RS2 Turbo - Naked!

[twoqu]

Hi!

I though it might be interesting to share some photos of the disassembly of an RS2 turbo. I have tried to keep the procedure in order so that each picture reveals a little more of the components that are hidden away.
I have skipped the compressor housing removal.
Primarily I wanted to see what if anything was different on the RS compared to its more mundane sister the K26. I have noticed differences. I'll discuss what I find later on.

First bit of information. Yes indeed, the RS2 shaft has a l/h thread, that is to say you remove the nut clockwise not anticlockwise.
Secondly, there is only one seal at the compressor end.
Thirdly, it does not have what I would call a 360 degree thrust bearing. Looks like a regular 270 degree to me.

The following pictures should give you an idea of how an RS2 turbo in particular and turbos in general are constructed. This picture shows the turbo with the compressor housing removed.

[twoqu]

This picture shows the seal plate and its 4 bolt attachment to the centre housing. These bolts are M6 torx I believe. You can just make out the flinger sleeve between the shaft and the seal plate. This serves not only to mount the compressor piston ring seal but also acts as a thrust piece for the compressor wheel to revolve upon.
Compared to a normal K26 the seal plate has a machined recess where the compressor wheel sits.

[twoqu]

This picture shows whats beneath the seal plate. The first component is what some describe as a "flinger sleeve". The compressor seal, imagine a small piston ring, sits around this and when compressed in the seal plate provides a mechanical seal. I will have to check but its looks like a 14mm seal rather than the 19.3mm seal of a normal K26. The O ring seals the centre housing to the seal plate.

[twoqu]

This picture shows the underneath of the seal plate.

[twoqu]

This picture shows what appears to be a flat washer like spacer. Underneath this spacer is another distance spacer sleeve which had stuck to the bottom. You can see all the individual components in a later post.

[twoqu]

This picture shows the oil deflector. The tang of the oil deflector projects into the oil return galley. The deflector is located either side by two tangs which sit inside the hollow pins that locate the turbo thrust bearing.

[twoqu]

This picture shows the actual turbo thrust bearing. It is located on two pins, one either side. As you can see, the bearing has a segment missing where the oil gallery is. So it is a 270 degree bearing. A 360 degree bearing would have virtually a full circle of bearing material. I believe that 360 degree bearing are available for this family of turbos. So thats something to investigate before rebuild.

[twoqu]

This picture shows another flat washer that sits behind the turbo thrust bearing. You can clearly see one of the pins thats locate the bearing in the housing. Presumably the circular hole is an oil supply gallery.

[twoqu]

This picture shows the top of the shaft poking through. You can see how the shaft is waisted. Difficult to be accurate but I have measured the shaft diameter in the bearing housing at 9.94mm and the waisted shaft section at 7.0mm. The normal K26 shaft has those dimensions and the RS2 compressor wheel is a snug fit on it.

[twoqu]

This picture shows the individual components in the order they were removed. Top first, bottom last. Note the spacer sleeve that was stuck to the bottom of the first flat spacer washer.

[SteveH]

Robin, nice write up

I've never seen the inside of the kkk unit, are you planning on putting it back together yourself or having it rebuilt by one of the well known turbo suppliers?

[twoqu]

So as I suspected, despite the K24 designation, the RS2 owes more to its K26 sister. I will be able to show some of the differences at a later point when (if) I dismantle the turbo further. The RS2 shaft appears to be undercut before the thread unlike the regular K26. Not entirely sure why, but ARP also does this with their studs. It appears that this permits greater clamp loadings if I understand it correctly. Although I can't see why that be necessary. As for the left handed shaft, I believe that this is to prevent the compressor wheel unwinding the nut when stalled.

Please note that this is for information only. I have only dismantled this turbo to try and salvage the compressor side as it has already suffered damage to the turbine wheel. The plan is to try and duplacte the "small" RS2 turbo that several of the German tuners used in their conversions and to stop Paul N bringing the subject up every few months I think I have a suitable turbine and shaft from an AET hybrid.
I hope I have illustrated that a turbocharger is a relatively simple bit of machinary. It certaintly would be possible to replace the bearings and seals youself providing there were no other issues. The only problems being the availability of such parts and basic information relating to the torque of the critical nut and the issue of balancing. Looking at the back of the RS2 compressor wheel, I would guess they are balanced to a certain tolerence as a seperate unit. Usually when a turbo has been balanced by a specialist you can see the grinding marks on the back of the wheel, whereas the RS has a nicely machined recess. I get a pic later. So perhaps the rotating components are selected on tolerances. That would make more sense than individual balancing of assemblies. I can't see KKK dismantling and reassembling turbos to get them spot on. Anyway thats just an observation.
If I feel up to, I'll try and dismantle the centre housing further and expose the turbo bearings in the housing and show the turbine piston ring seal. I can then compare the components better.

[twoqu]

Robin, nice write up

I've never seen the inside of the kkk unit, are you planning on putting it back together yourself or having it rebuilt by one of the well known turbo suppliers?

Steve,

Well it depends. Ideally I would like to have it professionally assembled. Perhaps even looking at upgrades like the 360 degree thrust bearing. I have seen a K14 one and it looks like it is located on the same way on the two pins. Pretty sure they used to bolt them in on T3's etc.
However, I guess they will turn their noses up at this because they will say every component is nacked and why don't I buy a new or reconned one from them. Errr.. well the last "hybrid" died before it had a chance to get its turbine shaft dirty thats why! Perhaps a compromise can be reached, without any warranty/guarantee. Need to cultivate someone.
If I fook it up that fine. Apart from the balancing, I can't see why I could not atempt a rebuild subject to getting the parts and some basic technical information. Indeed o/s and u/s are available but this presumes some knowledge of what the shaft diameters and seal dimensions should be. Might look across the pond. They seem more relaxed about supply of spares/rebuild kits.

[s2driveruk]

oddly i 'rescued' a K14 unit from the dump the other day in order to disassemble and get a bit of understanding about the insides having never seen it previously. Think it was from a peugeot/citroen but if there is something u want to look at/confirm then I'm happy to take apart and photo

[Jamo]

Excellent i had asked if the RS2 came with a 270 bearing (i suspected it might) and never got an answer.

The 270 vs. 360 Bearing Dilemma
Many conventional journal- bearing turbos use a 270-degree thrust-bearing washer (at left), while the new breed of conventional and ball-bearing turbos employ 360-degree thrust bearings. The advantages of a 360-degree bearing include a full circle of lubrication, six orifices on the washer instead of three for the 270-degree unit, and an updated pad strategy to better disperse oil where it's needed. Turbonetics uses 360-degree bearings on all of its T04B and T04E turbochargers. There isn't much of a dilemma here; if you have the opportunity to use a 360-degree bearing, jump at it.