Hi all! In my car the turbocharger is overboosting (from 1.4bar normal to 2-2.5)from 5500-6000rpm and on (due to the fact that the car is stroked to 2400cc and the turbine housing is the factory one-only compressor is larger) and also I can feel that it is limiting the exhaust breathing at high rpm. I know that the turbocharger wastegate is at it's limits and can not bypass any more exhaust gasses so If I put a large external wastegate would be able to control the boost on 1.4bar? I really don't like to replace the turbo since it's starting to boost from 2800 and on which is really cool.
Any opinions?

 

Anyone???

 

It's boost creep. Caused by a restriction on the exhaust side if you ask me.

Sounds like its the Wastegate from what you've said. What Turbo and which Wastegate do you run?

 

I have a sapphire cosworth 4x4 and it has the factory turbine housing with it's own internal wastegate...

 

forget to say that the turbo has larger compressor on but I don't know which one specific(I think the T4 one).

 

Right, so theres the problem then, surely?

 

I know that the internal wastegate is at it's maximum flowing capacity (I had kept it fully open with a spring and gave it a run on motorway and was overboosting after 5500-6000rpm again) so I am asking if the installation of a big external will make the boost to stay where it should be because I don't like to put a bigger (or different a/r) turbine than this... (this setup has exchellence response, the only problem is overboosting at high revs but if I control the boost with the throttle to 1.4bar the turbocharger is running normal,if I give it full it is screaming like hell)

 

The External Wastegate will fix your problem if the restriction is in the Wastegate itself. We'd all love to be able to run a small turbine housing, but sadly you'll get to a point where you can't have it all ways!

Also, of course you'll need to take a port off the manifold for the External Wastegate, which isn't easy!

Alternatively, get the wastegate ported on the standard housing and a larger penny fitted.

 

That last one sounds good! Is there any danger for the turbine housing to crack from the wastegate porting? Also what metal is the 4x4 exhaust manifold made of in case that I like to weld a pipe to the manifold?

 

Not if you have it done by a proper turbo company. We're only talking of enlarging the hole by 1-2mm I'd imagine.

 

Ok I 'll check about that... Thanks!