I originally posted this in the 2nd gen section but I thought putting it here might get more replies...

When doing the math to choose a turbo for a given application, how should I calculate displacement? I found a nifty online calculator at www.smokemup.com (you have to register to have access, but registering is free) but when I choose the built in "rotary" mode the calculated airflows are more than a 350ci V8, so something is borked in their math. I tried 160CID (80x2) but the numbers don't look right when I plot them on the compressor map for a T04 H3... That's what BNR uses for their Stage 2 and they claim full boost at 3800rpm, (12psi) but when I plot the data onto the map you'd be over the surge limit until you hit 4500rpm...

 

I had the same difficulty with that site, maybe someone should let them know. Try the two stroke calculator, I think that it's a good bit closer.

 

Using two stroke mode just doubles your CID number, which I thought was what you needed to do with the rotary too... 80ci rotary inhales 80ci every revolution... 160ci 4stroke piston inhales 80ci every revolution...