Step starter confusion

[TheLionDragon]

I posted this on my google+ account and I could use some help:

I am making a starter for a RIS, I made my starter wort at 1.036, added 2 packs of yeast for 1.25l and after a day there is foam on top but not a big krausen as i expected, Being that this was a big beer i was going to do a 2 stage starter, now, should i add another stage just to be sure? and make the next one a little bigger (1.5l) with a bigger OG 1.040?. I don't oxygenate my starter and don't add yeast nutrient.
I am using a stirplate and the viability its 37%, and I got about 3.5l. Now this means i have to step it up twice so i can get a 4l starter, I wont include the wort of the starter in my brew so my guess its that it will be good.
Also are the next steps with a higher OG or just about the same? heres where i get confused a little; If i added 2 packs on 37% Viability gives me about 74 million cells g.o.t , stepping it up will increase the cells on an estimated 2.5x factor per step, giving me about 185 million of cells on the 1st and then 400M cells on the second. right? so a second step starter shouldn't be bigger so it can have more sugars for the yeast to feed from?

Makes sense?

 

[Salmonhouse]

Do you have an accumulation of yeast cells on the bottom of your starters?

In all your starters i would suggest keeping the gravity less than 1.05, yeast get stressed after fermenting high gravities.

If your not sure about how much yeast you are pitching you could take a gander at the wyeast page:

Wyeast Laboratories : Commercial : Breweries : Technical Information : Yeast Harvesting

You can figure how many cells you have per ml and measure accordingly.

Otherwise you don't really know given your viability could be anywhere really and your attenuation could be off too, so your really just guessing how much yeast you have.

 

[Salmonhouse]

Here is a good description of how to step up your starters:

Stepping up a Yeast Starter

 

[TheLionDragon]

Thanks a lot Salmon! that really helped a lot!