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Benino

I've pulled the turbo from my '80 931. I also have an extra turbo that came from an '80 931. The one off of my car seems to have quite a bit of turbine shaft play (I don’t know the specs or have the tools to measure). The extra turbo I have has no play but the shaft doesn't spin freely. It spins easily by hand but won't continue spinning at all when I let go of it. I'm not sure if either is usable without having it rebuilt. My main question though is about the differences between the two turbos I have. The compressor side of the turbos seems to be identical. The differences are on the turbine housing side.

(on all the pictures the one on the left is the one from my '80 931 and the one on the right is the extra one)

the one on the left (my 931 turbo) has larger nuts on the compressor side of the turbine housing (13mm nuts). The other has smaller studs and 10mm nuts.

the one on the left has a groove and a metal ring around the exhaust inlet.

the fins on the left are flat all the way to the end and the ones on the right are curved in at the ends.

Here are the numbers on the turbine housings. Its hard to make them out. The one on the left has it on the back of the turbine housing on the exhaust inlet tube (on the side you can see the fins on when you look at the turbo). The one on the right has the numbers on the other side of the exhaust inlet tube.
as far as I can tell Left: 18 9 81 ? 7
Right: IIII 125 5328 701 8373 and then that other number under it?

I don't know if anyone will recognize these differences and know what they mean? Is one design better than the other? Which one should I try to have fixed or rebuilt or whatever?
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1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

John Brown · Joined: 07 Nov 2002 Posts: 903 Location: Leesburg VA

The housing with the sealing ring is a later unit. Check the tech section, IIRC the progression of the seals for turbo/exhaust is discussed there.

I think the bent blades on the second unit are just that: bent.

FWIW, I just had a rebuild by Majestic and the price was quite reasonable. Or would have been if they had not found bad compressor blades upon disassembly.

I would send the late style unit (with sealing ring) to be rebuilt, by someone. It's old.

BTW, the sealing rings are now superseded by a 993 part which is not round/solid but more of a crush style.
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John
80 931 - #931 44Cup
99 Escalade - tows track cars
gone but not forgotten: original 924.org car - 82

Benino · Posted: Tue Jan 24, 2006 3:25 am Post subject:

I looked through the turbo part of the tech section and didn't find anything about the different seals for turbo/exhaust. :-/ Am I looking in the wrong place?

That's weird that the blades would get bent like that. They don't seem to be near anything that could have caused that. Has anyone else seen the blades like that?

So. . . is there any other difference between the units besides the seal? Any differences that would affect performance? Was the later unit just a later 1980 unit or was my 1980 unit replaced with one from a later year at some point?
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1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

Smoothie · Posted: Tue Jan 24, 2006 3:55 am Post subject:

I was thinking those blades might be bent too, but don't know for sure. They're bent in the right direction based on the turbos' direction of rotation, but there are no gouges as you'd expect if it had hit something. -Just don't know.. I will say they don't look right though.

As far as one being from a later year - no. Looking at the numbers "K26-2664G4.10" and "5326 970 6407" - at least one, more likely both of those numbers would be different if from an '81-up. They're both the same, so they're equivalents as far as year, and have the same characteristics - compressor and turbine sizes, etc.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

npjester · Joined: 24 Jan 2006 Posts: 31 Location: Baltimore Maryland

The bent fins are not damaged, they are designed like that, it is a part of the spec. called "trim" ive seen numerous turbos with bent fins (bent in the direction of rotation). its common on several mitsu-turbos, and on some KKK turbos.
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1981 931
1982 931
2003 MINI Cooper

Smoothie · Posted: Tue Jan 24, 2006 4:21 am Post subject:

More on the numbers here - http://www.924board.org/viewtopic.php?t=10928
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

John Brown · Joined: 07 Nov 2002 Posts: 903 Location: Leesburg VA

Benino · Posted: Tue Jan 24, 2006 9:29 am Post subject:

I see the part numbers on the tech page and I see that later versions during the '80 model year used more crush ring seals instead of just gaskets, but the part number for my turbos "6407" is not on the list.

On the other thread linked above with more info on the numbers, someone said what each part of the K26-2664G4.10 number mean. . . but Both of my turbos have the same part number on the labels yet the turbine housings are different and they have different shaped blades on the turbine.

Does anyone know if the curved or flat blades are better?
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1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

Zuffen · Posted: Tue Feb 14, 2006 2:07 pm Post subject:

I suspect the one with "bent" fins is the rebuild unit. I've never seen the turbine with that configuration on the 931 turbos.

The part number is for one of six models that eventually cam down to the two and then the one final replacement unit.

I would find a reliable rebuilder and ask them the pluses or minuses
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Bob Dodd - 924turbo@cox.net
931 1982, 944 1982 euro, 924S 1988SE, 93 968 tip 06 Silver Cayenne S, 06 Black Cayenne S

I have Way too many cars, parts for the 931,944 and 951

numbbers · Posted: Wed Feb 15, 2006 11:13 am Post subject:

I have two spare turbo's for my '80. One has the "bent blades," one has the straight blades. I would guess that they are from different suppliers to KKK. As far as not spining freely, no used turbo will continue spinning after you let it go, just from the inertia needed to overcome the oil coaking that happens the first time the turbo gets hot. I think your second one will work fine, you just have to use the triangular shaped gasket, instead of the crush ring. The crush ring was an improvement, but the triangle gasket works good. I believe the gasket is still available from your Porsche dealer.
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1980 924 Turbo