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

[FrankCB@aol.com]

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         

In a message dated 5/24/04 1:51:04 PM Eastern Daylight Time, 
douglas.t.brown@navy.mil writes:

> I was wondering where to find information on how to size and install 
> a turbo, wastegate, intercooler and related parts on any engine.  
> I've read magazine articles on the subject, but they always seem to 
> skim the surface and don't get into how to develop a system that works 
> together.  Does anyone know of a good book on turbocharging?
> 
> Toby Brown