Cant boost past 25psi??????

[fwdeclipse]

Ok today I was trying to get some more boost out of my current set up which is a t4 60trim with a .68ar turbine housing and a e cover. Anyway I have been running 25psi for awhile with meth injection with no knock. Today I wanted to try and get a few more psi out of it. So I tried turning up my mbc and it did not increase so I thought maybe its cause my wastegate spring is only set for 7psi my mbc cant increase it any higher.


So I pulled the hose off the wastegate and still only 25psi. In first gear I can only get 17psi before I hit 7500 and it hits fuel cut. MY head is 100% stock which im thinking could be the problem. I think with the big exhaust side I need to rev higher to get more out of it. Do you think with cams the motor will be able to make more boost. I already am waiting for some bc 280s and the spring kit. I am also taking out my balance shafts. I already have my new dsmchip set for 8500 rpm rev limit. I was tempted to put it in now but afraid I might hurt something on the stock head. Sorry for such long post just want everyone to know everything thats going on, Thanks for any replies.

 

[ThingyNess]

If your wastegate spring is that weak (7psi), then boost is likely blowing the wastegate open. You will likely need a stronger spring in the wastegate.

 

[fwdeclipse]

Yeah I thought that was it also but I removed the line to the wastegate and nothing changed.

 

[TurboAnything]

No see there is pressure in your manifold and turbine housing. So if the spring is weak then the wastegate will push open. Try a different spring.

 

[oldman]

If your wastegate spring is that weak (7psi), then boost is likely blowing the wastegate open. You will likely need a stronger spring in the wastegate.

You mean exhaust pressure.

No see there is pressure in you manifold and turbine housing. So if the spring is weak then the wastegate will push open. Try a different spring.

That would be my suggestion as well.

 

[GSX_RCR]

Are you still running the Greddy Type S BOV?

 

[fwdeclipse]

Yeah I am still using the greddy. I will get a different spring then. I did not know that it would matter if I pulled the hose off but that makes sense. I will go ahead and order another spring thanks guys.

 

[CanadianTSi]

A boost leak test is always a good idea.

 

[DSM90AWD]

So I pulled the hose off the wastegate and still only 25psi. In first gear I can only get 17psi before I hit 7500 and it hits fuel cut

I'm confused, hitting fuel cut in 1st gear at 17psi (low load/airflow) and able to run 25psi in later gears (more load/airflow) makes no sense

My suggestion (as above) is to get a stiffer WG spring and check for boost / exhaust leak s

 

[fwdeclipse]

I'm confused, hitting fuel cut in 1st gear at 17psi (low load/airflow) and able to run 25psi in later gears (more load/airflow) makes no sense

My suggestion (as above) is to get a stiffer WG spring and check for boost / exhaust leak s

What I mean is in first gear I can only get 17psi out of it before it hits my stock rev limit. Its hitting the limiter at 7500 and only getting 17psi. I am guessing this is cause of the low load and the large t4 is hard to spool with low load as such in 1st gear. Hope that makes sense.

As far as boost leaks the only thing is its leaking into the crankcase, I have blocked off the pcv and it still does it. The turbo is pretty much new so I figure it could be rings or valve seals. I did a compression check awhile back and it was 155 across the board. When I build my head im gonna put all new seals in it while its out.

 

[oldman]

What I mean is in first gear I can only get 17psi out of it before it hits my stock rev limit. Its hitting the limiter at 7500 and only getting 17psi. I am guessing this is cause of the large t4 and cant boost much. Hope that makes sense.

Most people don't hit full boost in 1st due to less load.

 

[fwdeclipse]

Most people don't hit full boost in 1st due to less load.

Beat me to it before I could edit my post.