Boost source? Options

[bob91403]

Could someone tell me why this wouldn't work? This unit gives 7lbs of thrust. If you could flip a switch and go from NA to an extra 7lbs of air pressure, would a fuel injection system be able to adjust by itself?

[lapuwali]

7lbs of thrust does not equal 7psi of additional air pressure.

The problem here is one of volume. What you're essentially trying to do to get 7psi of boost is push 50% more air into a space than would normally be there. A 1.7 consumes 1.7 liters of air per cycle. At 5000rpm, that's over 4000 liters per minute, or about 230 cfm. 50% more would be 350 cfm. To pump that much air that fast requires a significant amount of power, on the order of 3hp if you could do so with 100% efficiency. You can't, of course, so it will always take more power because of pumping losses. Figure 70-80% efficiency for the very best air pumps. Those model airplane engines driving those (not very efficient looking) fans probably generate, what, 0.25hp? 0.5hp? It's impressive for their small size, but it's still a fraction of what's required. If you drove a good fan with, say, a decent lawnmower engine, you could provide a reasonable amount of boost. Or you could just use a turbocharger and recover otherwise lost power from the exhaust stream.