Originally posted by giddyup306:
Most will tell you that 70mm is overkill for a n/a 3L but, if you keep the secondaries functional, I don't think it'd hurt especially up top.


Considering the engine can't use but half of it's flow potential and the added size hurts velocity and causes a much greater pressure drop right at the mouth of the intake manifold. Gee why would people say it hurts performance???

A widened SVT UIM mouth is 67mm. You would have to port the UIM back a few inches to even allow the 70MM TB to flow properly.

Then do the math.
70mm TB outlet has a 73-75mm inlet.
The stock rubber boot is ~50mm
The SVT boot is ~54mm
The BAT pipe is ~62mm
The "huge" CTA pipe is ~72mm (That's 3" piping folks!!!)

The stock MAF has a flow area around 53-54mm


So large, small, large, small is how the incoming are goes. You can imagine this is not good for conserving energy & velocity. That is lost efficiency plain and simple.

BIGGER IS NOT ALWAYS BETTER!!! Far too many people just do not get this novel concept of flow dynamics.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.