Boosted ring gaps.

So much conflicting info on what's best for a boosted setup. 

I'm now leaning toward a wider second ring gap so it can vent any residual pressure that may stop the top ring settling correctly after TDC? 

Anyone care to offer enlightenment?!

In reply to Craigorypeck :

Open up rings or you will crack your pistons 

metal expands when it gets hot!  Under boost rings heat up and once they close all the gap they usually start to pry the piston apart 

Yep it's all about ring temps when you add power. More power --> more heat --> hotter ring --> less gap. If the gap shuts and the ring ends butt, you can scuff the cylinder and/or seize the piston and tear the piston apart. 

There are a ton of variables.  I suggest you call your ring manufacture of choice and see what they recommend for your application.

and the top would see more Heat than the Second and more than the third

What i have done is 2nd ring ~.004 looser than the top.  On my turbo caravan i ran top rings at .033" (bores are ~3.5") and they've never broken. Then i built another almost identical engine with .024 and broke one of those pistons. Considering that the blowby and oil consumption are acceptable with the .033" gaps, i plan to use that from now on. 

Loose rings will affect blowby more than they will affect power output.

On the other hand, too-tight rings will affect power output AND blowby, after they butt and rip the tops of the pistons off.

This is why my 82.5mm bore Audi engine has ring gaps of something like .026-.030" (I forget exactly, I built it in like 2013-2014ish).  I'd rather deal with blowby than worry about leaning on the engine too hard for too long.  Basically I want to be able to run 25psi boost constantly until the 18 gallon fuel tank runs empty.  Then refill and and do it again.

Vigo said:

What i have done is 2nd ring ~.004 looser than the top.  On my turbo caravan i ran top rings at .033" (bores are ~3.5") and they've never broken.

CRIPES.  And here I thought I was going thermonuclear overkill with what I did.

Oh well, good to know I was on the right track!  I have been constantly worried that I went too far with the ring gaps.  I've built a scadload of rotary engines but zero piston engines where I was in control of the build.  And also zero turbo engines of any type where I was in control of the build.  

It's a 7:1 compression 2.3l five cylinder that is to be fed a heavy diet of BOOOOOOOOOST.

In reply to Craigorypeck :what about Perfect Circle rings? 

As you know they are two part rings. Two rings in each groove that you can run gaps 180 degrees apart. That would allow plenty of room for large gaps without the blow by risk that a single ring offers.