Hi Dave Leonard,

Did you do your own turbo upgrade to the TO4 big shaft wheel, with
the  TO4E 50-trim compressor? Where did you buy the parts?

Paul Lamar


Yes, Paul,

BNR Supercars did the mods to the stock turbo housing.  Google them.  I
did the stage 4 upgrade, but selected a high pressure (instead of high
flow) compressor (they can install just about any TO4 compressor you
want.).


--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net


Where did you buy the parts for stage 4 upgrade high pressure
compressor?
Do you have the maps for both? I think I have your earlier map.

Paul Lamar



I just sent my turbo to BNR and they did all the work and supplied the
parts... boring out the housing, enlarging the waste-gate, making

everything fit, balance turbine and compressor...  Cost about 1 AMU.

I looked up the maps on the internet, easy search.  To be honest, I cant
say for sure which compressor I have right now...  but I think it is the
to4-e 50trim...  Garrett has a page with all the compressor maps.

--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net


I spoke to Bryan on the phone. He did not seem to grasp
the problem we are having. He kept talking engine HP.
That is the least of our worries :) I got the impression
he had never installed a tach.

Paul Lamar

Dave, do I have a deal for you. We are about to do a tach
install on Michael's turbo. My next door hangar neighbor Jim Poole
is an excellent machinist. It takes most of the time
setting up the compressor housing on the mill.
If you buy a tach kit we will do yours at the same
time. All you have to do is unbolt the compressor housing
and send it to me.

I am certain if you keep the turbo RPM below 80,000 RPM
at all altitudes you will not blow up another turbo.



Paul Lamar


You are right about Bryan, he does not really get our application.  I
had to basically make him put in the to4e instead of the v-trim.  But he
does a good job once you tell him what you want.  There are other good
turbo guys out there, but he is the only one I found (besides the guys
in Auz that John Slade used) that can put a TO4 into the stock housing.

If you want to keep the RPM under 80k at ALL altitudes and power
settings, you will probably have to go to a different class of turbo all
together, something larger than the TO4 stuff.  Or maybe sequentials.
80k is a pretty low number  Once you get above a P/R of about 1.6 all
the map I have seen will be above 80k, let alone the worst-case 2.5 P/R
that I expect.

Unfortunately, like I have said.  To remove the compressor housing, I
have to remove the whole turbo, exhaust, coolant and oil lines, drain
the coolant etc...I'm just not interested in the extra work.  Cause
no matter what the tach says, I'm going to keep doing the same thing I
am now.  (keeping EGT under 590C, and on the rich side if I am using any
significant amount of boost).

Sorry.


--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net

Maybe I am misunderstanding pressure ratio.

60 inches of HG sounds like a P/R of 2.

That means 400 HP I think.

What am I missing?

Pressure Ratio defined: Garrett.

* Pressure Ratio is defined as the Absolute
outlet pressure divided by the Absolute inlet pressure.
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

Why would you need more than about 1.5 ?

or 45" Hg.

My guess is find a compressor that puts out 1.5 P/R
at less than 80K.

BTW 590C is 1100 F. Rich as the ocean :)

Do the tach when BNR sends it back.
We have about a month.

I'll take off just the compressor housing today
on the mock up to see what is needed to be removed.
I can see your coolant line would be a problem.


Paul Lamar


Gents,
A few things to ponder:
1. What makes turbos come apart is more commonly abusive transient
operation, wheel resonance (fixed to design), poor balance (not an issue
with OEM turbos), and too high temperatures. You can over speed the
wheels to be sure, but 80krpm is quite conservative for a wheel the size
we would think of for a 2 rotor, especially at altitude. The compressor
maps are a good indicator of this. The OEM has mapped the compressor
performance on the above T04B to 126.3krpm, rest assured the impeller
can tolerate this speed in steady state. What will fatigue the wheel is
running up to max speed and back down to low speed in transient, think
race car or city bus. An aircraft however is mostly steady state
operation, which is why turbo-machines work so well, and reciprocating
machines often fair poorly. Turbine wheels are much more robust than
impellers (Inconel vs. Al) and characteristically have a higher speed
limit, so the impeller is your limiting factor.

2. A turbo tach. is a fantastic tool for validating a new turbo
application no doubt. However, once the match is done one can quite
accurately predict turbo speed based on the compressor map. If you know
X & Y, then Z is defined by the compressor map. It will be more
difficult without the raw map data to be sure.

3. The two most common methods for measuring turbo speed are using a
flat milled onto the turbine shaft and the sensor tapped into the
bearing housing, or a blade pass sensor tapped into the compressor
cover. The blade pass sensor is more accurate (much better resolution),
but more "difficult" to install as it requires some precision in placing
the sensor on the profile. It is also less robust for a permanent
installation.

4. Aftermarket turbo "up-fitters" make me nervous. I highly doubt their
ability to balance a rotor assembly to anywhere near the precision even
mass production turbo OEMs achieve. I just would not trust my safety to
one. Maybe not so bad if they are just fitting a NEW component balanced
rotor system, but whenever there is "trimming" involved that is not done
by the OEM I get nervous. A good balance machine is not cheap, and from
personal experience the after market for turbos is a scary place. There
is good reason most re-manufactured turbos only come with a 1 year
warranty. OK for a car, not OK for an aircraft IMO.

Cheers,
Zach Knutson