Sizing Turbos, et al.Re: <VV> Turbo Waste gate

[JVHRoberts@aol.com]

1. There are plenty of websites out there with turbo sizing help. And unlike 
MacInnes's book, these cover the modern state of the art turbos used on 
today's cars. Little to no trial and error is needed, since there's now a 
significant experience base. I'd go to these guys in lieu of MacInnes's book simply 
because they are more relevant. Just use google.com and search for turbocharger 
vendors. Turbonetics, et al, all handle the latest units, and are immensely 
helpful. I added a TO4B to my Mazda rotary boat engine, and we nailed the size 
perfectly on the first pass. 
2. WHo needs a 100% efficient intercooler? The ones that are presently 
available work VERY well in real life. Air to air or air to water both work well. 
Your choice is dependent on how you want to set it up. 
3. Look at turbo engines of an output similar to what you want to achieve. 
The output is more relevant than the displacement. 

Enjoy!


In a message dated 5/24/2004 5:39:03 PM Eastern Standard Time, 
FrankCB@aol.com writes:
Toby,
       IMHO, the best book for sizing turbos is still Hugh MacInnes' 
Turbocharging.  Unlike Corky Bell's book, MacInnes doesn't minimize the 
significant 
effects of temperature rise of the air going through the turbo compressor.  
Bell 
seems to expect you to use a 100% efficient intercooler which will completely 
remove ALL the heat picked up by compressing the air.  Unfortunately 100% 
efficient air/air intercoolers cost an infinite amount of $$$ and take up an 
infinite amount of space. You may have some difficulty fitting one to your 
Corvair 
even if you could afford it.(:-)  However, Bell does include good info on 
sizing the intercooler, whatever its efficiency.
       Be prepared to do trial and error calculations in sizing turbos.  
First you need to assume a compressor efficiency (65% is a reasonable 
starting 
point).  Then using that and following MacInnes' method, you calculate the 
amount 
of air flow AND the temperature rise through the compressor and into your 
engine.  Using the compressor map for the turbo you are considering, you then 
check out what the actual efficiency your calculation leads to.  This will 
likely 
NOT match the 65% value you assumed initially, so you have to redo the 
calculation using the new efficiency.  After a few times you will match the 
efficiency you started with.
       Now this calculation will change if you are using an intercooler (or 
water injection) to reduce the temp of the air before it enters the engine.  
The more efficient the intercooler, the more cooling it does, but larger it 
becomes.  So how big a unit can you fit into the Corvair?  You also need to 
take 
into account the pressure drop of the air going through the intercooler.  In 
addition, you need to take into account the cooling effect of the evaporating 
fuel on the airflow.  For gasoline this is typically a 40 to 50 degree F. 
temperature reduction (the exact value depends on your A/F ratio).
       MacInnes' book also contains the compressor map for the 180 turbo, so 
you can calculate the effect of adding an intercooler or water injection.  
Just remember that the intercooler can only be used on pure air (without 
fuel) so 
you can't use it with the stock Corvair draw through setup.  You can, 
however, use water injection with the stock Corvair setup.   
       As you can see, there's a lot of trial and error calculation involved. 
This is an ideal situation for a spreadsheet and I've started working on an 
Excel program that can (hopefully) incorporate all of these items on the 
intake side of the engine and permit you to run through many alternates in 
seconds. 
But perhaps someone knows of a spreadsheet that already exists that can do 
this.?????
       Frank "if it don't go, boost it" Burkhard