Yabo

What exactly does shimming the wastegate do? My current understanding of it (very little) is that it stretches the spring that holds back the boost pressure so that it can hold higher boost.

If I were to remove my boost enhancer, would the shim modify my boost at all by itself? My assumption is that boost would be unchanged from stock.

Trying to figure out how to get out of my improved autox class, apparently all that is bumping me into it is because my boost is modified. I'm wondering if I could just take out the boost enhancer/controller on race day and have that be the end of it.

I guess I also have to worry if my chips are OK with reduced boost levels from where they are at. All of these mods were done prior to me owning the car.

Thanks,

TurboTommy

The wastegate shim will, in fact, raise the boost all by itself.

azbanks

What is a shimmed wastegate worth?

Yabo

Worth for selling or in terms of boost? I still would be interested in a brief explanation of how it works too

CO951

You won't build higher boost with a shimed waste gate. They pre-compress the wastegate valve spring. This has two effects. First the waste gate will hold pressure better and will not bleed off as much prior to the set boost level. Second, it will slightly restrict the output, because the valve will no longer be able to open fully. In most cases the waste gate not opening fully probably has no effect boost level.
So basically it will help you build boost a little quicker, but won't change you max boost (unless you aren't using a boost controler).

Yabo

Did you mean to say that? If I'm not using a boost controller, then it will change my max boost?

67King

Porsche put one on the car. The factory spring will open at about 3PSI. The factory controller doesn't let any air to it until it makes what 12 PSI or so? So if you compress it so it won't open until 6 PSI (arbitrary), when the electric boost controller opens so a 12PSI "signal" goes to it, it will still open

reno808

you might as well put a tial in there

Yabo

Where is the factory boost controller, physically?

Xaerran

Under the intake manifold. It is a beige disc with the vac lines running to it.

jmj951

More commonly known as the cycling valve.
http://www.paragon-products.com/Vacu...606.117.00.htm

TurboTommy

???
No idea why you would say that.
You're arguing against the laws of physics; with a wastegate shim (it's in effect a stiffer spring) you will build boost a little quicker but also have a higher max boost; all else being the same (stock cycling valve, manual boost controller, etc).

Dutch944

Why would it be a stiffer spring? That could only be the case if it's an progressive spring and i'm very sure it's not. When it's a normal spring it does not matter how much you compress it, it will always take the same amount of force.

67King

Correction, it takes the same amount of force per unit distance. For example, if you have a coil spring on a car that is 8" long, and is a 500 pound per inch spring, to move it an inch requires 500 pounds of force. If, however, it is in a pre-compressed state such that it has already been compressed an inch, to move the system an inch would be like moving hte spring two inches, and thus require 1000 pounds of force.

CO951

Thanks Harry, that is completely correct on why it takes more force with a compressed spring.
Turbo, the boost control controls the max boost, unless you are just using the spring to control boost and not a controller. Putting a shim in has no effect on how much boost is achieved before the controller opens the waste gate.