Paul,

   What would be a safe top rpm for the 1989 stock turbo. The do not
   exceed
   speed.
   Thanks
   Rino

   We don't know. My guess is around 100,000 +/- 10,000
   I am going on the TO4_60-1 compressor map.
   As I recall, Dave added the TO4_60-1 compressor shown in the
   second jpg to the stock turbo and it fit. This loaded down the
   turbine. It seems to be working so far.


   Paul Lamar ...No rotor no motor.



   Paul,
   I've been looking at several turbo maps over the last several days, and
   the one below is the one I keep coming back to. The points I've plotted
   are based on both Gordon and David's spreadsheet. The only moving
   variable for each point was altitude. The first point was a SL and then
   every 3000 feet up to 15000. I was trying to look at how the Turbo
   would react to fixed power settings but increasing altitude. It looks
   like it spools up to about 100K RPM at 15K altitude. This Garrett turbo
   is both oil and water cooled ball bearings, and the turbine is available
   in A/R of 0.85, 0.95, 1.06, and 1.19. It doesn't say which turbine it
   comes, or which turbine is used to generate this compressor map. If I
   used one of the large A/R turbines (a larger one than used to generate
   the map shown), which way would it shift the plotted line? And would it
   slow the RPM by using a larger turbine? If it slowed it a little and
   shifted it left a little, it would be even better.

   Don


   No attachment came across Don. A larger A/R should reduce the HP
   of the turbine and the back pressure on the engine. I am not sure it
   would shift the dotted line. I suspect it would just move the
   equilibrium
   point down to a lower RPM area. I am not sure and I will research that
   interesting question when I get back to the barn.

   I would definitely start with the 1.19 A/R and go from there.

   Paul Lamar ...No rotor no motor.


   Don,

   The compressor maps are not generated by any turbine. They only show
   the volumetric flow characteristics of the compressor itself, based
   on rpm. In other words they are stand-alone.

   You could drive them off the engine with a belt, or even use a small
   engine dedicated to driving the compressor -- or an exhaust driven
   turbine, it does't matter.

   What matters is that your power source matches up well with the
   power absorbed by the compressor.

   Here is an example. Suppose you want to make a certain amount of
   boost at sea level. You can see on the spreadsheet how much hp your
   compressor will need to make this amount of boost.

   Now go to the exhaust side and find out how much power is available
   from your engine's exhaust for driving a turbine.

   I just put together such a calculator and sent it along in a
   previous message. This is still a work in progress and I will add it
   to the Turbochart and make everything work together.

   Anyway, you can use this spreadsheet to get a pretty good
   approximation of how much power your exhaust will have for driving a
   turbine at any given altitude. As you go higher, the turbine power
   goes up dramatically.

   So now you know how much power your compressor needs and how much
   power is available in your exhaust. What you do then is just match
   the two to go up together as you climb.

   As for A/R, you want to look at the charts that show pressure ratio
   versus flow. I will be adding turbine flow to the spreadsheet, as
   well as these charts, so you can see where you fall.

   With the bigger turbines you don't want to go with too big an A/R
   because you may not have enough flow.


   Regards,

   Gordon.



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