twin turbo blowoff problems!!!! help??

twn-trbo-svt

NEW GUY
Jan 23, 2009
785
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i am having this issue...i have twin turbos from turbo horsepower...the problem i am having is is when i at 20psi in 3rd and 4th gear the blow off is repeatingly blowing off about 4-6 times...any THP people ever heard of anything like this? got the car out for the first time this year yesterday and damit same thing again!! except this time (from running car in garage) moisture builds to rust inside and when the wastgates open during wide open throttle the dam thing lookes like i got orange smoke bombs in my exhaust!! horrible.........anyways the blow off is my problem...any1? thanks
 

Pressure Ratio

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TCG Premium
Nov 11, 2005
20,303
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Glen Ellyn
What you have posted is confusing. You say the blow off valve is opening under boost. OK Well it most likely needs a stronger spring. The top side of the valve is being fed the same boost the under side is seeing. So they cancel each other out. Unless the top side has a lot less surface area compared to the face of the valve has. So you will still have more force on the bottom side of the valve. More boost = more pressure to open the valve. So you basically have the spring pressure holding the valve shut. So a heavier spring may be needed for that kind of pressure. Unless there is another adjustment on the blow off valve to add pressure to the spring already in there.

Now what is confusing is the wastegate you think it opening and closing. When you loose boost the wastegate should be shut trying to gain the manifold pressure back the BOV is venting off. So there should be no smoke till it opens up at about 20 PSI (If that is what your max boost is). So is it opening and closing as fast as the BOV is?

Rust in the system is never good. Are you sure the wastegate is rusting? They usually are made of stainless. Is the valve rusting? Also usually stainless with a broze valve guide. But cheap stuff may be made with less quality parts.
 

twn-trbo-svt

NEW GUY
Jan 23, 2009
785
0
i agree this is all confusing......the rust issue is from running the car in the winter and stuff because my exhaust is solid no clamps all the way to the mufflers and the back was higher then the front.....everytime i would start it water comes shooting out....so i was guessing some rust was forming on the inside and being blown out yesterday from the wastegate side or something..just wanted to make sure this orange smoke doesnt mean i burning something up.........

now to the spring stuff......turbo horsepower is the 1 telling me the wastegate springs should be bigger....and i totaly agree with you saying the blowoff obviously seem to small.....the other thing i am trying to find out is maybe my vacum lines are wrong?? i cant find shit on a twin setup....but i do know i have 5# springs in waste gate and correct me if i am wrong but, i should only change the waste gate springs if im not reaching my desired PSI?

oh and all the gates and blo offs are tial......
 

Pressure Ratio

....
TCG Premium
Nov 11, 2005
20,303
11,728
Glen Ellyn
i agree this is all confusing......the rust issue is from running the car in the winter and stuff because my exhaust is solid no clamps all the way to the mufflers and the back was higher then the front.....everytime i would start it water comes shooting out....so i was guessing some rust was forming on the inside and being blown out yesterday from the wastegate side or something..just wanted to make sure this orange smoke doesnt mean i burning something up.........

now to the spring stuff......turbo horsepower is the 1 telling me the wastegate springs should be bigger....and i totaly agree with you saying the blowoff obviously seem to small.....the other thing i am trying to find out is maybe my vacum lines are wrong?? i cant find shit on a twin setup....but i do know i have 5# springs in waste gate and correct me if i am wrong but, i should only change the waste gate springs if im not reaching my desired PSI?

oh and all the gates and blo offs are tial......

You can hear the BOV venting during wide open throttle? Correct? So we know for sure this is your issue. At least one of them. Your boost issue would be directly related to that. If the boost is being vented off the wastegate can close to try and get as much exhaust energy to the turbine wheels. But because the BOV is opening the turbos can't over come the BOV venting.

The BOV is opening till it reaches a point where the spring & boost pressure can close the valve again. Then it builds boost till it gets to the point where the BOV can't stay shut and it opens again. Repeating the process.

A manual controller can only do so much. At some point you will need to change the spring to get more boost. If the turbos are capable at least. So lets keep this simple and not take into account the pressured put on the valve bottom is more than on the top. Now the spring is good for 5# of boost. So you have 5# of boost you can hold off. Now using the boost controller lets say you add all you can to it. Full closed wastegate. It may only reach 20# because of the pressure ratio of intake pressure versus exhaust pressure. Lets say your system is efficient and has a 1:2 ratio. So at 15psi of boost in the intake you have 30# or pressure in the exhaust pre turbos. So now 30 - 15 + 5 (for the spring) = 20psi. So no matter what the boost controller can not make more boost. And like I said that is with a good 1:2 pressure ratio and not doing the math to figure out the pressure difference between the top and bottom of the waste gate valve.

Solve the bov issue first. Once you solve that worry about the waste gate and boost not being above 20#.
 

twn-trbo-svt

NEW GUY
Jan 23, 2009
785
0
correct i can hear it.........and yes i agree....let me get a bigger BOV spring after i check to see what this one is for.....now it is all making sense due to the tune is set for 20 psi and the manual controller cranked all the way open......worked fine on the dyno at kurgan but as soon as i hit the street it started doing that...probably due to ground force and weight i take it? so all in all i am good for 18 psi on the street 20 dyno......so tomorrow i will get a spring for the BOV and see what happens. thanks alot man.....


i got the BOV off i am now gonna check what the spring is rated for.
 

twn-trbo-svt

NEW GUY
Jan 23, 2009
785
0
i have the white spring......im hoping i have the right chart

Engine Vacuum Reading / Color Use Spring​
Between:​
- 22 and -23 in/Hg Pink -12 Psi (-24 in/Hg )
-18 and -21 in/Hg Un-painted -11 Psi (-22 in/Hg )
- 14 and -17 in/Hg White -9 Psi (-18 in/Hg )​
-10 and -13 in/Hg Black -7 Psi (-14 in/Hg )
 
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