CrackHeadMel

iTrader: (2)

I have a greddy type C wastegate with a blue spring (aledgly 16ish lbs) which is higher than my likings

being i want to have the ability to run a lower boost level and crank it up with a boostcontroler i first set off in a quest to buy a spring only to find out there more than i really wanted to spend on a coil wond piece of steel


I then dug out my chassis engineering book and found the forumula for caluclating coil spring rates and plugged in the measurments i got from the spring

11.25^6 x wirediameter in inches^4 (.17) Over
8 x number of active coils (6) x mean coil diameter^3 (1.89)

to my amazment i got 29.xxxxxxxxxxxx lbs-in rate for the spring which sounds like i did my math correct because the manifold pressure which should be equal or +50% greater to compressor outlet pressure pushing on the wastegate valve (say 16lbs) added to the compressor outlet pressure (say 16lbs) is enough to push aprox 32lbs which is just over my wg spring rate to move it an inch which is fully open


now according to my caluclations there really isnt a way to drop the spring rate aside from changing the wire diameter. droping coils actualy raises the spring rate (drop 1 rate goes to 32, drop 1.5 coils rate raises to 40)

However there is a 3/4 of an inch preload on the spring when the wastegate is assembled which the adjustable stopper backed all the way out which could attribute as much as a 21lb preload on the spring

cutting 1 coil off would shorten the spring aprox 0.6 inches which should drop the preload down to aprox 14lbs however raising the spring rate to 32. to me this sounds like the spring would open earlier under less manifold pressure initialy, and being that its a 47mm gate even a 1/2 should be ample area to bypass a reasonable amount of exhaust gases

am i correct? is my math flawed? anyone try this?

absolute worse case, im back to square one, buying another damn wastegate spring, however i think this was a worth while 30min spent



-Jacob

impactwrench

I tried cutting coils on my HKS standard waste gate spring with no luck. I ended up, after starting with a 15# spring, getting a 7# spring before the minimum boost dropped to 10psi. Still able to boost to 20PSI+ on that spring.

CrackHeadMel

iTrader: (2)

well damn


will an hks style spring fit in a greddy wastegate? do you bychance have the dimensions of your spring handy?

impactwrench

do not have it

Azriel_Strife

iTrader: (5)

gate springs go by gate size. 50-60mm gates can use the same springs.

FYI I have had great luck with ebay wastegate springs. bout 10 bucks each plus shipping.

DriftDreamzSS

iTrader: (4)

I've cut a coil out of a tial spring before, the gate opened sooner but full boost was the same(very poor manifold/ wg runner design).

Jobro

iTrader: (2)

Did you take into account the surface area of the diaphragm and the valve area

Nosferatu

You're quoting a 4-1/2yr old post, Do you really think he cares at this point? lol

CrackHeadMel

iTrader: (2)

I did read the new posts though



No i didnt take into account the valve / diaphram area / ratio at the time.

Good to know about the ebay springs.

-Jacob