Kevin

I have finally had the chance to post a picture of some new technology. While visiting the factory a month ago. I was shown some top engineering at work. What is pictured is a K16/K24 compressor housing with a epoxy coating sprayed on the surface. This coating is dialed in at zero clearance between the housing and compressor wheel. To date this is the largest K16/24 turbo that has been developed for non racing uses. In theory we should obtain 100% efficiency (meaning all the air that enters the compressor housing gets compressed) It is wishful thinking, but we do get a 12-15% increase over the rated wheel. These are huge, jumps. In fact inlet air temps will lower dramatically. The benifit that we want is more boost being produced per shaft revolution.

This is a very time consuming task, but extremely worth it for our engines... These turbo's are being built for a fellow member...

Minis-are-slow

Can this process be applied to any Turbo?
If so, how much does the process cost?
What kind of gains can be expected?

Kevin

Yes, it can be applied to any turbocharger. The cost is variable on the size of the unit, however isn't cheap, plus the complete turbo has to be torn down and rebuild due to the dialing in (the wheel will rub the coating at high RPM on the test stand). If you start with a 74-76% efficient compressor wheel, bank on adding 10-15% on top of that. That gives you a ton of air that would normally would be lost in cavitation.

msindi

Kevin - I can not wait (nor can I sleep now!! thanx a lot - LOL)

Kevin

msindi- You are going to have to change the X50 to the X50+++ option!

Oak

zero tolerance turbos? that is theoretically impossible. c'mon Kev....

W8MM

OK, ... I'll bite.

What happens with zero clearance when the temperature of the parts change and some thermal expansion happens? Do all the parts have the same coefficient of thermal expansion? Does anything seize or loosen up?

Kevin

Class 101:

1)We must remember that on a well designed turbocharger, the radial clearance between the tip of the compressor wheel to the housing is typically .009-.010" (for each side of the wheel).
2)With a KKK turbocharger you have full floating bearings, they will ride on the turbine wheel shaft, and rotate in the bearing bore. We can manipulate these clearances with different bearing thicknesses and bore sizes to keep the radial movement to minimums.
3)We know that with Ball-bearing turbochargers the main advantage is not the lack of friction (marketing gimic) but the ability to keep the shaft centered in the bore! The typical clearance is .006 each side....
4)I took Sharksters Titanium rotating assembly to the factory to show what we have been doing with the small K16/24's, and they showed me the prototype developement work with zero-clearance turbochargers. Again the theory is to stabilize the shaft and wheel within the housings, and to try to maintain a zero-clearance.
5)As I mentioned earlier, we do have clearance between the bore, bearings, and turbine wheel. This is a given, and you cannot take this away, or your shaft will seize. I tried to get the compound out of the factory so that I could just go and buy it. However, instead of giving me the formula numbers, they gave me the name of the compounds used. So what we do is spray and cure each layer till we build up the tolorance to zero. The turbocharger gets assembled and test run. Yes, we have wheel rub, infact the wheel don't turn. You have to back the housings off and spin the turbo at high speeds to dial in your clearance. It doesn't take long to build up temps and desired running clearances.

After these processes are done, you basically get a .002 radial clearance on both sides of the wheel. Another important fact is that after the run in process is complete, we spray a high heat graphite-moly coating over the epoxy. Please understand that all of these compounds are softer than aluminum, and that turbo's will run at 150K in a wheel rub, aluminum to aluminum situation for many hours before a reduction of boost is noticed. I say that because I see many 930 owners just complain of oil leakage and smoke, but say "boost was great" and they have 1/8 of material ground of the compressor wheel.

The design principal is to provide a zero-clearance unit, and as time goes by, the wheel will rub the coating off, opening the diameter of the housing, matching the wear of the unit. A nice feature is that one can inspect this wear pattern to tell the condition of the turbocharger bearings!

Steve Weiner-Rennsport Systems

Kevin:

"Class 101",.....VERY well done, Sir.

Thank you.

Kevin

Thank you, Sir...

Oak

So........ actually it's zero tolerance for the first revolution?

I gotcha.....Just wanking your chain.

Kevin

I think its +1 & +2 for the first rev... SMILE

sharkster

Oak you are a hard-baller to please I still hate you for making me want to mod after looking at all of those pix you had over a year ago

adrial

Dare I even ask the cost?

Minis-are-slow

So if I had this process done to my measly little KO3(on my vwGTi) would it be beneficial? And how much would it cost?
I suspect that it wouldn't be worth it on my little baby Turbo!