One more wastegate question:

[Josh-stateside]

The manifold i'm probably going to use has a 38mm wastegate flange on it allready for something like a tial wastegate. I'm probably going to use the audi wastegate setup for now and just dump it straight out and not back into the exhaust until the cash flow is decent and i'd consider a tial 44mm wastegate?

Whatever the case maybe what are some High HP numbers that the stock wastegate can handle? Honestly, I like OEM audi/vw stuff etc. I'm not that into aftermarket parts but at the same point I'd like to build it simple but solid.

IF I can go without the larger wastegate i'll use the audi unit but i'm wondering what are it's limits?

Thanks
Josh

[JP]

A wastegate's job is to bleed of exhaust gases that you wish the turbine of the turbo to not see in order to control boost.

So say you want to run 2 bar of boost; Once your turbo has spooled to achieve 2 bar of boost any excess gases that are not required to sustain that boost level will be bled of by the wastegate.

If a wastegate is not big enough to support the volume of gases that need bleeding of you get something called boost creep. Which is where your wastegate has hit peek flow and the volume of gases that are still moving through the turbine exceed the amount that is required to hit say your target of 2 bar of boost pressure.

Reasons for running a large wastegate would be because you are using a small a/r hotside for your chosen application which is more prone to boost creep.

To keep things into perspective it doesn't matter how big the wastegate is if the pipework leading upto it or after it is smaller than the valve size as these will become the end restriction, so no point putting a 44mm wastegate on a 38mm fitting using an adapter. If the hotside of the turbo is correctly matched to the hp/boost pressure requirement and the exhaust setup is correct fort the hp/boost target then the stock wastegate is fine. AME used to run their 1046hp 16v turbo polo on a stock s2 wastegate with no issues.

If it really concerns you, you could get the stock seat, valve and wastegate itself reworked for improved flow. Running identical wastegate frequency values on a stock wastegate to a properly ported wastegate we dropped boost pressure from 28-29psi to 23-24psi on a 3076 with .63a/r as more exhaust gases where bled of on the same duty cycle. Showing that a lot can be had with some work on a lathe and valve refacer without spending loads of money.

hth JP

[Josh-stateside]

A wastegate's job is to bleed of exhaust gases that you wish the turbine of the turbo to not see in order to control boost.

So say you want to run 2 bar of boost; Once your turbo has spooled to achieve 2 bar of boost any excess gases that are not required to sustain that boost level will be bled of by the wastegate.

If a wastegate is not big enough to support the volume of gases that need bleeding of you get something called boost creep. Which is where your wastegate has hit peek flow and the volume of gases that are still moving through the turbine exceed the amount that is required to hit say your target of 2 bar of boost pressure.

Reasons for running a large wastegate would be because you are using a small a/r hotside for your chosen application which is more prone to boost creep.

To keep things into perspective it doesn't matter how big the wastegate is if the pipework leading upto it or after it is smaller than the valve size as these will become the end restriction, so no point putting a 44mm wastegate on a 38mm fitting using an adapter. If the hotside of the turbo is correctly matched to the hp/boost pressure requirement and the exhaust setup is correct fort the hp/boost target then the stock wastegate is fine. AME used to run their 1046hp 16v turbo polo on a stock s2 wastegate with no issues.

If it really concerns you, you could get the stock seat, valve and wastegate itself reworked for improved flow. Running identical wastegate frequency values on a stock wastegate to a properly ported wastegate we dropped boost pressure from 28-29psi to 23-24psi on a 3076 with .63a/r as more exhaust gases where bled of on the same duty cycle. Showing that a lot can be had with some work on a lathe and valve refacer without spending loads of money.

hth JP

Thank you for this post. I had a feeling everything will probably be ok. Also I know a few folks that can handle reworking the stock seat, valve and wastegate if necessary. I so love the look of factory parts these days. This vr6Tquattro is going to be a nice mix of OEM parts.