SE Turbo Wastgate

[THE REAL BORIS]

Who has done the wastegate enlargement and with what success? I am planning to open it out from 18mm to 21mm.

[MINX]

Ooh. What is the logic for this?
What will it achieve? How is it done?
EDIT
I found this info;
"The wastegate's role is simple - to bypass excess exhaust gas that would otherwise over-speed the turbocharger and cause overboosting.

Most production turbo cars are equipped with a turbocharger incorporating an internal wastegate. These integral bypass passages are generally less than 20mm in diameter and, as a result, aren't capable of flowing a huge volume of exhaust gas. This can cause high-load backpressure on the engine and - even worse - lead to the possibility of an overboost on a modified engine.

Enlarging and smoothing the internal contours of the bypass passage is one method of improving the flow through an internal wastegate. Expect only a small increase in flow, however - due to the relatively thin casting, the diameter of the bypass cannot be greatly enlarged.

In instances where maximum wastegate flow is required, an external wastegate must be fitted.

An external wastegate serves the same function as an internal wastegate, except it's a separate assembly with bypass pipes typically between 32 and 52mm in diameter (ie much larger than any internal wastegate). The fitment of an external wastegate requires a large diameter pipe to be tee'd into the manifold prior to the turbine housing. This usually requires the fabrication of an all-new custom exhaust manifold.

The traditional application for an external wastegate is on monster horsepower engine, where a huge volume of exhaust gas must be wasted to prevent overboost."

[zoomzoom]

I had overboost issues due to the wastegate being too small when I first fitted the turbo. I pulled it apart and managed to enlarge the port from 16mm to about 23mm with the flap still sealing on a couple mm around. The main thing to be careful of is how much material you take from the point where the flap first contacts the housing, as this can come close to catching on the flap as it closes.

Also after some advice from an experienced tuner and builder I used the die grinder to create somewhat of a trough from the inlet flange down to the wastegate port to promote flow through it as opposed to the turbine wheel.

I just used a die grinder which I was luck enough to be leant for the day, being a snapon with a brand new snapon bur, it worked wonderfully. Just be sure to use eye protection and gloves too if possible, because the swarf which is removed take the shape of tiny little needles and can be very painful.

All this and I managed to drop my overboost from the 1.1 bar at less than 3000rpm to what the actuator is supposed to be, 0.6 bar.

Cheers, Tim