Turbo advise needed

[layuca]

Hi folks,

I wrote before about a turbo that I purchased and asked whether it would make sense to install it in my car. I've spent a whole lot of time trying to find out the specs on the turbo, but have not been able to get any conclusory information.

The turbo is a K26 #8 hot side with a 16-blade compressor. The fellow who sold me the unit told me that a K27 wheel was installed on the compressor side. Now, all the information that I've seen on K27s is that the biggest wheel on a compressor side has 14 blades. The compressor housing is from a K26.

The compressor measures 75mm on the exducer and 51mm on the inducer.

I have a small K26 (#6) on my car. I don't want to add substantial lag to my car, but I am considering taking the large wheel from the other turbo and installing it with the compressor housing on my (#6) K26.

I also have some other bits and pieces that I need to install in my car, but need to sort this out first.

The #6 k26 in my car kicks in right at 3k rpms, and I'd like to keep it that way.

Unfortunately, I can't download a picture of the compressor wheel, but with the measurement and description, I hope that someone in the forum can help me with some info and direction on what to do.

Thanks in advance for the help!

Pedro

[Greg_S]

Pedro, are there any other part numbers or identifying bits on the turbo?

[layuca]

Hi Greg,

The compressor housing has 5236-970-6411 on the blue plate. It also states k26. The compressor wheel does not look stock.

Thanks,

Pedro

[porkkis]

The housing might be std audi 10v. It's just machined for the new wheel.
From the wheel measurements I'd say the wheel designation is 2970 or 3067 which have about 73,7 and 76,2mm diameters respectively. 2,9" and 3,0" and latter figure for inducer %.
10V audi compressor = 2664 -> 66mm -> 42,3mm.
If your #6 turbine wheel is also from audi, you should be able to swap hot side housings and just test which of the two suits you better. Audi 56mm #6 and porsche 56mm #8 use the same turbine wheel.

[layuca]

That helps. Thanks... It sounds like the the 2970 and 3067 wheels are KKK. Is there a list posted somewhere with all the different KKK wheels available? In all the pictures I have seen of compressor wheels, I have yet to see a 16-vane wheel. Thanks again...

[james_bufkin]

Yes, Porkiss is right on the estimate for the compressor wheel.

But what does it all mean...

As for Blade count, this will effect the solidity of the compressor wheel. You can't flow air through cast aluminum. The underside of blade is the source of compression, so a wheel with more solidity will make more compression sooner and as the blades are closer together, they can compress to a higher pressure at a lower turbine RPM. So the surge line is moved to the left. But, you don't get something for nothing. The overall peak flow of the turbo is dropped down because of the higher overall solidity which will restrict flow. However, the high solidity means high pressures are possible. The turbo map becomes very slender and tall. Hence, such a turbo is ideal for limited RPM ranges and has very good efficiency at a certain narrow operating range. Typically lower high boosted stuff. More blades means interference and turbulence between the blades. turbo'd Diesel power generators use turbos that have a high boost output at low steady flows.

So you have a compressor wheel that is larger than an RS2 comp. The hotside is also correspondingly larger. I'd say those dimensions sound alot like the Garret t04E/50 hybrids that were very popular a few years ago before the ball bearing rage. Yet, you have 16 blades instead of 12 blades, so for each revolution, your turbo does (simplistically) 33% work. In Layman's terms.... I'd say you'd cut the typical 3500 rpm boost threshold of the T04E/50 by the inverse of 1.333 or down to 2625. And the peak flow will also be dropped down by the same ratio. The old T04E/50 would flow about 400 cfm. This will drop to ~300 cfm because the compressor will get quite inefficient flowing that high due to its solidity.

I'd say the turbo is imbalanced in that the hotside is too big for that compressor wheel.
You will have very low turbine pressures and it might effect the usefullness of that compressor wheel at low RPMs. Also the high blade count will make the turbo on/offish. Very good for making low end torque. But completely wrong for up top power. I could see this turbo being used on a restricted rally car (with a smaller hotside) or a small diesel (as is)