K04 Turbo Compressor and Turbine Size Variations

[rdcyclist]

I purchased a set of CHRA's from a guy on AZ last week and they arrived on my doorstep Saturday. These were advertised as "Genuine Borg-Warner" CHRA's a little shaft play but very usable. He said they were in a set of "Genuine Borg-Warner" K04 turbochargers and would fit any standard Borg K04. I have a set of low mileage Borg K04's I purchased some time ago that ingested some bits of hard crap that dinged up the compressor wheels so a set of "usable" CHRA's would be perfect for these turbos. My dinged up CHRA's have zero shaft play but the fouled up compressors makes them unusable.

The CHRA's had the promised "minimal shaft play" and looked pretty good. Pulling my old units apart was easy as pie (right, getting the hot side apart was pretty challenging) and everything cleaned up nicely. Unfortunately, the "new" CHRA's have compressor and turbine wheels of much larger diameter. Here's how the dimensions vary:

My K04's: Compressor, 40/51mm; Turbine, 42/49mm
Used CHRA's: Compressor, 42/56mm; Turbine, 44/50mm

The seller is sure his turbos are standard Borg K04's and has sent me pictures of the Borg tag on the compressor housing. I have not seen a pics of the size of the turbo inlets or outlets. He is standing on his "as is" disclaimer and refuses to discuss an equitable return based upon his insistence that he bought Borg CHRA's to replace these and by God, they'll fit Borg-Warner K04 turbos.

I've got a set of other Borg CHRA's that were given to me with what was thought to be excessive shaft play. They came in the boxes the replacement units from Borg were delivered with. Those match up with my units exactly.

It has been difficult to find real data on wheel size in the various turbos used on our beloved B5S4 platform other than the RS4 K04 turbos which seems to match up with what I've got in my turbos.

Now that you're slogged through all that BS, the questions are:
1. Are my turbos "Real" RS4 K04's?
2. Are there other size RS4 K04's?
3. What are the used CHRA's supposed to fit really?
4. Have I been sold up with river with these CHRA's?
5. Anybody interested in buying them?

Here's my compressor housing:

Here's the Borg turbo label:

Here's my compressor wheel complete with dings:

Here's the used compressor wheel:

Here's the seller's "compressor label":

[Steve Bassen]

42/56 4+4 is a 2275 compressor wheel, aka RS6.

[S4James]

I concur. I have the same ones in my housings.

they require machining to fit.

If you can find someone to have the work done, its well worth it. Ive got over 10 years/100,000km on mine, and no issues with them still. Very solid combo that served me well.

[Cysco abt S4]

I'll rebuy them from you

Sent from my HTC331ZLVWPP using Audizine mobile app

[slow ride]

RS6 turbine size also.

[aysix]

It might be worth sending or getting those housings machined out instead of reselling the CHRA's.

[milehighkid24]

Those are RS6 sized turbines. Are they from SRM? I ran into the same sizing issue when replacing my turbos last summer because my car has K04's with RS6 compressor and RS4 exhaust turbine wheels.

[DxC]

Yea sounds like u got rs6 k04 instead of rs4 k04 - so technically everyone is correct

U know it's a blessing in disguise bc u can machine the housings to accept a full rs6 cartridge and have improved performance

[bruddha]

Revisiting for future build option! Who has successfully used either 2283 or 2275 CHRA in K04 housing?
Did you have to modify the K04 housing to fit or will they go in without issue? Prefer to hand upgrade what I have vs. Buying new