Strange, I always thought the boost level was controlled by the ECU, not the dump pipe.

Boost cut levels can be changed if your target boost is too close to the cut level. (i.e. different atmospheric conditions will give you different boost, which may just knock you over the limit).

Does the AVO have a different flange to a VF series? What else would change in the dump pipe to correct the 'dodgy design'?

Also how did you disconnect the wastegate and hold it fully open on an internally gated turbo?

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]

Disconnect actuator thingy and wire gat open externally

The conclusion we came to is simply that the exhaust side of the turbo is to small to allow the amount of air that the 2.5 can push through once it has less resistance.

The stock dump directs the waste gate air straight into the flow through the compressor so you get higher pressure on the exhaust side of the turbo which slows the spool up reducing the air going through the motor and leaving less air to get out through the exhaust.

With the butler dump the waste gate doesn't interfere with the main flow so it spools up quicker, more air through motor, more air to try get out the exhaust so greater spool. It can't all get out the waste gate so goes through compressor and get excess boost.

Spool was awesome but boost cutting sux chocolate salty balls.

This is what the back of the AVO's look like ( this is a 320 though )



The difference is the exhaust side on a 450s is huge in relation to the inlet when compared to the VF43. It really would hurt the spool when both are on a stock exhaust ( Though i don't thing with that divider you could even run the avo on a stock dump ) but VF43 on stock exhaust and 450 on the Butler isn't much difference at all and well and truly made up for through the bulk of the power band.

Do you really want to raise / remove the boost cut limit on a motor that the consensus seems to be that it won't last above 20 PSi.

I might not have explained it very well Kato but no bullshit this was what was happening and have spoken to 4 other Pig owners that have had exactly the same issue with the stock turbo. You cannot tune it out you need some other way to let the extra airflow out if you want to control the boost level. You could go an external get. I didn't like that Idea. AVO450s FTW.

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Stoner & Webber 2011 World Champions

I've taken a few logs in the past and it seems to just overshoot slightly when boost rises quickly i.e. when you nail the throttle at about 4000rpm. The peak value on the boost gauge is normally 1.5bar on the street, but it was peaking at 1.7bar at least twice yesterday.

Meh, at the end of the day I had an absolute blast out there.