10psi of boost on a stock 11.1:1 compression ratio F20/F22 is generally considered the safe limit. This puts the effective compression ratio at 18.65:1
ECR = ((boost psi/14.7) + 1) X engine compression ratio
With a 2mm head gasket (9.83:1 engine comp. ratio) 13.2psi boost = 18.65 ECR
With a 3mm head gasket (8.86:1 engine comp. ratio) 16.3psi boost = 18.65 ECR

So the (loaded) questions are: is anyone safely running over 14+ psi on a 2mm HG or 16+ psi on a 3mm HG?

Are you using meth/water injection?

-I left charge temp, baro. pressure, compressor efficiency, crappy tuning, etc, variations out - assume a typical FI setup without any extremes in the mix.

 

I am planning up boost my greddy kit to 14-15 psi with 2mm HG and 750 injector, far as i know Rob at Nippon Power is running Full race kit 2 mm HG 15psi making 420+ WHP.

 

I believe the Inline Pro R&D car that John drives has been running 20psi for years and has been daily driven to and from the shop.

 

18 pounds here. 3mm HG. 19.709 ECR

 

i've heard of people running 12psi safely on stock motors with no HG.

 

I've run 19 psi on a really rich tune from IP for 4k miles, then ran 18psi on a much better tune for 3k miles and have had no issues at all.

 

I was running an ECR of 23 for a few thousand miles before a ring land let loose.

 

Wow, thats around 23.5 pounds of boost, with a 3mm headgasket! What happened when you lost compression? Any type of backfire, misfire? Was the loss in compression drastic? Or just a 30-40% difference? Was it driveable? Did you know it was down on power? Burning oil etc...?

I'm running 18psi for high boost, but have rarely used it. My 10 pound spring feels more than powerful enough for everyday stuff, especially with the lack of traction i have right now anyway!

 

It started making a ticking sound that progressed quickly.

 

like a scored bore?
http://www.youtube.com/watch?v=dyBllnMZaLE