Do you have a intake or OEM?

OEM bov?

 

Nothere,

The three feet of snow is where I was heading (Powder Mountain) to hit the slopes (season pass).

 

GST Motorsports,
Factory on both the diverter valve and intake. Filter is a K&N drop in.

 

Ok.

It gets even worse with a open intake and aftermarket or crushed OEM bov.

I have a open intake and crushed OEM Bov on my personal evo and it's almost undriveable up in Lake Tahoe. If the boost is close to 0 pressure, either positive or negative and I let off just slightly the car surges like it has no bov at all. The AFRs go from stoich to around 11 afr when this surge happens so I know it's the BOV opening. It gets worse the higher the altitude and colder the temps get.

Last year I only had open intake and OEM bov (non crushed) and it wasn't as bad. I also put the OEM intake back on and it barely did it at all.

There where a couple times I had to apply opposite lock to get the car straight again because the surging upset the car so badly in a snowy curve. I'm actually surprised I haven't crashed the son of a ***** yet.

Next trip the oem airbox and my plastic POS oem bov goes back on.

 

Thanks for the insight on the intake situation. The car will pull through the surging (not bad but there) and clear up around 3000 RPM if I stay in it. The IX OEM metal valve I've tested on my EVO to 30 PSI without leaking in a static pressure boost leak test. On my old GS-T I ran a Greddy with one spring that worked well to hold boost, vented without surging and recirculated post MAF sensor.

 

Maybe the car was being choked with fuel at the 9 afr range

 

I also have noticed that surge isn't as bad with the stock plastic DV as compared to the metal oem DV. Wonder why? My plastic piece will leak at anything past 20psi, so at least the metal one holds 24psi pretty steady, although I'd prefer no leaks at all. Even a Greddy RS valve I tried with a single soft spring held 28psi without leaking and only had mild compressor surge, but for some reason my car really didn't like that valve at all and letting off the throttle would open the valve and my AFR would drop into the 10's range briefly and make the car stutter and hesitate. I'm really getting fed up with maf systems, I may finally look closer at the speed density conversion or save up some money and pony up for a full stand alone down the road.

 

Looks like compressor surge to me and the compressor map seems to back that up from some quick numbers I ran from a datapoint in your log: