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K27-7200 issue

My turbo destroyed it self last w/end, on the track. beyond repair.
So likely I will get a new one. The guy who builds my turbos says oil flow was fine, excessive heat killed it.
Anyone had a similar issue with the K27? I never melted a 3LDZ. Just that I am not keen on just bolting another one on to have it do the same. I like to try and find long term solutions to these problems, rather than repeat them. Anything I could/should be doing to prevent this again? That turbo had about 5 hrs use on a rebuild. Basically seized.
And here is the irony. The car that had been chasing my bumper for several laps was driven by the guy who builds the turbo. He got to see his work first hand :-) Could not have planned it better. I am quite happy with this result - it was a much better outcome than an engine failure - given the massive trail of smoke when it went boom. Leak downs all 1-2%. Amen. New P/Cs about 5 hrs ago.
Thanks for any advice (and don't tell me to drive slower - was going the quickest it has ever gone).
Alan

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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-09-2018, 01:02 PM
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How about a water cooled turbo?
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'86 930 Guards Red - EFI MS3Pro, 80lb inj, 3.4, GT35R, Tial 46, Bosch 044, B&B Headers, 3.2 carrera manifold, Turbokraft Full bay IC
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Old 04-09-2018, 01:43 PM
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Yes, that would fix it - but I can't fit a water cooled unit. Race rules.
regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-09-2018, 01:58 PM
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K27 is a very robust turbo, if heat killed it then the oil flow or volume could not keep up or something was causing excessive heat. I've seen them run cherry red before due to a lean fuel or timing issue. I'd check that with a 3LDZ before spending good money on a new turbo.
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Old 04-09-2018, 02:43 PM
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He said the oil flow was not an issue. I did ask him to check that - if it is checkable. I think they can basically do a diagnosis by inspecting for signs in the internals. Copied below;

"glad you found the nut. I have stripped the turbocharger there is not issues with oil supply. The issue is excessive turbine temperature, this is very evident from the heat colouring on the turbine shaft. Unfortunately the turbine wheel has ground into the turbine housing venturi, rendering the turbine housing and shaft un useable. You will need a "

The thing nipped up, then unwound the nut on the intake side and the two wheels parted company in the housing. That meant I had to find a stray nut. It was sitting in the intake pipe waiting to eat the next turbo. Yes, I guess I could bolt the 3LDZ on again. But the running conditions of the engine have not changed between turbos. And no 3 LDZ failed with exact same conditions. Just contemplating options before bolting a new K27 on again.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-09-2018, 03:48 PM
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Quote:
Originally Posted by RarlyL8 View Post
K27 is a very robust turbo, if heat killed it then the oil flow or volume could not keep up or something was causing excessive heat. I've seen them run cherry red before due to a lean fuel or timing issue. I'd check that with a 3LDZ before spending good money on a new turbo.
I made an error in the K27 designation. Mine is a 7006. Here is what my turbo guy has sent me;
"There are a couple of noticeable differences, one the 3ld has a larger diameter turbine journal shaft, can absorb and displace heat a little better. Two the 3ld has the turbine end bearing closer to the turbine head, hence not the same amount of unsupported weight as that of the K27 7006. Three the 3ld runs at a slower shaft speed to that of the K27."
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-09-2018, 06:04 PM
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didn't you have a lot of issues getting a good turbo or was that someone else?

do you run a BOV?

my car came with no BOV, (partial RUF conversion and RUF does not use one). durabuilt rebuilt mine and they said there was an issue with the shaft if I remember correctly, maybe a crack.

I hear with no BOV it can be hard on a turbo is why I was asking.
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Old 04-10-2018, 03:21 AM
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do you monitor EGT? if you have data logging capability it would be interesting to get some EGT data. perhaps your EGTs are too high, and a little tweak to ignition timing could help.
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Old 04-10-2018, 07:29 AM
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There was a guy on the forum that had 4 rebuilds. but I have had a decent run from the 3LDZ (modified). I did have an early issue where a turbo was spilling its guts on the garage floor while parked. But running wise I have not had an issue, until now.
Not sure what you mean by BOV. I have the waste gate, and the recirc valve is deleted and replaced with the plastic housing thing that the 964 has (if I recall correct). These changes , and a 964 IC were made when I fitted the 7006. So, you are right in that everything is not exactly the same as when I ran the 3 LDZ. Maybe this is the issue?
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-10-2018, 10:56 AM
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Check your diverter valve is working. The only time we've had them back-spin a comp nut is when the valve has failed, or cannot flow enough (Ruf BTR with Ruf K29 and single small diverter valve -- had to incorporate a 2nd one).
The -7200 series use a left-hand threaded nut, never come loose. That would ideal.
Are you allowed to change out the compressor wheel at all on the K27? You could have one helluva cheater turbo...
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Old 04-10-2018, 11:28 AM
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Thanks Chris. Has to be a reason. Maybe this. I had just changed into 4th when it let go.
The diverter valve is the small plastic valve body on the rubber elbow?
How would I check it?
Yes, I can probably change the internals - I had a modded 3 LDZ. As long as the plate and housing body tie up with 930 or 930 S spec, I would be OK.
Looks like we are looking for another 7006 core.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-10-2018, 11:55 AM
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Agree with Chris (duh). 7006 is going to move more air than your old turbo and maybe you can’t flow enough with your unknown divertor. Also bigger turbo could run cause you to run leaner up top. As Jacob (hey bud) suggested, EGT or AFR monitoring would add valuable data to the issue.
7006 is a very stout turbo.
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Old 04-10-2018, 12:51 PM
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Quote:
Originally Posted by Alan L View Post
The diverter valve is the small plastic valve body on the rubber elbow?
How would I check it?
Alan
The plastic Bosch recirc valve used is not especially well-regarded in the high-boost watercooled world. They may react faster than the piston type (less mass), but really not by much and flip side is that they're prone to diaphragm tears. And sealed, so can't be serviced.

