[CSG Mike]

Originally Posted by Irace86.2.0

If my theory from earlier holds any water then the reason why a tune can't fix the dip alone is because the motor will try to avoid knock regardless of the basic parameters set by the tune, and knock may be problematic on some high compression NA motors at low rpms where slow exhaust speeds increase combustion chamber temperatures from residual exhaust gases.

If my theory is true then trying to hard tune out the dip without a header could be dangerous or increase the chance of engine knock.



The FB20 is a stroked FA20 (minus port injection). The FB20 has a lower compression, so it would make a good apples to apples comparison for comparing the effects of compression ratio on low end torque (to demonstrate my theory true or false), but it isn't a good apples to apples comparison because the engine is undersquare (longer stroke and smaller piston diameter than our square setup). Usually a stroked motor will have more low end torque, so any dip alleviation from not being as high compressed could just as likely be from being stroked. Thus, I agree with you that the FB20 isn't an apples to apples comparison for my theory or for his theory.

It doesn't.

A stock FA20 tuned on Motec, still exhibits the dip.