" From: Tom Jennings <tomj@xxxxxxx> " " " I made a spreadsheet with some of the basic turbo calcs. With the " TE06 and motor at 6000 rpm, one turbo would produce 20psi and " r=2.4. A second TE06 at r=2.4 with input at 20psig makes 45psig " output. wild guess: 'r' is pressure ratio, right? then, using a for atmospheric pressure and b for boost, ( a * r ) - a = b right? if so, r=2.4 gives b=20, and r=4.1 gives b=45, pretty closely. " With those numbers, the nomograph 650 - 700 hp looks about right. " " If I 'play' the calcs and assume a turbo can do atmospheric to " 45psi in one step (for comparison purposes only) it would be " r=4.1. " " It seems very likely that two turbos in series probably is less " than twice as efficient (since obviously a lot of energy is taken " out of the exhaust gas by the first turbo) a total r=4.1, far less " than the theoretical r=5.76, seems ball-park reasonable. if my equation above is right, then for two equal-step turbos in series the equation would be ( a * r * r ) - a = b and r=2.4 gives b=70! r=2.0 gives b=44. single stage compressors get less efficient as pressure ratio climbs, so at some point two low-compression stages are -more- efficient than a single high-compression stage. i believe it's due to heating of the charge, which destroys density. " But 50 psi plus or minus has got to be the number, to get 700 hp " from 182 ci. just fyi and fwiw, two turbos of r=2.1 give b=50 on the nose. also, you wouldn't want two turbos of equal size, which is what i presume 'te06' suggests. since the first one has already compressed the input charge by ~50%, the second should be about half the size. one t06, one t04? -- you can improve turbo efficiency by spraying water [or alcohol, or a mix] into the eye of the compressor. it soaks up the heat of compression by evaporating right as the work is being done. going to run intercoolers? ________________________________________________________________________ Andrew Hay the genius nature internet rambler is to see what all have seen adh@xxxxxxxxxxxxxxxxx and think what none thought