EGR vs Speed Density Tuning
 

A thought just occurred to me: On cars running a parallel setup, would the opening of the EGR valve theoretically screw up the VE calculations because part of the mass of "air" in the manifold is now exhaust gas rather than the standard air (roughly 79% N2 + 20% O2) composition on which the calculations were based?

I assume this is mostly inconsequential though since it should only be opening during low-load cruising right? But would it be better to disable the EGR valve when fine-tuning cruising cells?

Also, do any of the MegaSquirt variants have pre-configured provisions for controlling EGR? I'd eventually like to start converting things over to MegaSquirt's control and move away from the parallel install.

It will but the O2 feedback system will compensate.

So if you've got closed loop turned off and are autotuning cruise cells, it would be good to disable the EGR temporarily until the autotuning is done, then turn closed loop control back on.