Originally Posted by KPV

Hey Guys,
I linked to this thread through the recent wastegate thread since I am in the midst of tweaking this mod as well. I figured I would shed some light on this topic for anyone interested in the theory.....

First off, to reiterate, a pressure gage and source of pressure is essential. The device that John D. (Hey John!) posted a picture of is a great tool and cheap to make. Although I haven't gone through the process yet, I would concur with two posters that the gates should start to crack at about 12psi for GIAC Stage 4 programming (approx. 600 crank hp and K24's).

Some definitions......
1 bar equals the standardized atmospheric pressure at sea level = 14.5 psi.
0.7 bar = 10.15 psi
0.8 bar = 11.60 psi
0.9 bar = 13.05 psi
1.0 bar = 14.50 psi
1.1 bar = 15.95 psi
1.2 bar = 17.40 psi
1.3 bar = 18.85 psi
1.4 bar = 20.30 psi

We all know the turbos, regardless of size, need to bleed off excess boost that the intake system and programming cannot handle. This is where the springs come into play. They are very simply the means to keep the lip shut. The lid is the actual wastegate.

Springs are very simple and function according to:

F = (k) times (x)

F = force on spring
k = spring constant (varies with stiffness of spring)
x = displacement of spring

Remember algebra???!!! LOL

Example...
F = 100 pounds
k = 100 pounds/inch
x = 1 inch for every 100 pounds applied to it.

For that example, 100 pounds will depress the spring 1 inch, 200 pounds depresses the spring 2 inches, 300 pounds depresses the spring 3 inches, etc. But, remember, adding more and more force will eventually compress the spring completely leaving no travel.

This works with all springs except progressive springs.

So, the point of the whole spring upgrade is to allow the spring to be commensurate with the increased boost pressures of aftermarket programming. The apparent problem with the stock spring is that it is designed for a system that is boosting to 0.7 bar or 10.15 psi (see above). With the aftermarket programming, the pressures are upwards of 18.85 psi or 86% higher!! So, you can crank up the stock springs adding resistive force (pretension force) with each crank, however, you are running out of travel at the same time. As you crank the rod nuts tighter and tighter, you are compressing the spring and eliminating more and more travel. This will eventually, if overdone, limit the opening size of the wastgate since the spring doesn't have any more travel to allow it to open farther. Hence, stiffer springs are necessary to move the working range into something appropriate for the higher boost pressures.

I haven't done it yet, but if someone has some time on their hands, I would REALLY like to know the stiffness difference between the stock vs. upgraded springs. The test is simple. Hang a weight on the uninstalled rod mechanism and measure the movement of the rod. Do this for the stock spring and for the upgraded spring. Post the results here. Remember, the weight cannot bottom out the spring. It has to be appropriately weighted to allow the spring to work in its usable range. They can be different weights. Just record the weight and distance the rod moved for both circumstances, stock vs. upgrade.

OK, I guess that is enough of that!!! LOL