924Board.org

[Sharky]

Hi All,
I managed to get a brand new (didn't believe it at first) turbo from Europe for my '81 931.

It's definitely brand-spankin-new, got it in the mail and she is fresh as.

I noticed there was a difference in the numbers and I'm wondering about Compression ratio for some new pistons....

The original Turbo we pulled out has part no:
5326 970 6022

The new one's part no:
5326 970 7007

I am having a hard time finding information on these turbos, in particular the original one.

Can any of you gurus help shed some light on this please??

Kind regards.

[Cedric]

http://www.924board.org/viewtopic.php?t=15595

Acording to the older discussion the specs are 2470 compressor and 6.10 turbine housing on the new one.

And the older turbo K26-2660 GA 4.10

You will notice boost coming on later if you swap turbo since the turbine is one step larger in throat area, the 2470 compressor is the worst of them all, very low efficiency at high rpm.


Not and Ideal swap, but a brand new turbo is still a great find. Dont know the condition of the parts, but maybe you could swap over the "old" compressor to the new one you bought, that makes Carrera GT specification if I remember correctly. It will still alter the character of the car towards the top end, but give you more room for tuning. Better efficiency and lower pumping work from the larger turbine.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Carrera RSR]

Yep, you bought a RoW series 1 turbo K26 2470 6.10. The big confusion is the differences between the RoW S1 + S2 cars versus the US specs and forum misinformation over multiple threads. Your old unit is a K26 2660 4.10. The added confusion is many cars both sides of the pond had replacement turbos fitted by Porsche, non specialist garages and PO's who didn't know any better. My S2 parts car had an S1 engine, S2 ignition and a CGT spec turbo. This in addition to a 951 IC gave 200bhp at 0.62 bar boost.

I'd go with Cedric's suggestion and rebuild the new turbo with the compressor off the old unit and put it on the new unit. Chances are the old compressor wheel is possibly still good. Worst case is you need a new one. The turbo will need rebalancing afterwards either way. At least the turbine housing, wheel, shaft and bearings/seals are all good. This will give you CGT spec K26 2660 6.10 turbo. This should give you a nice push down the road even without an IC.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

[ideola]

The setup Cedric describes is what I have on both the 941 and Club Sport. I've never understood the complaint about turbo lag with the S1 cars because I like to rev high before shifting (at least 5K, even driving on the street). If you baby the car and don't rev it, it will feel anemic. But if you drive it the way it was meant to be driven, you won't even notice the "lag", especially with the gearing in the Euro-spec G31.

All of my exhaust components are ceramic-coated on both of the above cars, which keeps the heat in the exhaust tract, and I believe that this makes a difference in earlier spooling of the 6.10 hotside. My boost gauge shows boost starting to build at 2500 RPM, especially from 2nd gear on up.

I agree with the described approach. Send both units to a reputable rebuilder and ask them to make a hybrid using all of the components from the new old stock unit, but swapping on the compressor wheel and compressor housing from the original unit (assuming the wheel isn't damaged). The reality is that the NOS unit is going to need to have its seals refreshed anyway since sitting on the shelf for so long. As hard as these units are to install, it would be silly to put it in and expect it not to leak after sitting on a shelf for 30+ years.
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erstwhile owner of just about every 924 variant ever made

[Fasteddie313]

your 6022 is a somewhat small compressor also.. its compressor 2660

if you could get your hands on any good compressor from

6407 - 931s1 us spec - 2664 compressor

951 k26/6 - 2667

951 k26/8 - 2670

those are quite in order from smallest to largest with your 2470 being the smallest of them all...

a 2664 compressor from a 931 s1 would give you the blowoff/recirculation valve with it...

2667 or 2670 compressors you would have to make custom charge piping for and install your choice of an aftermarket recirculating blow off valve.. I believe you should keep the back plate with these also because they carry a different part number..

or you could have your original 924 compressor housing machined for any of those wheels I do believe if you wanted to keep the integrated BOV (witch is very nice) and not do any custom charge piping


a k26/6 with the 2667 compressor could be had very cheap to snag parts from..

but you do have the best turbine housing out of them all, its the one you want if your going to shoot for big power, and afaik they are somewhat rare and desireable..

says 1,000 hours of research.. whatever that's good for
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80 Turbo - Slightly Modified

[Sharky]

Alright, there is some great info there guys, thank you all very much for your input.

Cedric/Carrera, I'm going to take your advice and send both the units to MTA Turbochargers on the gold coast and see if they can make me a neat little hybrid. I am quite sure the old unit is fine, it was working great when we pulled the motor out. I thought it was leaking oil and burning it off, but when we pulled the motor out we found the oil was weeping from the oil feed line and burning off on the turbo. There is absolutely no play in the shaft of the old unit.

Dan, I had the same thought. I am looking at a turbo seal kit from Autohauz AZ or Pelican parts (only because I couldn't find the kit in your garage )
I'm going to send that to MTA with the units so they have the gear there to make with the go-go.

Fasteddie, Thank you for the info on those parts. TBH, I'm not exactly "shooting" for big power, but who says no to more HP?? I will go ahead and ask MTA if they have any suggestions for the compressor side of things, perhaps they can source something a little more 'juicy'.
I'm not exactly sure what turbo to look for to pillage the 2664, 2667 or 2670. I've found a few K26 turbos online going for a fair price but I have no idea of the part numbers that correspond to these particular compressors.

[Fasteddie313]

here...

http://www.924board.org/viewtopic.php?t=40119&highlight=

the 924-944 turbochargers and more if you ask for it..
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80 Turbo - Slightly Modified

[Carrera RSR]

I had two turbos which were running fine in both cars. When I pulled them I sent them both to a turbo specialist. Both turbine housings were cracked and unserviceable. Both turbine wheels, shafts, bearings, seals and compressor wheels were not reuseable. That was an expensive lesson!! Just because they run OK doesn't mean they haven't gone beyond their service life.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252