ksattic

iTrader: (5)

I have a 2005 VIII and it has always been fairly strong from the factory. The only mods are a WORKS drop-in filter and a Defi BF boost gauge. It would normally boost to 23psi and taper to 21psi, according to the gauge. Whether or not this is accurate is beside the point - it has been consistent like that for two years.

For the last three months the boost levels have been very unpredicatable, in both cold (<32F) and warm weather. Some days it will only hold 12psi of boost and others 19. I don't see it hold 21psi any more.

I did a boost leak test from the turbo inlet, and found that the DV/BOV was leaking from the main outlet all the way down to 2psi. I pressurised the system to approx 15psi and all of the air leaked out within a couple of minutes. This is the stock plastic DV.

I replaced the DV with the steel MR one, and it now holds a little more boost, but only approx 5psi. The car still has the same issues when driving.

Is the DV supposed to leak like this or should I expect a functioning DV to seal completely below a certain pressure? I was under the impression that this depends on the vacuum applied to the vacuum line. However, I need to know whether a Forge DV would fix this problem at all or if it would behave in the same way.

Disclaimer: I spent quite a while searching for solutions on this.

C6C6CH3vo

iTrader: (9)

The valves are designed to delay open and never really close all the way. The vac/boost reference on top of diaghram opens and closes the valve, but there is a small inner port that routes boost (in a lag fassion) under the diaghram to open it. You can rig a solenoid on this internal port to get it to hold under WOT (via ICS relay for 03 and 04) and still have stock like characteristics while not WOT but it take some level skill in the art

ksattic

iTrader: (5)

Thanks for the info. I am still trying to find an answer for the change in behaviour of my boost levels. If this isn't it and I have no other leak, what else could it be?

The air filter element is clean, the sparkplugs are new (stock Iridiums) and I can't see any other obvious problems.

ksattic

iTrader: (5)

I took my car into the dealership last month to ask them to look into the problem since it is stock and still under warranty. A tech drove the car with me in the passenger seat and noted that the car had a problem, but after they looked at it, they changed their tune and said there is no problem, saying that the tech was mistaken. They were "kind" enough not to charge me over $200 for the "look".

What options do I have in this situation? That car clearly isn't performing as required, and every diagnostic I have performed has not shown a problem. Yet I am still seeing erratic boost levels when accelerating in all kinds of weather.

I do have a Tactrix cable and datalogging software and have not noticed any obvious issues there either, although I am a complete novice in that area.