500 BHP with a K26/7????

[twoqu]

Thats the trouble with turbochargers. Whilst simplistic in components they have precise tolerences.
Unless these aftermarket compressor wheels come with precise machining dimensions, looks like a recipe for trouble. If there is contact between the wheel housing whose fault is it going to be? Answer - Yours! Either because the dims were incorrect or the assembly was.
Another issue is that there are more than one K27 compresor housing. The 7200 was I believe a superback design like the RS2 so was a step change in design from the regular stuff. That means the backplate and associated hardware would also be different. So you may not be able to fit a desired wheel within your comp housing anyway.

[twoqu]

I suppose another issue is gong to the lack of data like compressor maps on which to make an informed choice.
Unless we apply the bigger must be better rule.

http://www.ebay.com/itm/K27-Borg-War...-/121897264159

You can see from this example that it is intended to be a drop in replacement for what I believe is the 7200 (2208) cast wheel. It claims to be superior by nature of the extended tip and other design features. See the proviso about balancing!

[Quattronaut]

It does seem that the KX500 was basically a MTM 428PS replica! Essentially the 3072 Comp wheel with the larger K26 turbine and #8 housing which apart from the centre housing was all Porsche based. The compressor side from the 7200 911 and the turbine shaft/housing from the 944T 250 bhp version.

That´s right, the 8 hotside housing is from Porsche 944 turbo S. The 3072G is from Porsche 964 turbo, where it is fitted to a K27.2 turbo. But the turbine shaft from the 944 turbo S was a K26 contour 3 as I know, and steve´s KX500 seems to have contour 1 as his measurements are correct. Turbine wheel and shaft are one piece.

There appears to be both Turbonetic and presumably KKK #10 housings. The KKK one appears to have a rectangular entry rather than the familiar to us round one.

KKK indeed, and yes, as I think turbonetics made some, too. But I never found one

Whilst not wishing to put a downer on this project, the problem is going to be who you are going to trust to do the machining of the compressor cover/backplate to match whatever wheel you are going to choose, apart from the balancing issues and the precise measurements needed to assemble and even attach the comp wheel to the shaft.

Yes, that is completely right. Since I do not know the housings and backplates, and I do not build turbos, I do not know, what else is necessarly to fit the compressor wheels.

Having said that even you you bought a turbo with a warranty and it went pop, undoubedly they would blame you for its demise anyway!

That is, what most of the tuners do, even well-known. They all tend to blame everything else. And to be honest: Often enought, they are right.

[twoqu]

The Porsche 944 S turbine shaft is the same as the larger Audi K26 shaft thats why you can interchange the #6 and #8 housings. Depends whether we are using the shaft extuder dimension or the turbine exit dimension.
You are obviously quite well informed.
To be honest it might be worth considering selling your good turbos/components to someone who is satisfied with whatever performance they deliver and put the funds into one turbo that will do what you want achieve if thats at all possible. Otherwise you end up dismembering perfectly good turbos and keep tripping over the bits. Don't ask me how I know!

[Quattronaut]

Yes, it is tricky to fit a wanted compressor wheel to a given housing. You gotta have a trustable turbo-guy who knows his work and who knows the stuff he uses. Maybe it will fit, maybe the housing can be machined that it fits, maybe you can and need to buy extra parts to make it fit.

[SteveH]

It does seem that the KX500 was basically a MTM 428PS replica! Essentially the 3072 Comp wheel with the larger K26 turbine and #8 housing which apart from the centre housing was all Porsche based. The compressor side from the 7200 911 and the turbine shaft/housing from the 944T 250 bhp version.
There appears to be both Turbonetic and presumably KKK #10 housings. The KKK one appears to have a rectangular entry rather than the familiar to us round one.
Whilst not wishing to put a downer on this project, the problem is going to be who you are going to trust to do the machining of the compressor cover/backplate to match whatever wheel you are going to choose, apart from the balancing issues and the precise measurements needed to assemble and even attach the comp wheel to the shaft.
Having said that even you you bought a turbo with a warranty and it went pop, undoubedly they would blame you for its demise anyway!

