need wastegate help....

[euro_urs4]

so a little bio about the car running a built motor in my urs4 with a holset super 40, with vems and a stock waste gate with a 2.2 bar spring, (correct me if im wrong but this spring should hold 32.5lbs) , my problem is that i cant hold 32 lbs (or whatever this spring should hold) regardeless of the spring size should it be able to hold that desired amount of boost? or the fact that the turbos so big it over powers the wastegate and make it spike all the time.?

im assuming i have to go with a biggeer waster gate (something in the tial 44mm range), however for the time being seeing if i can hold 32 or so pounds without it spiking, possibly have something setup wrong in vems, (or the turbo is just to powerful)
would love all your input guys thanks so much in advance

[JP]

Are you saying you are boosting more than the 32psi? If so then the wastegate is too small for the amount of gases that need by passing and you are getting boost creep. Or you have a leak in the diaphragm so you have no boost control and getting freespool.

If you are saying you can't boost as much as 32psi then either the spring you were sold is not 32psi or you have a boost leak somewhere.

It have you fitted a 32psi spring and are trying to use boost control to make it less? Which is impossible as the spring will always represent the absolute minimum and boost control can only make it more.

Sorry for all the different options as an answer but the question wasn't phrased the easiest to comprehend.

Have yourself a good Christmas :-)

[euro_urs4]

Are you saying you are boosting more than the 32psi? If so then the wastegate is too small for the amount of gases that need by passing and you are getting boost creep. Or you have a leak in the diaphragm so you have no boost control and getting freespool.

If you are saying you can't boost as much as 32psi then either the spring you were sold is not 32psi or you have a boost leak somewhere.

It have you fitted a 32psi spring and are trying to use boost control to make it less? Which is impossible as the spring will always represent the absolute minimum and boost control can only make it more.

Sorry for all the different options as an answer but the question wasn't phrased the easiest to comprehend.

Have yourself a good Christmas :-)

sorry about the not so well worded question, but im trying to boost 32lbs, or whatever the spring is made for and hold that, however like you said i believe i have boost creep and it goes over that, (in which i set the fuel cut of at 35lbs to keep from any damage happening), yet im not sure if i have a small leak which isnt allowing it to hold and pull at 32lbs, (or like you said the wastegate is to small for the amount of gasses going through and will just always boost past what the recommended spring pressure is rated for..

so in other words i am boosting way past 32lbs,

[JP]

Ok if overboosting first of all make sure you are running no external boost control just spring pressure. Next make sure the boost signal pipe from the turbo to the lower chamber of the wastegate has no leaks.

Lastly get a vacuum tester and apply vacuum to the top chamber of the wastegate make sure it can hold vacuum to ensure there is no tears in the diaphragm.

What you are describing is freespool with no boost control whatsoever. Boost creep is much more gradual and progressive where you boost the set target and as rpm increases and more exhaust gases are created you slowly start to overboost. So basically you are looking for either incorrect boost control plumbing or a leak to or within the wastegate.

[Thuppu]

Propably you have a too stiff spring. With 034 1,9bar spring in stock WG and HX40 Super (#16 housing) turbo, the boost spiked to overboost. Tried also a 2,2bar spring and it was totally hopeless, owerboosted like crazy. After switching to stock spring the boost started to act like it should.

[euro_urs4]

Propably you have a too stiff spring. With 034 1,9bar spring in stock WG and HX40 Super (#16 housing) turbo, the boost spiked to overboost. Tried also a 2,2bar spring and it was totally hopeless, owerboosted like crazy. After switching to stock spring the boost started to act like it should.

Yeah I'm thinking the spring might be to stiff, I only have the stock spring other than that, I can give that a try and see if it will hold.

However you don't think the turbo is overpowering the stock wastegate with the 2.2 bar spring and just opening it up and running excessive amounts of boost?

I'm looking into upgrading to a tial Q wastegate regardless so I can run more boost regardless (thoughts on this)

[Billman]

the 2.2 bar spring is 1.2 bar relative. So with spring pressure you should see approx 1.2 bar boost.

[euro_urs4]

the 2.2 bar spring is 1.2 bar relative. So with spring pressure you should see approx 1.2 bar boost.

Seems its running way over 1.2bar

[Billman]

Connect the N75 the right way and leave the connector unplugged. Unscrew the spring till you get 1.2 bar.

But i really dont see why you need that hard spring. I use the original with holset HX40. Others use 0.9 bar one.

[euro_urs4]

Connect the N75 the right way and leave the connector unplugged. Unscrew the spring till you get 1.2 bar.

But i really dont see why you need that hard spring. I use the original with holset HX40. Others use 0.9 bar one.

yeah thats whats not making sense to me the stock wastegate with the stock spring, or 1.9 or 2.2 bar spring should produce and hold plenty of power, however im pretty sure i have the n75 valve connected correctly. (but could always be that chance that its not, anyone have a pictures or a description how its supposed to be connected to make sure i have mine right?

also is our n75 from the urs4 the same as say a n75 for a newer car? (i think i have one from a newer audi in my car right now (looks exactly the same as ours and has the 2 pin connecter with it )

[prj]

The spring has nothing to do with achieved boost.
Using electronic boost control the only thing the spring is counteracting is exhaust backpressure...

I think a good idea would be to take the car to a tuner who knows what he is doing, because 2 bar and higher boost pressure is not childs play on 2.2, and you can destroy even the most hardened of engines very quickly.

Certainly not a good idea to play with springs and boost with pressures in excess of 30 psi, especially if you have little experience/grasp of tuning concepts.