Why does boost rise with mods on TII's?
#26
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Originally posted by adamlewis
Yes I was on LS ( keyword: WAS )
I was banned as well. Probably one of the first people to be banned from there. Havent been back since.
I remember the truck from the races but I dont believe Ive ever met you personally.
No, I dont own a red vert.
Yes I was on LS ( keyword: WAS )
I was banned as well. Probably one of the first people to be banned from there. Havent been back since.
I remember the truck from the races but I dont believe Ive ever met you personally.
No, I dont own a red vert.
So uh back on topic here...uh boost=power, and power=nothing without control, and, uh, control=hard to come by.
#27
Ok, so my series 4 motor is on an engine stand and has yet to be installed into my 510. I am gonna do all the prepping that I can while the motor is on the engine stand. Planned mods include full 3" downpipe and exhaust". K&N cone filter/cold air box., Front Mounted Intercooler, 720cc secondary injectors, haltech ecu, smog equipment removed, and ported wastegate. I am getting ready to pull the turbo and port the wastegate. My question is regarding the "twin scroll" flapper. Should I permanently remove this and port the exhaust manifold while porting the wastegate? This will not be a drag car. It will be a mostly high performance street and some track car. Emphasis will be on handling and turns. How will removing the twin scroll flapper and porting the exhaust manifold effect my power band? Will I have alot more turbo lag? Or will it not matter since I am running a wide open exhaust for the most part? I am probably looking to keep the boost around 12 psi (if this is possible with just porting the stock wastegate). Don't know exactly how much boost I will want till I try it in the car. A datsun 510 is considerably lighter than a 2nd gen rx7 so I probably wont want as much hp as someone in a 2nd gen. So should the twin scroll system stay or go?? If I didnt want to boost over 12, would I even need to remove the twin scroll? Thanks guys.
John
John
#29
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I think twin scroll should go, S5 manifolds dont have it at all.
Port the manifold too, check out this site
http://fc3s-pro.com/ it has a how-to of wastegate porting, manifold porting, and many other very helpful things.
Port the manifold too, check out this site
http://fc3s-pro.com/ it has a how-to of wastegate porting, manifold porting, and many other very helpful things.
#30
I'm a boost creep...
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Originally posted by 2kwik4u
...what gets me is that the factory set boost at 7.5lbs (S5) yet people can regulary hit 10-16psi....Telling me that the stock boost control is not working very well. Which leads me to see that there is a wastegate problem.
...what gets me is that the factory set boost at 7.5lbs (S5) yet people can regulary hit 10-16psi....Telling me that the stock boost control is not working very well. Which leads me to see that there is a wastegate problem.
Any turbo will produce more boost if you free up airflow restrictions, but in the case of the S4 turbo the wastegate port is so small that boost starts to rise uncontrollably. The S5's double wastegate is much better, but I hear it eventually reaches the same problem.
If you want to really improve the wastegate, replacing the flap with a bigger one means the port can be made even bigger, further improving boost control. Another way to improve flow through the wastegate (more flow means more control) is to divide the turbine and wastegate exhaust flows into two seperate pipes that merge further downstream. The dramatic reduction in turbulance where they normally mix increases flow through both the turbine and the wastegate.
BTW, according to the FSM stock boost for the S4 is 6.56psi, the S5 is 8.25psi.
#31
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Originally posted by Jahoo88
I think twin scroll should go, S5 manifolds dont have it at all.
I think twin scroll should go, S5 manifolds dont have it at all.
#32
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My 89 TII boost to a little over 7, not 8.25. Do I have a boost leak or something? Also, I noticed that it will boost up to like 8 or so, then it drops off to 7 and is steady after that..
#33
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Originally posted by T24U
My 89 TII boost to a little over 7, not 8.25. Do I have a boost leak or something? Also, I noticed that it will boost up to like 8 or so, then it drops off to 7 and is steady after that..
My 89 TII boost to a little over 7, not 8.25. Do I have a boost leak or something? Also, I noticed that it will boost up to like 8 or so, then it drops off to 7 and is steady after that..
You say you get a max of 8psi boost, and I doubt your boost gauge is accurate to 0.25psi, so it sounds like you're running stock boost levels and have nothing to worry about.
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