Springs shape
 

Sorry guys, if you take two springs, with same wire diameter, same lenght, etc, but with different number of coils, which one will be the stiffest?
The one with more coils or the one with less?

what is the point of reference here?

have you ever stretched pen springs, to shoot the cartridges into the ceiling tiles in class, or annoy the cute blonde in the front row? similar concept to your question.

the number of coils will have very little difference in stiffness, but an increasing amount of coils will drastically reduce the overall spring height, reducing the available shock stroke length.

A straight line from point a to point b would resist deformation the most.
You'll have to divulge more succinct parameters to proceed from there.

There's barrel shaped springs so the coils can get out of each others way.
More coils will be heavier and hysteresis will make them react slower, and, and ...

... you can move the world with a lever long enough. I haven't tried this yet.

the real problem there is what one would use for a fulcrum.

The longer the wire? the softer the spring. So more coils would mean longer therefore softer

There are large count of parameters at play but just diameter/coil count/thickness of coil, shape (eg. as with progressive coils), and most importantly - material and manufacturing QA.
By just few of them known i see no way to tell except testing/measuring by yourself.
Any practical case you may need answers to this? Have pile of springs with no specs from manufacturer? Imho known quality spring manufacturers should provide specs for their products w/o need to measure yourself or playing guesswork with just few variables known. Not sure i'd wish to use springs of unknown quality and possible variance in spring rates between them due worse QA in manufacturing.

Doubling the number of coils gives half the spring rate.
Halving number of coils doubles spring rate.

K = (G * d^4) / (8 * N * D^3)

K is stiffness
G is material shear modulus
d is wire diameter
N is number of active turns or coils
D is mean spring diameter

So, more coils, more soft. This is what I was looking to, thanks!

No. It is not that simple. As Dan said the number of coils is only one part of the equation. You can not simply ignore all the other required data and go by number of coils.

Yup, my soft STi springs have fewer coils than my stiff RCE springs.

Perhaps you missed the first post:

Based on his first post, this is correct:

Yes guys, I just wanted to know how this parameter influences the stifness, I know there are a lot of other ones to consider...

We can go deeper :)
https://www.armoredworks.com/metalcl...NG-TYPES-1.jpg

Perhaps you missed the fact that there are many materials that springs are made of and that is a major part of the equation.
You can not just take two of the parts of the equation and get an answer. Not even a ball park one.
But go ahead just make shit up and run with it since it makes no difference to me.