Originally posted by taylormadem5
You have a good point in that more boost is easier to tune, but a trubo that makes that kinda boost and is reliable is not cheap. A 6lb SMALL turbo like a t3 or t4 or a t3/4 hybrid is a great little turbo that you can get 6lbs out of and not have much tuning issues on an all stock motor. I think thats what this guy is probably gonna do is use a small turbo on a stock block. With a T3/4 hybrid he could easily get 40-60hp out it with an air to air intercooler. 6lbs on a stock block isnt that hard on it, 20+lbs and i dont care how small the turbo is and how little CFM it makes, your gonna have to rebuild the bottom end for sure and probably the top end to be safe. For the cost of just the rebuild im sure he could locate a good small turbo setup that makes less than 10lbs of boost.
There are no 6lb or 20lb turbos, that's not how turbos are rated. If you put a turbo sized for a B16 @ 6 psi onto a Viper, do you really think it'll produce 6 psi for the Viper? Come on. Turbos are rated in cubic feet per minute (CFM), and CFM dicates boost pressure. If a turbo kit says the included turbo will provide 6 psi, that means the turbo will flow enough air on the given motor to produce 6 psi of positive pressure in the intake manifold.
Surf to:
http://www.turbofast.com.au/TFcompB.html
Since I have the information handy I'll once again use a B16 as my example.
Bore: 3.189 inches
Stroke: 3.047 inches
VE: 100% (to keep the math simple)
10.5:1 + 1 psi = 11.15:1 boosted compression ratio
10.5:1 + 2 psi = 11.79:1 boosted compression ratio
10.5:1 + 3 psi = 12.43:1 boosted compression ratio
10.5:1 + 4 psi = 13.08:1 boosted compression ratio
10.5:1 + 5 psi = 13.73:1 boosted compression ratio
10.5:1 + 6 psi = 14.38:1 boosted compression ratio
10.5:1 + 7 psi = 15.02:1 boosted compression ratio
8.5:1 + 10 psi = 13.60:1 boosted compression ratio
8.5:1 + 11 psi = 14.11:1 boosted compression ratio
8.5:1 + 12 psi = 14.62:1 boosted compression ratio
8.5:1 + 13 psi = 15.13:1 boosted compression ratio
After doing these calculations I see that I was off by a fair amount, my apologies. But my point still stands that 8.5:1 + 10 psi requires very nearly the same amount of air as the 10.5:1 + 5 psi. Not only that, but the effective compression ratio inside the cylinders and therefore the pressure felt by your headgasket and cylinder walls is nearly the same. (off by a very very small amount.)
If you were to match up an appropriate turbo for a B16 it won't matter if you run high compression or low compression, you'll still need the same air flow. Check out this page on calculation horsepower and air flow requirements:
http://www.turbofast.com.au/tfcalc.html
Notice they never ask for the compression ratio of the motor, it simply isn't required. The engine still has the same displacement, still draws in the same volume of air. Same volume of air, same turbo requirements.
For more information, read this post:
https://www.honda-acura.net/forums/s...316#post333316