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boost is rising higher than wastegate spring 

 

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 Post subject: boost is rising higher than wastegate spring
Posted: Thu Apr 10, 2008 11:54 pm 
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since ive upgraded to the new larger turbo, ive noticed that im producing more boost than the actual wastegate spring... its rising up to 10psi, maybe more but im not gonna risk my engine to find out.

info:
no boost controller
geniune Tial 44mm gate with 7.35psi (0.5 bar) spring
old turbo = T04b
new turbo = T04e (front A/R 0.7, rear A/R 1.15)


the gate is definately opening http://tinypic.com/player.php?v=vo8y2c&s=3

the boost gauge, is pumbed into the intake manifold ...
the actuator line just goes from turbo to wastegate, nothing else connected, and im using telfon stainless braided hose due to the fact everything else i used just melted (even high temperature silicon)


what would cause this over boosting? and how would i solve this?

it was mentioned to me that:
Quote:
if u run a big turbo on a big engine with little boost
u need a big gate, since a lot of the air is being release from it, if u ran more boost u might find it would be more stable

this true?


photo of setup
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Posted: Fri Apr 11, 2008 9:43 am 
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im only new wto the turbo game , are you running a BOV.. maybe u need a bigger wastegate?

 

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Posted: Fri Apr 11, 2008 11:15 am 
Getting Side Ways
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Design of wastegate pluming ??
Is the wastegate at 90* off exhaust housing ???
10 to 12 Lb would be around turbo's efficiancy range. The higher boost levels the more efficiant the wastegate should be also...
The angle the pipes off exhaust makes heaps of difference, even when it joins back into dump pipe and make sure the exhaust isn't too restrictive around merging area too...
I wouldn't let the spring out of the equation either?? An EBC connected to top of diaphram would make it adjustable...

 

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Posted: Fri Apr 11, 2008 11:45 am 
Getting Side Ways
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thanks for replying guys :)

actually, ive been told by the tuner (ovaboost) that the wastegate position is quite good.

the exhaust is pretty smooth, its 3.5" dump to 3" exhaust

ive got a few springs lying around, including a 10.3psi one. maybe i should try that and see if that eliminates the over boosting?
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Posted: Fri Apr 11, 2008 1:09 pm 
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I would hazard a guess that the wastegate is not big enough, or the exhaust cant escape quick enough ( by design ??) i am no expert, but if you think about it, if more exhaust goes through the turbine than what exits the gate, then it will still boost. I read a previous post in another thread, that said you can never have a wastegate to big.
I am keen to see how my DIY set-up performs.

Cheers

Daz

 

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Posted: Fri Apr 11, 2008 4:38 pm 
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wastegate venting point is whats giving you trouble.. find my thread about it, i went through hell to prevent overboosting

you need a nice direct vent path, thats why wastegates plumbed into the turbine housing works the best, mounting it on the collector can spell trouble, unless the angle is really good

 

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Posted: Sat Apr 12, 2008 12:34 am 
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A 44mm Tial gate is a big enough gate..
We have 44 mm on T04Z with NO overboost issues.. Runs E2 Turbosmart Boost controler..

Actually a wastgate too big can be apita as it can open and dump too much and hard to keep lineal..

IF tune is too retarded and rich fuel is burnt in manifold, turbine.. Vertually a jet engine...

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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