which way to slow spool?

[twinturbozxtacy]

ok so the problem i have been battling to fix turns out to be true compressor surge. problem is the turbo is spooling too fast i guess and everything cant cope ie waste-gates and bovs..... so my simple question is whats the best way to slow my spool down semi accurately?? should i restrict after the turbo, before the turbo or the exhaust?

also could my wastegates be partially to blame? they are adjustable and when i had the motor out i set them to crack open at 16psi fwiw

[nissanfreak12]

What problem are you having? How did you come to the conclusion the turbo is spooling too fast?

[twinturbozxtacy]

no boost, turbos spool fine with tb pipes disconnected. did a boost leak, everything is tight and leak free. new plugs ohmes all the coils and injectors, new ptu. after a long search i found it to be my turbos spooling too fast and not getting enough air and what is happening is a compressor "stall" meaning it sucks the air in so fast that there becomes, for lack of a better word, slack in between the compressor wheel and incoming air. Once this happens the compressor is rendered useless and then once the lagging inake air "catches" back up the process repeats... at least thats how it came across to me.

-A compressor stall is a situation of abnormal airflow resulting from a stall of the aerofoils within the compressor of a jet engine. Stall is found in dynamic compressors, particularly axial compressors, as used in jet engines and turbochargers for reciprocating engines.
Compressor stalls result in a loss of compressor performance, which can vary in severity from a momentary engine power drop (occurring so quickly it is barely registered on engine instruments) to a complete loss of compression (compressor surge) necessitating a reduction in the fuel flow to the engine.
Modern compressors are carefully designed and controlled to avoid or limit stall within an engine's operating range. Stall was a common problem on early jet engines with simple aerodynamics and manual or mechanical fuel control units, but has been virtually eliminated by better design and the use of hydromechanical and electronic control systems such as Full Authority Digital Engine Controls.

[nissanfreak12]

You realize, the definition of "stalling" are base on a jet engine? The concept is there, but different worlds. The turbo speed is based upon the exhaust output, relatively simple. If you are not getting enough intake air, you have another issue and the engine will suffer, not the turbos.

If you are not building any pressure and you have done a boost leak, how are the turbos? Whats the age? What kind are they? How is the engine running? Any codes from ECU, not the idiot light on the cluster? How is your timing? How is the shape of the timing belt? How did you do a boost leak test? Are you sure the gauge works? Compression of the engine? Have you tested vacuum of the engine?

I think your over complicating things as to why you are not building boost. There is a write up in the Z section under "everything you need to know about the Z32", look under that it has the 6 P's. Read through that, get back to us.

[nissanfreak12]

also could my wastegates be partially to blame? they are adjustable and when i had the motor out i set them to crack open at 16psi fwiw

Not sure how I missed that, is your car tuned for this? What turbos are you running? What wastegates are they? What size injectors do you have in your car? Soo many questions.......

[twinturbozxtacy]

car petty much has everything, sport 530bbs, jwt cams and springs, msp manifolds, full exhaust 550 injectors, ebc, new plugs, newly built engine, new timing belt and belt pulleys, selin dual maf, 2.5 ic piping, etc... timing is at -15 where is should be. i do a lot of mechanics so im not a newbie but im stumped on this one. just re-tuned my ecu too and no change.

[scheffler]

I would check your turbos...... set the waste gates back to original setting and get a MBC.

[twinturbozxtacy]

Found it, was a shop rag someone left in the ic piping from when the motor was out. It was completely blocking flow through the ic oh well at least it was a simple fix...

[twinturbozxtacy]

the culprit... it was as hard as a baseball from the compressed air being forced against it! left in the coupler for effect i did not forget to take it out lol!