I've been thinking about my options with the turbo, there is something I can't get clear. Maybe one on here knows, average internet search result is either worthless or at the best inconclusive... * i found a bw catalog with sizes, see pics.*
A k04-015 looks very easy to machine to accept the 020 wheel, but I only want to do that if the A/R is the same. *BW CATALOG SHOWS DIFFERENT A/R*
If its not, I will stick to the 02x housing and fabricate a manifold adapter or a simple tubular manifold.
*the k03-073 seems to have the same turbine a/r as the k04-020. This could be a cool discovery, utilizing a k03 housing to match the k04-02x bolt on
Is it true? Has anybody built a machined k03-073 turbine with k04-02x chra and compressor housing?
K03-073 a/r 5cm2


K04-023 a/r 5cm2


K04-015 a/r 4cm2

Yes, I have decided to go for a milder upgrade and build this 225 unit in a new k03 turbinehousing. I read about extra clearance and clipped turbines, I will see about my strategy when we start machining the housing. I will try to enhance the a/r as well, by machine and hand porting the housing. I dont want to blow all my money on this upgrade so I just buy a china turbine housing (45$), and have someone check my turbine wheel, with possible modifications. If its unuseable I might get a rs6 spec turbinewheel in there. Then new seals/bearing kit and balance and in she goes

All that traction needs strong driveshafts to finally kill the clutch, so when I found these 2 abandoned porsche driveshafts at the scrapyard for 25€ each I just had to take them home. Quickly dismanteled and cleaned up they really put a smile.on my face, they are in excellent condition and around 100€ for each CV joint new...
These units slide right on the bus driveshafts, and are stronger and allow for an additional 5 degrees of angle.

Havent been tuning lately, way too busy at the moment. I had ordered some materials though, preparing for the next part of the build.
One set of oem rs6 mafs, one for me and one for my friend. So I can use the standard maf scaling again instead of the wrong sensor unit scaled for 80mm housing. (It's just not super accurate and more work to get it right than buying the right sensor) My friend has ordered 2 sets of 440cc's, I will be running them at 3 bar and he will get my 4bar regulator to go with the 2871r turbo.
I will stick with the oem k04-020 housing, but with a Mazdaspeed turbine wheel (44.5mm - 50mm full back) and the housing will be machined and ported to fit. Why? The turbine wheel is damaged, so I rather upgrade it to suit future needs. I will build a manifold that places the 02x housing slightly tilted at the same location as my current k03 is sitting, meeting the downpipe without modification. The compressor cover will be clocked to aim towards the ic. For now I will stay with the std compressor, but I am not sure about the driveability of the combo, might change the compressor too when I get near the end of the build. Balancing will be done at the very end anyway.
Air filter will go outside of the enginebay, with a straight 80mm diameter tube about 40cm long between the filter and the maf. Hope to see clean readings from then on  
K04 tilted to longitudinal k03 downpipe position, clocked compressor:


New turbo inlet for the k04 (52-70mm), replaces my k03 reducer on my current tip (45-70mm).


# The rs6 maf is in and logs show a clean 150g/s now. Looks spot on for this k03-005 turbo! I do have heat soak issues so I will move my intake to a cooler place and put some wind guides on the ic's.

I received my laser cut flanges yesterday, looking forward to constructing my own bolt on k04-02x for the longitudinal engine.

Still not sure if I go hybrid or not, might rebuild the turbo with a new turbine first. That's all for future concern, first holiday and building the manifold.

By the way, if you want to save some fuel, make your cruising lambda about 1.15. If you can go leaner without misfiring, go leaner.
On LPG you can go as high as 1.3 on some engines with no issues at all, and you will save quite a bit of fuel.

This will require some mods to the ECU though. As it does not like requesting leaner than 1.
Or hack lambda linearization around the needed area somewhat.

Working on the new clutch kit.
Ordered the parts, 240mm v8 disk and LT II pressure plate:




Then went to the breakers to find a suitable flywheel. Removed 3 solid flywheels from 1.6 petrol Audi's. On the lathe for resurfacing:


Then I made a tool to center the flywheel and clutch cover on the turning base of the mill.


Blind threading




Done!


Now I just need to get it balanced and borrow someone's hoist for a couple of hours

Today I swapped out my larger injectors with my friend, he was running my 370cc set at 4bar to keep his car on decent power until his new injectors went in. We replaced them with 550's wich run excellent now. So, finally my 370cc's back, cleaned them and put new seals on them. They run just fine on the 1.8t, maybe not as smooth as the 550's but well enough. They will support my k04 when it goes in, should outrun the turbo in any case at 4 bar. (We drove them up to 225g/s at decent afr)