Folks,
 Few bits on turbos:

 - All turbine wheels made in at least the last 30 years will be cast
 Inconel unless otherwise stated, regardless of manufacturer. No
 worries on melting stuff!

 - Most automotive turbine housings are cast iron (obviously), though
 some are made of higher temp stuff than others. The good higher temp
 ones are high sil. moly or D5 Ni-resist, assume low grade D3 for
 off-the-shelf after market. For some Garrett turbos after market
 automotive companies have made stainless turbine housings of various
 A/Rs, this is the way to go for a high duty cycle rotary IMO. Don't use
 V-bands if you can help it, they are difficult to seal and are
 expensive. Do use high temp bolts (B16 is terrific stuff!)

 - First thing to worry about when matching is the compressor, it is
 the most performance sensitive (turbines are like big paddle wheels
 compared to compressors). Special consideration will have to be taken
 for the high Pressure Ratios (PR) experienced at altitude however, so
 you're going to have to choose where you want efficiency (take-off or
 cruise)

 - Rotaries are good at spooling turbos, but don't assume they are TOO
 good when choosing a turbine A/R (you will end up with a supercharger
 like boost curve. The Hitachi turbos used on s5 RX7s do use the
 waste gate like any proper match, just after torque peak. All matching
 work is validated on engine, so expect to try a few A/Rs before getting
 it dialed in where you want (I agree with wanting a large AR for
 pressure equalizing, you will have plenty of turbine power with the
 expansion ratios you can get up there! Especially if you are not
 concerned with take off power)

 - After market waste-gates are not terribly reliable, using an
 adjustable built-in is the way to go for A/C, but a standard one may
 be difficult to keep closed at altitude unless you install a higher
 rate spring (you can build an adjustable pressure actuator with a
 turnbuckle and some clamp plates, I'll try to find a link to an
 example)

 - TEST YOUR LUBE SYSTEM!!! Make 100% sure it flows oil quickly and at
 the rate specified by the manufacturer, poor oil supply (& dirty oil)
 is a major killer of turbos. Return lines should be above the sump!

 - Water cooling is mostly chosen in non-A/C applications to prevent
 oil coking during a hot-shutdown, but I agree that it should be
 considered mandatory for a high duty cycle application (with tight
 packaging). Return lines should be as high as possible in the cooling
 system to aide thermal siphoning

 - Typically ball bearings are only chosen when transient performance
 is crucial, as journal bearings will get you 80% of the performance
 with better steady state efficiency, but ball bearings are better with
 low oil conditions and can handle higher loads. IMO unless you have
 the $$ burning a hole in your pocket standard bearings will do just
 fine, and they have MANY more hours of design history behind them.
 (eg. To my knowledge no production engine uses a ball bearing turbo
 except the Garrett on the new Ford Scorpion engine.)

 I saw someone ask about cooling system additives. Redline Water Wetter
 is well thought of.
 FWIW unused oil has a thermal conductivity of around 0.1 W/(m-K),
 water is around 0.6, ethylene glycol around 0.2

 Cheers,
 Zach K
 Guy that works in the industry

 Thanks Zach. Some of the best info we have received so far.

 Paul Lamar

Thanks Zach,

I learned a few new things. What part of the industry are you involved in?

Doug in Japan


No problem, turbos are a tricky device and real information is very
sparse in the aftermarket world.

Fundamentals of Turbocharging by Dr. Nicholas C. Baines is an
excellent text for turbo knowledge.
http://www.conceptsnrec.com/Education/Engineering-Textbooks.aspx

Near the bottom of the page is a picture of an actuator with
replaceable spring where the 2 halves of the actuator are held together
using clamp-plates.
http://powerenterpriseusa.net/products/turbo/list_spec/index.htm

I do applications and development for a turbo OEM.

Cheers,
Zach


Zach,

Is there significant performance difference from a TE04E turbine
housing with a tangential inlet compared to a more centrally located inlet?
In the size I want, the tangential turbine is not offered with
a split inlet, however the central housing is.  The central
housing (like the old Raja turbines) has some advantages to get a close fit.
The sales rep. says I can order the unit with Inconel shaft and
turbine (extra) as well as ceramic bearings.    I am considering
P trim and 1:15 turbine AR,  Compressor 50 which  I assume is
the nominal size.   Not sure which size turbine to get.  Several options.

Housing unfortunately is ductile cast iron and having the housing
cast in Ni resist  may not be possible.  Only a few of the GT 28
series used that alloy.  E-85 will help cool the inlet charge as
well as a log type exhaust manifold.   Good news is this size of
turbine is in the 15lb range.
External waste gate is   necessary.

Doug in Japan

http://tinyurl.com/26zwdgf