tbi and supercharger

[KasaRyan at aol.com]

There are about 3 ways to get a sc engine to play with tbi.

1. - The right way - use an ecm set up to do 2 bar map, and use a 2 bar map 
sensor.  Does anyone know if I can use the 7427 or 8625 to do this?  Will the 
sy/ty ecm control a 4l60e?  This is what I would like to do on my 93 truck.

2. - I'm pretty sure B&M and Whipple both use a 1 bar calibration with the 
stock map sensor mounted on the boost side.  When above 100kpa, the spark is 
dropped, and the extra fuel comes via the way of a 1:1 FPR.  ie 5 psi boost 
gives you 5 psi fuel pressure increase.  If the stock FP is around 10-13, and 
atm is 15 psi ish.  Then if you add say 7 pounds of boost, you will get about 
50% more fuel.  The fueling isnt too bad, but then you need an external box 
to turn the timing back when under boost.  Both of them use a water heated 
TBI mounting - is TB icing really that likely, or is it increased with the 
vacuum drawn on the units?

3 - use a 2 bar map sensor on a 1 bar application and halve the inj/pphr in 
the ecm.  This way when the engine is at 100 kpa, it thinks it is at 50 kpa 
and uses maps accordingly.  then you set maps up to account for the doubling 
of map.  This reduces resolution, and the dumber your pcm is, the more it is 
apparent.  It does allow control of fuel and timing under boost though.    

BTW - when holley bought b&m superchargers they added $1000 to the cost of 
the 88-95 truck kits.  Does anyone know why, or just because they can.  Also, 
say a person was to buy a standard 144 blower, could you get the pulleys and 
brackets to allow it to be used on the TBI trucks.  Also, boost on a 
roots/screw should go up linearly with RPM with constant VE.  A centrifugal 
should go up exponentially with the square of RPM.  This is what makes them 
harder to size.

Does Carl Summers have anything to input on this conversation?

Thanks for listening!
Ryan Hampl - a K-State Grad!  kasaryan at aol.com
139 Hoover CT  Controls Engineer 
Salina, KS  67401                  
phone  (785) 825 5831           
http://hometown.aol.com/kasaryan
<A HREF="http://hometown.aol.com/kasaryan">Ryan Hampl and his happenin' 
Hotspot</A> - updated 11/20/00
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