I was playing with an Evo 9 for the first time today, and the boost is really weird. It runs 20psi and tapers to around 17 (seems normal), then in an instant it goes to like 8psi (around 6 grand). Logging the WGDC% in Evoscan, it stays at 100%. I set the MIVEC maximum advance to 0 (hoping that's a decent way to disable MIVEC), to see if turning off MIVEC would stabilize the boost. It made the calculated load shown in Evoscan quite a bit smoother overall, but the boost still dropped about the same on top.

I don't think that a boost leak would cause that drastic and instant of a change in boost. What do you guys think? We weren't too thorough checking things out, but is there something simple in the ECU I'm not thing of? He also has some stupid aftermarket BOV.

Could the ECU cut boost without the logged WGDC changing for some reason? Back when I was tuning on my cousin's 8, on the stock boost map it made a fluttering sound when the ECU would cut the boost from 20 to 15, and this 9 makes the same noise at the moment that boost drops.

I'm using Evoscan 2.6 beta 11 (Evoscan 2.5 refused to connect).

 

no the ECU will run whatever DC is in the WGDC (As logged by evoscan)

post up a snippet of the log.

try a higher gear (Where boost is held for longer), if it suddenly drops then you got a dodgey seal somewhere...

 

Sounds like a leak to me, remove the aftermarket BOV and try again.

 

Sounds like the BOV is opening...

Other thing to check is if he is using the stock airbox and snorkel, check the two plastic clips at the end of the snorkel where it meets the hood, if these are missing the snorkel will be pushed up into the hood with decent amount of air flow on the front of the car and will starve the turbo of air, thus the boost will drop...