Wastegate advice

[Dan]

As I understand it:

When the DV opens, it allows the turbo to keep spinning... it gives somewhere for the compressed air to go. In doing this however, it's also continuing to suck in air.

In a dump value scenario, all that air has to come from the airbox, past the MAF. That means for that period, it's pulling air through the MAF and letting it go. That's a false increase for the MAF.

If all the air is recirculated post-MAF however, the turbo can pull that same air back in again, effectively in a loop. The net pressure just after the MAF balances out and so more air doesn't need to move through the MAF.

In the real world of course, the turbo does have friction - as it slows, existing pressure has to go somewhere if it isn't just getting moved around... so yes, it could go back out the airbox.

The difference though, is "some" vs "all"... with a diverter the MAF reading is inaccurate, with a dump value it's almost irrelivent.

I'll wait for prj to correct my inaccuracies.

[Thuppu]

I did a bypass inlet like this that forces the airflow to the direction of the turbo. Don't know if it helps anything, hope not cut the maf thread so easily...

[prj]

You are correct Dan...
Though, if there is a reversion of flow on this system, the engine will stall or bog very heavily.

That is why care needs to be taken when routing the bypass outlet back before the turbo if it is not in stock location.
If you route it too close to the MAF some air will indeed go back out the MAF and that will cause lots of running issues, stalling at intersections etc.

[newsh]

The 3B MAF hose is better than the ABY MAF hose in this respect as the return hose from the diverter aims straight at the turbo inlet.

[Rocco]

Use search, blow off valves have been discussed to death.
If you use a BOV instead of a bypass, every time you shift, your engine will be overfuelled and slightly bog down. On stock engine management, you need to use a recirculating valve (bypass) to avoid losing performance.

If you are the kind of guy who prefers "cool sounds" over performance, then feel free to disregard my advice though.