First I would like to start by saying this isn't specifically miata related. However, the Greddy turbo kit uses a 15g so I thought this may be useful to someone on here. Also I saw some discussion of this a while ago on this forum but no one had done it. One disclaimer is the turbo I used has a TD04HL wheel where I believe the Greddy turbo uses the smaller TD04 wheel. This writeup should sill work but the nut on the shaft may not be reverse threaded for the TD04 wheel. Feel free to let me know of any changes that may need to be made. Also if I refer to something mysterious its probably because I wrote this for a volvo forum.
I kept seeing 19t wheel and housing sets on ebay and decided to give one a try. The one I ordered cost around 170 shipped and was made by Kinugawa Turbo. I looked into them a little bit and the European subie guys seem to like their turbos. They claim they are good quality parts and not just cheap Chinese knock offs. The wheel and housing I got seemed decent.
For parts you will need the following:
TD04HL-15g (you could in theory
use a 13c but it has a smaller exhaust wheel)
BOV (if you get a housing without a CBV like me)
Rebuild Kit for a superback wheel
For tools you will need:
Snap ring pliers
Lathe (or take it to a shop)
Also you will need to get the turbo balanced
The first step is removing the turbo. Duh. The easiest way I have found is to just remove all piping, oil and coolant lines and then just undo the central v band. After that it pulls out.
Next the large c clip holding the compressor housing on needs to be removed. This is a pita and is easier to do with two people. One compressing the clip and the other prying it with a screwdriver.
Once the clip is removed the CHRA can be freed. Remove the nut on the compressor wheel. Note: The nut is reverse threaded (may not be on a greddy turbo).
Also be careful to not put a lot of side load on the shaft as to not bend it.
Just for laughs here is a comparison of some wheels. From left to right we have a 13C, 15g and then the 19t.
Next this c clip needs to be removed. Once it is removed use two flathead screwdrivers to pop out this piece.
Here is why the rebuild kit is needed. The 19T wheel is a superback, where the 15g is a flatback. The only difference is two parts seen below. The superback parts are on the left.
At this point it would make sense to replace the rest of the parts in the turbo. This is not too difficult but I won’t discuss it and rather link to another thread.
Next there is a recess that the compressor wheel fits into that needs to be enlarged. The 19t wheel is too big for it. To do this you need a lathe so I just took it to a shop. In the pic below you can see the part that was lathed. Also make sure you take all the internal bits out. That journal bearing was placed in after I got it back.
The next step is crucial. You need to take the turbo to a shop and have it balanced.
The place I took it to only needed the compressor and exhaust wheels. Here it is after I got it back:
Now the reassembly. Just follow the disassembly in reverse or look at the previous link. Be careful when putting the exhaust wheel back in. There is a clip on the wheel that needs to be seated right. If not, you will have a hard time with it. Make sure the clip is starting to go into the housing with a flat head screwdriver. At this point it should look like this:
However, this is not how the wheel is supposed to sit. I just hit it with a rubber mallet a few times until it snapped into place.
Next put the compressor wheel on and tighten the nut down. The torque spec for it is something lower than my torque wrench can read, so I guestimated it and put some loctite on as insurance.
Lastly you need to do something about the wastegate actuator. The compressor housing has plenty of threaded holes so this shouldn’t be too hard. I used an ac compressor bracket and a wga from a T3. Reason for the T3 actuator is the Mitsubishi one is supposed to suck. Luckily for me the bracket I made for the 15g worked perfectly with this housing.
And that is it. Reinstall the turbo and all the other bits and you are good to go.