What's the impact of 2.2 bar WG spring

[karlblues2]

I currently have an MD147 turbo setup, MRC mapped and a stock WG spring. I have the opportunity to use a new 034motorsport WG spring rated at 2.2 bar. My question is, what will it do?
I note the 3071 034motorsport comes with a 1.9 bar WG spring.

Can someone please tell me:
What is the pressure of a stock spring?
What does the 1.9 bar WG spring do?
What are the advantages / disadvantages of using a 2.2 bar WG spring?

Cheers in advance
Karl
Oz

[A80Avant]

there are posts in the past about this.

the stock wastegate spring gives you 0.4bar mech.boost. (that is with the N75 disconnected). The 1.9bar spring gives you 1bar mech.boost. I would suppose that the 2.2bar spring will give you something like 1.2bar mech.boost.

That means that once you connect the N75 valve with your current map, the boost will go sky high and will cut out. YOu need a remap with those springs. Their benefit is faster spool and better ability to hold boost on high rpm.

[Jamo]

1.9 will give 0.9 boost, 2.2 will give 1.1 bar boost before wastegate will open.

The 2.2 is overkill, will defo make the car feel quicker but electronic boost control goes out the window, you'll be running mechanical boost

[S2central.net]

Golden rule is you want mechanical boost to be ...

a) Lower than the maximum that the turbo can withstand at the redline on max load

b) Lower than electronic / software boost levels - so that when the ECU (or boost controller) detects some sort of fault that it can reduce boost to safer levels provided by the mechanical spring

The stiffer the WG spring - the quicker the onset of boost - for the WGFV duty cycle that accompanies it.

Audi is of course VERY cautious with the 1.4bar spring as it sets a very low level of mechanical boost.

I think a 2.2bar spring is TOO much except for a very large turbo that can safely run at 1.2bar boost even if the ECU has decided to pull the plug - The ECU can never reduce boost below what the spring provides.

I'm with Jamo that 1.8 - 1.9bar spring is about as much as you dare on anything but a monster... Even with that - you need to be careful that you dont get compressor surge if the accompanying WGFV duty cycle is too high.. Lets say 50% cycle hits max boost nicely with 1.4bar spring - the same 50% could give you surge and boost control issues with the bigger spring. Motronic is smart enough to dynamically adapt the WGFV cycle to hit target boost - but there limits to how far it can stretch.

[Rusty]

The pre-load affects WG crack pressure, the spring rate then affect behaviour thereafter. By adjusting the preload you can make your 1.9 bar spring crack at 2.2 bar and save some money in the process. I doubt you'll notice much difference TBH but you'll need to have the mapping adjusted if the original WGFV boost map is a lot less aggressive than the mechanical effort. The stock homefries really didn't like a 0.9bar setup for example.

Paul, the spring you have from me is set up for about 2.2/3 bar nominal, it can be increased or decreased a fair bit on the WG cap screw.

[S2central.net]

I've yet to try that spring (sorry)... Someone else sent me a different one to try as well... Like many things - its on 'the list'.

[Rusty]

I know mate, no worries, was just letting you know as it was relevant to this thread.