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Old 03-10-2008, 09:19 PM   #1
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Default Flow and boost gauge question

1. im running a t25. my boost gauge (routed off the inetake mani.) reads vacume till 2800 to 3000 rpm and hits positive (boost as opposed to vac.) 4psi at 4k rpm till redline. if i routed the boost gauge pre-TB wouldnt it read more accuratley?

2. how does the diamiter affect responce and power? more specifically am i crazy for thinking a 1.75" diamiter pipe from turbo to TB is too small for 4-6 psi? i read somewhere that the pipes in and out of the turbo should be the same size.
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Old 03-10-2008, 09:24 PM   #2
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1. if you are running the stock exhaust and only 4 psi you are probably getting back spool. the combination of a leaking wastegate (lack of tension running such low boost) and the restrictive stock exhaust 4K rpm seems quite possible for hitting 4 psi. It's also possible you have a boost leak or an exhaust leak before the turbo. Your boost gauge is already plumbed in pre-TB or you wouldn't read vacuum at all.

2. At that low a boost level it really won't matter what size pipe you are running between the turbo outlet and the TB. It won't have any noticeable affect on your power until you hit at least 200 whp, which you are nowhere near at 4psi with a t25.
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Old 03-10-2008, 09:44 PM   #3
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1. i dont have a stock exhaust. its a custom job with no cat and just a resonator if memory serves. its between 2.5 and 3" in diam. my DP is 2" to 2.5" with a divorces wastegate pipe. when i say pre-TB i mean between the turbo and TB. currently is plumbed off the mani after the TB. it seems like it would be a more accurate reading of boost produced pre-TB.

2. how do i up boost? just change the waste gate actuator? can i just thighten the rod from the actuator to the waste gate valve?
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Old 03-10-2008, 11:02 PM   #4
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there is no difference in the readings pre tb and in manifold. pressure is pressure in a connected system.
Tighten your wastegate actuator.
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Old 03-11-2008, 12:07 AM   #5
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maybe you should get into this
http://youtube.com/watch?v=Coj2wfPouuk
its lot simpler than turbocharging a car.
lol
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Old 03-11-2008, 12:29 AM   #6
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you should be able to see 0 vac at any rpm by going WOT
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Old 03-11-2008, 12:29 AM   #7
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Quote:
Originally Posted by musanovic View Post
maybe you should get into this
http://youtube.com/watch?v=Coj2wfPouuk
its lot simpler than turbocharging a car.
lol
I think my last turbo install was easier than doing that! thats cool
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Old 03-11-2008, 10:44 AM   #8
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i dont see why you went with the 1.75", even though it doesn't hurt now, but you will have to change it later once you start wanting more power (and you will) and spend the money again...do it once do it right dude, best advice i can give you...

your exhaust does not sound restrictive, you should spool somewhat quick, i would have to say your WG needs some tightening
do you know how to adjust your WG? i would recomend you take of your DP and take a pic if you dont know how to do it and im sure someone more knowledgable than me can walk you though it...
.good luck
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Old 03-11-2008, 10:50 AM   #9
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Quote:
Originally Posted by zebro racing View Post

2. how do i up boost? just change the waste gate actuator? can i just thighten the rod from the actuator to the waste gate valve?
You will need a manual or electronic boost controller.
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Old 03-11-2008, 11:45 AM   #10
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Quote:
Originally Posted by zebro racing View Post
how do i up boost? just change the waste gate actuator? can i just thighten the rod from the actuator to the waste gate valve?
To up your boost first be sure to make sure that your flapper that the wastegate controls is able to close completely, and make sure that the wastegate is pulled tight...I believe your 4 psi reading is due to a loose wastegate or some kinks/tears in your boost line (if mechanical). After checking this then use a MBC of some sort to regulate boost...no need in just slapping on a MBC to give more boost if you are already losing it elsewere...i.e. loose wastegate
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Old 03-11-2008, 07:31 PM   #11
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Quote:
Originally Posted by whaaamx5 View Post
i dont see why you went with the 1.75", even though it doesn't hurt now, but you will have to change it later once you start wanting more power (and you will) and spend the money again...do it once do it right dude, best advice i can give you...

your exhaust does not sound restrictive, you should spool somewhat quick, i would have to say your WG needs some tightening
do you know how to adjust your WG? i would recomend you take of your DP and take a pic if you dont know how to do it and im sure someone more knowledgable than me can walk you though it...
.good luck
1.75" pipe was on the car when i got it.

the WG was a little loose. huge improvement in the lower rpms. i think im just going to get a new actuator. which brings me to my next question: what is the point of a dual port actuator(http://cgi.ebay.com/ebaymotors/Waste...agenameZWDVW)?
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Old 03-11-2008, 07:33 PM   #12
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helps hold higher boost to redline......
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