Hello everyone,
I am new to this board. I bought a 930 two months ago after having enjoyed a number of air cooled normaly aspirated flat 6s (SC, carrera 3.0l, 3.2).
It is a fine example, but I have decided to embarq in the fabulous journey we all enjoy with our machines: the endless quest for more power!

It is a euro machine in perfect health, fitted with a free flow exhaust and a 1 bar WG spring by PO. I have a Kokeln that will be mounted soon. While I am here... I am contemplating the move to a more efficient turbo, reliable and street usable.
I have heard praise for the K27 7200 but I understand that K27 is a family name for a lot of different items. I have different propositions as we speak.

1. I could get a K27 11-11 from a reliable source. The only strange thing is that it is supposed to come from a 965 and I thought all 965 came with K27 7200 as standard... Could someone shed some light on this??

2. A rebuilt and upgraded K27. Please see photos attached, it is a rebuilt turbo with a lot of performance part to make it spool faster and stronger as I am told (lighter turbine and bigger exhaust port notably). If you have any opinion based on the photos, let me know...

Thanks

Thanks

 

Another image

 

depending on who built the turbo, it could be great or it could simply be well advertised. I have a very very trusted source for rebuilding and modifying the KKK turbos, it took me a long time and a lot of headaches to find the fellow, but he comes very highly regarded by people I regard highly.
One of the things I tell all my customers is to sit down and really think abot the goals for your car. If you dont I can almost promise you that you will end up spending money at least twice on things that if the goals had been more carefully considered, could have been bought once and forgotten.
If you care to talk turbo I am always willing to bench race and will be happy to help you determine what fits your needs and even help you track down bits and pieces if you like.

 

Look up Imagine Auto. I got my car last summer and did their K27S a couple of months ago, and it's almost night and day. No affiliation, etc. Oh, you'll probably have to go back to the .8 bar spring; I now get about 1 bar with my stock spring since upgrading my turbo (had already done turbo-back exhaust upgrade). And post pics of your car!

 

That turbocharger has suffered a bearing failure in it's previous life. The clearance between the compressor wheel and compressor housing is to great...

The turbine wheel is clipped, you do NOT need a clipped wheel with a stock displacement CIS car without cams. It is also a first gen small diameter shaft. ala they break.

I have new ones on the shelf. Take your pick 7200, 7200 "S" 7006's 7006 Hybrids, HyFlows..

 

are you saying that the turbo he has was remaned? and what do you mean by "clipped"? if anything, that looks like a factory reman as the factory plate is in place.

 

When it comes to turbos, Kevin is the man to talk to. He supplies IA and others.

A happy customer.

 

The new Rennlister (congrats) mentioned that it is a rebuilt unit (pictured). The clipped turbine wheel is shown on the hot side. One can see the machined blades. This reduces the energy applied to turn the rotating assy. This is good on a higher HP engine, but for a stock engine, spool up is hindered. One clips the turbine wheel when the A/R is too tight. This is not the case for this application.

BTW, one can change tags at any time during the rebuild or life/history of the turbocharger, for the good or bad.

 

Hi Kevin, thank you for your remarks.
A couple of additional points:
- What is the effect of such "clearance" issue (that you mention below)?
- For my complete information, can you give me a quote for a 7200 S shipped to Paris, France; thanks (you can use my email mathieu.prot@gmail.com if you wish)

Regards

Mathieu

 

The effect of the excessive clearance is to make it harder for the turbo to make boost and it will feel quite laggy as the efficiency of the compressor wheel and housing will have be just about non-existant. A clipped wheel will only exaccerbate the problem, especially on a small engine.
I personally do not care much for clipping, and I see it as a poor band-aid for poor or lazy turbo selection/build in most cases. Obviously in some situations it cannot be avoided when the needed size simply doesnt exist or is not readily available, but many times I have seen it used is to "save" the cost of new components, usually the cost of a new properly sized turbine wheel and housing.

I think what Kevin was getting at is the turbo has not been properly "rebuilt", just new or new-looking parts swapped in. When you have a CHRA bearing failure quite often the comp wheel "touches" the housing causing the wheel to basically machine the inside of the housing, sometimes in dramatic fashion. In this case, both the comp wheel and the comp housing should be replaced to return the turbo to service.
It is possible and quite common for the turbo to be modified to save the comp housing as well. This is done by using the next size up comp wheel, then machining the damaged housing to fit. You need to be very careful if you are buying such a modified turbo however, as the profile that needs to be machined into the comp housing is quite complex and it is highly unlikely that a simple visual inspection will tell you that is was done wrong. If it is wrong however the turbo will never perform properly and be a complete waste of your money. The devious thing is that there will be no way for you to prove that it uas been improperly machined and so you are likely to be stuck with a crappy turbo.

 

Thank you very much for this valuable info.
Well I am a bit puzzled: the seller tells me that once rebuilt, this turbo spooled sooner and stronger on its 965 3.3. The engine with this turbo was dynoed at about 350HP (at the crank) according to him of course.
I know it is not easy to "speak on photos" but, can it be reasonably believed that the clearance is "too much" from the pictures above? If so I will choose another route.
Thanks again to everyone for their help.

Mathieu

 

I have no input regarding any claims made about the turbo, just can comment on what others have said and the pictures show. We know nothing about the engine this turbo came off of or went on, and have no actual specifications as to what it is or isnt.

I cant say whether the clearance is too great or not, only on what the result of too much clearance is. What I can tell you is to NEVER EVER buy a turbo based on someones claims. You buy a turbo based on FACTS- the FACTS of what your engine is or is not, the FACTS of the turbos compressor map and turbine characteristics, and the FACTS of your realistic goals. 90% of what I do involves turbocharging. Every single day I get to hear about how great this or that turbo is or isnt, how so-and-so got fabulous and surprising results on XXYY turbo, etc., mostly always accompanied by "Which turbo do you think I should use?" I make turbo recommendations based on specific customer goals and habits compared against the specific known characteristics of a turbo. We speak in lbs/min and efficiency around here. Since we are at altitude here what works for the rest of the country doesnt work here, and my recommendations are often at odds with "what everyone else says", especially bits posted on interweb forums by people who often are at sea level with completely different requirements.