Mine made 426bhp and 615NM @ 30 degrees ambient on the dyno at MRC with an RS2 exh manifold and reversed AAN inlet and 3B cams, so that sounds about right. Boost of 32psi by 3500 rpm. I now have a tubular exh manifold and duel plenum inlet. Spools earlier and must be 450bhp. Nice bullet proof turbo and relatively cheap. Looks like the best option for 500+ would be a new unit and sell the KX500 as it is!

[twoqu]

I suppose another way to look at this is to try and find a documented 500bhp K27/26 set up and duplicate the spec!
I seem to recall that others tried bigger comp wheels without much success.

[K Simmonds]

I really do see your point about using after-market wheels, they are something of an unknown quantity and whoever does the job needs precise data to get the machine work right.

That's why I'm keen on the 3071 O wheel Quattonaut was good enough to steer me towards, plus he's said it's known combination that works well with the parts I have.

I've given up on hitting 500BHP, I don't think there's a cold-side that would allow me to do it and retain my Wagner EM and RS2 air-box.

I've managed to find the original KKK rebuild data on-line, will post a link when I have more time.

[Quattronaut]

I suppose another way to look at this is to try and find a documented 500bhp K27/26 set up and duplicate the spec!
I seem to recall that others tried bigger comp wheels without much success.

Few weeks ago, a turbo very similar to mine (same compressor, little smaller turbine, but "10" hotside) was sold via ebay in Germany. This one definitely can do 500hp+, but I did not speak to the seller and don´t know the buyer.
Mine should be able to hit it, too- but that will take a while, sadly.

There are many KKK wheels that can be fit to K26/27 combinations, which can flow enough air for 500hp, the problem is the hotside. With the common K26 turbine, the "8" hotside is too small for 500hp, and the "10" one is (was...) quite ungettable. And the bigger K26 turbines are simply not known by anybody.

K.Simmonds, maybe there are some comp wheels that can be fit to your housing, but you hotside will limit that thing. You would need a bigger turbine or/and another housing- I have the feeling you want to use your both turbos, and not buy a nearly complete other one- especially, when we watch the KKK prices

If you do not find a KKK distributor that can help you, PM me for a try.

[twoqu]

Might have been a bit quick to judge the KX500 as looking at some pics it appears to have a 14 blade comp wheel rather than the 12 blades that the KKK 3072 should have. So that might be the 3071 wheel in that!
There is a lot of interesting technical info one one of the German sites that might be of interest. You have to sort of familiarise youself with German terms but the data is useful. I seem to remember you have to register which is a little bit difficult as it asks some strange German related questions. Having said that it might be worth the struggle.

[Quattronaut]

Might have been a bit quick to judge the KX500 as looking at some pics it appears to have a 14 blade comp wheel rather than the 12 blades that the KKK 3072 should have. So that might be the 3071 wheel in that!
There is a lot of interesting technical info one one of the German sites that might be of interest. You have to sort of familiarise youself with German terms but the data is useful. I seem to remember you have to register which is a little bit difficult as it asks some strange German related questions. Having said that it might be worth the struggle.

I did'n search the KX500, just took a look at the single pic Steve posted, thought it's his own compressor wheel. And this seems to have 12 blades. Maybe he has an old version and they sell it with another wheel right now?

[twoqu]

Here is a pic of Sonic's one I think!

[SteveH]

My unit has 12 blades, Sonic's must have been a more recent unit. They don't make them anymore and weren't interested in refurbing and upgrading mine with a billet wheel.

[Quattronaut]

This is the one Steve posted- hope, this is ok for you, Steve?

I´m quite sure there are 12 blades. Behind the shaft there is only one pair. The blades geometry also is quite different- from above, you can see all 12 blades, because the bigger blades end before the smalles ones do. If you watch the newer wheels from above, the smaller blades are so small, that they hide under the bigger ones, and you only can see 7 blades. So Steve´s turbo should be different from Sonic´s. His measurement also fit the 3072G quite good. There is only 0,1mm difference inducer, that may be reading failure, ok- but the exducer difference to the 3071O is 0,8mm, I don´t think he reads that wrong

Edit: Ok, Steve was faster

[K Simmonds]

Cool, this is turning into an interesting thread.

Robin, do you by any chance have a link to the German website you mention?

Quattronaut, thanks for the offer regarding acquiring a 3071 O wheel, I may well be in touch.