I was wondering the rule of thumb for wastegate spring rating vs desired boost level? I want to boost around 14psi, so should I use the 10-12psi spring? I will be using an electronic boost controller.

What about bov spring pressure? I don't want too much attention, so I was tightening it quite a bit, and I didn't hear any surge

 

10-12 psi would be fine and you can control the rest with the boost controller. I'm not aware of any rule of thumb but to get the desired boost pressure you just run the same or lower pressure spring on the wastegate. You can control the wastegate duty and thus the boost spiking all with the boost controller.

For the BOV, that's usually based on the design. The one's that whistle like F &F are typically the ones that attract attention.

 

I'm wondering how my boost would be if I set my controller lower than the rated spring pressure of the wastegate. I know the spring pressure is an estimate, and just a stiffness for a desired boost.

I'm getting my car tuned soon and my wastegate is coming with a 14psi spring tension. I only want to hit 14psi max. I will have a boost controller anyways, so why would I need to buy a spring rated lower? Will I boost spike? I know lower is safer and better, I'm wondering if anyone had problems.

I guess my new question should be. I know a boost controller is always used to add boost, how about lowering boost?

 

the spring holds the wastegate shut (unless you have a BMW), and the pressure from the turbo pushes against the spring to open the wastegate.

the boost controller vents pressure between the turbo and the WG spring, so it can only raise boost, and not lower it.

you're also correct in the assumption that a 14lbs spring is sort of a ball park number, it will probably be accurate in that if you give the actuator 14psi, the wastegate will open, but due to the different manifold/turbine/compressor/engine combinations its hard to say what the boost will actually be.

the BMW 335's i think are setup backwards, the spring holds the wastegate open?

 

If you want to hold 14 psi and no more I would definitely get a weaker spring, say 10-11 psi. If you have a free flowing exhaust and a small wastegate it will be pretty difficult to hold that low of boost though.

 

BOV spring pressure is related to the VACUUM your engine makes under lift. The Tialsport website has a nice chart for their bovs in the tech section. Ported engine = less vacuum = softer spring.

 

Generally a wastegate will be able to hold twice its rated spring pressure with a prioper boost controller. That being said, the spring pressure is where the wastegate BEGINS to open. So if you want to run 14 psi, I would start with something like a 10 or 12 lb spring.

 

I say this with all the love possible to Ihor, I would never run a WG at twice the rated pressure. More often than not once you get too high over spring pressure you will start to see(graph) or hear oscillations. There has been more than one time on the dyno where we've heard the wah wah wah wah... Overall it is best to stay within 5psi or less of spring pressure for the typical build otherwise the spring can be too soft to hold.

~S~

 

I installed 12psi springs (grey and maroon) on my Tial MVR WGs but saw 14 - 14.5psi with boost controller switched off, how's that possible?

 

You wont necessarily run 12psi on a 12psi spring usually you will run slightly higher then the spring pressure on the gate.

~S~

 

As I said above, the spring pressure is when the wastegate STARTS to open. You will generally run slightly higher boost than the rated spring pressure.