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Wastegate enlarging & Turbo Removal, Needed with big exh

Posted: Sun Aug 13, 2006 10:21 am
by James
If you fit a free flowing exhaust to your city often the factory wastegate size can no longer control the boost, this leads to over boosting and fuel cut. Fortunately there is an easy way to fix this, you can enlarge the wastegate hole while you have the exhaust off.

Firstly you need to remove the exhaust like you would if you were going to get a new one made, for this youll need lots of WD40 or CRC and probably a hex 14mm socket. Some of those bolts can be very tight, I suggest for the tough ones spray them the day before and every couple of hours to help it soak right in, especially the turbo ones.

So once youve got the exhaust and the cat convertor bracket off then you can take the turbo off. First take off the oil lines, plug up the hole in the crankcase so you dont get shit in there. Then the turbo is held on by 4 14mm nuts. To get at the ones on the gearbox side you may have to undo the torque arm and swing it up out of the way.

Youll then need to remove the circlip holding the wastegate actuator arm onto the wastegate flapper arm, this mean you can fold the flapper up out of the way to do the porting. If you can get hold of circlip pliers use them, otherwise a screwdriver or two can make do. Take care not to lose the circlip its a slippery little sucker.

Now you can actually start the porting. :D


(Cheers to MikeNZ for the pics 8) )

The picture above shows the wastegate before and after porting, you can see the shiney section where the wastegate flapper has rubbed on the exhaust housing. When you inspect it you should be able to see the the wastegate can move around about 1mm in all directions, this means you cant enlarge the hole right up to just below the diameter of the flapper but you can get it big enough.

If you plan to udnertake the grinding yourself you will either need a rat tail file and a fair bit of spare time, or an electric or air powered die grinder which will make short work of it. (If you get a shop to do it it shouldnt take them more than 30mins, althought youll probably get charged the base rate of 1 hour first, so dont pay more than like $40-50).

I recommend you use a burr like this

in the die grinder, these chew through the iron housing.

So stick the bit in your grinder and go nuts, try to keep the hole as round as possible and be carefull not to stay in one place too long or else you might make it too wide. Get the hole pretty much to size with the burr then you can finish it off with a cheap mitre 10 die grinding stone or something to make it all smooth.

Once you have done this then you can re-assmeble the wastegate assembly, then bolt the turbo back up. Dont forget to do the oil lines nice and tight.

Now you can drive it nice and noisy down to your exhaust shop (dont worry its not actually too bad with the exhaust off).


EDIT: NZ_Mike took some more great pics, they really help with the turbo removal.


Posted: Thu Aug 17, 2006 8:21 pm
by James
This modifcation on an otherwise factory T2 lowers the boost to around 8.5 PSI, so you will need a boost controller to bring it back up to factory.