Cost was very obviously a major factor in the design. (And there's more than one SEAT/VAG part that seems to be identical to the Porsche part, but is much cheaper to buy....)

I held a plastic 965 valve in my hand for about 30 seconds looking at it - then headed inside and bought a Forge billet replacement for $60 on Ebay instead... They're double the price now, but same principle...


http://www.vaglinks.com/Docs/Misc/VAGLinks.com_DIY_Testing_a_Bosch_Diverter_Valve.pd f
https://www.audizine.com/forum/showthread.php/357594-Everything-you-want-to-know-about-Bosch-Diverter-Valves
https://rennlist.com/forums/944-turbo-and-turbo-s-forum/505532-inside-of-a-dead-bosch-recirculation-valve.html

Many aftermarket choices, including brand names like Forge, Tial and TurboSmart, all making recirc/dump valves. Routing is the only difference; you can't dump metered air on CIS, so you recirc back into the intake between the metering plate and the compressor, a dump valve just dumps back to atmo.

The Forge lasted well for me - I'd take the top off every year or so, say "hmm, still lubed/clean/moves", screw the top back on and forget it again.

The Tial dump valve I have seems very high quality too. Oddly, it's much cheaper than the Forge...
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Old 04-10-2018, 01:21 PM
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I might have a bit to learn about recirc stuff. Hopefully Chris can put me on the right track.
AFRs were conservative - mid 11s at top end. I was slowly tuning/ leaning it out between races. I have run it (with the 7006) in mid 12s previous. Ran the 3 LDZ in mid 12s always. I was previously running short on fuel at top end. Just re done all the system and got more fuel - so was starting out at the rich end and working my way up.
1 bar boost.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-10-2018, 01:34 PM
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Quote:
Originally Posted by jwasbury View Post
do you monitor EGT? if you have data logging capability it would be interesting to get some EGT data. perhaps your EGTs are too high, and a little tweak to ignition timing could help.
I used to run EGT, but it basically pegged the gauge, and I had a distracting red flashing light in the corner of my eye. So I disconnected it long ago. Yes, the EGts are well up there. 900 deg C (approx 1600F) comes to mind. Close to that anyway. maybe slightly north of there.
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-10-2018, 02:44 PM
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Quote:
Originally Posted by Alan L View Post
I used to run EGT, but it basically pegged the gauge, and I had a distracting red flashing light in the corner of my eye. So I disconnected it long ago. Yes, the EGts are well up there. 900 deg C (approx 1600F) comes to mind. Close to that anyway. maybe slightly north of there.
Alan
Chris has forgotten more than I will ever know about such things, but 1600 could be kinda high. I never monitored EGT on my 930, had CHT and bought an EGT sensor but sold the car before getting around to installation.

(Whatup Ken)
Old 04-10-2018, 03:04 PM
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BTW Alan, curious what Racing you’re up to in that 930. Any links to the series you run with the car, info about other cars you run against. I race an ‘83 911 (naturally aspirated)...I like to read about air cooled 911s racing...seems fewer and fewer of these cars are being raced these days.
Old 04-10-2018, 03:08 PM
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Spuggy - very helpful. Thanks. looks like a critical piece of kit. Just checked mine. It is still working.
If I understand it right, this piece of gear bypasses the boost pressure in the IC etc, either to waste, or in this case into the turbo intake side. It does this when the throttle plate shuts and the vacuum on the underside of the plate sucks the valve open, allowing the dump of pressure?
Is this so the turbo doesn't stall since no air is being sucked thru while the butterfly is shut?
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-10-2018, 03:10 PM
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Quote:
Originally Posted by Alan L View Post
It does this when the throttle plate shuts and the vacuum on the underside of the plate sucks the valve open, allowing the dump of pressure?
Is this so the turbo doesn't stall since no air is being sucked thru while the butterfly is shut?
Regards
Alan
You've got it figured right Alan
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Old 04-10-2018, 03:20 PM
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Quote:
Originally Posted by jwasbury View Post
BTW Alan, curious what Racing you’re up to in that 930. Any links to the series you run with the car, info about other cars you run against. I race an ‘83 911 (naturally aspirated)...I like to read about air cooled 911s racing...seems fewer and fewer of these cars are being raced these days.
Jacob, here are a couple of u tube links - give you an idea. Basically anything pre mid 80's. Classic racing. Race what you relate to. So a mix - alfas, Bmers, occasional mustang, Datsun 260Z etc. You can extract as much HP from the engine as you want. But the gear must be as came with the engine. Eg can't inject what was a carburetted motor. Body aero etc has to be as per original. Turbo has to be as what the car left the factory with.
Not many aircooled running here either. Even our national Porsche series only has a handful - 964 cup car types. All the rest water pumpers - old and new. 944S still a strong following. Solid performing race car. I wonder if the aircooled are just too valuable now. Mine would be the only 930 in the country on the track. I could race the Porsche series - but the panel damage is a bit severe. They seem to consider GT3 panels as throw aways. 930 bits much harder to get. The Classic guys are really into their cars and make an effort not to damage theirs or others. S..t still happens of course - but more accidental than desperate racing stuff.
Go pro quality is a bit crap - but ;
http://youtu.be/S6yCYlfS6OU
http://youtu.be/9WHrLUinIvw
Regards
Alan

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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Old 04-10-2018, 03:58 PM
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