Thought this might help some people - I rebuilt Jake's rebuild post.
Original is here, but images are no longer working, but I had saved a copy just in case:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=1841Here is where I started today:
The wastegate was stuck...
So following Andy2's advice, I slide hammered those heat shields out of there! Here is what it looked like when they came out... lots of carbon built up:
The wastegate passages are kind of interesting. The gasses flow in toward the wastegate. Could the wastegate really get a good seal on this valve seat???
Some wastegate measurements:
wastegate valve seat ID: 24mm
wastegate valve head diameter: 31mm
wastegate installed travel/pre-load: 2mm
pressure to reach 2mm travel: 10 psi (approximate. Note: it is very "sticky" when completely closed.)
max travel: 10mm (8mm travel from touching the valve seat)
pressure to reach max travel: approx 14 psi
These wastegate pressure measurements pretty closely match what is published in the SAE paper:
Some detail of the turbine wheel. The vanes look pretty aerodynamic. I am impressed overall with the quality of this KKK turbo...
Turbine wheel specs:
OD: 59mm
exducer bore diameter: 49.5mm
thickness of fin section: 21mm
Compressor section "GW" before disassembly:
Here is what the inside of the compressor housing looks like:
Diffuser style is like most modern turbos, a parallel wall diffuser. The outer wall looks like a separate piece of metal that is pressed into the main housing.
Compressor wheel is a backward curved impeller type. This allows for more efficiency although less pressure ratio capability. Detailed shot:
The measurements of the compressor wheel are:
inducer bore: 37.5mm
OD: 60.5mm
And here is what the cartridge looks like (AKA the "guts" of the turbo...) A large colored o-ring seals the compressor housing to the cartridge.
I also tried to get some measurements necessary to calculate the turbine housing A/R ratio...
This thickness of 8mm was measured at a 59mm diameter.
I made some more progress with the turbo disassembly today...
To get the compressor wheel off, I first removed the nut, then I played some heat onto the compressor wheel with an oxy-acetylene torch. At about the point where the wheel got hot enough that the oil residue started smoking, I tapped it into a coffee can lined with some paper towel cushioning. The compressor wheel fell right off.
Behind the compressor wheel, I found four T-30 bolts holding on the compressor backing plate:
(New) I checked the torque and I got 70 in-lbs
After removing those bolts, the backing plate came off without trouble.
Here is what it looks like behind the backing plate:
Anyone have a good source on a rebuild kit for one of these? I'd like to continue taking everything apart, and freshen it up with new bushings, seals, etc as I put it back together
I got the turbine wheel out yesterday...
Here is the thrust bearing exposed. It is resting on two dowel pins in the center section:
This shot shows the back of the throwout bearing and the oil supply passage in the center section. You can see the channel machined into the back of the thrust bearing, (shaped like a "C"), which routes oil from the center section supply hole to the thrust bearing surfaces through two tiny oil galleys that are drilled in the thrust bearing:
To get the turbine wheel/shaft out from here you just have to pound it out squarely on the end of the shaft, to overcome the tension from the piston-ring type oil seal which is holding it in. The seals on both turbine and compressor side are two little piston rings with their gaps offset 180 degrees. Here is how coked-up mine looked just after it came out. There are some really hard, nasty carbon deposits around the turbine seal:
kkk compressor:
blades: 6 major, 6 minor (12 total)
wheel diameter: 60.5mm
inducer bore: 37.5mm
tip height: 4mm
findings: nearly identical compressor wheel OD means pressure ratio capability of the two are about equal. However, ~6% larger inducer bore of the KKK means it can flow a bit more air. There is also a very significantly greater tip height with the KKK turbo (33% greater on the KKK).
garrett turbine:
blades: 11
wheel diameter: 59.00 mm
exducer bore diameter: 49.00mm
kkk turbine:
blades: 12
wheel diameter: 59mm
exducer bore diameter: 49.5mm
findings: except for one additional blade on the kkk turbine, the turbine sections have nearly identical specs.
The trim of the compressor and turbine wheels can be calculated from the major and minor wheel diameters using this formula:
trim = (minor_diameter ^2 / major_diameter^2) x 100
I'd love to measure the A/R of the K24 turbine housing, but to do so requires the accurate measurement of the cross-sectional area of the turbine housing and also of the radius to the "centroid" of the area. I don't know how to do these measurements... got any ideas?
Here is a pic of the turbine housing where it has numbers on it:
Best I can make sense of these numbers is:
"NI CR 202" - the alloy of the metal in the casting. Nickel - Chromium 202, an austenitic grade stainless steel.
"/03 05 83" - looks a lot like a build date. 1983 Jibes.
"5324 101 7097 [1?]" The 5324... number sequence of 11 digits indicates a KKK part number. The 1 at the end might be a casting mistake.
"[1 ...] 39" - unidentified number. Could the "39" be the A/R ratio of the turbine housing - .39? That would be right in the ballpark of what we might expect.
I leakdown tested my wastegate:
I found a steel plate that I drilled and tapped for an air fitting and bolted it sealed to the turbine inlet.
Here's how I sealed the turine inlet area. I jammed a couple thick rubber wedge-shaped pieces deep into it and sealed the cracks with grease. The only route left for pressurized air to go was to to the wastegate valve, though the side port.
Results: Sure enough, the wastegate valve was leaky. At 30psi pressure, it only held 25.5 psi (so it had a 15% leakdown.) For engine cylinder head valve standard, that would be a very poor valve seal. But I am not sure about what is expected for wastegate standards. What do you guys think? Would that much wastegate leakage cause a noticeably added lag in turbo spool-up?
To make sure all the leakage was through the wastegate valve, after the test I remove the wastegate, sealed it's valve, re-assembled, and re-tested. It had 0% leakdown (held the full 30psi.)
Thanks for the info, and also an update: I am having good results with restoring my wastegate valve seal! ( I will be including detailed instructions with my K24 turbocharger rebuild kit. )
original:
restored:
I think I've finally figured out the A/R ratio for this turbo, and it's .3. This comes from the KKK catalog. I also heard that the A/R for KKK turbos are sometimes cast inside the turbine inlet. Well I took a look at mine, and sure enough, was able to locate a "3" right there!
Here is a comparison of my Dieselicious 360 degree thrust bearing upgrade versus the stock 1.6lTD K24 thrust bearing:
