What size pulleys you running to get 11psi.?

 

I am also considering an adapter plate for the input side of my blower so I can bolt on the 90mm LS2 throttle body I have. I wonder what kind of gains I would see from that? 78mm -> 90mm should let a little more air into this starved 2.3L I would imagine. I like the idea of porting the intake side of the blower too.

 

I could figure out how much you'd gain approx. if you give me the vacum readings @WOT from the inlet elbow.

 

Hmmmm....I would have to build a plate with a gauge and stuff. I know there would be a performance gain of some kind so I will probably install it either way. How much vacuum would you expect to be there at WOT? Just wondering if it would be enough of a gain to feel it or not.

 

The throttle body cannot be downstream from a screw compressor or a roots blower. The inlet has to be restricted or the supercharger will be pushing full boost all the time. Even if this air is being bypassed it will be superheated. The amount of power this will consume will cut into fuel economy severely. Centrifugal superchargers and turbo chargers pump a variable volume of air based on outlet pressure and rpm, this volume per RPM rises exponentially relative to RPM increase. Screws and Roots move a fixed volume of air from the inlet to the outlet that only varies slightly relative to RPM increase. Outlet pressure has almost no effect on their capacity to take in air.

There's another thing to consider, if you restrict the inlet or the outlet of a centrifugal turbine it will consume less input torque. You can see this if you plug the hose of your vacuum cleaner and hear the RPM increase - same effect. If you restrict the outlet of a roots or twin screw supercharger the input torque required will increase and the supercharger will fight against the back-pressure. A tremendous amount of mechanical energy will be converted into heat if this happens. The only way to limit the flow through a roots or twin screw supercharger while also reducing input torque is by restricting the inlet.

The bottom line is moving the throttle body downstream from a Whipple would be quickly regrettable.

 

That was my thinking, as an HVAC tech, we learned that this applies to any pump, even centrifugal air blowers (squirrel cage). Just as a FYI, refrigeration screw compressors have slide valves in the suction side for capacity control.

 

The only way a bypass could keep the compressor from compressing would be if there was a valve to close the compressor inlet during bypass.

 

Listen guys I have drove the truck like this.I can tell you the blower does not draw very much hp open inlet long as its blown off.Yes it does draw more than with the tb on the inlet of the compressor but not much 2-3 more at idle.IAT's are lower than any GM vehicle with a twinscrew I have ever read about or seen.Remember the circulated air also keeps the charger cool as long as its not compressing air in the intake tract.I have drove it enough to know this will work.So far it come down to a matter of timing with the bypass it seems to be closing too fast on part throttle but there are ways around it.I am on a limited budget so the project is slow process.

Hey I am outside the box here now while I don't recommended that people follow exactly what im doing.One thing I know for sure the inlet on the whipple kits suck ***** and is costing most of you guys a lot of ponies.I will get back with you guys when I get this thing runing the way I want.

OHH PS. if your dead set on running the tb up stream of the compressor and wanted to put one on the intake.Then a 90mm dbw could be setup.Hell I may even end up like that.

I have also been a HVAC Installer/tech for 11yrs.So is my dad 35yrs. my brother11yrs.So there is not a shortage of knowledge in the air flow deptment.

 

Not for argument's sake, but just for my knowledge, who did it?

 

MB 271
VW Caorrado G60
There are few more instances of PD's being before the throttle on other engine's non automotive application.I just can't remember what and where for sure.