I was just wondering what is the big difference in why someone would go from a 38mm wastegate to a 44 ? or like a 70 mm?> Thanks

 

TurboByGarrett.com - Turbo Tech101

It's the size of the valve inside the wastegate which indirectly relates to how well you can control boost.

Most "medium" build 4 cyl applications run one 38mm gate. If you are running a "big" build on a 4 cyl or 6 cylinder, you want to look into a 44mm gate.

You can use two gates in parallel if more effective gate diameter is needed to control boost.

In most applications, too small of a valve is bad because the boost will "creep" above where you want it to be. However, running a 60mm gate on a 1.6L turbo motor could potentially cause a little extra lag because you are running a gate meant for at least a big turbocharger, if not a "big motor" running a large turbocharger. You might not ever notice running to big of a gate on a small application but ultimately you try to match up what works best rather than sliding to far to the left or to the right if you think about it like a number line.

The average internal gate size is between 30 and 34mm depending on the turbocharger, but more often than not this is accurate. By switching out to a 38mm gate, you essentially have a larger gate helping to control the boost teamed with the fact that more often than not it is mounted on the manifold, so you are controlling exhaust flow before it enters the turbine volute.

Tial's site has all different sizes and spec's and may be a good place for you to take a look around.

TiAL Sport.com

If this doesn't make sense let me know as I am typing like a mad man in between projects at work.