Originally Posted by Tracy;1737011;
When I was making a wastegate for my 93 with GM-3 I found that a spring that would crack/compress at 16 in/pds would get me 8psi boost. Boost lever and spring in stock location and angle . Not sure why I got different figures than you, maybe differant turbo and not talking apples to apples?
The spring rate will determine how the wastegate behaves once it cracks open, not the maximum level of boost. When you talk about a spring giving you X lbs of boost before the wastegate cracks, that has more to do with spring pre-load than spring rate. The pre-load is adjustable (hence the ability to adjust boost) by cranking down the wing nut on the threaded rod. I could lower the max boost on my setup as well, by backing the wing nut off, but that would not change how it reacts once the wastegate cracks open.
I have seen many people here asking how much spring or what kind of spring to use on a homemade T/M. This will give them an idea of what kind of spring to purchase. McMaster is a great place to find springs with specs so you can get one similar to mine AND some with a slightly and or slightly lower rate if you choose...