the cooler pipe clamps not done up tight enough. It eventually blew off, so I knew to tighten it. Now the car runs 11-12psi depending on weather, totally stock.
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Thu, 09 June 2005 09:13
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update:
...after driving the car for a few weeks now its settled upon .85 bar. .05 bar more from fitting dumps and a superior exhaust, which is sfa (not even 1psi more)
although boost does come on hard and stronger now.
| Mofo III wrote on Sat, 28 May 2005 17:55 |
H.A.I apexi pod filter
stock fmic
stock dumps
3" downpipe
2.5" gutted cat
gtr middle muffler
genie rear canon
no boost control
steel wheels
11.6psi (.8bar)
same setup again but with twin dumps
full 3" system with 3" cat and resinator
13.1psi (.9bar) upon initial test drive.
will update when ive driven the car again.
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Location:
Gold Coast
Registered:
June 2004
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Re: 1JZ boost pressure with mods
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Thu, 09 June 2005 11:50
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I have very bad boost creep.
fmic
cai
3" exhaust with gutted cat
stock dumps
.8 bar initial then after 4000+rpm it climbs quite steadily to .97 bar and engages boost cut. Even without my front mount on a cold day it would hit the cut in the higher gears.
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Thu, 09 June 2005 16:41
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could be a problem with either the actuators or the short pressure lines connected to them, ie. the actuators loose pressure after a few seconds, either that or your wastegates arnt openning fully...
have you got a boost controller connected up, or have your turbos ever been tampered with?
when did this start happenening?
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Location:
Canberra
Registered:
October 2004
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Re: 1JZ boost pressure with mods
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Thu, 09 June 2005 23:54
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i'll be running stock dump pipes, but big exhaust and pig intercooler, wondering how much boost its likely to make running the standard computer, and whether im likely to have any overboost issues or anything?
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Location:
Gold Coast
Registered:
June 2004
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Re: 1JZ boost pressure with mods
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Fri, 10 June 2005 11:12
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I've been thinking of manually blocking the gates open to see if this could be the problem.
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Fri, 10 June 2005 11:41
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how do you plan on doing this?
| tyottsoarer wrote on Fri, 10 June 2005 19:12 |
I've been thinking of manually blocking the gates open to see if this could be the problem.
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Fri, 10 June 2005 11:42
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probably make 11 - 12psi, as for the boost creep, just wait and see i guess. 
| SL666 wrote on Fri, 10 June 2005 07:54 |
i'll be running stock dump pipes, but big exhaust and pig intercooler, wondering how much boost its likely to make running the standard computer, and whether im likely to have any overboost issues or anything?
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Location:
Gold Coast
Registered:
June 2004
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Re: 1JZ boost pressure with mods
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Fri, 10 June 2005 14:39
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I guess disconnect the actuators from there brackets and pressure lines. Try to hold them in a position to have the gates constantly open. This was just a thought, I haven't looked into actually doing it.
On a side note, my turbos are fucked so if I were to do this they would be coming off very soon after.
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Location:
Newcastle, NSW
Registered:
February 2003
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Re: 1JZ boost pressure with mods
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Sat, 11 June 2005 12:06
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my JZX90 Chaser .....
boost pressure was 8psi when 100% stock standard. then jumped up to around 12psi with twin dumps, exhaust system, pod filter and fmic.
i was hitting boost-cut due to wastegate creep also
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 02:52
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boost creep... i hear about it and apparently i should be experiencing it by now with my level of mods, but im not.
i have a full house legal exhaust system including twin dumps, 3" cat and resonator, apexi power intake, steel wheel ct12a's, no form of boost control whatsover and my wastegates have no problem controlling boost @ 11.5 psi.
have a look at my current dyno sheet and note how flat and controlled the boost pressure is.
http://members.iinet.net.au/~supraman/hosted/11-06 -05%20JZA70R%20-%20HyperDrive.jpg
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 02:58
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btw 245.2 rwhp is 182.8 rwkw.
that run was done in 4th gear, but it is the same story with every other gear, infact i cant remeber the last time it hit boost cut, 1st gear maybe in the wet if its cold enough.
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Location:
Gold Coast
Registered:
June 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 11:13
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Maybe the fact that you have high flowed ct12a's has something to do with it. It is my understanding that the waste gates size is increased as well, thus giving you a lower boost with the same mods. Not having a go, just offering my opinion.
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 13:06
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my turbos arn't high flowed. they merely had the rear turbine's replaced with steel items, and the wastegates havent been touched. ive had them apart and inspected them myself. so signs of machining.
ive even bench-tested and filmed the actuator and wastegates in action using a air pressure regulator. with no exhaust gas influencing them the wastegates start to open at 1 bar and are full open at 2 bar.
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Location:
Gold Coast
Registered:
June 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 15:45
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This may be a stupid question but. If the stock 1jz ecu triggers boost cut at 1.0 bar shouldn't the actuators be set to open before 1.0 bar is reached? So as to keep the boost level within the stock ecu mapping capabilities. Again I'm not doubting what you're saying just trying to understand it.
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Location:
Kelmscott, Perth, W.A
Registered:
March 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 15:54
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| Mofo III wrote on Sun, 12 June 2005 21:06 |
with no exhaust gas influencing them the wastegates start to open at 1 bar and are full open at 2 bar.
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Location:
Gold Coast
Registered:
June 2004
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Re: 1JZ boost pressure with mods
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Sun, 12 June 2005 16:02
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My bad, I get you now. 
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